National Readjustment

DALE PURSELLACSM2006

NATIONAL READJUSTMENT

• WHAT?

• WHY

• HOW

• WHEN

• POST

• QUESTIONS

NATIONAL SPATIAL REFERENCE SYSTEM• A component of the National Spatial Data Infrastructure

(NSDI) - http://www.fgdc.gov/nsdi/nsdi.html

• Contains all geodetic control contained in the National Geodetic Survey (NGS) Data Base:– Horizontal and vertical control points– Geoid models such as GEOID 03– Gravity– Precise GPS orbits– Continuously Operating Reference Stations (CORS)– National Shoreline data as observed by NGS

NATIONAL SPATIAL REFERENCE SYSTEM• MULTIPURPOSE – Supports Geodesy, Geophysics, Land

Surveying, Navigation, Mapping, Charting and GIS

• ACTIVE – Accessible through Continuously Operating Reference Stations (CORS) and derived products

• INTEGRATED – Related to International services and standards (e.g. International Earth Rotation Service, International GPS Service etc.)

• DOCUMENTED – Complete metadata is provided for elements.

NATIONAL GEODETIC SURVEY

WEB SITEhttp://www.ngs.noaa.gov

NATIONAL READJUSTMENT

WHAT

WHY?

HOW

WHEN

POST

QUESTIONS

The NAD83(86) Adjustment Team

NAD83(86) DOPPLER STATIONS

COMPARISON OF DATUM ELEMENTS

NAD 27 NAD 83ELLIPSOID CLARKE 1866 GRS80 a=6,378,206.4 m a=6,378,137 m 1/f = 294.9786982 1/f = 298.257222101

DATUM POINT Triangulation Station NONE Meades Ranch, Kansas Earth Mass Center

ADJUSTMENT 25k Stations 250k Stations few hundred Base lines 30k EDMI base lines

few hundred Astro Az 5k Astro Azimuths Doppler and VLBI

NAD 27 and NAD 83

Results of NAD83(86)

• Network Accuracy - 1 Meter

• Local Accuracy – First-Order (1 part in 100,000)

NAD 83(86) NETWORK PROBLEMS

Not “GPSABLE”

POOR STATION ACCESSIBILITY

IRREGULARLY SPACED

POSITIONAL ACCURACY

HIGH ACCURACY REFERENCE NETWORKS“GPSABLE”

Clear Horizons for Satellite Signal Acquisition

EASY ACCESSIBILITYFew Special Vehicle or Property Entrance

Requirements

REGULARLY SPACEDAlways within 20-100 Km

HIGH HORIZONTAL ACCURACYA-Order (5 mm + 1:10,000,000)B-Order (8mm + 1:1,000,000)

HARN ADJUSTMENT

A-Order Adjusted to VLBI-Existing FBN-CORS

B-Order Adjusted to A-Order

Existing Horizontal (Conventional & GPS) Readjusted to A/B-Order

New Adjustment Date Tag e.g. NAD83(1995)

HIGH ACCURACY REFERENCE NETWORK

GPS & CLASSICAL ADJUSTMENTS COMPLETEDGPS ADJUSTMENT COMPLETED

1990

-GPS

170

1990-GPS120

1991GPS222

1992GPS366

1997GPS11791992

GPS412

1992 GPS3831992

GPS450

1992GPS419

1992GPS394

1992GPS341

1993

1993

GPS585

1993 GPS667

1992GPS376

1995GPS887

1997.

GPS577

1991GPS197

GPS2601991

1995GPS908

GPS610

1993 GPS725

HARN & STATEWIDE NETWORK STATUS

1993

1994GPS404

GPS611

1994GPS633

1991 GP S291 reobs 9/97

1994 GPS721

reos 7/96 GPS1047

reos 1/96 GPS936

1997GPS1133

reos-6/95-GPS904

1995GPS852

1995GPS882

1993GPS606

1996GPS1048 1996

GPS8051996GPS941 1994

GPS7301996GPS1121

1997GPS1178

1997 GPS 12001997

GPS1150

reos-1996

FEDERAL BASE NETWORK

NGS FUNDEDNGS MARK MAINTENANCE

MINIMUM 100 KM STATION SPACINGA and B-ORDER HORIZONTAL ACCURACY

FIRST-ORDER CLASS II ORTHOMETRIC HEIGHTS or

SECOND-ORDER CLASS I ORTHOMETRIC HEIGHTSSECOND-ORDER CLASS I ELLIPSOIDAL HEIGHTS

REVISIT EVERY 3 TO 5 YEARS

FBN/CBN Surveys

Current Status: Observations complete for 48 contiguous states

and the District of Columbia Additional major surveys in Alabama (reductions

underway), California and Minnesota will be included-perhaps others

West Virginia still needs to be reprocessed (Leica SR399 antennas); possibly other states or portions of states (study underway)

Statewide GPS Readjustments

Complete (or unnecessary) for 43 of 48 States,+ DC, PR Readjustment of EH’s and/or Positions (5cm tolerance) Layered Adjustment Approach Used

States not Completed CA-Requires special analysis-underway MO, TN, KY-not started (4/18/05) OH underway (4/18/2005)

FBN GPS ADJUSTMENT COMPLETED

FBN/CBN SURVEYS

GPS READJUSTMENT COMPLETED

1999GPS1347

1998GPS1273

1997GPS1250

1998GPS1267 1998

GPS1264

1998GPS1258

1999GPS1394

1999GPS1397

1997GPS1207

1999GPS1378

1999GPS1370

1999GPS1356

1998GPS1288

1998GPS1333

1998GPS1340

1999GPS1377

1999GPS1381

1999GPS1399

2000GPS1411

2001 GPS1629

2000 GPS1463

2000 GPS1462

2000 GPS1481

2000 GPS1492

2000 GPS1506 2000 GPS1514

2000 GPS1519

2000 GPS1530 2000

GPS1188

2001 GPS1712

2001GPS1554

2001GPS1641

2001 GPS1596

2002 GPS1686

2002 GPS1687

2002 GPS1731

2003 GPS1752

2003

GPS1825

2003 GPS1851

2003 GPS1753

2003 GPS 1850 MEANS

2003 GPS1682WILLIAMS

2003 GPS1726 2002

GPS-1547

http://www.ngs.noaa.gov/PROJECTS/FBN/

http://www.ngs.noaa.gov/PROJECTS/FBN/

IMPROVING POSITIONAL ACCURACY

TIME NETWORK LOCALNETWORK SPAN ACCURACY ACCURACY

NAD 27 1927-1986 10 METERS (1 part in 100,000)

NAD83(86)1986-1990 1 METER (1 part in 100,000)

HARN 1990-1997 0.1 METER B-order (1 part in 1 million)

A-order (1 part in 10 million)

CORS 1996 - 0.01 meter 0.01 meter

Reasons for Readjustment

• Multiple epoch dates• Inconsistencies between states• Need to be Consistent with CORS• Compute Network and Local accuracies

September 24, 2003 NGS Executive Steering Committee approved a plan for the readjustment of the horizontal positions and ellipsoid heights for GPS stations in the contiguous United States.

What about Orthometric Heights?

Decision was made not to perform a National Readjustment of orthometric heights at this time Control = NAVD 88 not the CORS Since no change in control most orthometric elevations

would not change significantly Network & Local Accuracy numbers for the orthometric

heights would be the primary reason for readjustment Would require relevant network accuracies for the

NAVD 88 network-This would require a complete analysis of the NAVD 88 network

NATIONAL READJUSTMENT

WHAT

WHY

HOW?

WHEN

POST

QUESTIONS

NGS Adjustment Team (1986)NGS Adjustment Team (2005)

NAD 83 READJUSTMENT

ONLY GPS DATA WILL BE USED

CONTINUOUSLY OPERATING REFERENCE STATIONS

FEDERAL BASE NETWORKCOOPERATIVE BASE NETWORK

USER DENSIFICATION NETWORKAIRPORT SURVEYS

NAD 83 READJUSTMENT

STATE/LOCAL FUNDEDSTATE/LOCAL MARK MAINTENANCE

25 TO 30 KM STATION SPACINGB-ORDER HORIZONTAL ACCURACY

THIRD-ORDER CLASS I ORTHOMETRIC HEIGHTTHIRD-ORDER CLASS I ELLIPSOIDAL HEIGHT

REVISIT AS NEEDED

USER DENSIFICATION NETWORK

STATE/LOCAL FUNDEDSTATION SPACING AS REQUIRED

GPS OBSERVATIONS ONLY (HORIZONTAL)FIRST-ORDER HORIZONTAL ACCURACY

REVISIT AS NEEDED

PHASE I PLANNING - RECONPHASE I OBSERVEDPHASE I PROCESSEDPHASE II OBSERVEDPHASE II PROCESSEDPHASE II RELEASEDPHASE III PLANNEDPHASE III PHOTOPHASE III OBSERVEDPHASE III PROCESSEDPHASE III RELEASED

ANA STATUS 10/31/2004

AIRPORT SURVEYS

The National Readjustment General Comments

The CORS will provide the control Only GPS projects will participate The FBN/CBN Surveys are a key element since these are

high accuracy (2 cm) surveys that tie the HARN to the CORS throughout the contiguous United States and provide more accurate values for the ellipsoid heights of most HARN stations.

The required free adjustment analysis of each GPS project that contributes to the National Spatial Reference System is complete.

Project Adjustment Analysis

3375 Projects complete Free Adjustment Residual Plot Outliers Rejected Connectivity to A/B Order Network Verified Summary sheet with Project Information Created 69117 stations

TRASH

Projects Not Recommended for Inclusion Currently 149 Projects with 9903 stations

Many Third Order FAA Projects from 1980’sSome Projects that have no ties to the NetworkOriginal TN HARN (Macrometer Data)Original Eastern Strain Network Project

The National Readjustment More Comments

Computation and database loading of scale factors for each project is underway.

Statewide GPS Readjustments are providing extra information about the network on a state by state basis.

Concept of Operation

Modified ADJUST, GPSCOM, LLSOLV software will be used plus new residual analysis software

Helmert Blocking strategy will be used. Coordinates Produced and Published for both NAD83

(NSRS) and ITRF Adjustment in NAD83-Transformed to ITRF

Canadian (Mexican?) Data Integrated at top layer Network and Local Accuracies also Produced

Helmert Blocks

CORS provides control at top block Canadian data Each state will comprise a separate block of data

Helmert Blocking Strategy

STATE #5STATE #4

Upper Block #3

STATE #3

STATE #2STATE #1

Upper Block #1

Upper Block #2

Upper Block #4CORS

TOP BLOCK

Local Accuracy

Local Accuracy of a control point: A value that represents the uncertainty of its

coordinates relative to other directly connected, adjacent control points at the 95-percent confidence level

An approximate average of the individual local accuracy values between this control point and other observed control points used to establish its coordinates

Network Accuracy

Network accuracy of a control point A value that represents the uncertainty of its coordinates

with respect to the geodetic datum at the 95-percent confidence level

Datum is considered to be best expressed by the Continuous Operating Reference Stations (CORS)

Local and Network accuracy values at CORS sites are considered to be infinitesimal (approach zero)

These accuracies will be implemented with the National Readjustment

NEW STANDARDS FOR GEODETIC CONTROL

(http://fgdc.er.usgs.gov/standards/status/swgstat.html)

• local accuracy -------------- adjacent points• network accuracy ---------- relative to CORS

• Numeric quantities, units in cm (or mm)• Both are relative accuracy measures• Will not use distance dependent expression

ANTICIPATED SHIFTS

• Based on a preliminary adjustment of all FBN’s to the published values.

< 5 cm. in the horizontal component with an average shift of 2.2 cm. < 10 cm. in the vertical component with an average shift of 4.6 cm.

NATIONAL READJUSTMENT

WHAT

WHY

HOW

WHEN?

POST

QUESTIONS

Time-line for National Readjustment Positions and Ellipsoid Heights

All projects guaranteed to be included in the adjustment must be loaded in the database no later than 06/01/2005

Projects submitted after 06/01/2005 will be accepted and loaded into the database but will not be included in the readjustment

Anticipated completion by February 10, 2007 Project Report

3 months-February, 2007 through May, 2007

We will be celebrating our 200th anniversary on February 10,

2007

NATIONAL READJUSTMENT

WHAT

WHY

HOW

WHEN

POST?

QUESTIONS

For Stations not Included

NGS recommends that NAD 83 data that is NOT part of the NSRS readjustment be readjusted by contractor/user with the original observations.

A set of national transformation parameters for “classical” non-GPS stations and GPS stations that were excluded from the National Readjustment will be developed by NGS.

Because of the relatively small shifts anticipated, a model such as NADCON will not be developed.

Post National Readjustment

Areas outside the US may need to be readjusted (e.g. Hawaii, Puerto Rico, Pacific Islands).

New adjustment procedures will be developed that incorporate local and network accuracies.

A reference frame maintenance strategy (NAD83, ITRF, either or both) needs to be developed.

Design and Publish new data sheets.

Important Facts

• DEADLINE for data submittal June 1, 2005• COMPLETION DATE – February 10, 2007• NEW DATUM TAG - NAD83(NSRS)

For the latest information- visit the national readjustment webpage at:

(http://www.ngs.noaa.gov/????

OTHER ISSUES

• We will streamline the process of project acceptance and database loading

• Require that all projects (submitted after the June 1, 2005 deadline) be tied to CORS

• Accept/require more data in digital format-e.g.. reports, logs…

• Photographs???

NATIONAL READJUSTMENT

WHAT

WHY

HOW

WHEN

POST

QUESTIONS?