Projections and Datums within ArcGIS

1. Projections and Datums within ArcGIS Melita Kennedy

2. 2012 Datum Series Sponsored by GPSMMS Subcommittee This is the third webinar in a 3-part Series on Datums. • Datum Primer – Dave Doyle* • GPS Software Datums - Joel Cusick / Alison Walker (Nov 18)** • Projections and Datums in ArcGIS – Melita Kennedy (Dec 17)*** Tim Smith Chair; Joel Cusick Co-Chair * http://www.anymeeting.com/tgadgets/EC51DA87854B ** - Sharepoint Site – Datum Webinars *** - This Webinar Sharepoint Site – Datum Webinars

3. Topics • Esri projection engine • Coordinate systems • Transformations • Future work • Review

4. Esri Projection Engine

5. Esri projection engine • One universal library for all ESRI products • pe.dll • Not tied to just one product • Improve maintenance/ease of programming • Speed, consistent results, standardization • Accuracy – tight forward/inverse round trips • Must have inversibility • Engine versus Factory

6. Engine Objection creation & processing Transformations Projections Math functions Factory Predefined objects Coordinate systems, ellipsoids, units, etc Well-known ID lookup PE library sections

7. 10 Angular Unit 57 Linear units 217 Spheroids 15 Prime Meridians 44 Parameters 14 Geographic methods 2 Horizontal methods 9 Vertical methods 74 Projections 607 Datums 635 GCS 1240 Geographic Transforms 3567 PCS 117 Vertical Datums 124 VCS 47 Vertical Transformations 17 Horizontal/Vertical CS Number of Objects in PE Factory Total = 6796 at 10.0

8. 10 Angular Unit 59 Linear units 218 Spheroids 15 Prime Meridians 44 Parameters 14 Geographic methods 2 Horizontal methods 9 Vertical methods 76 Projections 644 Datums 671 GCS 1375 Geographic Transforms 4289 PCS 126 Vertical Datums 133 VCS 69 Vertical Transformations 17 Horizontal/Vertical CS Number of Objects in PE Factory Total = 7771 at 10.1.1

9. Coordinate Systems

10. ArcGIS 10.1 coordinate systems • Coordinate system definitions always stored in library • ‘prj files’ installed separately • At 10.1 over 5000 files • Now store the folder information in the library • Display a ‘virtual’ directory structure

11. NAD 1983 and variant support • GCS, UTM zones, SPCS zones, Albers • NAD 1983 • NAD 1983 HARN • NAD 1983 CORS96 • NAD 1983 NSRS2007 • NAD 1983 (2011) + UTM zones • State Plane zones in 10.1.2

12. ArcGIS 10.1 coordinate systems • User interface updated • ‘Layers’ • Listed each layer • Open to see its coordinate system • Now list each coordinate system • Open to see which layers use it

13. spatial filter favorites create or import coordinate system search well-known ID

14. Coordinate system search and filter • Spatial filter • Current extent • Layer extent (any in the map) • Custom extent • Search/filter by • Name • Only folders that contain matches will be shown • Well-known ID (WKID) aka 4326, 26906

15. Favorites • Now visible (and usable) everywhere • Stored in your user profile • C:\Documents and Settings\melita\Application Data\ ESRI\Desktop10.1\ArcMap\Coordinate Systems (Windows XP) • Supports folders • Import coordinate system from • Data • Prj file NEW

16. Coordinate System Demonstration

17. Transformations

18. Geographic transformations • ‘Datum’ transformations • Convert between GCS • Includes unit, prime meridian, and spheroid changes • Defined in a particular direction • All are reversible

19. Transformation methods • Equation-based • Molodensky, Abridged Molodensky, Geocentric Translation • Coordinate Frame, Position Vector, Molodensky-Badekas • Longitude Rotation, 2D lat / lon offsets • File-based • NADCON, HARN, NTv2

20. ArcMap 10.1 transformations • Sorted by applicability • Area of use • Accuracy • Will create compound (two-step) transformations automatically • Ex. NAD_1927_To_NAD_1983_NADCON + NAD_1983_To_WGS_1984_5

21. Combined transformations

22. ArcMap 10.1.1 transformations • NAD_1927_To_NAD_1983_NADCON • ArcMap default • Until 10.1.1 • No more default transformations!

23. Transformation metadata • Areas of use • Accuracy • C:\Program Files\ArcGIS\Desktop10.1\Documentation\ geographic_transformations.pdf http://support.esri.com/en/knowledgebase/techarticles/detail/21327

24. Methods in Alaska • Coordinate Frame • Equation-based • Seven parameters • 3 translations, 3 rotations, 1 scale factor (in XYZ) • NAD_1983_To_WGS_1984_5 • WGS_1984_(ITRF00)_To_NAD_1983 • NADCON / HARN • File-based • Generally most accurate • NAD_1927_To_NAD_1983_Alaska • No transformations released for current adjustments

25. Transformations with same parameters (1) Officially, NAD83 (CORS96) to ITRF96* NAD_1983_To_WGS_1984_5* NAD_1983_HARN_To_WGS_1984_3 Source: http://geodesy.noaa.gov/CORS/coord_info/ coordtrans_no_support_tables.shtml *Paper: http://www.ngs.noaa.gov/CORS/Articles/SolerSnayASCE.pdf Table 1, page, 51, Last column _5 is Default for DNRGPS And ArcGIS prior to 10.0

26. Transformations with same parameters (2) Officially, ITRF00 to NAD83 (CORS96) ITRF_2000_To_NAD_1983_CORS96 ITRF_2000_To_NAD_1983_HARN ITRF_2000_To_NAD_1983_2011 WGS_1984_(ITRF00)_To_NAD_1983_HARN WGS_1984_(ITRF00)_To_NAD_1983_CORS96 WGS_1984_(ITRF00)_To_NAD_1983_2011 WGS_1984_(ITRF00)_To_NAD_1983 Source: http://geodesy.noaa.gov/CORS/coord_info/ coordtrans_no_support_tables.shtml

27. NGS CORS past coordinates website http://geodesy.noaa.gov/CORS/coord_info/coordtrans_no_support_tables.shtml Paper: http://www.ngs.noaa.gov/CORS/Articles/SolerSnayASCE.pdf Table 2, page, 52

28. Transformations with same parameters (3) ITRF08/WGS84 transformations ITRF_2008_To_NAD_1983_2011 WGS_1984_(ITRF08)_To_NAD_1983_2011 Pacific Plate ITRF_2008_To_NAD_1983_PA11 WGS_1984_(ITRF08)_To_NAD_1983_PA11 Marianas Plate ITRF_2008_To_NAD_1983_MA11 WGS_1984_(ITRF08)_To_NAD_1983_MA11 Source: http://www.ngs.noaa.gov/CORS/coords.shtml

29. NGS CORS coordinates website http://www.ngs.noaa.gov/CORS/coords.shtml

30. Bookkeeping transformations Parameters are zeroes! ITRF_2000_To_WGS_1984 NAD_1983_CORS96_To_NAD_1983_HARN NAD_1983_CORS96_To_NAD_1983_NSRS2007 NAD_1983_CORS96_To_NAD_1983_2011 NAD_1983_HARN_To_NAD_1983_NSRS2007_1 NAD_1983_HARN_To_NAD_1983_2011 NAD_1983_NSRS2007_To_NAD_1983_2011 NAD_1983_NSRS2007_To_WGS_1984_1

31. Geographic Transformation Demonstration

32. Current and Future Work

33. Geodetic features • Editing • Advanced Editing toolbar • Lines, circles, and ellipses • Geoprocessing Tools • Bearing Distance to Line • XY to Line • Table to Ellipse • Buffer • Geographic coordinate system • Calculate Grid Convergence Angle

34. Geodetic features • Types • Geodesic • Great circle / great elliptic • Rhumb line / loxodrome • Normal section • Measure tool

35. Future work • Vertical transformations • Customizable ‘factory’ • Limited selection of coordinate systems and transformations • 14 parameter (time-based) datum transformations

36. Vertical transformation methods • Vertical Offset • Vertical Offset and Slope • VERTCON • Geoid models • EGM84, EGM96, EGM2008 • US geoid models • Generic model/file type for user-defined ones

37. 14 parameter time-based transformation • Base 7 parameters are updated based on velocity values

38. Review

39. WGS84/ITRF Review:Datums Change Sats ITRF00 Base Provider Export Using NAD83(CONUS)CORS96 GIS SSF COR SHP

40. How to Do it • In Garmin Workflows with DNRGPS (Formerly DNRGarmin)… • Tag all your data as “plain vanilla” “NAD83”

41. How to Do it • In Pathfinder Office, select the Projection file to match the Exported Coordinate System. • Today tag your CORS corrected data to “CORS96” NAD83

42. How to Do it • In ArcGIS *Assuming the standards of how the data “got to NAD83” were followed…

43. Conclusions • As spatial references continue to evolve, it is important to understand how such evolution affects the Mapping software that we use for collecting and processing GPS data. • As we navigate to previous GPS datasets or update them (at submeter), it is extremely important to transform properly to get back to the right place • Options in the field and office GPS software can change the spatial reference of the GPS data that we collect. • Esri software options can also change the spatial reference of any GPS data we collect. • Knowing how these changes occur can eliminate much confusion and lead to satisfactory positioning results.

44. References • Soler, T. & R.A. Snay (2004). Transforming positions and velocities between the International Terrestrial Reference Frame of 2000 and North American Datum of 1983, J. Surv. Engrg., ASCE, 130(2), 49-55. http://www.ngs.noaa.gov/CORS/Articles/SolerSnayASCE.pdf • Trimble, “GPS Pathfinder Office Software or the GPS Analyst Extension: Resolving the NAD 83 Datum Transformation Issue,” [online]. http://trl.trimble.com/docushare/dsweb/Get/Document-170369/SprtNote_PFOGPSA_NAD83Datum.pdf • Dr. Richard Snay is Retired Manager of the National Continuously Operating Reference Station (CORS) program and a geodesist with the National Geodetic Survey • http://support.esri.com/en/knowledgebase/techarticles/detail/21327

45. Questions?

46. Thank you!