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Datums and Projections Demystifying the Reference Frame

Datums and Projections Demystifying the Reference Frame. Georgia Geospatial Conference 2012 Where W e Are Now. Presentation by Lonnie Sears, LS Originator ; Dave Doyle NGS Chief Geodetic Surveyor dave.doyle@noaa.gov , 301-713-3178.

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Datums and Projections Demystifying the Reference Frame

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  1. Datums and ProjectionsDemystifying the Reference Frame Georgia Geospatial Conference 2012 Where We Are Now Presentation by Lonnie Sears, LS Originator ; Dave Doyle NGS Chief Geodetic Surveyor dave.doyle@noaa.gov, 301-713-3178

  2. 1807President Thomas Jefferson signs legislationestablishing the Survey of the Coast

  3. Our Positioning History What’s In a Name? 1807 - Survey of the Coast 1836 - Coast Survey 1878 - US Coast and Geodetic Survey 1970 - National Ocean Service National Geodetic Survey 1970 - National Geodetic Survey (NOS geodetic functions)

  4. ACRONYMS US R NAD 27 GRS 80 ITRF 00 CORS WGS 84 NAVD 88 NGVD 29 NAD 83

  5. GLOBAL NAVIGATION SATELLITE SYSTEMS(GNSS) • POTENTIAL CONSTELLATION DEVELOPMENTS • (10 Years??) • GPS MODERNIZATION – BLOCK IIR-M & III • GLONASS ENHANCEMENTS • EUROPEAN UNION - GALILEO • CHINA - COMPASS • 100+ Satellites • Second and Third Civil Frequency – GPS • More Robust Signal Transmissions • Real-Time Unaugmented 1 Meter (or better!) Accuracy

  6. GRACE Gravity Model 01 - Released July 2003 Orthometric Heights are related to the Geoid Image credit: University of Texas Center for Space Research and NASA

  7. THE ELLIPSOIDMATHEMATICAL MODEL OF THE EARTH N Horizontal Coordinates and Ellipsoid Heights are related to the Ellipsoid b a a = Semi major axis b = Semi minor axis f = a-b = Flattening a S

  8. An ellipsoid of revolution is the figure which would be obtained by rotating an ellipse about its shorter axis. An ellipsoid of revolution describing the figure of the Earth is called a reference ellipsoid. Earth GRS80 NAD83 • b = 6,356,752.31414 m Squash the sphere to fit at the poles • a= 637813.000007 meters • b= 6356752.31414 meters • f= 1/((a-b)/a) = 298.2572220972 • a = 6,378,137.00000 m

  9. ELLIPSOID - GEOID RELATIONSHIP H = Orthometric Height(NAVD 88) h = Ellipsoidal Height [NAD 83 (2007) or (CORS96)] N = Geoid Height (GEOID 09) H=h– [N] h H N GEOID09 Geoid Ellipsoid GRS80

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

  11. NATIONAL SPATIAL REFERENCE SYSTEM • ACCURATE-- cm accuracy on a global scale • MULTIPURPOSE-- Supports Geodesy, Geophysics, Land Surveying, Navigation, Mapping, Charting and GIS activities • ACTIVE-- Accessible through Continuously Operating Reference Stations (CORS) and derived products • INTEGRATED-- Related to International services and standards (e.g. International Earth Rotation and Reference Systems Service, International GNSS Service etc.)

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

  13. GEODETIC DATUMS • A set of constants specifying the coordinate system used for geodetic control, i.e., for calculating coordinates of points on the Earth. Specific geodetic datums are usually given distinctive names. (e.g., North American Datum of 1983, European Datum 1950, National Geodetic Vertical Datum of 1929) Characterized by: A set of physical monuments, related by survey measurements and resulting coordinates (horizontal and/or vertical) for those monuments

  14. GEODETIC DATUMS • HORIZONTAL • 2-D (Latitude and Longitude) (e.g. NAD 27, NAD 83 (1986)) • VERTICAL/GEOPOTENTIAL • 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 (1993), NAD 83 (2007)) also 4-D (Latitude, Longitude, Ellipsoid Height, Velocities) Coordinates change with time (e.g. ITRF00, ITRF05)

  15. 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

  16. VERTICAL DATUMS • A set of fundamental elevations to which other elevations are referred. • Datum Types • Tidal– Defined by observation of tidal variations over some period of time • (MSL, MLLW, MLW, MHW, MHHW etc.) • (NOS Center for Operational Oceanographic Products and Services) • (CO-OPS) • Geodetic– Tided to Local Mean Sea Level at one or more points at some epoch • (NAVD 88, IGLD85)

  17. HISTORICAL VERTICAL DATUMS OF THE UNITED STATES First General Adjustment - 1899 Second General Adjustment - 1903 Third General Adjustment - 1907 Fourth General Adjustment - 1912 Sea Level Datum of 1929 National Geodetic Vertical Datum of 1929 (NGVD 29) Guam 1963

  18. NGVD29 The National Geodetic Vertical Datum of 1929 is referenced to 26 tide gauges in the US and Canada

  19. NAVD88 The North American Vertical Datum of 1988 is referenced to a single tide gauge in Canada

  20. VERTICAL DATUMS OF THE UNITED STATESCurrent Reference Systems North American Vertical Datum of 1988 (NAVD 88) Federal Register Notice: Vol. 58, No. 120, June 24, 1993, pg. 34245 “Affirmation of Vertical Datum for Surveying and Mapping Activities” American Samoa Vertical Datum of 2002 (ASVD 02) Northern Marians Vertical Datum of 2003 (NMVD 03) Guam Vertical Datum of 2004 (GUVD 04) Federal Register Notices for American Samoa, Guam and Northern Marians: Vol. 74, No. 13, January 22, 2009, pgs 3990 - 3991

  21. VERTICAL DATUMS OF THE UNITED STATESWorks in Progress Puerto Rico Vertical Datum of 2002 (PRVD 02) Virgin Island Vertical Datum of 2009 (VIVD 09) Hawaiian Islands Vertical Datum (HIVD)

  22. HISTORICAL HORIZONTAL DATUMS OF THE UNITED STATES Bessel Ellipsoid Camp Colonna Datum St. Paul Island Datum New England Datum Flaxman Island Datum UnAlaska Datum U.S. Standard Datum Golofnin Bay Datum Valdez Datum North American Datum Kripniyuk Datum Yakutat Datum North American Datum of 1927 Point Barrow Datum Yukon Datum Johnson Island 1961 Puerto Rico Datum Port Clarence Datum Midway Astro 1961 SE Alaska Datum Old Hawaiian Datum American Samoa Datum 1962 St. George Island Datum Wake Island Astro 1952 St. Lawrence Island Datum Guam Datum 1963 Barter Island Datum St. Michael Datum

  23. NORTH AMERICAN DATUM OF 1983 Federal Register Notice: Vol. 54, No. 113, June 14, 1989, pg. 25318 “Affirmation of Datum for Surveying and Mapping Activities” NAD 83 (1986) – 2D & passive ~ 1m national integrity (1986 – 1990) NAD 83 (199x) – 3D & passive ~ 10 cm national integrity (1990 – 1997) NAD 83 (CORS96) – 4D & active ~ 2 cm national integrity (1994 – Present) NAD 83 (2007) – 3D & passive ~ 2 cm relative to CORS (2007 – Present)

  24. Tectonic Motions

  25. 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). ITRF89, ITRF90, ITRF91, ITRF92, ITRF93, ITRF94, ITRF95, ITRF96, ITRF97, ITRF2000, ITRF2005, ITRF2008, ITRF2010

  26. 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)

  27. ARE NAD 83 & WGS 84 THE SAME? IT DEPENDS If requirements are greater than 3m then Yes If requirements are less than 3m then No Federal Register Notice: Vol. 60, No. 157, August 15, 1995, pg. 42146 “Use of NAD 83/WGS 84 Datum Tag on Mapping Products”

  28. WORLD GEODETIC SYSTEM 1984 DATUM = WGS 84(G873) 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(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 DATUM = WGS 84 RELEASED - SEPTEMBER 1987 BASED ON OBSERVATIONS AT MORE THAN 1900 DOPPLER STATIONS HOW MANY WGS 84s HAVE THERE BEEN???? DATUM = WGS 84(G730) 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)

  29. ARE NAD 83 & WGS 84 THE SAME? NAD 83 to ITRF00 dX = 0.9956 m dY = - 1.9013 m dZ = - 0.5215 m S = 0.62 x 10-9 rX = 25.915 mas rY = 9.426 mas rZ = 11.599 mas

  30. MY SOFTWARE SAYS I’M WORKING IN WGS-84 Unless you are doing autonomous positioning (point positioning +/- 6-10 meters) you’re probably NOT in WGS-84 Project tied to WGS-84 control points obtained from the Defense Department -- Good Luck! You’re really working in the same reference frame as your control points -- NAD 83?

  31. PLANE COORDINATE SYSTEMS • STATE PLANE AND UNIVERSAL TRANSVERSE MERCATOR GRID COORDINATES ARE A DIRECT MATHEMATICAL CONVERSION FROM LATITUDE AND LONGITUDE TO A CARTESIAN NORTHING AND EASTING (Y & X) COORDINATE SYSTEM, AND MUST MAINTAIN THE SAME DATUM TAG [e.g. NAD 27 or NAD 83] AS THE LATITUDE AND LONGITUDE)

  32. So What Is A Projection NORTHING EASTING

  33. MAP PROJECTIONSCONIC AND CLYNRIDCAL

  34. UTM ZONES

  35. STATE PLANE COORDINATE ZONES

  36. What Are State Plane Coordinates • State plane coordinates are the projection of latitudes and longitudes from the GRS80 ellipsoid To: • A flat mapping surface that is usually defined by state law

  37. STATE PLANE COORDINATE SYSTEM1927 • Developed by U.S. Coast and Geodetic Survey from a request in 1933 from the North Carolina Department of Transportation • Two basic map projections used: • Lambert Conformal Conic – States or parts of states that have a more East-West orientation • Transverse Mercator – States or parts of states that have a more North-South orientation • Zone boundaries along International, State and county boundaries • Zones typically 154 miles wide – this limits the maximum geodetic to grid distance distortion to 1:10,000 • All coordinate values in U.S. Survey Feet • Conversions to/from latitude & longitude calculated using tables • (e.g. USC&GS Special Publication. 316 Plane Coordinate Projections Tables – New Jersey) • State Plane Coordinates by Automatic Data Processing (USC&GS 62-4)

  38. STATE PLANE COORDINATE SYSTEM1983 • Geometric parameters of original SPC zones left unchanged unless requested by “the State” • All states get new false northing and false easting defined in meters. • All values in meters – conversions to feet defined by individual state legislation or Federal Register Notice • 1 m = 3.2808333333. U.S. Survey Feet • 1 m = 3.2808398950 International Feet

  39. Utah is now a U.S. Survey Foot State (Blue)

  40. PLANE COORDINATE CONVERSION TOOLS UTM UTMS (Both NAD 27 & NAD 83) http://www.ngs.noaa.gov/TOOLS/utm.shtml CORPSCON (Both NAD 27 & NAD 83) http://crunch.tec.army.mil/software/corpscon/corpscon.html STATE PLANE COORDINATES GPPCGP (NAD 27 only) SPCS83 (NAD 83 only) http://www.ngs.noaa.gov/TOOLS/spc.shtml CORPSCON (Both NAD 27 & NAD 83) http://crunch.tec.army.mil/software/corpscon/corpscon.html

  41. DATUM TRANSFORMATIONS • 1. WHAT DATUM ARE THE EXISTING COORDINATES/HEIGHTS ON? • 2. WHAT DATUM DO I WANT THE NEW COORDINATES/HEIGHTS ON? • 3. HOW LARGE A GEOGRAPHICAL AREA DO I WANT TO CONVERT AT ONE TIME? • 4. HOW MANY POINTS ARE COMMON TO BOTH DATUMS? • 5. WHAT IS THE DISTRIBUTION OF THE COMMON POINTS? • 6. HOW ACCURATE ARE THE EXISTING COORDINATES/HEIGHTS? • 0.01 Meter • 0.1 Meter • 1.0 Meter • 7. HOW ACCURATE DO I WANT THE NEW COORDINATES/HEIGHTS?

  42. DATUM TRANSFORMATION IDEAL METHOD • SATISFIES ALL USERS’ REQUIREMENTS • CAPABLE OF TRANSFORMING LARGE DATASETS • NEAR-REAL TIME APPLICATIONS • SIMPLE - METHOD SHOULD NOT REQUIRE AN EXPERT OR DECISIONS TO BE MADE • ACCURATE

  43. DATUM TRANSFORMATIONS • MOLODENSKY • For continental regions accuracy can be +/- 8 to 10 meters • Does not model network distortions very well. • Assumes heights in both systems are ellipsoidal (NAD 27 did not have ellipsoidal heights).

  44. NGS DATUM TRANSFORMATION MODELS VERTCON (NGVD 29 only) NADCON (NAD 27, OLD HAWAIIAN, PUERTO RICO, 3 ALASKA ISLANDS) (HPGN/HARN) Federal Register Notice: Vol. 72, No. 132, July 11, 2007, pg. 37732 “Notice to Adopt a Standard Model fro Mathematical Vertical Datum Transformations” Federal Register Notice: Vol. 55, No. 155, August 10, 1990, pg. 32681 “Notice to Adopt Standard Method for Mathematical Horizontal Datum Transformation”

  45. DATUM TRANSFORMATIONS • MOLODENSKY • Converts latitude, longitude and ellipsoidal height to X,Y,Z Earth-Centered Coordinates. • Applies a 3-dimensional change in the origin (dX, dY,dZ) • Applies a change in the size and shape of the reference ellipsoid • Converts new X,Y,Z Earth-Centered Coordinates back to latitude, longitude and ellipsoidal height

  46. MOLODENSKY TRANSFORMATION

  47. d= +0.12438 dλ = -1.86547 d= +0.12354 dλ = -1.8594 d= +0.12431 dλ = -1.86291 d= +0.12441 dλ = -1.83879 NADCON d= +0.12344 dλ = -1.87842 d= +0.12249 dλ = -1.88963 d= +0.12396 dλ = -1.85209 = +0.12423 λ = -1.81246 d= +0.12568 dλ = -1.83364 d= +0.12449 dλ = -1.88905 d= +0.12640 dλ = -1.85407 d= +0.12499 dλ = -1.86543

  48. COORDINATE COMPARISONNAD 27 to NAD 83(1993) • MOLODENSKY • ADJUSTED vs. TRANSFORMED • Station: OBSERVATORY (HV7843) • LATITUDELONGITUDE • 38-12-06.79868 077-22-22.35067 - PUBLISHED • 38-12-06.59040077-22-22.34223 - MOLODENSKY • .20828” .00844” • 6.422 m 0.205 m • THIS CORRESPONDS TO A POSITIONAL • DIFFERENCE OF 6.425 m (21.08 ft)

  49. COORDINATE COMPARISONNAD 27 to NAD 83(1993) • NADCON • ADJUSTED vs. TRANSFORMED • Station: OBSERVATORY (HV7843) • LATITUDELONGITUDE • 38-12-06.79868 077-22-22.35067 - PUBLISHED • 38-12-06.79920077-22-22.34823 - NADCON • .00052” .00244” • 0.016 m 0.059 m • THIS CORRESPONDS TO A POSITIONAL • DIFFERENCE OF 0.061 m (0.20 ft)

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