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National Readjustment of NAD 83

National Readjustment of NAD 83. Indiana Society of Professional Land Surveyors Indianapolis, IN January 18, 2008. NATIONAL SPATIAL REFERENCE SYSTEM(NSRS). Consistent National Coordinate System Latitude Longitude Height Scale Gravity Orientation

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National Readjustment of NAD 83

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  1. National Readjustment of NAD 83 Indiana Society of Professional Land Surveyors Indianapolis, IN January 18, 2008

  2. NATIONAL SPATIAL REFERENCE SYSTEM(NSRS) • Consistent National Coordinate System • Latitude • Longitude • Height • Scale • Gravity • Orientation • and how these values change with time

  3. ACRONYMSUS R NSRS2007 NAD 27 NAVD 88 WGS 84 ITRF NGVD 29 NAD83(1986) NAD 83 Clark 1866 GRS 80 HARN NAD83(1997)

  4. NATIONAL SPATIAL REFERENCE SYSTEM North American Datum of 1983 (NAD 83) North American Vertical Datum of 1988 (NAVD 88) First civilian datums designed to be consistent with space-based observations (GPS) First civilian datums to be best-fitting globally not locally First geodetic reference systems to be Accessible through Continuously Operating Reference Stations (CORS) and derived products First geodetic reference systems to be available free from WWW Only reference system to freely integrate data from outside sources MULTIPURPOSE – Supports Geodesy, Geophysics, Land Surveying, Navigation, Mapping, Charting and GIS ACTIVE – Accessible through Continuously Operating Reference Stations (CORS) and derived products

  5. +Z H b Z f Y X l a -Y +X Cartesian system X = -2691542.5437 m Y = -4301026.4260 m Z = 3851926.3688 m Horizontal Datums • A horizontal datum is the coordinate system that we use to locate ourselves on the earth • Involves the origin and orientation of coordinate axes • geocentric cartesian (X,Y,Z) • Usually the origin is near the center of mass of the earth • one axis intersects the earth’s surface at the intersection of the prime meridian and the equator • and a reference ellipsoid • Latitude Longitude and height • Specific geodetic datums are usually given distinctive names. • North American Datum of 1983, • International Terrestrial Reference Frame (YYYY) • WGS84 Lat Lon f = 37o 23’ 26.38035” N l = 122o 02’ 16.62574” W H = -5.4083 m

  6. GEODETIC DATUMS Classical • Horizontal – 2 D (Latitude and Longitude) (e.g. NAD 27, NAD 83 (1986)) • Vertical – 1 D (Orthometric Height) (e.g. NGVD 29, NAVD 88) Contemporary PRACTICAL – 3 D (Latitude, Longitude and Ellipsoid Height) Fixed and Stable – Coordinates seldom change (e.g. NAD 83 (1996) or NAD 83 (NSRS 2007)) SCIENTIFIC – 4 D (Latitude, Longitude, Ellipsoid Height, Velocity) – Coordinates change with time (e.g. ITRF00, ITRF05)

  7. N b a S HORIZONTAL DATUMS • 8 Constants • 3 – specify the location of the origin of the coordinate system. • 3– specify the orientation of the coordinate system. • 2 – specify the dimensions of the reference ellipsoid

  8. UNITED STATESELLIPSOID DEFINITIONS BESSEL 1841 a = 6,377,397.155 m 1/f = 299.1528128 CLARKE 1866 a = 6,378,206.4 m 1/f = 294.97869821 GEODETIC REFERENCE SYSTEM 1980 - (GRS 80) a = 6,378,137 m 1/f = 298.257222101 WORLD GEODETIC SYSTEM 1984 - (WGS 84) a = 6,378,137 m 1/f = 298.257223563

  9. International Earth Rotation and Reference System Service(IERS)(http://www.iers.org) The International Terrestrial Reference System (ITRS) constitutes a set of prescriptions and conventions together with the modeling required to define origin, scale, orientation and time evolution ITRS is realized by the International Terrestrial Reference Frame (ITRF) based upon estimated coordinates and velocities of a set of stations observed by Very Long Baseline Interferometry (VLBI), Satellite Laser Ranging ( SLR), Global Positioning System and GLONASS (GNSS), and Doppler Orbitography and Radio- positioning Integrated by Satellite ( DORIS). Plate tectonics is accommodated giving each coordinate a velocity ITRF89, ITRF90, ITRF91, ITRF92, ITRF93, ITRF94, ITRF95, ITRF96, ITRF97, ITRF2000, ITRF2005

  10. International Terrestrial Reference Frame 4 Global Independent Positioning Technologies International Global Navigation Satellite Systems Service (IGS) International Laser Ranging Service (ILRS) International Very Long Baseline Service (IVS) International DORIS Service (IDS)

  11. WORLD GEODETIC SYSTEM 1984 http://earth-info.nga.mil/GandG/publications/tr8350.2/tr8350_2.html DATUM = WGS 84(G873) 5 USAF GPS Tracking Stations 7 NIMA Evaluation Stations Datum redefined with respect to the International Terrestrial Reference Frame of 1994 (ITRF94) +/- 10 cm in each component (Proceedings of the ION GPS-97 pgs 841-850) DATUM = WGS 84(G730) 5 USAF GPS Tracking Stations 5 DMA Evaluation Stations Datum redefined with respect to the International Terrestrial Reference Frame of 1992 (ITRF92) +/- 20 cm in each component (Proceedings of the ION GPS-94 pgs 285-292) DATUM = WGS 84(G1150) Datum redefined with respect to the International Terrestrial Reference Frame of 2000 (ITRF00) +/- 2 cm in each component (Proceedings of the ION GPS-02) http://earth-info.nima.mil/GandG/sathtml/IONReport8-20-02.pdf HOW MANY WGS 84s HAVE THERE BEEN???? DATUM = WGS 84 RELEASED - SEPTEMBER 1987 BASED ON OBSERVATIONS AT MORE THAN 1900 DOPPLER STATIONS

  12. Tectonic Plates NUVEL-1A

  13. NAD83 ITRF00 vs NAD83 velocities

  14. Seismic cycle • Seismic cycle consists of 2 main phases • Inter-seismic phase when elastic strain accumulates in the crest around the fault • Strain is widely distributed • co-seismic phase when elastic strain is converted to slip on the fault

  15. model of the secular field • An analytical model representing horizontal crustal motion • Incorporates all major active faults in a single model. • Provides a more accurate model of crustal deformation in western US • data comprise • 4890 GPS velocities • 170 fault slip rates from paleoseismic & paleomag studies • 258 fault slip vectors taken from earthquakes and geologic studies

  16. Earthquakes in Contiguous US

  17. MEADES RANCH 1891 – KANSASOrigin for USSD-NAD-NAD27

  18. COMPARISON OF DATUM ELEMENTS NAD 27NAD 83 ELLIPSOID 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 1.8 million observations

  19. NAD 27 to NAD 83 (86)

  20. Results of NAD83(86) • Network Accuracy - 1 Meter • Local Accuracy – First-Order (1 part in 100,000) Second-Order (1 part in 50,000) Third-Order (1 part in 10,000)

  21. NAD 83(86) NETWORK PROBLEMS NOT “GPSABLE” POOR STATION ACCESSIBILITY IRREGULARLY SPACED POSITIONAL ACCURACY

  22. HARN/HPGN 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(1997)

  23. REGIONAL CORS NETWORK

  24. SPRINGFIELD (ILSA), ILLINOIS _____________________________________________________________________________ | | | Antenna Reference Point(ARP): SPRINGFIELD CORS ARP | | -------------------------------------------------- | | PID = DH3759 | | | | | | ITRF00 POSITION (EPOCH 1997.0) | | Computed in June 2005 using 14 days of data. | | X = 33385.872 m latitude = 39 46 43.08683 N | | Y = -4908474.031 m longitude = 089 36 37.07435 W | | Z = 4059224.563 m ellipsoid height = 152.900 m | | | | ITRF00 VELOCITY | | Predicted with HTDP_2.7 June 2005. | | VX = -0.0168 m/yr northward = -0.0018 m/yr | | VY = -0.0015 m/yr eastward = -0.0168 m/yr | | VZ = -0.0012 m/yr upward = 0.0003 m/yr | | | | | | NAD_83 (CORS96) POSITION (EPOCH 2002.0) | | Transformed from ITRF00 (epoch 1997.0) position in Jun. 2005. | | X = 33386.406 m latitude = 39 46 43.06026 N | | Y = -4908475.428 m longitude = 089 36 37.05230 W | | Z = 4059224.662 m ellipsoid height = 154.039 m | | | | NAD_83 (CORS96) VELOCITY | | Transformed from ITRF00 velocity in Jun. 2005. | | VX = 0.0000 m/yr northward = 0.0000 m/yr | | VY = 0.0000 m/yr eastward = 0.0000 m/yr | | VZ = -0.0000 m/yr upward = 0.0000 m/yr | |_____________________________________________________________________________| ITRF00 – NAD 83(CORS96) DHoriz = 0.973m DEHt = 1.139m

  25. IMPROVING POSITIONAL ACCURACY TIME NETWORK LOCAL NETWORK 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 (1.0 ppm) A-order (0.1 ppm) CORS 1996 - 0.01 meter 0.01 meter

  26. National Geodetic Survey, Retrieval Date = DECEMBER 6, 2007 KB0684 *********************************************************************** KB0684 DESIGNATION - ASSUMPTION KB0684 PID - KB0684 KB0684 STATE/COUNTY- IL/CHRISTIAN KB0684 USGS QUAD - ASSUMPTION (1982) KB0684 KB0684 *CURRENT SURVEY CONTROL KB0684 ___________________________________________________________________ KB0684* NAD 83(2007)- 39 31 12.72891(N) 089 02 56.47681(W) ADJUSTED KB0684* NAVD 88 - 196.394 (meters) 644.34 (feet) ADJUSTED KB0684 ___________________________________________________________________ KB0684 EPOCH DATE - 2002.00 KB0684 X - 81,771.588 (meters) COMP KB0684 Y - -4,926,226.861 (meters) COMP KB0684 Z - 4,037,138.456 (meters) COMP KB0684 LAPLACE CORR- -0.20 (seconds) DEFLEC99 KB0684 ELLIP HEIGHT- 164.133 (meters) (02/10/07) ADJUSTED KB0684 GEOID HEIGHT- -32.27 (meters) GEOID03 KB0684 DYNAMIC HT - 196.282 (meters) 643.97 (feet) COMP KB0684 KB0684 ------- Accuracy Estimates (at 95% Confidence Level in cm) -------- KB0684 Type PID Designation North East Ellip KB0684 ------------------------------------------------------------------- KB0684 NETWORK KB0684 ASSUMPTION 0.57 0.41 1.76 KB0684 ------------------------------------------------------------------- KB0684 MODELED GRAV- 980,049.7 (mgal) NAVD 88 KB0684 KB0684 VERT ORDER - FIRST CLASS I KB0684 KB0684.The horizontal coordinates were established by GPS observations KB0684.and adjusted by the National Geodetic Survey in February 2007. KB0684 KB0684.The datum tag of NAD 83(2007) is equivalent to NAD 83(NSRS2007). KB0684.The horizontal coordinates are valid at the epoch date displayed above. KB0684.The epoch date for horizontal control is a decimal equivalence KB0684.of Year/Month/Day. KB0684 KB0684.The orthometric height was determined by differential leveling KB0684.and adjusted in June 1991. KB0684 KB0684.Photographs are available for this station.

  27. KB0684.The X, Y, and Z were computed from the position and the ellipsoidal ht. KB0684.The ellipsoidal height was determined by GPS observations KB0684.and is referenced to NAD 83. KB0684 KB0684.The geoid height was determined by GEOID03. KB0684 KB0684 KB0684; North East Units Scale Factor Converg. KB0684;SPC IL W - 317,315.488 796,100.180 MT 1.00005484 +0 42 40.6 KB0684;SPC IL W - 1,041,059.23 2,611,872.01 sFT 1.00005484 +0 42 40.6 KB0684;SPC IL E - 316,974.300 238,460.283 MT 1.00002161 -0 27 19.6 KB0684;SPC IL E - 1,039,939.85 782,348.45 sFT 1.00002161 -0 27 19.6 KB0684;UTM 16 - 4,376,511.174 323,870.958 MT 0.99998195 -1 18 15.2 KB0684 KB0684! - Elev Factor x Scale Factor = Combined Factor KB0684!SPC IL W - 0.99997425 x 1.00005484 = 1.00002909 KB0684!SPC IL E - 0.99997425 x 1.00002161 = 0.99999586 KB0684!UTM 16 - 0.99997425 x 0.99998195 = 0.99995620 KB0684 KB0684: Primary Azimuth Mark Grid Az KB0684:SPC IL W - ASSUMPTION 1920 TP 1976 010 03 10.2 KB0684:SPC IL E - ASSUMPTION 1920 TP 1976 011 13 10.4 KB0684:UTM 16 - ASSUMPTION 1920 TP 1976 012 04 06.0 KB0684 KB0684|---------------------------------------------------------------------| KB0684| PID Reference Object Distance Geod. Az | KB0684| dddmmss.s | KB0684| KB1363 ASSUMPTION 1920 TP 1976 APPROX. 0.5 KM 0104550.8 | KB0684| KB0685 ASSUMPTION RM 2 7.062 METERS 01146 | KB0684| KB1368 ASSUMPTION AZ A PT 1976 489.179 METERS 0994730.6 | KB0684| KB1367 ASSUMPTION AZ MK 483.552 METERS 1001424.8 | KB0684| KB1362 ASSUMPTION A PT 1976 9.725 METERS 24325 | KB0684| KB1361 ASSUMPTION MUN TANK 145.607 METERS 24654 | KB0684| CI6654 ASSUMPTION RM 21.330 METERS 26717 | KB0684| KB0686 ASSUMPTION RM 3 26.388 METERS 27304 | KB0684|---------------------------------------------------------------------| KB0684 KB0684 SUPERSEDED SURVEY CONTROL KB0684 KB0684 ELLIP H (10/15/04) 164.141 (m) GP( ) 4 2 KB0684 NAD 83(1997)- 39 31 12.72890(N) 089 02 56.47672(W) AD( ) B KB0684 ELLIP H (07/17/98) 164.137 (m) GP( ) 4 1 KB0684 NAD 83(1986)- 39 31 12.73871(N) 089 02 56.46320(W) AD( ) 2 KB0684 NAD 27 - 39 31 12.59480(N) 089 02 56.15910(W) AD( ) 2 KB0684 NAVD 88 (07/17/98) 196.39 (m) 644.3 (f) LEVELING 3 KB0684 NGVD 29 (??/??/92) 196.484 (m) 644.63 (f) ADJ UNCH 1 1 KB0684 KB0684.Superseded values are not recommended for survey control. KB0684.NGS no longer adjusts projects to the NAD 27 or NGVD 29 datums. KB0684.See file dsdata.txt to determine how the superseded data were derived.

  28. POSITIONAL CHANGESStation: ASSUMPTION (KB0684) TIME POSITION DATUM SPAN Lat/Long/E Hgt POSITION SHIFT USSD/NAD 1901 – 1927 39-31-12.70400 89-02-56.05500 Undetermined NAD 27 1927 – 1986 39-31-12.59480 89-02-56.15910 4.186 m (13.73 ft) Undetermined NAD 83 (86) 1986 – 1997 39-31-12.73871 89-02-56.46320 8.512 m (27.93 ft) Undetermined NAD 83 (97) 1997 – 2007 39-31-12.72890 89-02-56.47672 0.442 m (1.45 ft) 164.141 NAD 83 (07) 2007 – (?) 39-31-12.72891 89-02-56.47681 0.002 m (0.06 ft) 164.133 0.008 m (0.03 ft)

  29. Reasons for Readjustment • Multiple epoch dates • Inconsistencies between states • Need to be Consistent with CORS • Compute Network and Local accuracies • Some HARNs exhibit 4 – 7 cm difference with CORS 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. Orthometric Height adjustment will not be attempted

  30. NSRS(2007) READJUSTMENT of NAD 83 ONLY GPS DATA WAS USED CONTINUOUSLY OPERATING REFERENCE STATIONS FEDERAL BASE NETWORK (A & B) COOPERATIVE BASE NETWORK (B) USER DENSIFICATION NETWORK (First) AIRPORT SURVEYS (B & First)

  31. www.ngs.noaa.gov/NationalReadjustment

  32. Errors • All real observations contain errors • Two types of errors • Random errors which mean to zero • systematic errors which do not • Least square will only give improved results if your errors are predominantly random Random error Systematic error

  33. A B 1 2 3 7 11 4 5 6 8 9 10 12 Example of redundancy Suppose we are trying to determine the distance between two points We have 5 measurements all have equal precision Any one measurement is enough to determine the distance but because every measurement contains measurement errors so each measurement gives a slightly different result

  34. This means that each time we add an equation, we have one unknown residual to solve for plus the distance So we will never have enough equations to solve for the unknowns Observation equations • For each observation we can write an equation relating the parameter we are trying to determine (the distance) to the observation and the residual.

  35. Least Square condition • Since we do not have 1 equation per unknown • We have to add at least one more so we have enough information to determine all of the unknowns • We add a condition that the sum of the squares of all of the residuals is a minimum • This just means that the data is as close to the parameters (in this case the mean value) as possible

  36. Weighting • All least square adjustments include some sort of estimate of the accuracy of the measurements • This allows measurements that are precise to have more importance (or weight) than approximate measurements • The weighting for each observation is equal to the inverse square of the standard deviation • The idea is that if then error is small the weighting the weighting is large

  37. Minimally Constrained Adjustment • Hold the minimum number of control points fixed to allow the least square process to work • One fixed point for GPS • 2 for triangulation survey without distance measurements • The purpose of this adjustment is to • Check the internal consistency of the network • Detect blunders or ill-fitting observations • Obtain accurate error estimates How big do you make the bolt holes?

  38. Critical t Critical t Outliers Outliers Residuals • Residuals are the difference between the observed survey measurements and values calculated form coordinates from the least squares adjustment • They follow a known statistical distribution • and we can use statistics to identify observations with residuals are large enough to represent blunders that should be investigated further s 4 3 2 1 1 2 3 4

  39. Fully Constrained Adjustment • Hold all control points in the network fixed at values from the NGS database • Minimum of 2 for GPS surveys • 3 for triangulation survey without distance measurements • The purpose of this adjustment is to • Reference the network to existing control and develop final coordinates for the new control points that are being established • Verify existing control. • If any control points are wrong • the standard error of unit weight and residuals will increase compared to the minimally constrained adjustment

  40. Helmert Blocks • Each state will comprise a separate block of data.

  41. Helmert Blocks • CORS/CGPS provided control at the top block CGPS coordinates were determined by Scripps’ Sector utility projected to the 2007.0 epoch. • An attempt was made to create a separate block of data for each state to minimize the number of junction observations between blocks. • California, Florida, Minnesota, North and South Carolina were broken into multiple blocks because of the number of stations located in these blocks.

  42. You are here HELMERT BLOCKING STRATEGY This is how each state fits into the National Readjustment

  43. The National Readjustment General Comments • The CORS/CGPS sites were the control • Only GPS projects participated • 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 HPGN stations.

  44. 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 • Order/Class codes will no longer be used

  45. SHIFTS (National results) < 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.

  46. ILLINOIS STATISTICS • Total # of Stations: 2515 • Max Horizontal Shift: 0.106 (m) • Average Hz Shift: 0.011 (m) • Max Vertical Shift: 0.173 (m) • Average Vt. Shift: 0.014 (m)

  47. NAD 83 Adjustment 2007 - Ellipsoid Height

  48. Time-line for National Readjustment Positions and Ellipsoid Heights All projects loaded in the NGS database prior to November 15, 2005 were included in the National Readjustment Projects submitted after 11/15/2005 were accepted and loaded into the database but were not included in the readjustment Completed adjustment by February 10, 2007 deadline New Datasheets including new positions and network accuracies available now. Project Report (pending)

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