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NOAA Report NOS 11 5, CGS 8
IMPLEMENTATION OF NORTH AMERICAN DATUM OF 1983 INTO THE NOS NAUTICAL CHARTING PROGRAM August 1985
U.S. DEPARTMENT OF COMMERCE National Oceanic and Atmospheric Administration National Ocean Service
NOAA Report NOS 11 5, CGS 8
IMPLEMENTATION OF NORTH AMERICAN DATUM OF 1983 INTO THE NOS NAUTICAL CHARTING PROGRAM Oren E. Stembel, Jr. William J. Monteith
Marine Chart Branch Nautical Charting Division Rockville, MD 20852
August 1985
U.S. DEPARTMENT OF COMMERCE Malcolm Baldrlge, Secretary
National Oceanic and Atmospheric Administration Anthony J. Calio, Administrator
National Ocean Service Paul M. Wlff, Assistant Administrator
Office of Charting and Geodetic Services R. Adm. John D. Bossler, Director
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ACKNOWLEDGMENT
The authors would like to express their appreciation to the following persons who provided input or reviewed this report: John Spencer, Edward McKay, John Love, and Jim Stem of the National Geodetic Survey Division; Capt. C. William Hayes, Capt. Lavon Posey, Cdr. Donald Nortrup, Dennis Romesburg, James Gearhart, Howard Danley, Erich Frey, John Weir, Jeffrey Stuart, Frederick Ganjon, and Richard Hogan of the Nautical Charting Division.
We would like to express our special appreciation to Eleanor Andre'e for her editorial assistance, and to Mary Himelfarb, Annie Gorgone, and Rolland Gant for their timely word processing and reproduction support.
Mention of a commercial company or product does not constitute
an endorsement by the U. S. Government. Use for publicity or
advertising purposes of information from this publication
concerning proprietary products or the tests of such products is
not authorized.
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CONTENTS
Acknowledgment ................................................. ii
Executive SuII1Illary ............................................... 1
I . Introduction ............................................. 3
I1 . Datum Conversion Considerations .......................... 5
A . B . D .
Existing chart datllI[Is ................................ 5 Magnitude of datum shift ............................. 6
C . Criteria for changing projection ..................... 6 State plane coordinate systems ...................... 10
E . Datum conversion constraints ........................ 14
I11 . Datum Conversion Alternatives ........................... 17
A . B . C .
Cartographic datum conversion options ............... 17 Impact on chart production .......................... 21 Resource requirements ............................... 24
D . Conclusions ......................................... 25
IV . Datum Conversion Plan Options ........................... 27
A . Objectives .......................................... 27 Plan options ........................................ 27 Discussion of options ............................... 28
V . Recommendations ......................................... 33
B . C .
A . NAD 83 datum conversion policy ...................... 33 B . NAD 83 datum conversion plan ........................ 34
Appendix A Report to the United States-Canada Hydrographic Commission by Committee on Horizontal Datums. March 1980 ......................................... 35
Appendix B NAD 83 conversion factors and proposed implementation schedule for NOS nautical charts .... 46
Appendix C Option 4: Datum conversion costs ................... 71
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FIGURES
1 . Expected latitude change from NAD 27 to NAD 83
Expected longitude change from NAD 27 to NAD 83
(in meters) ............................................ 7
(in meters) ............................................ 8 2 . 3 . Plot of projection shift criterion .................... 11
TABLES
1 . Specifications for standard features appearing on NOS nautical charts .................................. 9
2 . NOS charts/insets: summary by scales .................. 12 3 . Datum conversion options .............................. 21
4 . "Conversion note" implementation schedule ............. 27 5 . Option 1: Automated information system (AIS) datum
conversion schedule ................................. 29
6 . Chart edition (print) cycles .......................... 31
7 . Option 4: Hybrid datum conversion schedule ............ 32
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EXECUTIVE SUMMARY
The National Ocean Service (NOS) publishes approximately 960 nautical charts in support of recreational, military, and commercial navigation on the coastal and inland Federal waters of the United States and i t s terr i tor ies . More than 2 million charts are sold annually, with the military purchasing about 40 percent of this total. Intended to facilitate the movement of waterborne commerce and promote marine safety, the nautical chart is designed and compiled to provide accurate marine information for users ranging from the unsophisticated to those who employ satellite navigation for determining vessel position. The nautical chart has been recognized in the United States as such an indispensable navigation tool that the U.S. Code of Federal Regulations requires commercial vessels in excess of 1,600 gross tons to carry charts of the waters upon which they operate.
The conversion of the NOS suite of nautical charts to North American Datum of 1983 (NAD 83) will require careful planning to minimize the workload impact upon an already heavily strained cartographic system, to assure efficient utilization of resources, and to accomplish the full datum conversion in a timely manner. Although the datum conversion will require extensive cartographic effort to revise both the graphic and digital nautical charting data bases, most nautical chart users will not be aware of this change to the horizontal datum.
This report discusses the following problems or considerations that must be addressed before an effective datum conversion plan can be developed:
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NOS has approximately 140 charts that are not compiled on the North American Datum of 1927 (NAD 27).
NOS has 236 charts and 187 insets that contain State plane coordinate grid ticks which will have to be revised to reflect the relationship of the various State plane coordinate systems to NAD 83.
NOS has 262 charts containing LORAN and/or OMEGA electronic positioning lattices which have to be revised because of NAD 83.
The magnitude of the datum shift varies from a few meters to more than 4 nautical mile.
No cartographic policy exists for identifying the criteria that justify shifting a chart's projection.
These important factors have been considered in formulating the conclusions and recommendations for the conversion of NOS nautical charts to NAD 83.
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Several constraints are addressed that affect timely datum conversion. These constraints involve current personnel re- sources, current availability of only preliminary NAD 83 values, and the current and near-future production capability of the developing automated chart production system.
Several alternatives for conversion to NAD 83 are identified. Each alternative is a different mix of cartographic actions and production techniques producing a variety of nautical products. Each produces either a temporary or permanent conversion solu- tion, requires different and varying amounts of resources to accomplish the conversion, and causes an impact on the normal cartographic workload associated with the annual production of charts.
Finally, four datum conversion plans are discussed with a hybrid manual/automated cartographic plan recommended as the most feasible for accomplishing NAD 83 conversion within a 5-year time frame. The cost of this conversion is estimated to be $1,098,400. The successful accomplishment of this conversion will require several policy decisions by upper management within the Office of Charting and Geodetic Services (C&GS) . Specific datum conversion policy recommendations are also presented.
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I. INTRODUCTION
On April 17, 1978, at the first meeting of the United States-Canada Hydrographic Commission (USCHC), R.Adm. Allen L. Powell (U.S. member), suggested that both the Canadian Hydro- graphic Service (CHS) and the National Ocean Service (NOS) should begin addressing the problems expected in adopting the new horizontal datum for North America.
In May 1979, Mr. David Gray, CHS, and Mr. William Monteith, NOS, were named by the USCHC as members of a two-person ad hoc Committee on Horizontal Datums to i d e n t i f y and study expected problems when each agency converted its nautical charts to the new geocentric datum. By then, the new datum had been identified as the "North American Datum of 1983," or "NAD 8 3 . "
A report was prepared by the committee and presented to the USCHC in March 1980 (appendix A). This report identified 16 major issues, questions, or problems which would have to be addressed for an effective and efficient transitioning to NAD 83 by both organizations. A review of that report finds the conclu- sions and recommendations drawn in 1980 to be essentially valid today.
The purpose of this 1985 report is to discuss several options available for datum conversion of nautical charts to NAD 83 within the NOS nautical charting program. Discussed will be the probable conversion time and resources required under each option for the suite of NOS charts. A recommended conversion schedule will be proposed which considers fully the operating realities faced by NOS today based on an expansion of the conclusions and recommendations formulated in 1980.
In preparing this report, the following questions were considered in arriving at the eventual conclusions and recommendations:
o Upon which datums are NOS chart projections referenced or compiled?
o Considering each existing chart datum, how much projection shift will be required for the chart to be on NAD 83?
o How will the State plane coordinate grids be affected?
o How will NAD 83 affect the "graphic" nautical chart?
o How will NAD 83 affect the automated nautical charting data base?
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o What constraints are imposed on immediate conversion of nautical charts to NAD 83?
o What options exist for implementing NAD 83 on the graphic chart?
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11. DATUM CONVERSION CONSIDERATIONS
The Chief, Nautical Charting Division (NCD), has identified the timely conversion of all NOS nautical charts to NAD 83 as a pri- mary operating objective for the Marine Chart Branch (MCB). To achieve this objective, several cartographic factors will be con- sidered and their impacts on datum conversion discussed. The principal factor is the amount of actual positional shift re- quired between the present chart datum and NAD 83. Knowing the magnitude of the shift and the scale of the chart, the effect of this shift on each nautical chart will be assessed and appro- priate datum conversion methods discussed. of the cartographic and reproduction services workload also will be determined. Finally, datum conversion policy recommendations fo r implementing the new horizontal datum will be developed and a realistic implementation schedule proposed. A methodology was developed to evaluate various factors and arrive at this realis- tic implementation schedule. The following considerations were investigated and an assessment made of their respective impact on the production of nautical charts.
The resulting costs
A. Existing Chart Datums
The current suite of NOS nautical charts is compiled on or referenced to the following datums:
Datums
North American Datum of 1927 U . S . Standard Datum* Old Hawaiian Datum Puerto Rico Datum Local Astronomic Datum Guam 1963 Datum Preliminary NAD 27 Preliminary NAD 83 Local datum
No. of charts Percentage
830 51 36 29 15 2 2 1 1
85.6 5.3 3.7 3.0 1.5 0.2 0.2 0.1 0.1
*Sometimes referred to as "1902 Datum" or "NAD 1902".
In addition, two charts are compiled on unknown datums, and the recreational chart of the New York State Barge Canal is published without a datum projection. In total, there are 140 charts which are not compiled on NAD 27. These charts are referred to in this report as "orphan datum" charts and their respective impact on NAD 83 conversion will be discussed later.
Appendix B provides a complete listing of all NOS nautical charts and their respective datum.
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B. Magnitude of Datum Shift
Figures 1 and 2 portray graphically the amount of latitudinal and longitudinal shift in meters between NAD 27 and preliminary NAD 83 values for the coastal areas of the continental United States, including the Great Lakes. Overall, the smallest amount of shift occurs in the Great Lakes region while the greatest shift in both latitude and longitude is in the Aleutian Islands of Alaska (in excess of 150 m along both axes). In general, the range of shift varies from 0 to 25 m in the Great Lakes, 15 to 50 m along the Atlantic coast, 20 to 40 m along the coast of the Gulf of Mexico, 80 to 100 m along the Pacific coast, and 100 to 160 m in Alaska.
The shift between the "orphan" datums and NAD 83 will be greater in most cases. For example, the National Geodetic Survey (NGS) reports that for charts of the Hawaiian Islands, the shift between the Old Hawaiian Datum and NAD 83 will be approximately 360 m in latitude and 285 m in longitude. The resultant shift between the Puerto Rico Datum and NAD 83 is about 220 m.
The NOS charts of the Pacific Islands (Guam, Wake Island, Kingman Reef, Palmyra Atoll, Samoa Islands, Johnson Atoll, and others) will be converted to the World Geodetic System 1984 (WGS 84) datum and will require a projection shift in excess of 150 m. Final WGS 84 datum values had not been released by the Defense Mapping Agency (DMA) at the time this report was prepared.
C, Criteria for Changing Projection
Once the probable magnitude of datum shift had been determined, it was necessary to define the criterion that would determine whether the chart projection would be shifted cartographically. In developing these criteria, the existing line weights for projections and other charted features were considered. Table 1 lists three line weight groups of cartographic features routinely found on NOS nautical charts. Since the standard width for a chart projection line is 0.1 m, or 0.004 inch, it was decided that a projection would be revised whenever the datum shift resulted in a space between the old and new projections equal in width to one projection line. This meant that whenever the datum shift at chart scale equalled or exceeded 0.2 mm, the projection would be reconstructed; when less than 0.2 mm, only a revision to the datum reference note would be required. The 0.2 mm is the centerline-to-centerline dimension between the old and new projection lines with a 0.1 mm space between the lines.
Using this 0.2 mm projection shift as a criterion, a 1:50,000-scale chart, for example, would have its projection revised when the datum shift exceeds 10 meters.
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Figure 1.--Expected latitude change from NAB 27 to NAD 83 (in meters).
Figure 2.--Expected longitude change from NAD 27 to NAD 83 (in meters).
Table 1.--Specifications for standard features appearing on NOS nautical charts
Line weight Feature
0.10 mm ( 0 . 0 0 4 " ) Contour line--topographic ( intermediate)
Depth curves Tint outline--blue, gold, green (when
not low water line) Traffic lane precautionary area--
Projection lines Electronic positioning lattice--LORAN
outline for screen
and OMEGA lines
0.15 mm (0 .006") Bridge detail (including fenders) Crib-bare at shoreline datum (to
scale) Line, misc.--runway, tunnel entrance,
fort, etc. Mineral lease block boundary--block
subdivisions Groin and jetty Range line--navigable portion Shoreline--apparent
--manmade Structure--large, hatchured (to scale)
--visible (generally detached from shoreline); i.e., crab pen, floating drydock, hulk (to scale)
Wharf, bulkhead, breakwater, and pier
0.20 mm ( 0 . 0 0 8 " ) Anchorage berth Anchorage area Isogonic and agonic lines Mineral lease block boundary--exterior Contour line--topographic (index)
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Figure 3 shows the relationship between chart scale and datum shift, or the condition where the user of NAD 83 data would incur a 0.2 nun plotting error if the existing chart projection was not shifted. For the purpose of evaluating the cartographic impact of implementing NAD 83, the controlling scale for each chart was considered to be the largest scale panel or inset on the chart. Table 2 is a tabulation of the charts by scale, including control- ling insets, which were evaluated against the 0.2 nun projection change criterion. This evaluation identified those charts that would require only a revision to the existing datum reference note. tion. More than 80 percent of the charts and chart panels are compiled at a scale larger than 1:100,000. Since most coastal areas have a total shift in either latitude or longitude greater than 20 m, it was concluded that more than 90 percent of the charts would require a projection shift before they could be considered as having been compiled on NAD 83.
The remainder would require a revision of the chart projec- Appendix B provides a detailed chart-by-chart analysis.
D. State Plane Coordinate Systems
The NOS receives an extensive amount of new data each year which is used to revise existing nautical charts or to compile new charts. Not all of the.data received are referenced-to the same geodetic projection of the chart, but may be referenced instead to a local or State plane coordinate system. For example, even though most of the charts are compiled on a Mercator projection, the majority of new charting data received from the U.S. Army Corps of Engineers (COE), such as channel improvement depths, breakwater and pier construction, etc., are usually referenced to a local or State plane coordinate system. These data would normally be converted to a projection common to the chart before being applied.
State plane coordinate systems for the United States were defined for most States in the 1930's. These coordinate systems were initially intended to render greater utility to geodetic contro1,stations for highway engineers, land surveyors, and others who were accustomed to using grid (rectangular) coordi- nates (x and y) rather than geodetic (geographic) coordinates (latitude and longitude). The State plane coordinate projections were designed so that the scale factor (the ratio of the geodetic to grid distances) did not exceed 1 part in 10,000. Actually the scale factors range from 0.99990 to 1.00010. This required the larger States to be divided into several zones. The Lambert conformal conic projection was chosen for those States, or zones, that were long in the east-west direction, such as Pennsylvania. The transverse Mercator projection was chosen for States or zones of long north-south extent, such as Indiana.
When the COE began using the State plane coordinate systems for referencing or controlling their surveying, dredging, breakwater construction, and other harbor and waterway improvement projects,
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1 ,000,000
500,000
200,000
100,000
50 , 000
20,000
10,000
5,000 0 5 10 20 40 60 80 100 120 140 160 180 200
Datum Shift Imeters)
Figure 3.--Plot of projection shift criterion.
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Table 2.--NOS charts/insets: summary by scales
Scale (1:K)
5 10 15 20 25 30 40 50 60 80 100 120 150 200 250 300 400 500 600 1000 1500 2000 3500 10000
TOTAL
Atlantic Gulf
Charts
4 44 14 64 7 3
126 6 1
89 5
4 2 1 2
11 1 2 3
1
-
-
- - - -
Cnsets*
9 63 14 77 7 4
106 5 1
75 2
4 2 1 2
11 1 2 3
1
-
- - -
390
Charted area
Pacific
Charts
11 39
61 17 10 93 42
57 14 1 6
21 3
11 1
11 5 4 2 5 1
- a
-
-
423
Insets - 24 84 13 73 16 9 66 40
34 7 0 4 16 3 8 1
10 4 3 2 5 1
-
-
-
Great Lakes
Charts
4 15 18 3 4
19 24 1 7 17 3
19 1
1 2 2 3 2
1
-
-
- - - -
146
Insets*
19 4
27 8 2
10 20 0 2 2 1 2 0
1 0 2 3 2
1
-
-
- - - -
Total
:harts
19 98 40 128 28 32
243 49 8
163 22 20 11 23 5
15 14 4 15 8 5 3 5 1
-
- 959
:nsets*
52 191 54 158 25 23
192 45 3
111 10 2 8
18 5
10 14 4
14 7 4 3 5 1
-
- *Figures represent the number of charts or insets (panels) in the
NOS nautical chart suite for the scale shown. Whenever a chart contained multiple scales, insets or panels, the largest scale was counted.
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the NOS cartographers soon recognized the benefit of having a State plane coordinate grid system on the chart to facilitate application of COE data. nate grid ticks along the borders and within selected charts and insets for almost 40 years. NOS currently publishes 236 charts and 187 insets that contain State plane coordinate grid ticks. Generally, the scale of these charts and/or insets is 1:40,000 or larger.
The NOS has printed State plane coordi-
The implementation of NAD 83 will require the existing State plane coordinate systems to be revised. Correspondingly, every nautical chart and/or inse t containing State plane coordinate grid ticks will also have to be revised. Some of the reasons for these revisions are as follows:
1. The State plane coordinate systems currently shown on charts and insets are mathematically dependent upon NAD 27. The NAD 83 is based on a different ellipsoid than NAD 27. This ellipsoid is earth-centered rather than the North American "best fit" position for NAD 27. This will result in a shift in the present State plane coordinate systems when the charts are con- verted to NAD 83. Whether the shift is noticeable will depend on the magnitude of the shift and the scale of the chart or inset.
2. The NAD 83-dependent State plane coordinate systems will have grid values published in meters. The present NAD 27- dependent State plane coordinate grid values are published in feet. The impact of this units' change will be evident in the rounding of metric coordinate values assigned to the ir,itial point in each State plane coordinate system. For example, if the 'longitudinal false easting value for the initial point in a Lambert conformal projection zone was 2,000,000 ft under the NAD 27-system, a value of 609,600 m would result for the NAD 83- system if a true conversion of units was performed. However, to preserve easy-to-use values for the new metric grid system, a value of 600,000 m might be selected. This rounding off in selecting values for the initial point in each State plane coordi- nate system will require every State plane coordinate system charted to be recompiled.
3. Many of the State plane coordinate zones will change numerical values because the States have selected new false northings and false eastings. that are radically different from the simple feet to meter conversion. For example, most NAD 27 false northings were selected to be 0 ft. Many States are choosing false northings of 100,000, 200,000, or 1,000,000 m for the initial point in the new NAD 83 State plane grids.
To assess the impact of and justification for converting the charts and insets to the new State plane coordinate values, three questions must be addressed. The first is the timetable for when the preponderance of NAD 83-dependent State plane coordinate referenced data will begin to arrive from suppliers such as the Corps of Engineers. The second is whether there will be an
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orderly and timely transition by all COE districts? question results from recognizing that the State plane coordinate grid ticks are shown for the primary use and benefit of NOS cartographers. Therefore, is the cost of correcting the existing charts justified when evaluated against the benefit derived by the cartographers? These questions will be addressed when devel- oping NAD 83 implementation recommendations later in this report.
The third
E. Datum Conversion Constraints
1. Personnel Resources
In the past year the number of production cartographers (i.e.l cartographers available to manually compile and review nautical charts) has steadily declined due to transition of the NOS nauti- cal charting program from manual to automated cartographic opera- tions. Recently a large number of cartographers previously available for manual production were transferred to the Automated Cartographic Production Group (ACPG). The remaining small staff of cartographers who were not transferred to the ACPG will have difficulty maintaining these manually produced charts. impact of adding NAD 83 conversions to their already heavy work- load will be discussed later in this report. A correspondingly similar reduction in the number of negative engravers supporting chart production has occurred also in recent years. During the last 4 years, the number of NOS negative engravers has been reduced by 7 4 percent, while over the past 9 months the number of manual nautical cartographers has been reduced by 63 percent.
The
2. Preliminary NAD 83 Data
At present, only preliminary NAD 83 figures are available. The final values will not be available until December 1985. The difference between the preliminary and the final figures is esti- mated by NGS to be approximately 3 to 5 m. A 5-meter error translates into a longitudinal error of about 0!'2 along the North Carolina coast, or a shift of about 0.2 mm at a scale of 1:25,000. The impact of using preliminary NAD 8 3 values on the manual and automated data bases is assessed as follows:
a. Manual Data Base. The manual data base is graphic in nature and chart-scale dependent. The data base is made up of individ- ual discrete charts. Datum shifts below a certain threshold, at chart scale, would have no effect on the data base. When the datum shift at chart scale is less than the 0.2 mm plotting threshold, the chart's horizontal datum will be considered to be NAD 83 with no revision to the projection required.
b. Automated Data Base. This data base comprises charting data that, prior to loading, are either position-dependent or scale- dependent. Position-dependent data, for example, have been obtained from the digital records of contemporary NOS field surveys, while scale-dependent data have been obtained by
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digitizing an existing graphic, such as a chart. Even though chart feature data are either position-dependent or scale- dependent, once loaded these data are qualified or treated alike; i.e., the data are defined as having a positional accuracy of a hundredth of a second in latitude and longitude regardless of their source.
In summary, preliminary NAD 83 values can be used to convert many of the graphic charts to NAD 83 because the expected shift between preliminary and final values will not be significant at the scale of the chart. number of charts currently requiring a projection shift depending on the magnitude and direction of the change between preliminary and final NAD 83 values. In the case of the automated data base,, use of preliminary values will require that the data base be revised once again when final NAD 83 figures become available.
However, final values may change the
3 . "Orphan" Datums
Charts which are not compiled on NAD 27 are classified as being compiled on "orphan datums." In section I1 A it was stated that 51 charts of the Great Lakes are currently published on the U . S . Standard Datum. In other regions, an additional 15 charts are published on astronomic datums (mainly in Alaska and the Pacific Islands), 36 charts are on the Old Hawaiian Datum, and 29 charts are on the Puerto Rico Datum. In addition, two charts are com- piled on unknown datums, and a recreational chart is published without a datum projection. An assessment is being made of each of these charts to determine if NAD 83 datum conversion can be achieved with the information currently available. It may be necessary to request special field survey support to obtain NAD 83 positions for prominent features on several of'these orphan datum charts before new chart projections can be constructed. Appen- dix B lists the approximately 140 orphan datum charts.
Even though NAD 83 can be extended to the NOS charts of other Pacific Islands, such as Guam and Samoa, it was decided by the director of Charting and Geodetic Services that these charts will be compiled on WGS 84. For charting purposes, there is virtually no difference between WGS 84 and NAD 83, and the use of WGS 84 will satisfy a Department of Defense requirement. It is expected that DMA will be able to provide the information necessary to accomplish the datum conversion in these areas.
4. Electronic Positioning Lattices
Because of the great distances between the master and slave transmitting stations comprising a LORAN or OMEGA chain, it is expected that the datum conversion values for the position of each transmission station will vary. present is how these variations will affect the hyperbolic lat- tice for those charts which are located in the outer reaches of the lattice. It is possible that many of the LORAN and OMEGA lattices will have to be recompiled and this might require
What is not known at
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assigning a higher production priority for these charts. At present, NOS publishes 248 LORAN charts, 22 additional charts containing both OMEGA and LORAN lattices, and 2 charts containing only OMEGA. These charts are identified in appendix B. The same 0.2 mm criteria used to justify a projection shift will be employed in assessing the need to shift or replot an electronic lattice.
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111. DATUM CONVERSION ALTERNATIVES
A. Cartographic Datum Conversion Options
The NOS employs a variety of chart printing classifications and other nautical products in an effort to update its nautical charts, or transmit critical nautical information to chart users in the interim between new edition printings of the charts. of these methods may be applicable for accomplishing the conver- sion to NAD 83. Before discussing these options, however, it is necessary to identify those cartographic actions which could be used to accomplish the datum conversion. These specific actions are used in the production of a type of chart printing or the publishing of a separate product: i.e., Notice to Mariners.
Some
1. Cartographic Actions
Several cartographic actions are appropriate options for converting an existing nautical chart to NAD 83, for producing new charts on NAD 83, or for transmitting NAD 83 conversion information to the chart user independent of a chart printing. Before these cartographic actions can occur, however, the nauti- cal chart data base must be updated. Update of the data base and possible cartographic actions that may follow are discussed under the following headings:
a. b.
d. e. f. 9. h.
C.
Data base update (graphic and/or digital) Temporary datum conversion note Datum reference note revision New projection NAD 83 projection ticks State plane coordinate grid ticks Chart overprinting Chartlet
a. Data Base Update. Before a new edition of a chart can be published on NAD 83, the appropriate manual and/or automated data base must be updated to reflect NAD 83 chart projection informa- tion. For the manual data base, this will involve applying NAD 83 note and projection information to the current chart drawing. For the automated data base, this will involve converting the existing digital data base to NAD 83. and loading new data only after they have been converted to NAD 83. It is concluded that new digital source data and the existing digital data base should be converted using only final NAD 83 values.
b. Temporary Datum Conversion Note. When the shift in projection is plottable, the projection on the black plate should be revised on the next new edition of the chart. If available resources or other considerations do not permit revising the projection at that time, a temporary note describing the magnitude of the shift
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to NAD 83 could be added to the new edition. The values shown in the note will represent the mean difference, over the limits of the chart, between the chart datum and NAD 83. An example of a temporary note follows.
HORIZONTAL DATUM
The horizontal reference datum of this chart is
(name and date). Geographic positions on North American
Datum of 1983 (NAD 83) must be corrected an average of
II northward/southward and I' eastward/westward
to agree with this chart. For charting purposes, NAD 83
is considered equivalent to the World Geodetic System 1984
(WGS 84) datum. The correction values are based on
preliminary NAD 83 data.
This note would be retained until the chart is fully converted (projection shifted) to NAD 83. At that time the wording of the note would be reversed to facilitate the transfer of data from NAD 83 to the previous datum. This revised note would remain on the chart until it was deemed no longer necessary. An example of the revised note follows.
HORIZONTAL DATUM
The horizontal reference datum of this chart is North
American Datum of 1983 (NAD 83), and for charting purposes
is considered equivalent to the World Geodetic System 1984
(WGS 84). Geographic positions referred to the (name and
date) must be corrected an average of I' northward/
southward and I' eastward/westward to agree with this
chart. The correction values are based on preliminary
NAD 83 data.
Note: The reference to preliminary 'NAD 83 data will be deleted from all horizontal datum notes when final values are published.
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c . Datum Reference Note Revision. When the magnitude of the shift between the existing chart datum and NAD 83 will not result in a significant plottable difference (less than 0.2 mm), the conversion to NAD 83 can be accomplished by revising the datum reference note in the title block of the chart and, for informa- tional purposes, adding a temporary chart note describing the magnitude of the datum shift. .An example of this note follows.
HORIZONTAL DATUM
The horizontal reference datum of this chart is
North American Datum of 1983 (NAD 831, and for charting
purposes is considered equivalent to the World Geodetic
System 1984 (WGS.-84). Geographic positions referred to
the (name and date) do not require conversion to NAD 83
for plotting on this chart.
d. New Projection. Whenever the shift between the present chart datum and NAD 83 is significant (0.2 mm or greater at chart scale), the chart projection will have to be revised. The most efficient and cost-effective method available to recompile the chart on the new projection is to use the NOS Automated Informa- tion System (AIS). The AIS is basically comprised of a nautical charting digital data base and a computer/work station inter- active system by which the digital chart information can be loaded and updated. These data are then used to drive plotters in the automated nautical charting system which make the different graphic plates used to print a chart when a new edition is re- quired. However, the production capability of the AIS is not up to a level required for an ambitious program such as the datum conversion of the suite of NOS nautical charts. Even if the production level existed, much of the data for the charting area of responsibility is not yet loaded into the digital data base, nor will it be loaded in the near future. Therefore, it is not possible to convert all of the new editions to NAD 83 using the AIS. The alternative is to revise the projections manually at the time the chart is scheduled for printing a new edition. The recompilation of the projection would become part of the new edition compilation procedure and would use computer-assisted cartographic techniques. The amount of shift at chart scale would be determined from data provided by the NGS. The cartog- rapher would make the necessary projection corrections to the drawing. This action will be hampered by the fact that in most cases automated plots of the NAD 83 projection cannot be used to revise the chart. These mathematically correct projection plots will not fit the existing chart drawings due to distortions in the graphic that have occurred over the years.
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e. NAD 83 Projection Ticks. When the shift between the datums is significant,.the NAD 83 projection ticks could either be added along the neatline or at the projection intersections within the chart. Adding projection ticks has some of the same drawbacks as revising the projections; i.e.8 it is both time-consuming and labor-intensive. Unlike revised projections, however, projection ticks add little useful information and they tend to degrade chart clarity.
f. State Plane Coordinate Grid Ticks. State plane coordinate grid ticks are currently printed on 236 nautical charts and 187 insets. raphers in the application of charting information received from the COE. For this reason, these NAD 27-dependent grid ticks will not become obsolete until the COE begin to furnish charting data on the new NAD 83-dependent State plane coordinate systems. Dis- cussions with COE personnel have indicated that it will be close to 10 years before they begin extensive implementation of NAD 83 State plane coordinate control in their survey and waterway main- tenance programs. have led to the conclusion that it might be justified to simply delete the existing grid ticks when the chart projection is con- verted to NAD 83 and allow the cartographers to use other methods to apply future COE data. If it is decided to publish NAD 83 State plane coordinate grid ticks when the COE begin to use this control, then the present cartographic methods will prevail when the charts and insets are revised.
These grid-ticks are primarily used by NOS cartog-
In-house discussions with NOS cartographers
g. Chart Overprinting, Whenever a projection requires a shift of 0.2 mm or greater for the chart to be on NAD 83, this conver- sion could be accomplished by overprinting the NAD 83 projection in a screened color on the next new edition, or revised printing of the chart. the following problems: it would increase chart clutter, add to the already heavy cartographic workload, and it would be costly. Furthermore, a degradation of projection accuracy could result from the projection being produced on a plate independent of the black plate. A poor projection registration could exceed the 0.2 mm projection change criterion, thereby defeating the intent of this cartographic action. It was concluded that overprinting an NAD 83 projection on an NAD 27 chart should be avoided.
However, this option is a temporary solution posing
h. Chartlet. to Mariners would be a temporary solution for NAD 83 conversion of a small-scale chart containing large-scale insets. The carto- graphic work involved to achieve this result is considered too great, and it was concluded that using a chartlet to achieve NAD 83 conversion should be avoided.
The compilation of a chartlet as part of a Notice
2. Types of Printings/Products
The previously discussed cartographic actions can be used to produce several types of nautical products for either temporarily or permanently converting the nautical charts to NAD 83. These
20
products are the traditional Notice to Mariners and/or the various types or classifications of chart printings; i.eop new edition, revised printing, reprint, new chart, and reconstructed chart. Table 3 shows the relationship between the cartographic action and the type of product or printing which it impacts.
Table 3.--Datum conversion options
~~
Cartographic Actions
a. b.
d. e. f. g* h.
C.
Data base update Temporary datum conversion note Datum reference note New projection NAD 83 projection ticks State plane coordinate grid ticks Chart overprinting Compile a chartlet
~ ~-
?rinting Classifications* - NM
X X X
-
X -
- RP
X X X X X X X
- - NE
X X X X X X X
-
-
- RC
X X X X
X
-
-
- NC
X X
X
X
-
- * NM = Notice to Mariners NE = New edition of chart Rep = Reprint of existing RC = Reconstruction of
chart chart
chart RP = Revised printing of NC = New chart (1st edition)
When the available cartographic actions are analyzed against the product produced, several general conclusions can be reached. One, the "reprinted" (Rep) chart will not aid in the conversion to NAD 83. Two, only actions 2 , d, and - f will result in nontemporary conversion results. This, of Eourse, recognizes that data base maintenance is a priority activity for all subsequent cartographic actions taken in the production of NOS charts.
B. Impact on Chart Production
The manual revision of the chart projection and State plane coordinate grid ticks, would have a significant impact on the number of charts produced, given the present number of production cartographers available. The amount of impact can be roughly estimated by examining the amount of time it now takes to compile an average chart and then determining how much extra time it will take to revise the chart projection and/or the projection on any chart panel or inset.
In 1983, Arthur Young & Company (AYC) conducted a management efficiency study of the MCB. To develop their conclusions and recommendations, AYC first had to collect workload data associated with the production of nautical charts. AYC concluded
21
that MCB personnel required 229 hours to produce a new edition of an existing nautical chart from a maintained data base. An additional 42 hours per chart were required in the compilation and review processes associated with the compilation of Notice to Mariners published during the period between new editions. Collectively, these hours (271) were determined to be essential if the nautical charting data base was to be maintained at a level which prevented an accumulation of unapplied source data between new editions. A separate in-house study completed in 1984 concluded that 245 hours per chart were necessary to respond to the same nautical charting and Notice to Mariners workload identified by AYC. consistent in identifying the generic tasks performed in the production of a new edition. These tasks include:
Both the AYC and the in-house studies were
Receive and evaluate source data Update the nautical chart data base Approve data base update Compile Notice to Mariners for production Prepare chart drawing for production Order type Review of compilation Clear new edition for distribution
For the present suite of nautical charts, approximately 500 new editions must be produced annually to maintain the present edi- tion cycle for each chart. As a conservative measure, using the workload hours per chart developed by the in-house study team in 1984, approximately 70 cartographers would be required to handle the inherent cartographic workload. In June 1984, the MCB had a cartographic staff of 71. With the present staffing (June 1985) of 26 cartographers, the annual manual chart production capability is estimated to be 185 charts.
In addition to the routine compilation hours discussed above, the cartographic time required to revise the projection on a chart will require an additional 24 hours, and on a chart panel, 20 hQurs. A count of the insets and panels on the existing chart suite shows that there is an equivalent of 0.45 insets per chart. Therefore, considering the number of panels per chart, each chart requiring a projection shift would require an average of 33 hours additional cartographic compilation time. This amounts to a workload increase of 13 percent, or an annual chart production decrease of 22 charts if additional resources are not provided. The 26 cartographers will only be able to produce 163 charts annually as a result of increased NAD 83 conversion workload, down from 185 charts.
Chart production would be further impacted by revisions to the electronic navigation lattices; i.e., LORAN and'OMEGA. These revisions are estimated to require an additional 32 hours per chart. Of the 272 charts containing electronic lattices, it is estimated that 163 will require revisions. This will result in a
22
cartographic workload increase of 5,216 hours. If these revisions are spread over 5 years, a decrease in chart production of 4 4 charts per year would result.
An additional workload impact will also result from the conversion to NAD 83 of the NAD 27-dependent State plane coordi- nate systems which are currently published on various charts and insets. All existing grid ticks will require revision when NAD 83 is implemented as a result of both the difference between NAD 27 and NAD 83 and the related decision to publish the NAD 83- dependent State plane coordinate grid values in metric units. It was estimated that the time, and therefore cost, to revise the grid ticks on the charts will be about 50 percent of the effort required to shift a chart projection, or 12 hours per chart. Revising the grid ticks on chart insets would require an addi- tional 5 hours per inset. The impact of revising the State plane coordinate grid ticks on the 236 charts and 187 insets on which they are currently shown will result in an increase in the carto- graphic workload of 3,770 hours. If the total revision was to be accomplished during a 1-year period, a decrease in production of 16 charts would result. If the revision was spread over 5 yearsp the chart production decrease would be approximately 38 charts per year .
Reproduction time required to shift an existing chart projection is estimated to be 35 hours, and for a chart panel, 20 hours. Therefore, each chart requiring a projection shift would require an average of 44 hours additional reproduction time. The reproduction time required to revise the State plane coordinate grid ticks would approximate the same percentage of compilation time identified above, or 174 hours per chart and 5 hours per inset.
As stated above, the conversion of NOS charts to NAD 83 by adding or revising a datum reference and/or transformation note would have little impact on chart production because these notes require little in the way of resources. This assumes that source data are received on the same datum as the chart. If source is received on some other datum, a datum conversion will be required and the cost incurred would adversely impact available resources.
It should be noted that the continuing decline in the number of nautical cartographers is also compounding the problems of effec- tive and timely nautical chart production. Any increase in the cartographic workload resulting from NAD 83 conversion will only add to this problem.
C. Resource Requirements
Of the seven cartographic actions discussed in section 111 A, exclusive of maintaining the data base, two accomplish the datum conversion through the use of notes. These actions should require relatively little in the way of additional cartographic
23
compilation time, reproduction services time, and materials. However, these two actions, as well as the others mentioned, do depend on the data base being maintained as a priority effort. Initially, the resources required to add these notes are consid- ered to be within the realm of normal chart production costs and, therefore, these costs have not been computed for this report. However, all incoming chart (source) data will not be on NAD 83. Therefore, compilation and review time can be expected to increase because of the conversions required to plot the data on the new datum. the resultant cost on future manual chart production. However, it will be easier to handle if automated procedures can be employed. base and the production capabilities of the automated nautical charting system under development.
It is difficult at this time to assess this impact and
This will depend on the extent of the digital data
Of the five other actions discussed, all would accomplish the conversion by an actual change to the chart's reference system; i.e., geodetic projection and/or State plane coordinate grid. As such, these methods would require a significant amount of person- nel resources and material to implement if accomplished using manual cartographic procedures. However, if the projection and grid shifts were performed employing the AIS, the costs would be negligible once the digital data base has been converted to NAD 83. The reason for this is that the first edition of an AIS- generated chart will have a new black plate which contains the new projection. Under automation, a new projection can be gener- ated each time a new edition is prepared for printing. There- fore, it makes no difference which datum the data are on. Furthermore, those AIS-generated charts not on NAD 83 will be easily converted once the AIS data base has been updated to NAD 83. It has been estimated by the ACPG that this data base conversion could cost $50,000.
If the datum conversion is accomplished manually by adding NAD 83 projection lines or grid ticks onto the existing projec- tion, the amount of resources required for cartographic services and materials would be roughly the same as required for shifting the projection, but would be somewhat less for.,reproduction services. Overall, however, this alternative would be more costly since it is considered to be only a temporary solution and would eventually require additional cartographic effort to permanently place the projection on NAD 83.
To assess the resources required to convert the NOS charts to NAD 83, the additional workload associated with the conversion of inset or chart panel projections must be considered. At a cost of $19.89 per staff-hour-for cartographic services and $21.50 for reproduction services, the labor cost of shifting a projection is estimated to be $1,602 per chart. chart and $207 per inset will be required'to revise the State plane coordinate grid ticks. When material costs of $60 per chart and $30 per panel are included, the total cost,of imple- menting NAD 83 is approximately $1,675 for each chart requiring a projection shift.
An additional-cost of $615 per
24
When LORAN lattices need revision, even though the plotting is done by automation, it is estimated that an additional 32 hours of cartographic services and 35 hours of reproduction services would be required. Material costs would add an additional $150. In total, an additional $1,540 would be necessary for each chart requiring a change in the LORAN or OMEGA lattice.
In summary, it will require $1,507,000 to shift the projections on approximately 900 NOS nautical charts if accomplished by manual cartographic methods, and $420,000 to revise the elec- tronic positioning lattices on 272 charts if accomplished by manual and automated cartographic methods. An additional $145,000 will be required to publish new State plane coordinate grid ticks on 236 charts and $39,000 to revise the grids on another 187 insets.
D. Conclusions
Whenever the required shift of the existing chart projection to NAD 83 is less than 0.2 mm at chart scale, the conversion shall be accomplished by revising the datum reference note on the chart. For informational purposes, a temporary datum transfor- mation note will also be added to the new edition of the chart. Approximately 72 charts will be converted to NAD 83 in this manner.
For the remaining charts, only two cartographic options were concluded to be cost effective and feasible under present opera- ting conditions. These two options are (1) the addition of a temporary datum transformation note or (2) the shifting of the chart projection. Another option considered, the addition of projection ticks, was concluded to be inefficient, not in the best interests of the chart user, and should not be used.
The decision to either revise the chart projection or to add a datum transformation note can be interpreted as deciding to fully implement NAD 83 or to partially implement NAD 83. If NAD 83 is implemented fully, the majority of the NOS chart suite, about 93 percent or 900 charts, will require a projection revision. A projection revision will result in increased costs and, without additional cartographic personnel, a decrease in the annual production of new editions. If NAD 83 is to be implemented as soon as possible, in lieu of waiting for increased production capability of the AIS, then the use of a temporary datum transformation note is considered justified as an interim measure because of the inherent cost of shifting a chart projection by manual cartographic procedures. Again, manually revising a chart projection is time consuming and costly, and would result in a correspondingly significant reduction in annual chart production. On the other hand, revising the chart projection using the AIS would cost virtually nothing once the data base has been con- verted to NAD 83. The drawback of using the AIS to implement the new datum is that it will take about 10 years to accomplish the conversion.
25
It is concluded that the least costly strategy for converting a chart to NAD 83 is to add an interim datum transformation note until a future new edition of the chart can be produced at a later date by the AIS using a data base on NAD 83. A faster implementation schedule can be realized through a hybrid manual/ automated cartographic effort. This would require some chart projections to be manually revised which will require additional chart compilation time, additional reproduction services and materials, and would result in decreased annual production of new editions.
The State plane coordinate grid ticks were added to the nautical charts to assist the NOS cartographers in the applica- tion of COE data referenced to these coordinate systems. Although the implementation of NAD 83 as the national horizontal control datum is close at hand, the COE is not expected to convert to an NAD 83-dependent State plane coordinate system in the near future. Until it can be determined with some certainty when the COE will begin publishing their survey data on an NAD 83-referenced control system, it is concluded that NOS should delay shifting the exist- ing grid ticks to the new NAD 83 positions. However, if this conclusion is accepted, it would result in nautical charts compiled on NAD 83 projections which would contain NAD 27- dependent State plane coordinate grid ticks. This could lead to confusion for any user outside of NOS. Another alternative is to delete the existing grid ticks when the chart projection is converted to NAD 83. This would require the NOS cartographers to employ other cartographic procedures in the application of COE data. This alternative is under consideration within NOS.
26
IV. DATUM CONVERSION PLAN OPTIONS
A. Objectives
The objective of a datum conversion plan is to identify an effective process for converting the suite of NOS nautical charts to NAD 83 in a timely and efficient manner, or to WGS 84 for the nautical charts of the Pacific territorial islands. It is con,- sidered essential that any conversion plan recommended result in minimal adverse impact on normal chart production. It is also essential that the recommended plan fully consider the contem- porary budgetary and personnel resources available to NOS.
B. Plan Options
In considering the above objectives, it is concluded that NOS has several options available for implementing NAD 83 into its nautical chart program. The options available, however, are dependent upon the level of conversion to be accomplished and the desired time frame for completing the conversion.
The level of conversion can be categorized as: (1) charts requiring only a change in the datum reference note and the addition of a datum transformation note, and (2) charts requiring a change in the datum reference note, the addition of a datum transformation note, and a shift in the chart projection and/or State plane coordinate grid.
Category 1
A chart would be identified under category 1 when its required projection shift is less than the 0.2 mm plotting threshold discussed previously. datum shift required for each chart and the scale of the chart indicates that approximately 72 charts require only a revision in the datum reference note for the chart to be considered on NAD 83. A datum transformation note would be necessary also for informa- tion purposes. Because of the varying life cycle of each edition and the projected printing schedule of these charts, table 4 shows that 5 years will be required for their datum conversion .
A preliminary assessment of the probable
Table I.--"Conversion note" implementation schedule
FY Charts I I 1985 1986 1987 1988 1989
22 31 9 9 1
I I TOTAL 72 J 27
These charts could be converted more quickly through the issuance of a Notice to Mariners or by issuing a "revised print" (RP) in lieu of a normal new edition. The issuing of a Notice to Mariners is considered a temporary solution that would be of benefit only until a new edition,could be printed.
Category 2
Charts falling under category 2 (approximately 900) will require significant cartographic action before they can be con- sidered constructed or compiled on NAD 83. Four viable options were identified for converting these charts to NAD 83. These options are as follows:
Option 1. Automated Nautical Chartinq System
exclusively the automated nautical charting system. This option would accomplish the conversion to NAD 83 using
Option 2. Automated and Manual Nautical Charting Systems
This option would employ a realistic blend of automated and manual cartographic procedures to convert nautical charts to NAD 83. Manual procedures would be concentrated in areas where a digital data base is not scheduled to be operational for several years; i.e., Pacific coast and Alaska.
Option 3. Hybrid Cartographic System
This option would accomplish the conversion to NAD 83 at the time of the next printing of the chart using the most efficient cartographic methods available; i.e., automated and/or manual.
Option 4 . Constrained Hybrid System
This option would also accomplish the conversion to NAD 83 using both manual and automated cartographic procedures, but would accomplish the conversion within a specified time frame.
C. Discussion of the Options
The major difference between the four options presented is the number of projection revisions that would be accomplished using manual cartographic procedures. In general, the sooner the datum conversion is accomplished, the greater the number of projections or grids that will have to be revised manually. The greater the number of manual revisions required, the higher the cost and the greater the impact on the annual production of new editions.
28
Specific comments on each option follow:
Option 1: Automated Nautical Charting System
Option 1 would rely entirely on the automated nautical charting system to convert the existing charts to NAD 83. Manually main- tained charts would have an interim transformation note placed on the next edition of the chart which would remain until the projec- tion or grid could be shifted using the AIS. A Notice to Mariners could be issued and distributed citing interim transfor- mation notes prior to the publication of the new edition. While the primary drawback of this option is the time required to complete the conversion, the temporary nature of this note would be an additional disadvantage. While the conversion cost and impact on chart production using the AIS are concluded to be low, the length of time to convert fully the entire suite of charts is considered excessive. If the AIS can achieve a production capa- bility of at least 100 charts per year by FY 1989, if the AIS can perform required chart maintenance in support of annual increases in the number of new editions produced by automation, and if resources are provided consistent with these chart production and maintenance requirements, it is estimated that at least 10 years would be required to complete the NAD 83 conversion (table 5). This estimate considers also the projected data base load sched- ule, so that even if the AIS could produce more than 100 charts per year, the data base would constrain production to the levels indicated.
Table 5.--Option 1: Automated information system (AIS) datum conversion schedule
FY 1986 - Convert existing data base to NAD 83 FY 1987 - 25 charts FY 1988 - 4 5 charts FY 1989 - 100 charts FY 1990 - 100 charts FY 1991 - 100 charts FY 1992 - 100 charts FY 1993 - 100 charts FY 1994 - 100 charts FY 1995 - 100 charts FY 1996 - 100 charts FY 1997 - 60 charts
Option 2: Automated and Manual Nautical Charting Systems
The major emphasis under this option would still be on using the AIS to convert a majority of the charts. However, projec- tions and grids on manually maintained charts would also be revised whenever resources could be made available. This would increase the datum conversion cost somewhat, but should have
29
little impact on chart production. implement NAD 83 would also be reduced somewhat. would permit the shifting of the chart projection and State plane coordinate grid using manual cartographic procedures. It assumes that required resources would be available. This option is pre- sented as a method for a more timely datum conversion in areas where the digital data base would not be operational for several years. It is intended that this option could be used to address emergency NAD 83 chart production requirements, such as the compilation of new and reconstructed charts.
The time required to fully This option
Option 3: Hybrid Cartographic System
This option would convert all charts to NAD 83 at the time the next new edition is printed. nautical charts are manually maintained, and will be for the next few years, most of the projections and grids would be revised manually. This would result in higher costs and have a major impact on either chart production or chart completeness (e.g., if this option is chosen, only critical corrections could be accom- modated on the next edition.) On the other hand, this option has the advantage of rapidly implementing NAD 83. level of resources, it would be extremely difficult to expect that full conversion could be completed within 8 years. However, if resources can be provided consistent with the Resource Requirements stated in this report (Sec. I11 B), about 90 percent of the nautical chart suite can be converted in 4 years. disadvantages of this option are the additional manual cartographic workload and the high cost of conversion.
Since the vast majority of the
With the present
The
Option 4: Constrained Hybrid System.
This option sets a 5-year time constraint for the full implementation of NAD 83 using hybrid manual/automation datum conversion methods. Within this framework, the datum revision would be accomplished using the AIS to the maximum (assuming "estimated" production capabilities of the system) with a realis- tic blend of manual cartographic conversion support. Through careful scheduling, the impact on the manual-production chart schedule would be minimized. However, it is expected that the amount of noncritical revisions applied to the charts during this period would be reduced significantly. Although this option would result in a moderate cost, and have a moderate impact on chart production, it would provide the benefit of full NAD 83 implementation in a reasonably short period of time. This option was .developed to strike a "happy medium" between time of conver- sion and resource requirements. As such, it is the only option where artificial time restraints have been imposed and detailed scheduling has been developed. In developing the conversion schedule under Option 4, the impact of several cartographic and charting factors was collectively considered. These factors, and the special consideration or impact of each, are discussed below:
a. Location of the chart. The geographic location of the chart is important in assessing the status of the AIS in the
30
corresponding area. Is the area presently loaded in the digital data base? Has the ACPG established a probable date for loading data for the area? Is the area not presently considered for automated chart production in the near future? For example, digital data for the charts along the coasts of New Hampshire and Maine are scheduled for loading in 1985. Therefore, the conversion of these charts to NAD 83 would be performed by automated techniques and would be reflected in the AIS first editions published in the post-1985 time frame.
Charts Edition cycle (months)
issue 6 12 18 24 36 48 60 96 144
953' 10 215 0 243 116 266 1 32 70
on
-
b. Scale. When the magnitude of shift to NAD 83 is known, its relationship to chart scale dictates whether only a change in the datum reference note will suffice or whether a projection shift is necessary as well.
e. Datum. determine whether a direct conversion to NAD 83* is possible or whether additional survey data will be required. This is a major scheduling consideration in evaluating the impact of those charts currently on orphan datums.
Knowledge of the existing chart datum is necessary to
d. Magnitude of datum shift. Knowledge of the magnitude of shift between the existing datum and NAD 83 is necessary to determine the type of cartographic action required to convert the chart. This provides a measure of the overall cartographic workload involved; i.e., actual shift in the projection and State plane coordinate grid or simply a revision to the datum reference note, which is essential in developing an annual conversion schedule.
e. Print cycle. Knowledge of the general print cycle (table 6) is essential to the scheduling of the chart conversions. Because there is, less flexibility in scheduling charts having extended print cycles, those charts having print cycles in excess of 36 months were considered on a priority basis when developing recommendations on a schedule for datum conversion.
Table 6.--Chart edition (print) cycles
'Six additional charts are printed on variable cycles when requested by the Defense Mapping Agency.
*Charts produced of Guam and the associated trust territories will be converted to WGS 84.
31
f. Conversion Method. The identification of whether a manual or automated cartographic method will be used to convert an existing chart to NAD 83 is also important in identifying the most appro- priate time for accomplishing the conversion. Because of the state of flux of the automation development, it was often neces- sary to venture a "best guess" on the chart production capabilities in future years.
FY
1985 1986 1987 1988 1989
TOTAL
Appendix B lists the charts published by NOS with information provided relative to each of the above factors.
Projection Shift
Manual Automated I Datum Note
4 6 22 164 22 31 122 110 9 72 129 9
120 138 1
482 405 72
The conversion schedule developed under this option integrates the expanding automation capabilities, including the probable loading of the digital data base, with the remaining manual cartographic capability within the NCD. conversion schedule is presented in appendix B, table 7 summa- rizes how the NAD 83 conversion will be accomplished over the next 5 years. The heading "Datum Note" refers only to those charts which do not require a projection shift. "Manual" and "Automation" indicate the mode of cartographic technique to be used in shifting or reconstructing the chart projection.
While the chart-by-chart
Table 7.--Option 4: Hybrid datum conversion schedule
Total
210 259
959 I
For example, in FY 1985 a total of 32 nautical charts will be converted to NAD 83. Twenty-two will be converted by revising the existing datum reference note and adding an informational datum transformation note. The remaining 10 charts will have their projections shifted, 4 by manual cartographic techniques and 6 by automation. Consult appendix B for specifics on which charts would be converted and by what cartographic action.
32
V. RECOMMENDATIONS
Effective and timely implementation of NAD 83 into the NOS nautical charting program will involve establishing datum conver- sion policy as well as developing a realistic conversion schedule. Therefore, the recommendations contained in this report have been developed to: address (A) NAD 83 Datum Conversion Policy and propose (B) NAD 83 Datum Conversion Plan.
A. NAD 83 Datum Conversion Policy
It is recommended that a datum conversion priority be established which will have the least adverse impact on the nautical charting program as a result of using preliminary values .
It is recommended that a 0.2 mm projection shift be established as the criterion for deciding whether a chart requires a new projection or simply a revision to its datum reference note.
It is recommended that NOS begin conversion of its nautical chart suite to NAD 83 using preliminary values for the new datum on charts with a controlling scale smaller than 1:25,000. (Final values to be available in December 1985.)
It is recommended that minimal use be made of the AIS in accomplishing the datum conversion until the digital data base can be converted using final NAD 83 values. However, once the data base is converted, it is recommended that maximum use be made of the AIS to convert existing charts, and to compile new and reconstructed charts on NAD 83.
It is recommended that the MCB review all orphan datum charts and advise NGS where datum conversion problems are anticipated; e.g., New York State Barge Canal. Datum conversion coordination meetings between NGS and MCB personnel should be scheduled to identify areas where special field survey support is required to resolve chart datum conversion problems.
It is recommended that the contemporary requirement be determined for including State plane coordinate grid ticks on the nautical charts and/or insets. If a viable requirement is identi- fied which justifies the cost of adding the new State plane coordinate values, then the grid ticks should be added at some future time consistent with the datum conversion plans of the suppliers of charting data; i.e., COE. If it is determined that the past users of State plane coordinate grid information con- tained on the nautical charts no longer require this information, the grid ticks shall be removed from the. charts/insets when the chart/inset projection is converted to NAD 83.
33
It is recommended that the AIS and associated software be modified as soon as possible to reflect that NAD 83 is based on the new Geodetic Reference System 1980 ellipsoid instead of Clarke's Reference Spheroid of 1866. This is necessary before any NAD 83 chart projections can be plotted correctly.
It is recommended that all new and reconstructed charts be compiled exclusively on NAD'83, except for charts of the Pacific territorial islands which would be compiled on WGS 84.
It is recommended that any initial conversion to NAD 83 via the issuance of a Notice to Mariners be restricted to those charts requiring only a change in the datum reference note.
It is recommended that the automated data base be systematically converted to NAD 83 to minimize the impact on the existing chart production schedule. The ACPG expects to be able to convert the data base with a minimal impact on chart production through effective use of software.
B. NAD 83 Datum Conversion Plan
Of the several options presented, Option 4 was concluded to be the most effective in accomplishing the conversion in a timely .
(5 years) and efficient (hybrid) manner. The proposed "constrained hybrid conversion plan" integrates the changing operational capabilities of both the manual and automated carto- graphic systems. It considers the contemporary resource levels, availability of NAD 83 information, and the projected scheduling of new edition charts over the next 5 years, and is viewed as a balanced and achievable datum conversion plan.
As in any ambitious undertaking with so many combinations available for accomplishing a goal, many views were offered by other NOS cartographers, and much constructive criticism received before Option 4 was selected as the most acceptable plan for all concerned, both producers and users of nautical charts. Table 7 portrays the annual number of charts to be converted during the next 5 years through either a change in the datum reference note or in combination with a shift in the chart projection. These datum conversion actions would be accomplished by both manual and automated cartographic procedures. The cost of this conversion effort is estimated to be $1,098,400. (See appendix C for datum conversion costs.)
It is recommended that this.datum conversion plan/schedule be approved and implemented immediately.
34
APPENDIX A
REPORT
t o
THE UNITED STATES-CANADA HY DRuGRAPH
by
c COMM
C OMF4 I TT E E OF! H 0 R I Z 0 NT A L DATUMS
March 1980
. . .i’ I’ /’ ,,.A. +-~..-.+--- David H. Gray Canadian Hydrographic Service
s I ori
/ William J. Monteith National Ocean Survey
35
REPORT OF THE COrlFlITTEE ON HORIZONTAL DATUMS
Bac kqround
On May 14, 1979, a c t i n g upon formal recomnendations o f the Great Lakes Char t ing Advisers, t he Uni ted States-Canada Hydrographic Commission (USCHC) es tab l i shed t h e ad hoc Committee on Hor izon ta l Datums. p u ~ t f iif t h i s Committee was t o i d e n t i f y and study a n t i c i p a t e d problems ex- pected t o be encountered by t h e Canadian Hydrographic Serv ice (CHS) and the Nat iona l Ocean Survey (NOS) when each agency converts i t s cha r t i ng program t o a new geocentr ic ho r i zon ta l datum. Messrs. David H. Gray o f CHS and W i l l i a m J . Monte i th o f NOS were appointed as members o f t h i s Com- m i t t e e .
The pur-
The work o f t he Committee began i n Ottawa, Ontar io, on May 16, 1979, when a meet ing was convened w i t h several representa t ives of both agencies t o c l a r i f y Commission o b j e c t i v e s and t o i d e n t i f y o ther r e l a t e d and p e r t i - nent sub jec ts f o r t h e Committee t o consider. On August 2 , 1979, the Corn- m i t t e e met i n Rosslyn, V i r g i n i a , t o consider the problems prev ious ly iden- t i f i e d and t o d iscuss t h e course of a c t i o n necessary t o prepare the r e - qu i red r e p o r t f o r p resen ta t i on a t t h e next scheduled Commission .meeting. Most o f t he contac t between t h e committee members i n conducting t h e study and prepar ing t h i s r e p o r t , p a r t i c u l a r l y i n reso lv ing the minor prob- lems which arose, was by telephone.
Problems (Quest ions) Considered
The problems and quest ions considered by the Committee and the answers o r recommended course o f a c t i o n f o r each are presented below:
1.Q. What i s t h e name o f t h e new North American Datum?
A . The name o f t h e new datum i s "North American Datum of 1983." ho ld t r u e regard less o f t h e da te the new datum becomes e f f e c t i v e .
The accepted acronym i s "NAD 83." This name and acronym will
A. The Geodetic Survey o f Canada (GSC) and the Nat ional Geodetic Survey (NGS) o f NOS adv ise t h a t t h e .framework o f pr imary h o r i - zon ta l c o n t r o l adjustments f o r Nor th America has s l ipped by 12 t o 18
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months so t h a t i t i s now estimated t h a t t h e NAD 83 primary adjustment w i l l be completed i n l a t e 1984. be adjusted o r transformed t o new coord inate values soon a f t e r t h a t date.
Secondary and t e r t i a r y con t ro l w i l l
3.4 . Besides conversion t o an ear th-centered (geocent r i c ) sys- tem. what o the r r e s u l t s w i l l be produced by NAD 83?
A. A major reason t h a t t h e NGS and GSC are d e s i r i n g the NAD 83 i s t o e l i m i n a t e e r r o r s i n the e x i s t i n g Nor th American Datum o f 1927 (NAD 27) and t o p rov ide the survey ing and mapping programs o f Canada and t h e Uni ted States w i t h one common ho r i zon ta l datum based on a wor ld re ference e l l i p s o i d . For example, some known problems i n the NAD 27 a re :
- 100 ppm scale e r r o r i n t h e n o r t h B r i t i s h Columbia coast and Alaska Panhandle
- 10 meter misc losure i n t h e west Lake Super ior area
- 10 ppm scale e r r o r i n t h e Mar i t ime Provinces
These problems and s i m i l a r ones i n t h e lower order surveys may mean t h a t some char t s may have t o be reconst ructed from the o r i g i n a l data once the lower o rder c o n t r o l has been p roper l y ad justed t o t h e primary c o n t r o l framework. Reconstruction w i l l depend on the magnitude o f t h e e r r o r s and must be based on a char t -by-char t ana lys is .
4.4. What a re the expected changes i n l a t i t u d e and lonq i tude between NAD 27 and NAD 83?
A. The NGS has publ ished p re l im ina ry changes between
These composite l a t i t u d e and long i tude dif ferences ( i n meters) NAD 27 and NAD 83 i n NOAA Technical Memorandum NOS NGS-16, dated A p r i l 1979. f o r Nor th America are shown i n F igure 1.
5.4. W i l l t he re be d i f f e rences between char ts publ ished by t h e Defense Mapping Agency (on WGS /2 Datum) and cha r t s publ ished by NOS and CHS (on NAD 83)?
A. Ground p o s i t i o n a l dif ferences between these two ear th - centered coord inate sys temswi l l be inconsequential f o r bo th the hydrog- rapher and t h e mar iner s ince i t i s est imated t h a t t h e maximum di f ference w i l l be about 5 meters, w i t h t h e average d i f ference being l ess than a
37
Ant ic ipa ted S h i f t i n Pos i t ion ( i n meters) due t o Change t o Earth-Centered E l l i p s o i d
3
Figure 1
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meter. The Committee concludes t h a t t he d i f f e rence between these two datums w i l l n o t be observable when cha r t s compiled on each datum a re v i s u a l l y compared.
6.4. GJhat i s t h e ho r i zon ta l datum o f the present cha r t s?
A. The m a j o r i t y o f t h e char ts produced c u r r e n t l y by CHS and NOS are on NAD 27, o thers on a v a r i e t y of hor i zon ta l o r reference datums, such as:
Old Hawa i ian Datum Nor th American Datum o f 1902 (U.S. Standard Datum) Various Astronomic Datums Uncontrol 1 ed Reference Datums
For t h e 977 cha r t s c u r r e n t l y publ ished by the NOS, t h e f o l l o w i n g datums are used:
Datums Charts - :.
Nor th American Datum o f 1927 844 86.4 Nor th American Datum of 1902 (Great Lakes) 50 5.0 Old Hawaiian Datum 36 3.7 Puerto Rico Datum 24 2.5 Local Astronomic Datums 21 2.2 Guam 1963 Datum - 2 - 0.2
977 100.0
Datums used by the CHS on char ts c u r r e n t l y publ ished are:
Nor th American Datum o f 1927 Nor th American Datum of 1902 ( o r i g i n a l l y U.S. Standard
Local Astronomic Datums (Chart d i s t r i b u t i o n on these datums i s not a v a i l a b l e )
Da t urn)
7.Q. When should CHS and NOS pub l i sh cha r t s on NAD 83?
A. Depending on t h e work load p r i o r i t y comprising each
However, t he Comni t t e e considered t h e r e l a t i v e l y
agencies' c h a r t p roduc t ion schedule, t he dec is ion "no t t o conver t t o NAD 83" was recognized as a v i a b l e op t i on f o r a l i m i t e d number of cha r t s c u r r e n t l y produced. small number o f cha r t s which might f a l l i n t o such a category and answered
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t h i s quest ion on t h e assumption t h a t CHS and NOS would u l t i m a t e l y con- v e r t a l l o f t h e i r cha r t s t o NAD 83. The Corn i t t ee agreed t h a t conversion t o NAD 53 should n o t begin u n t i l t h e f i na l datum computations and ad jus t - ments have been completed and r e l i a b l e p o s i t i o n s are a v a i l a b l e f o r con- v e r t i n g a l l e x i s t i n g c h a r t data t o t h e new datum. seen reasons occur beforehand, the Committee recommends t h a t product ion o f cha r t s on NAD 83 should be scheduled t o begin i n January 1985, o r as soon the rea f te r as t h e data w i l l permi t .
Unless some unfore-
8.4. How should a c h a r t be converted t o NAD 83?
A. The Committee assumed t h a t both manual and automated car tograph ic techniques would be a v a i l a b l e t o each agency t o accomplish t h i s datum conversion. It was a l s o decided t h a t t he car tographic method se lec ted would be dependent upon the magnitude of t he d i f ference between NAD 83 and t h e var ious e x i s t i n g c h a r t datums, the scale of the char t , and an eva lua t i on o f t h e bas ic survey data from which the cha r t was com- p i l e d . Whether performed by manual o r automated techniques, the pro- cedures expected t o be used are:
0 conversion o f g r i d o r p r o j e c t i o n po in ts t o I iAD 83 us ing AX, AY, and AZ o f nearby ( o r char ted) geodet ic con t ro l ,
0 recomp i la t i on o f survey data used fo r compi l ing t h e c h a r t i n c l u d i n g o f f sho re hydrography acqui red us ing hyperbolic or range-range survey p o s i t i o n i n g techniques,
0 survey o f se lec ted char ted features t o ob ta in NAD 83 coord inates when t h e e x i s t i n g cha r t datum i s i n quest ion.
The C o r n i t t e e recommends t h a t each agency se lects the bes t method f o r conversion t o NAD 83 based on a char t -by-char t analy- s i s o f a l l fac to rs .
9.Q.
t h e source in fo rmat ion . sca le l a r g e r than t h e convent ional c h a r t manuscript, the Committee recom- mends t h a t t h e accuracy standards f o r conver t ing e x i s t i n g d i g i t i z e d data t o NAD 83 be es tab l i shed t o assure t h a t a g rea ter accuracy i s achieved than i s necessary f o r cha r t i ng . NOS expects. t o use an e x i s t i n g computer program t o app ly a l e a s t squares adjustment t o convert i t s e x i s t i n g d i g i t a l 'data base t o NAD 83 on a char t -by-char t bas is . Th is program,
How w i l l e x i s t i n g d i q i t i z e d data be converted t o NAD 83?
A. The conversion method se lec ted w i l l be dependent on Since t h e d i g i t i z e d data a re o f t e n used a t a
. .
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requ i res t h a t t he p o s i t i o n of t h e four n e a t l i n e corners o f each c h a r t be known on NAD 83 and w i l l be so lvab le us ing the procedures c i t e d i n the d iscuss ion of Quest ion 8. There i s t h e p o t e n t i a l problem t h a t some data might be transformed tw ice and safeguards should be es tab l ished to e l i m i - nate this error,
l0.Q. How long w i l l i t take t o complete t h e conversion o f a l l NOS and CHS cha r t s t o NAD 83?
A. (NOS) The Committee recognized t h a t a reasonable t ime requ i red f o r each agency t o accomplish f u l l datum conversion would depend on several fac to rs w i t h t h e most impor tant being whether each agency (beginning i n 1955) would have the car tograph ic c a p a b i l i t y t o compile t h e changes a t a r a t e t o meet t h e p ro jec ted p r i n t i n g c y c l e fo r each cha r t . The Committee assumed t h i s c a p a b i l i t y would e x i s t w i t h now- developing methods and, there fore , concentrated i t s e f f o r t s on es t ima t ing t h e reasonable t ime t h a t would be requ i red t o produce new char t e d i t i o n s on NAD 83. The NOS issues about 500 new e d i t i o n s per year.
The NOS has e i g h t d i s t i n c t p r i n t i n g cyc les f o r c h a r t s . These cyc les and the number o f cha r t s a f fected a re l i s t e d below:
P r in t Cycle
6 mos. 12 mos.
18 mos. 24 mos.
36 mos. 48 mos. 96 mos.
144 mos.
12 ( Inc ludes 1 minera l lease c h a r t ) 270 ( Inc ludes 3 minera l lease and
193 ( Inc ludes 1 minera l lease and
112 270
32 ( Inc ludes 7 spec ia l use cha r t s ) 70
3 t r a i n i n g c h a r t s )
2 t r a i n i n g cha r t s )
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- 977
Theore t i ca l l y , t he 12-year p r i n t c y c l e cha r t s would extend t h e conversion pe r iod t o 1996 if datum conversion were begun i n 1985 and if 1984 were the l a t e s t e d i t i o n of these 12-year char ts . a rev iew of t h e NOS long-range c h a r t p roduc t ion schedule i n d i c a t e d t h a t bo th t h e 8- and 12-year p r i n t c y c l e cha r t s cou ld be converted t o NAD 83 by the end of 1991 (see below).
However,
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Charts Printed
8-year Edition 12-year E d i t i o n Year - 1985 1986 1987 1988 1989 1990 1991
1 2 5 4 3 * 4 * 1 3 -
0 4
18 20 10 1c) 8 -
32 70
* Special Use Charts for U.S. Navy
A. (CHS) There are approximately 1,000 CHS navigational c h a r t s i n stock a t any one t ime. The number changes s l i g h t l y as new char ts a r e published and o l d ones are withdrawn. I n any one year approximately 10 new charts, 95 new editions, and 98 corrected reprints are published. The dis t inct ion between new edition and corrected reprint i s t h a t the l a t t e r d i f f e r s from the previous p r i n t i n g by application of information published i n Notices to Mariners ( N M ) and hence the previous p r i n t i n g i s not cancelled. chart when there are no new surveys or to reduce the amount of hand cor- rections (the application of items published i n the N M ) t h a t are necessary for a chart. A t f irst glance i t m i g h t appear t h a t w i t h almost 200 charts coming off the presses each year, t h a t i t would take only 5 years t o go through the 1,000 navigational charts. Unfortunately, some charts are not printed as frequently as t h a t a n d some much more frequently. By i n - spection of the CHS chart indexes, i t takes about 7 1/2 years to get through approximately half of the charts, 15 years for three-quarters of the charts, and 30 years for 99 percent of the charts.
Corrected reprints a r e issued to replace stock of a
Over h a l f of the charts sold are newer t h a n 7 1 / 2 years o l d since they are i n greater demand, whereas there is l i t t l e demand for charts t h a t are p r i n t e d once every 30 years. vious t h a t CHS cannot match the NOS prediction of conversion of a l l charts t o NAD 83 i n 7 years. conversion period even t o 15 years.
Nevertheless i t i s ob-
I t will take a concerted e f fo r t by CHS to reduce the
1 l .Q. What would happen to existing chart stock?
A . U n t i l a l l charts are converted t o NAD 83, the Com- mittee recommends t h a t a NM statement should be published annual ly which would ident i fy each chart not on NAD 83 a t t h a t time and the respective AQ7 and A h conversion values between the existing chart projection and NAD 83.
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As conversion to NAD 83 occurs through the printin9 of new editions in conformance with prior established edition cycles, existing chart stock will continue to be treated as obsolete and can- celled, as is the present practice.
12.Q. Should CHS and NOS recognize that people use obsolete editions o f charts and, therefore, recommend the publishing of NFI in- formation on i n d i v i d u a l items i n t h e new and old chart datum for an in- terim period?
A. No! The publishing of information on more than one datum would be too confusing. quire the use of the latest editions of charts and it is believed that any action to promote or support the use of obsolete charts would be in- consistent with the legal positions of both countries.
Canadian and United States law re-
13.Q. How can a chart not on NAD 83 be referenced to, or used w i t h , NAD 83 i n f o r m a t i o n ?
A. The Committee recomnends as an interim measure the addition of a "transformation" note on the chart which will inform the user of the amount of correction needed to shift the chart projection to NAD 83.
14.Q. How will NM information be published?
A. The Committee considered two basic procedures for publishing NM information. lished consistent with the datum of the chart affected. Multiple charts affected by a single NM item could mean publishing that information on more than one datum, especially in the early period of transitioning the charts to NAD 83. remain large until the number of charts not on NAD 83 is significantly reduced. This procedure will also require developing a fail-safe data checking system to assure a high credibility level for the data published. The 'CHS presently handles NM information affecting charts of different datums and scales in this way.
The first would require information be pub-
It would be expected that the size of the MM would
The Comnittee also considered the impact of pub-
Included in the NM would be a special note advising
lishing (after January 1985) NM infomation exclusively on NAD 83, re- gardless of the datum of the affected chart(s). a formidable task.
This would also present
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the user on how to transform the NM information to the datum o f each chart affected. This note would be opposite in content to the note pro- posed in the answer to question 13 above. note could reduce significantly the size of each NM and still enable the user to utilize this information correctly. The following is an example o f a note in a NN pertaining to a NOS chart of Cape Hatteras:
It is believed the use of a
PLOTTING ADJUSTMENT
Geographic positions o f data given on North American Datum 1983 (NAD 83) may be plotted on this chart by applying the following corrections:
Latitude: Longitude:
+0.4.8", or +12.4 meters, or +13.5 yards -1.04", or -32.0 meters, or -34.0 yards
The GJorld Geodetic System 1972 (WGS 72) datum is considered equivalent to NAD 83 for this chart.
The Comnittee believes this question can be answered following future discussions between CHS, Canadian Ministry o f Transport, U. S. Coast Guard, Defense Mapping Agency Hydrographic/Topographi c Center, and the NOS. These discussions would be scheduled in a period 3 to 6 months in advance o f the implementation o f NAD 83 into the respective charting programs o f both countries. This question should be made a point of future discussions by the Comnission as well.
15.4. Should charts be drawn with a double border, one on NAD 83 and the other representing the existing chart datum?
A. No! Cartographically, it would mean drawing the neatline (border and projection ticks) twice, initially to show the old and new datum projections, and later to show only the NAD 83 projection. In the f i r s t case, i t i s be l ieved' the users would be confused by the two projectjons displayed, particularly in the adaptation of NM information. Until the charts are compiled on NAD 83, it is recomnended that an interim note and example be added to the existing chart to instruct the user how to transfer from existing chart datum to NAD 83, as recommended in the answer to question 13.
16.4. Will chart borders and lattices have to be redrawn?
A. Analysis to date indicates there should be no visible difference in charted area between chart neat1 ines (borders) drawn based on ellipsoid parameters defining NAD 83 and any other datum
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previously used, such as NAD 27 (Clarke's Reference Spheroid o f 1866). The neat l ines o f a char t def ine the "window," or the area charted, and regardless of the datum used i n compil ing the chart , the window remains the same even though the char t p ro jec t i on may be shi f ted. cha r t p ro jec t i on i n te rsec ts the neat1 ine, new subdivisions w i l l be re- qu i red t o r e f l e c t t h i s p ro jec t i on s h i f t t o NAD 83.
Where the
Elect ron ic pos i t i on ing l a t t i c e s , however, w i l l probably have t o be redrawn since both the e l l i p s o i d parameters and the geographic coordinates o f the e lec t ron i c pos i t i on ing system t ransmi t ters have been changed. These changes w i l l produce non-uniform differences between new and o l d data used t o generate these l a t t i c e s .
Other Considerations and Sumnary
Although predicted s h i f t s between N.4D 27 and NAD 83 appear t o be systematic and predictable, the Comnittee has concluded t h a t there are many charts compiled on o lder datums and based on o lder surveys where a predicted s h i f t i n coordinates i s no t feasible. s i s of each cha r t w i l l have t o be done t o resolve the e f f e c t o f s h i f t i n datums.
An ind i v idua l analy-
Beginning i n ea r l y 1985, o r as soon as f i n a l coordinates f o r char t ing con t ro l are ava i l ab le from NGS and GSC, the Committee recommends t h a t
/chart pro ject ions ( g r i d s ) be s h i f t e d . t o the NAD 83 a t the New E d i t i o n stage of construct ion. p ro jec t i on s h i f t s ( l a t i t u d e and longi tude) should be pub1 ished (annual ly) i n NM f o r t he mariner who wishes t o change datums p r i o r t o an e d i t i o n of the char t being published on NAD 83.
It i s fur ther recomnended t h a t a l i s t o f char t
The Committee has not determined whether NF1, L i g h t L i s t s , S a i l i n g Di rect ions ( P i l o t s ) and other publ icat ions quoting geographic pos i t ions would use the p ro jec t i on datum of the current e d i t i o n of the char t ( i f not NAD 83) o r would use NAD 83 exclusively. t i o n i n t h i s area i s required p r i o r t o 1985. mission i d e n t i f y t h i s f o r Charting Advisers ac t i on a t a l a t e r date.
Further study and coordina- It i s recommended the Com-
Elect ron ic pos i t i on ing system l a t t i c e s w i l l have t o be redrawn on the new datum. Some offshore surveys done i n hyperbol ic and range-range mode w i l l r equ i re r e p l o t t i n g because o f the non-uniformity 04 the s h i f t s i n t ransmi t te r pos i t ions and because o f new e l l i p s o i d parameters. It i s expected t h a t CHS and NOS w i l l not be able t o handle t h i s r e p l o t t i n g manu- a l l y , but w i l l r equ i re automated cartographic techniques t o e f fec t i ve l y and e f f i c i e n t l y accomplish transformation t o the new NAD 83.
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APPENDIX B
NAD 83 CONVERSION FACTORS
AND
PROPOSED IMPLEMENTATION SCHEDULE
FOR
NOS NAUTICAL CHARTS
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Abbreviations are u8ed extensively thmugbut Appedx B. l h e abbreviations, keyed to the major colrmn hdinge, are defined belaJ.
Datum - chart -
spc (State mane coarcunates) + Qlulartschly - Q1Insetsally * Ql chart end Ineet(s)
NY = NESJ York oR=oregcal PA = Parnsylvwia pM=palmygaAtoll PR=RsertoRico RI=RhodeIsland RL=RairgL&e sc=sauthcarollna SCR = St. clair River SI=SamaISlands !3LR = St. Lawrenre River sa = St. Marys River TX=TexaS VA = Virginia V I = V i r g t n I s p w d s WI=bh&ngtm WcSr=WestCaast wI=mkeIaland
. probable Year For printing N&r Edition x Y e a r F O r h w e r t h g c h a a T o W 8 3
4 7
'acific xilf Mexico 'acific 'acific
xilf Mexico EAtIantic itrait/Fla wf MexLco
-Tx
-IA -M
-LA
- tale LrlL oooo 2160 3500 3500 3500 3500 4860 2100 3121 875 1200 1 2 0 460 80 40 40 80 40 80 40 40 10 80 40 40 80
40 80 40 80 25 80 25 10 10
250 40 80 458 80 40 4c 80 175 M 40 80 4a 80 175 80
o m
-
1-50 411
1-5OCU.I I-501L 1-51s I-514L 53oL 531L 54cHJ
llam 11m 110131. 113oaL 1130lL 11302Sc 11303Sc 11304L 11306sc 11307L ll#)8sc 11309 1131 1 1131% 11314SC 11315SC 11316L 11317 11319SC 1132L 11322sc 113231. 11324 11326sc 11327 11328 11329 1133aL 11331sc 113321, 11% 1134lL 11342 11343 11344L 11345 11347s 11- 1134% 1135osc 11351L 11352 11354s
cc LAT - -
28
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19 19 19 19 19 19 19
19
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-6 -30 -24 22 26 26 26 25 26 26 26 26 26 25 26 25 24 25 24 23 23 22 22 22 22 22 22 20 21 20 15 19 20 20 17 16 18 16 14 14 13 11 12 -
d Max. bift
-
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Area chart:- 1:K
11355S2 40 11356L 80 11357L 80 113581, 80 1135% so
+S 1136aL 456 -IA1136lL 80/40
11363L 80 11364 80 11365% 50 11367sC 40 11368 15 1136% 80 1137OSC 40
-IS 1137lL 80 11372SC 40 11372 80 11374% 40 1137s 20
-AL 1137Q W/25 11378SC 40
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- -
-
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- Max.
21 22 22 22 22 20 21 19 19 21 20 20 20 21 19 19 18 18 18 17 17 17 17 17 17 18 18 18 18 19 26 21 20 20 21 21 23 26 28 30 30 31 31 41 33 33 35 35 38 40 40 43 -
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50 50 180 D/10 80 30 80 40 10 40 40 180 80 80 467 80 40 40
0/10 40 10 10
0/20 80 10 80 60 10 450 80 40 80 80 40
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40 40 40
433 80 40 20 20 20
80 40 40 80 80 40 80 40
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417 80
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io/20 20 20 20 5 20 197 40 80 40
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m/20 40 20 40
4o/m 400 80 4a 40 15 2a 40 10
8o/m 8a 40 8c io io 15 2(1 15 1c 1c 2c 5 1c -
12241 12243 12245 12248 12251 12253 12254 12255 12256 1m 12261 1226% 12264 12266 12268 12270 12272 1227% 12274 12277 12278 12281 12282 12283 12284 122853 12286 12287 12288 12289 123oaL 123041, 12311 12312 12313 12314 12316!3 12317 1231% 12323 123M 12326L 12327 12330 12331 12332 12333 12334 12335 12337 12338 12339
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11 10 11 11 10 11 11 11 11 8 8 8 8 8 8 8 8 8 8 8 8 8 8 8 8
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8 7 7 7 8 8 7 7 7 7 7 7 7 7 7 7 7 7 7
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- -
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32 31 32 32 31 32 32 32 32 30 31 31 30 31 31 30 31 31 31 31 31 30 30 30 30 30 29 30 28 28 40 33 32 32 32 32 34 33 34 35 35 35 35 35 35 35 35 35 35 35 35 35
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24 24 12 12 24 12 12
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10 10 40 10 10 40 40 10 20 20 80 80
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1200 675 500 400 220 80 40 20 20
10/5 2a 40 15 8(3 15 4c 20 2c 1c
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35 35 35 35 35 35 35 35 35 35 35 36 36 36 35 35 35 35 35 35 36 36 36 36 36 36 36 36 42 45 45 44 46 39 39 39 39 39 39 39 40 40 40 40 40 40 40 40 40 40 41 41 -
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A r e a c h a r t
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5 20 80
!0/10 40 10 40 80 m 20
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m/10 378
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13235 13236
13238 13241 13242 13244 13246L 13248 13249 13250 13251 13253 132601, 13267L 13269 13270 13272 13274S( 13275 13276 132781, 13279 13281 13282 13283 13285 13286L 13287 132881, 13290 13292 13293 13295 132% 13298 13301 133OZI.l 13303 13305 13307 13308 13309 133121. 13313 13315 13316 13318 13321 13322 13323 13324
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6 6 6 6 6 6 6 5 5 5 5 5 5 4 5 5 5 5 5 5 5 5 5 5 5 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 -
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-41 -41 -42 -43 -43 -43 -43 -43 -43 -43 -43 -43 -42 -46 -41 -41 -40 -40 -41 -40 -40 -41 -41 -41 -40 -40 -40 -42 -42 -43 -42 -42 -43 -43 -43 -43 -43 -44 -45 -44 -44 -45 -45 -45 -45 -45 -45 -46 -46 -46 -46 -47
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A r e a c h a r t
1332!jL 13326 13327 13328
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14788 14791
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Great Lskes 145(xa
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cale 1:K 80 40 40 a/ 5 1500
30 30 30
;O/ 15 30
0/10 0/10
30 15 15 15 15 15 40 40 40 40 10
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n/10 400 80
B/15 B/15 n/10 B/10 100/1( 30/5
10 10 io 30 400 80
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m / 5 5
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500 12015 120/1( 120/1:
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B/lO @/XI 40
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137 145 145 145 149 155 154 155 158 158 158 158 158 158 152 160 160 158 152 140 142 140 140 140 140 140 137 137 137 139 139 139 139 139 138 138 137 135 136 136 135 135 134 133 133 132 130 130 130 130 129 129
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460 460 460 460 460 460 460 460 460 460 460 460 460 460 460 460 460 460 460 460 460 460 460 460 460 460 460 460 460 460 460 460 460 460 460 460 222 222 222 222 222 222 222 222 222 222 222 222 222 222 222 222
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66
APPENDIX C
OPTION 4: DATUM CONVERSION COSTS
The hybrid manual/automated datum conversion plan presented as Option 4 is intended to provide f u l l conversion to NAD 83 within 5 years. During this time, 72 charts would be converted by revising the existing datum reference note on each chart and adding a datum transformation note. The remaining charts would require additional cartographic and reproduction actions to shift the existing chart projection. A total of 482 charts would have their projections shifted by manual cartographic procedures; 405 charts would be converted by automated methods.
In addition to the shift in projection, up to 272 charts could require a shift in their LORAN or OMEGA electronic positioning lattices. For planning purposes, it was estimated that 60 per- cent of the lattices would require revision.
In determining the conversion costs, it was assumed the compi- lation and reproduction costs under automation would be insig- nificant. These costs are estimated to be $50,000. The manual costs of datum conversion under Option 4 were computed as follows:
A. Cartographic Conversion Costs
1. Chart Projections
a. Number of charts for manual conversion = 482 charts b. Staff-hours per chart for new projections = 24 hours c. Cartographer cost per hour = $19.89"
Cost = $230,087
Inset Projections
d. Insets per chart = 0.45 e. Staff-hours per inset for new projection = 20 hours
Cost = $86,283
LORAN/OMEGA Lattices
f. Number of charts with lattices = 272 charts g. Assume 60 percent will require shifting h. Staff-hours per chart to shift lattice = 32 hours
Cost = $103,873
*based on salary of GS-11, step 7 (includes overhead, inhouse indirect and other service level user charges)
67
4. Total cartographic labor and materials costs to shift chart and inset projections, and LORAN/OMEGA lattices.
TOTAL Cost = $420,243
B. Reproduction Conversion Costs
1. Chart Projections
a. Number of charts for manual conversion = 482 charts b. Staff-hours per chart for new projection = '35 hours c. Reproduction cost per staff-hour = $21.50 d. Material cost per new projection = $60/chart
Cost = $391,625
2. Inset Projections
e. Insets per chart = 0.45 f. Staff-hours per inset for new projection = 20 hours g. Material cost per inset = $30
cost = $99,774
3. LORAN/OMEGA Lattices
h. Number of charts with lattices = 272 charts i. Number of charts having lattices requiring
j. Staff-hours per chart = 32 hours k. Material costs per chart = $150
shift = 60 percent
Cost = $136,761
4. Total reproduction costs to shift chart and inset projections, and LORAN/OMEGA lattices.
TOTAL Cost = $628,160
C. Total conversion costs for manual cartographic and reproduction services for Option 4 is $1,048,400.
D. Estimated cost to convert the AIS Data Base to NAD 83 = $50,000
E. Total NAD 83 Conversion Costs are $1,098,400.
68
