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1
FGDC ACCURACY STANDARDS
NEW JERSEY SOCIETY OF PROFESSIONAL LAND SURVEYORS
ATLANTIC CITY
FEBRUARY 6, 2013
Dave Doyle
National Geodetic Survey (Retired)
Jesse Kozlowski
True Measure Consulting
2
POSITIONING ACCURACY STANDARDS
WORKSHOP OUTLINE
Introduction
Definitions
Evolution of Accuracy Standards
Classical Surveying Standards
GPS Surveying Standards
Development of New Accuracy Standard
Implementation of New Accuracy Standards
Guidelines & Procedures Documents
Computations/Software
Data Publications
Summary/Future
DEFINITIONS
DEFINITIONS
Survey Standards
Survey Specifications
Precision
Accuracy
WHAT IS A
SURVEY STANDARD?
WHAT IS A SURVEY STANDARD? (SOME PREVIOUS RESPONSES)
A level of precision of closure
A reasonably accepted error
A numerical limit on the uncertainty of
coordinates
Position relative to other points
Such as 0.1 (units) + X ppm
SURVEY STANDARDS
Survey standards may be defined as the
minimum accuracies deemed necessary to
meet specific objectives. (e.g. .1 ft, or
1/20,000)
For the present, the practice of defining these
criteria by the maximum acceptable
uncertainty in length and/or position and
assigning some nomenclature to them will be
continued.
WHY DO SURVEYORS NEED
ACCURACY STANDARDS?
WHY DO SURVEYORS NEED ACCURACY
STANDARDS? (SOME PREVIOUS RESPONSES)
To provide quality assurance of accuracy
Such as within 8 mm + 1 ppm; 5 cm; 0.5 m
To provide consistency
To re-establish survey monuments
SURVEY SPECIFICATIONS
Specifications can be described as the field
operations required to meet a particular survey
standard. (e.g. 1” theodolite, 8 positions D&R,
5 distances forward and back)
Also included are the specified precision and
allowable tolerances for the data collected, the
limitations of the geometric form of acceptable
figures, monumentation, and description of the
points.
DEFINITION OF PRECISION
Precision (1) In statistics, a measure of the tendency of
a set of random numbers to cluster about a number
determined by the set.
The usual measure is either the standard deviation with
respect to the average, or the reciprocal of the quantity. It is
distinguished from accuracy by the fact that the latter is a
measure of the tendency to cluster about a number not
determined by the set but specified in some other manner.
From: Geodetic Glossary, National Geodetic Survey,
September 1986
STANDARD ERROR OF THE MEAN
m =
v2
n (n - 1)
Where m is the standard error
of the mean, v is a residual (that is,
the difference between a measured
length and the mean of all measured
lengths of a line), and n is the number
of measurements.
The term “standard error” used here is computed under the assumption
that all errors are strictly random in nature. The true or actual error is a
quantity that cannot be obtained exactly. It is the difference between the
true value and the measured value. By correcting each measurement for
every known source of systematic error, however, one may approach the
true error. It is mandatory for any practitioner using these tables to
reduce to a minimum the effect of all systematic and constant errors so
that real accuracy may be obtained.
STANDARD DEVIATION
s =
v2
n - 1
Where s is the standard deviation,
v is a residual (that is, the difference
between a measured length and the mean
of all measured lengths of a line), and n
is the number of measurements.
= sigma or 1 standard deviation
= 68.3% certainty
2 = 2 sigma or 2 standard deviations
= 95.0% certainty
Which would you pick, 1 or 2 sigma??
accuracy (1) Closeness of an estimated (e.g., measured or
computed) value to a standard or accepted value of a particular quantity.
Accuracy is commonly referred to as “high” or “low” depending on the size of
the differences between the estimated and the standard values.
(2) The square root of the average value of the sum of the squares of the
differences between the values in a set and the corresponding values that
have been accepted as correct or standard.
(3) The reciprocal of the quantity defined in (2).
Accuracy cannot be calculated solely from values based on measurements. A
standard value or set of standard values must be available for comparison
somewhere in the chain of calculations. The standard of reference may be:
(a) an exact value, such as the sum of the three angles of a plane triangle
being exactly 180°; (b) a value of a conventional unit as defined by a physical
representation thereof, such as the international meter; (c) a value
determined by refined methods and deemed sufficiently near the ideal or true
value to be held constant, such as the adjusted elevation of a permanent
bench mark or the graticule of a map projection.
From: Geodetic Glossary, National Geodetic Survey, September 1986
DEFINITION OF ACCURACY
15
CLOSURE
Is it a Standard
or
is it a Specification?
EXAMPLES OF CLOSURE
A B
B'
C
C'
D
D'
Starting
Azimuth Accurate Survey
Survey with
starting azimuth
error and systematic
distance error
Note that both surveys
produce excellent
closures - Regrettably the
vast majority of older
surveys exhibit this
condition
WHAT DOES FIRST-ORDER HORIZONTAL
ACCURACY MEAN?
JONES to SMITH = 45,230 feet
Therefore, the accuracy of the relationship between
JONES and SMITH is:
45,230/100,000 = 0.452 feet
JONES
SMITH
19
20 PERCENT RULE
Whenever the distance between two
new unconnected survey points is less than
20 percent of the distance between those
points traced along existing or new
connections, then a direct connection must
be made between those two survey points.
TYPES OF FIGURES WHERE IT MAY BE DIFFICULT TO
OBTAIN SATISFACTORY CLOSURES
WIPPER
(USGS)
PETERSON
FRANKLIN
(USGS)
HAFNER
MT PLEASANT
SNOW PEAK
LARCH
SQUAW
ZIGZAG
MT HOOD
CHINIDERE 2
Surveys between MT PLEASANT-
FRANKLIN (USGS) and MT HOOD-
ZIGZAG might not close to minimum
stated standards of points involved.
WHAT DOES FIRST-ORDER HORIZONTAL ACCURACY MEAN? (WHEN THE POINTS AREN’T DIRECTLY CONNECTED)
JONES
GEAN
SMITH
JONES to SMITH = 45,230 feet
JONES to GEAN = 37,467 feet
SMITH to GEAN* = 15,502 feet (* not observed)
The accuracy of the relationship between SMITH
and GEAN is:
√[(0.452)2 + (0.375)2] = 0.587 feet
NOT 15,502 /100,000 = 0.155 feet
ACCURACY STANDARDS FOR VERTICAL CONTROL
(K is the distance in kilometers between points)
Relative Accuracy
Between Directly
Connected Points
or Bench Marks
Classification (Standard Error)
First - Order, Class I 0.5 mm √K
First - Order, Class II 0.7 mm √K
Second - Order, Class I 1.0 mm √K
Second - Order, Class II 1.3 mm √√K
Third - Order 2.0 mm √K
WHAT DOES FIRST-ORDER, CLASS II
ACCURACY MEAN?
D 236 E 236
F 236 G 236
H 236
D 236 to G 236 = 3 miles = 4.8 km
Therefore, the accuracy of the vertical relationship
between D 236 and G 236 is:
0.7 √4.8 = 1.5 mm
24 WHAT DOES SECOND-ORDER, CLASS I ACCURACY MEAN?
(WHEN THE POINTS AREN’T DIRECTLY CONNECTED.)
D 236 to R 78 = 7 miles = 11.2 km
D 236
F 236 G 236
H 236
E 236
R 78 S 78
T 78 U 78
V 78
Therefore, the accuracy of the vertical relationship between
D 236 and R 78 is:
1.0 √ 11.2 = 3.3 mm
NOT: 1.0 √1.6 = 1.3 mm
25
EVOLUTION OF ACCURACY
STANDARDS
NATIONAL STANDARDS FOR HORIZONTAL AND
VERTICAL POSITIONING
Prior to 1921
Primary, Secondary, Tertiary
(No specific positional integrity defined)
(General Instructions for the Field Work of the USC&GS)
After 1921
Precise, Primary and Secondary
(Same as previous – not well accepted)
May 25, 1925
Board of Surveys and Maps of the Federal Government
1st, 2nd and 3rd – Orders adopted
1925
Horizontal (Relative accuracy between directly connected points)
1st- Order = 1:25,000
2nd- Order = 1:10,000
3rd- Order = 1:5,000
Vertical 1st- Order = 4 mm (0.017 ft) * √ k (k = length of section in km)
2nd- Order = 8.4 mm (0.035 ft)* √ k
3rd- Order = 12 mm (0.05 ft) * √ k
NATIONAL STANDARDS FOR HORIZONTAL AND
VERTICAL POSITIONING
Special Publication 120
Special Publication 145
1925
Horizontal No instrumentation specifications defined (e.g. 1” theodolite etc.). Only general
specifications “direction instruments of the highest grade should be used …”
Average triangle closure should seldom exceed 1”
Difference between measured and computed baseline not to exceed 1:25,000
Vertical 1st- Order = 4 mm (0.017 ft) * √ k (k = length of section in km – typically 1-2 km)
2nd- Order = 8.4 mm (0.035 ft)* √ k
3rd- Order = 12 mm (0.05 ft) * √ k
NATIONAL STANDARDS FOR HORIZONTAL AND
VERTICAL POSITIONING
March 1, 1957 – Office of Management and Budget, Circular A-16, Exhibit C Rational for changes in horizontal standards due primarily to significant developments in
Electronic Distance Measuring Equipment (EDM) (e.g. Geodimeter, Tellurometer)
Horizontal (Relative accuracy between directly connected points)
1st- Order Class I = 1:100,000
1st- Order Class II = 1:50,000
1st- Order Class III = 1:25,000
2nd- Order Class I = 1:20,000
2nd- Order Class II = 1:10,000
3rd- Order = 1:5,000
Vertical (Section closures)
1st- Order Class I = 3 mm* √ k
1st- Order Class II = 4 mm* √ k
2nd- Order Class I = 6 mm * √ k
2nd- Order Class II = 8 mm* √ k
3rd- Order vertical = 12 mm* √ k
NATIONAL STANDARDS FOR HORIZONTAL AND
VERTICAL POSITIONING
33
CLASSIFICATION OF CONTROL
The foregoing data concerning control classification may be tabulated as follows:
Special Publication No. 247
Manual of Geodetic Triangulation (1950)
First Order Second Order Third Order Fourth Order
Triangulation …...
Traverse ………...
Leveling …………
Average triangle clo-
sure 1”, check on
base 1/25,000.
Position check
1/25,000.
Error of closure of
section 0.017 ft.
miles or 4 mm.
kilometers.
Average triangle clo-
sure 3”, check on
base 1/10,000.
Position check
1/10,000.
Error of closure of
section 0.035 ft.
miles or 8.4 mm.
kilometers.
Average triangle clo-
sure 5”, check on
base 1/5,000.
Position check
1/5,000.
Error of closure of
section 0.05 ft.
miles or 12 mm.
kilometers.
Plane table or transit.
Stadia, tape, or wheel.
Flying wye levels, ver-
tical angles.
1974 Creation of Federal Geodetic Control Committee
(FGCC) – Chaired by Director, National Geodetic Survey
Publications:
“Standards of Accuracy and General Specifications of Geodetic Control Surveys”
“Specifications to Support Classification, Standards and Accuracy, and General
Specifications of Geodetic Control Surveys”
Minor changes in horizontal standards and more rigorous specifications (you must do)
adopted.
NATIONAL STANDARDS FOR HORIZONTAL AND
VERTICAL POSITIONING
1974 – Federal Geodetic Control Committee
Horizontal (Relative accuracy between directly connected points)
1st- Order Class = 1:100,000
2nd- Order Class I = 1:50,000
2nd- Order Class II = 1:20,000
3rd- Order Class I = 1:10,000
3rd- Order Class II = 1:5,000
Vertical (Relative accuracy between directly connected points)
1st- Order Class I = 3 mm* √ k
1st- Order Class II = 4 mm* √ k
2nd- Order Class I = 6 mm* √ k
2nd- Order Class II = 8 mm* √ k
3rd- Order vertical =12 mm* √ k
NATIONAL STANDARDS FOR HORIZONTAL AND VERTICAL
POSITIONING
1974 Examples
Horizontal Instrumentation specifications rigorously defined
1st – Order = 0.2” theodolite
16 positions D&R
Baseline Standard Error = 1: 1,000,000
2nd – Order Class II = 0.2” or 1.0” theodolite
8 positions D& R for 0.2”
12 positions D&R for 1.0”
Baseline Standard Error = 1: 800,000
NATIONAL STANDARDS FOR HORIZONTAL AND
VERTICAL POSITIONING
1974 Continued
Vertical Instrumentation specifications rigorously defined
1st – Order Class II= Automatic or tilting level with parallel plate micrometers and invar scale rods
Temperature compensated
Bubble sensitivity = 0.25 seconds of arc
Gravity requirement = 0.2 x 10-3gpu (geopotential unit)
Maximum line of sight = 60 m
2nd – Order Class II = Three-wire Geodetic levels with invar scale rods
Temperature not required
Bubble sensitivity = 0.5 seconds of arc
Maximum line of sight = 70 m
NATIONAL STANDARDS FOR HORIZONTAL AND
VERTICAL POSITIONING
1984 FGCC Updates Standards and Specifications
“Standards and Specifications of Geodetic Control Networks” http://www.ngs.noaa.gov/FGCS/tech_pub/1984-stds-specs-geodetic-control-networks.htm
NATIONAL STANDARDS FOR HORIZONTAL AND
VERTICAL POSITIONING
1989 FGCC publishes first GPS Standards and
Specifications’
“Geometric Geodetic Accuracy Standards and Specifications for using
GPS Relative Positioning Techniques”
New orders of accuracy created:
AA –Order -- (1:100,000,000)
A-Order -- (1:10,000,000)
B-Order -- (1:1, 000,000)
GPS technology changes so rapidly that this document never went beyond
“Draft”
NATIONAL STANDARDS FOR HORIZONTAL AND
VERTICAL POSITIONING
October 1990 – Office of Management and Budget
(OMB) creates the Federal Geographic Data
Committee (FGDC) -- 19 member interagency committee
composed of representatives from the Executive Office of the
President, Cabinet-level and independent agencies.
NATIONAL STANDARDS FOR HORIZONTAL AND
VERTICAL POSITIONING
FGCC becomes Federal Geodetic Control
Subcommittee (FGCS) under FGDC – still chaired
by the Director, National Geodetic Survey
1988
Geometric Geodetic Accuracy Standards and
Specifications for Using GPS Relative Techniques http://www.ngs.noaa.gov/FGCS/tech_pub/GeomGeod.pdf
NATIONAL STANDARDS FOR HORIZONTAL AND
VERTICAL POSITIONING
Established new horizontal positioning standards
that never existed before: A-Order 1:10,000,000
B-Order 1;1,000,000
Never formally adopted by FGCS – GPS technology changed too fast!
1998
FGDC/FGCS adopts
Geospatial Positioning Accuracy Standards
FGDC-STD-007.2-1998
http://www.fgdc.gov/standards/projects/FGDC-standards-projects/accuracy/part2/chapter2
Table 2.1 -- Accuracy Standards
Horizontal, Ellipsoid Height, and Orthometric Height
---------------------------------------------
Accuracy 95-Percent
Classification Confidence
---------------------------------------------
Less Than or Equal to:
1-Millimeter 0.001 meter
2-Millimeter 0.002 “
5-Millimeter 0.005 "
1-Centimeter 0.010 "
2-Centimeter 0.020 "
5-Centimeter 0.050 "
1-Decimeter 0.100 "
NATIONAL STANDARDS FOR HORIZONTAL AND
VERTICAL POSITIONING
Only sort of implemented – kind of!!
Horizontal and Ellipsoid Height (NAD 83) – Not Orthometric Height (NAVD 88)
NATIONAL STANDARDS FOR HORIZONTAL AND
VERTICAL POSITIONING National Geodetic Survey, Retrieval Date = DECEMBER 19, 2012
JU0320 ***********************************************************************
JU0320 DESIGNATION - LIGHTHOUSE PARK
JU0320 PID - JU0320
JU0320 STATE/COUNTY- NJ/ATLANTIC
JU0320 COUNTRY - US
JU0320 USGS QUAD - ATLANTIC CITY (1994)
JU0320
JU0320 *CURRENT SURVEY CONTROL
JU0320 ______________________________________________________________________
JU0320* NAD 83(2011) POSITION- 39 21 57.91963(N) 074 24 49.63659(W) ADJUSTED
JU0320* NAD 83(2011) ELLIP HT- -32.537 (meters) (06/27/12) ADJUSTED
JU0320* NAD 83(2011) EPOCH - 2010.00
JU0320* NAVD 88 ORTHO HEIGHT - 1.874 (meters) 6.15 (feet) ADJUSTED
JU0320 ______________________________________________________________________
JU0320 NAD 83(2011) X - 1,326,680.507 (meters) COMP
JU0320 NAD 83(2011) Y - -4,756,054.105 (meters) COMP
JU0320 NAD 83(2011) Z - 4,023,799.847 (meters) COMP
JU0320 LAPLACE CORR - -2.25 (seconds) DEFLEC12A
JU0320 GEOID HEIGHT - -34.43 (meters) GEOID12A
JU0320 DYNAMIC HEIGHT - 1.873 (meters) 6.15 (feet) COMP
JU0320 MODELED GRAVITY - 980,106.8 (mgal) NAVD 88
JU0320
JU0320 VERT ORDER - FIRST CLASS I
JU0320
JU0320 FGDC Geospatial Positioning Accuracy Standards (95% confidence, cm)
JU0320 Type Horiz Ellip Dist(km)
JU0320 -------------------------------------------------------------------
JU0320 NETWORK 0.94 1.39
JU0320 -------------------------------------------------------------------
JU0320 MEDIAN LOCAL ACCURACY AND DIST (005 points) 0.93 1.33 2.21
JU0320 -------------------------------------------------------------------
JU0320 NOTE: Click here for information on individual local accuracy
JU0320 values and other accuracy information.
JU0320
JU0320
JU0320.The horizontal coordinates were established by GPS observations
JU0320.and adjusted by the National Geodetic Survey in June 2012.
JU0320
JU0320.NAD 83(2011) refers to NAD 83 coordinates where the reference
JU0320.frame has been affixed to the stable North American tectonic plate. See
JU0320.NA2011 for more information. for more information.
JU0320
JU0320.The horizontal coordinates are valid at the epoch date displayed above
JU0320.which is a decimal equivalence of Year/Month/Day.
NATIONAL STANDARDS FOR HORIZONTAL AND
VERTICAL POSITIONING JU0320; North East Units Scale Factor Converg.
JU0320;SPC NJ - 59,142.748 157,428.861 MT 0.99990068 +0 03 16.9
JU0320;SPC NJ - 194,037.50 516,497.85 sFT 0.99990068 +0 03 16.9
JU0320;UTM 18 - 4,357,566.986 550,498.688 MT 0.99963140 +0 22 18.6
JU0320
JU0320! - Elev Factor x Scale Factor = Combined Factor
JU0320!SPC NJ - 1.00000510 x 0.99990068 = 0.99990578
JU0320!UTM 18 - 1.00000510 x 0.99963140 = 0.99963650
JU0320
JU0320: Primary Azimuth Mark Grid Az
JU0320:SPC NJ - RITZ 240 13 44.3
JU0320:UTM 18 - RITZ 239 54 42.6
JU0320
JU0320|---------------------------------------------------------------------|
JU0320| PID Reference Object Distance Geod. Az |
JU0320| dddmmss.s |
JU0320| JU2780 BRIGANTINE BEACH SOUTH TANK APPROX. 3.8 KM 0313051.0 |
JU0320| JU0321 LIGHTHOUSE PARK RM 1 36.890 METERS 05324 |
JU0320| CB2181 LIGHTHOUSE PARK RM 3 23557 |
JU0320| JU2765 ATLANTIC CITY CLARIDGE HOTEL APPROX. 1.8 KM 2383036.2 |
JU0320| JU2778 RITZ APPROX. 3.0 KM 2401701.2 |
JU0320| JU2779 ATLANTIC CITY RADIO WFPG MAST APPROX. 3.5 KM 2891617.0 |
JU0320| JU2770 ATLANTIC CITY MUNICIPAL TANK APPROX. 1.2 KM 2943015.1 |
JU0320| JU2772 ABSECON LIGHT 40.031 METERS 31045 |
JU0320| JU2771 BASIC BENCH MARK 1962 52.760 METERS 31746 |
JU0320|---------------------------------------------------------------------|
JU0320
JU0320 SUPERSEDED SURVEY CONTROL
JU0320
JU0320 NAD 83(2007)- 39 21 57.92001(N) 074 24 49.63736(W) AD( ) 0
JU0320 ELLIP H (02/10/07) -32.527 (m) GP( )
JU0320 ELLIP H (10/23/02) -32.498 (m) GP( ) 4 1
JU0320 NAD 83(1996)- 39 21 57.91974(N) 074 24 49.63728(W) AD( ) 1
JU0320 ELLIP H (05/14/99) -32.516 (m) GP( ) 4 1
JU0320 NAD 83(1986)- 39 21 57.91821(N) 074 24 49.63604(W) AD( ) 1
JU0320 ELLIP H (03/31/93) -32.580 (m) GP( ) 3 2
JU0320 NAD 83(1986)- 39 21 57.90902(N) 074 24 49.62921(W) AD( ) 3
JU0320 NAD 27 - 39 21 57.48690(N) 074 24 51.10000(W) AD( ) 3
JU0320 NAVD 88 (03/31/93) 1.87 (m) 6.1 (f) LEVELING 3
JU0320 NGVD 29 (01/10/92) 2.279 (m) 7.48 (f) ADJUSTED 1 1
First-Order
Fourth-Order