How To Understand The National Geodetic Survey

Transcription

1 MODERNIZATION OF THE NATIONAL SPATIAL REFERENCE SYSTEMS Surveyors Association of West Jersey Mount Laurel September 9, 2010 ftp://ftp.ngs.noaa.gov/dist/daved/nj Dave Doyle NGS Chief Geodetic Surveyor

2 Mission and Vision of NGS To define, maintain and provide access to the National Spatial Reference System to meet our nation s economic, social, and environmental needs Maintain the NSRS means NGS must track all of the temporal changes to the defining points of the NSRS in such a way as to always maintain the accuracy in the NSRS definition. Vision - Modernize the Geopotential ( Vertical ) and Geometric ( Horizontal ) datums

3 Problems with NAD 83 and NAVD 88 NAD 83 is not as geocentric as it could be (approx 1-2 m). Surveyors don t see this Yet NAD 83 is not well defined with positional velocities. Most surveyors still think of NAD 83 as 2-dimensional (lat/long, N/E) NAVD 88 is realized by passive control (bench marks) most of which have not been releveled in 40 years. NAVD 88 does not account for local vertical velocities (subsidence and uplift) Southern NJ appears to be subsiding at 2-3 mm p/yr (CORS multi-year solution should confirm movements late 2010) Post glacial isostatic readjustment Subsurface fluid withdrawal Sediment loading Sea level rise Trenton is beach front in approx. 13,300 years.

4 The National Geodetic Survey 10 year plan Mission, Vision and Strategy Official NGS policy as of Jan 9, 2008 Modernized agency Attention to accuracy Attention to time-changes Improved products and services Integration with other fed missions 2018 Targets: NAD 83 and NAVD 88 re-defined Cm-accuracy access to all coordinates Customer-focused agency Global scientific leadership

5 1807 President Thomas Jefferson signs legislation establishing the Survey of the Coast

6 Global Satellite Triangulation Network

7 ECHO/PAGEOS Balloon Satellite type of satellite photographed by BC-4

8 BC-4 camera photograph stars in circular pattern satellite is a series of dots in straight line.

9 US Navy Transit Satellite 1964 (Military), 1967 (Civilian)

10 DOPPLER and VLBI

11 GLOBAL POSITIONING SYSTEM st NAVSTAR Satellite Launched (October 22, 1978) 1995 Fully Operational 2000 Selective Availability turned off (May 1, 2000) 2005 Additional Band L2C 2010 Additional Frequency L5 added (May 28, 2010) 2020? cm real-time accuracy?

12 The Global Navigation Satellite Systems (GNSS) Constellations Three positioning and navigation systems Navstar/GPS US (Currently 31) GLONASS Russia (Currently 19) Galilleo EU (Currently 2) Beidou (Big Dipper/Compass) China(?) US - GPS Russia - GLONASS All satellites available for positioning purposes. EU - Galilleo

13 National Spatial Reference System (NSRS) Consistent National Coordinate System Latitude Longitude Height Scale Gravity Orientation and how these values change with time

14 NSRS COMPONENTS National Shoreline - Consistent, accurate, and up-to-date Networks of geodetic control points - Permanently marked passive survey monuments National CORS Network - A network of GPS Continuously Operating Reference Stations Tools -Models of geophysical effects on spatial measurements -e.g., NADCON, INVERSE, SPCS83, UTMS, FORWARD

15 The NSRS has evolved 1 Million Monuments (Separate Horizontal and Vertical Systems) 70,000 Passive Marks (3-Dimensional) Passive Marks (Limited Knowledge of Stability) 1,400 GPS CORS (Time Dependent System Possible; 4-Dimensional) GPS CORS GNSS CORS

16 GEODETIC DATUMS HORIZONTAL 2 D (Latitude and Longitude) (e.g. NAD 27, NAD 83 (1986)) VERTICAL 1 D (Orthometric Height) (e.g. NGVD 29, NAVD 88, Local Tidal) GEOMETRIC 3 D (Latitude, Longitude and Ellipsoid Height) Fixed and Stable - Coordinates seldom change (e.g. NAD 83 (1996), NAD 83 (2007)) also 4 D (Latitude, Longitude, Ellipsoid Height, Velocities) Coordinates change with time (e.g. ITRF00, ITRF08)

17 National Geodetic Survey, Retrieval Date = AUGUST 23, 2010 KV6044 *********************************************************************** KV6044 DESIGNATION - DOT SOUTH KV6044 PID - KV6044 KV6044 STATE/COUNTY- NJ/MERCER KV6044 USGS QUAD - PENNINGTON (1995) KV6044 KV6044 *CURRENT SURVEY CONTROL KV6044 KV6044* NAD 83(2007) (N) (W) ADJUSTED KV6044* NAVD (meters) (feet) ADJUSTED KV6044 KV6044 EPOCH DATE KV6044 X - 1,278, (meters) COMP KV6044 Y - -4,703, (meters) COMP KV6044 Z - 4,099, (meters) COMP KV6044 LAPLACE CORR (seconds) DEFLEC09 KV6044 ELLIP HEIGHT (meters) (02/10/07) ADJUSTED KV6044 GEOID HEIGHT (meters) GEOID09 KV6044 DYNAMIC HT (meters) (feet) COMP KV6044 KV Accuracy Estimates (at 95% Confidence Level in cm) KV6044 Type PID Designation North East Ellip KV KV6044 NETWORK KV6044 DOT SOUTH KV KV6044 MODELED GRAV- 980,166.0 (mgal) NAVD 88 KV6044 KV6044 VERT ORDER - FIRST CLASS I KV6044 KV6044.The horizontal coordinates were established by GPS observations KV6044.and adjusted by the National Geodetic Survey in February KV6044 KV6044.The datum tag of NAD 83(2007) is equivalent to NAD 83(NSRS2007). KV6044.See National Readjustment for more information. KV6044.The horizontal coordinates are valid at the epoch date displayed above. KV6044.The epoch date for horizontal control is a decimal equivalence KV6044.of Year/Month/Day.

18 KV6044 KV6044; North East Units Scale Factor Converg. KV6044;SPC NJ - 158, , MT KV6044;SPC NJ - 518, , sft KV6044;SPC PA S - 106, , MT KV6044;SPC PA S - 350, ,792, sft KV6044;UTM 18-4,456, , MT KV6044 KV6044! - Elev Factor x Scale Factor = Combined Factor KV6044!SPC NJ x = KV6044!SPC PA S x = KV6044!UTM x = KV6044 KV6044 SUPERSEDED SURVEY CONTROL KV6044 KV6044 NAD 83(1996) (N) (W) AD( ) B KV6044 ELLIP H (06/06/05) (m) GP( ) 3 1 KV6044 ELLIP H (10/23/02) (m) GP( ) 4 1 KV6044 NAD 83(1996) (N) (W) AD( ) 1 KV6044 ELLIP H (05/14/99) (m) GP( ) 4 1 KV6044 NAD 83(1986) (N) (W) AD( ) 1 KV6044 NAVD 88 (06/06/05) (m) (f) LEVELING 3 KV6044 NGVD 29 (01/10/92) (m) (f) ADJUSTED 1 1 KV6044 KV6044.Superseded values are not recommended for survey control. KV6044.NGS no longer adjusts projects to the NAD 27 or NGVD 29 datums. KV6044.See file dsdata.txt to determine how the superseded data were derived.

19 ELLIPSOID - GEOID RELATIONSHIP H = Orthometric Height (NAVD 88) h = Ellipsoidal Height [NAD 83 (1996) or (2007)] N = Geoid Height (GEOID 09) H = h N H h Geoid N GEOID09 Ellipsoid GRS80

20 Tectonic Motions

21 HORIZONTAL VELOCITIES

22 VERTICAL VELOCITIES

23 International Earth Rotation and Reference System Service (IERS) ( 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). ITRF89, ITRF90, ITRF91, ITRF92, ITRF93, ITRF94, ITRF95, ITRF96, ITRF97, ITRF2000, ITRF2005

24 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)

25 Simplified Concept of NAD 83 vs. ITRF00 h 83 h 00 Earth s Surface ITRF 00 Origin NAD 83 Origin Identically shaped ellipsoids (GRS-80) a = 6,378, meters (semi-major axis) 1/f = (flattening)

26 Problems using traditional leveling (to define a National Vertical Datum) Leveling the country can not be done again Too costly in time and money (Estimate ~ 1B$) Leveling yields cross-country error build-up; problems in the mountains Leveling requires leaving behind passive marks Bulldozers and crustal motion do their worst

27 How accurate is a GPS-derived Orthometric Height? Relative (local) accuracy in ellipsoid heights between adjacent points will be better than 2 cm, at 95% confidence level Network accuracy (relative to NSRS) in ellipsoid and orthometric heights will be better than 5 cm, at 95% confidence level Accuracy of orthometric height is dependent on accuracy of the geoid model Currently NGS is improving the geoid model with more data, i.e. Gravity and GPS observations on leveled bench marks from Height Mod projects

28 Height Modernization Bottom line 1. Using GNSS is cheaper, easier than leveling 2. To use GNSS we need a good geoid model

29 Types and Uses of Geoid Height Models Gravimetric (or Gravity) Geoid Height Models Defined by gravity data crossing the geoid Refined by terrain models (DEM s) Scientific and engineering applications Composite (or Hybrid) Geoid Height Models Gravimetric geoid defines most regions Warped to fit available GPSBM control data Defined by legislated ellipsoid (NAD 83) and local vertical datum (NAVD 88, PRVD02, etc.) May be statutory for some surveying & mapping applications

30 GGPSBM1999: 6,169 total 0 Canada STDEV 9.2 cm (2 ) GGPSBM2003: 14,185 total 579 Canada STDEV 4.8 cm (2 )

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32 Transition to the Future GRAV-D Gravity for the Redefinition of the American Vertical Datum Official NGS policy as of Nov 14, 2007 $38.5M over 10 years Airborne Gravity Snapshot Absolute Gravity Tracking Re-define the Vertical Datum of the USA by 2018

33 Gravity Survey Plan National Scale Part 1 Predominantly through airborne gravity With Absolute Gravity for ties and checks Relative Gravity for expanding local regions where airborne shows significant mismatch with existing terrestrial

34 Gravity Survey Plan Part 2 Epochal (annual?) absolute gravity remeasurements at key areas GOCE for more global signatures (Gravity field and steady-state Ocean Circulation Explorer) Monitor changes in gravity over time and model geoid changes Use GNSS to monitor changes in ellipsoid heights GOCE Gravity field and steady-state Ocean Circulation Explorer March, 2009 ~ October, 2011

35 GRAV-D: Campaign I Testing Test varieties of flight heights / speeds / spacings for optimal benefit Test area for proof of concept to define vertical datum from GPS + gravimetric geoid

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40 CONTINUOUSLY OPERATING REFERENCE STATIONS (CORS) Installed and Operated by various Federal-State-local Agencies NOAA/National Geodetic Survey NOAA/OAR Global Systems Division U.S. Coast Guard - DGPS/NDGPS Corps of Engineers - DGPS FAA - WAAS/LAAS State DOTs County and City Academia Private Companies

41 REGIONAL CORS NETWORK

42 TRENTON (NJTR), NEW JERSEY Antenna Reference Point(ARP): TRENTON CORS ARP PID = DG7014 ITRF00 POSITION (EPOCH ) Computed in September 2004 using 25 days of data. X = m latitude = N Y = m longitude = W Z = m ellipsoid height = m ITRF00 VELOCITY Predicted with HTDP_2.7 September VX = m/yr northward = m/yr ITRF00 NAD 83(CORS96) VY = m/yr eastward = m/yr Horiz = 0.915m VZ = m/yr upward = m/yr EHt = 1.270m NAD_83 (CORS96) POSITION (EPOCH ) Transformed from ITRF00 (epoch ) = position NAD 83(NSRS in Sep. 2007) X = m latitude = N Y = m longitude = W Z = m ellipsoid height = m NAD_83 (CORS96) VELOCITY Transformed from ITRF00 velocity in Sep VX = m/yr northward = m/yr VY = m/yr eastward = m/yr VZ = m/yr upward = m/yr

43 You ve got mail! OPUS solution

44 OPUS-DB OBSERVATION DATA STREAM GPS data Mark Information photo(s) Local References NGS website: OPUS-DB NGS magic DATASHEET

45 OPUS DB Simple Shared Data NGS Archived

46 FLAVORS OF OPUS OPUS-S $$ Receivers 2 Hours of data Results not shared OPUS-RS $$ Receivers 15 Minutes of data Results not shared OPUS-DB $$ Receivers 4 Hours of data Results shared OPUS Tool Box OPUS-Projects $$ Receivers 2-4 Hours of data Multiple Receivers Network Solution Results shared or not LOCUS Leveling Online Computing Service Integration with GPS? Results shared or not

47 Ten-Year Milestones (2018) 1) NGS will compute a pole-to-equator, Alaskato-Newfoundland geoid model, preferably in conjunction with Mexico and Canada as well as other interested governments, with an accuracy of 1 cm in as many locations as possible 2) NGS redefines the vertical datum based on GNSS and a gravimetric geoid 3) NGS redefines the national horizontal datum to remove disagreements with the ITRF

48 Predicted Positional Changes in 2018 Vicinity of Trenton, NJ. (Computed at DOT SOUTH pid KV6044) HORIZONTAL = 1.30 m (4.3 ft) ELLIPSOID HEIGHT = m (- 4.1 ft) Predicted with HTDP ORTHOMETRIC HEIGHT = m (- 1.3 ft) Predicted with HTDP and USGG2009

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50 GOOD COORDINATION BEGINS WITH GOOD COORDINATES GEOGRAPHY WITHOUT GEODESY IS A FELONY