National Readjustment DALE PURSELL ACSM 2006. NATIONAL READJUSTMENT WHAT? WHY HOW WHEN POST...
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Transcript of National Readjustment DALE PURSELL ACSM 2006. NATIONAL READJUSTMENT WHAT? WHY HOW WHEN POST...
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National Readjustment
DALE PURSELLACSM2006
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NATIONAL READJUSTMENT
• WHAT?
• WHY
• HOW
• WHEN
• POST
• QUESTIONS
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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
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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.
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NATIONAL GEODETIC SURVEY
WEB SITEhttp://www.ngs.noaa.gov
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NATIONAL READJUSTMENT
WHAT
WHY?
HOW
WHEN
POST
QUESTIONS
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The NAD83(86) Adjustment Team
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NAD83(86) DOPPLER STATIONS
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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
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NAD 27 and NAD 83
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Results of NAD83(86)
• Network Accuracy - 1 Meter
• Local Accuracy – First-Order (1 part in 100,000)
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NAD 83(86) NETWORK PROBLEMS
Not “GPSABLE”
POOR STATION ACCESSIBILITY
IRREGULARLY SPACED
POSITIONAL ACCURACY
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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)
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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)
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HIGH ACCURACY REFERENCE NETWORK
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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
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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
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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)
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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)
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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
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http://www.ngs.noaa.gov/PROJECTS/FBN/
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http://www.ngs.noaa.gov/PROJECTS/FBN/
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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
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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.
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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
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NATIONAL READJUSTMENT
WHAT
WHY
HOW?
WHEN
POST
QUESTIONS
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NGS Adjustment Team (1986)NGS Adjustment Team (2005)
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NAD 83 READJUSTMENT
ONLY GPS DATA WILL BE USED
CONTINUOUSLY OPERATING REFERENCE STATIONS
FEDERAL BASE NETWORKCOOPERATIVE BASE NETWORK
USER DENSIFICATION NETWORKAIRPORT SURVEYS
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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
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USER DENSIFICATION NETWORK
STATE/LOCAL FUNDEDSTATION SPACING AS REQUIRED
GPS OBSERVATIONS ONLY (HORIZONTAL)FIRST-ORDER HORIZONTAL ACCURACY
REVISIT AS NEEDED
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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
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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.
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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
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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
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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.
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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
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Helmert Blocks
CORS provides control at top block Canadian data Each state will comprise a separate block of data
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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
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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
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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
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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
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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.
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NATIONAL READJUSTMENT
WHAT
WHY
HOW
WHEN?
POST
QUESTIONS
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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
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We will be celebrating our 200th anniversary on February 10,
2007
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NATIONAL READJUSTMENT
WHAT
WHY
HOW
WHEN
POST?
QUESTIONS
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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.
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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.
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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/????
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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???
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NATIONAL READJUSTMENT
WHAT
WHY
HOW
WHEN
POST
QUESTIONS?
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