Projections and Datums within ArcGIS Melita Kennedy 2012 Datum Series Sponsored by GPSMMS Subcommittee This is the third webinar in a 3-part Series on Datums. 1) Datum Primer – Dave Doyle* 2) GPS Software Datums - Joel Cusick / Alison Walker (Nov 18)** 3) 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 Topics • Esri projection engine • Coordinate systems • Transformations • Future work • Review Esri Projection Engine 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 PE library sections • Engine Objection creation & processing - Transformations - Projections - Math functions - • Factory - Predefined objects - - Coordinate systems, ellipsoids, units, etc Well-known ID lookup Number of Objects in PE Factory • 10 Angular Unit • 607 Datums • 57 Linear units • 635 GCS • 217 Spheroids • 1240 Geographic Transforms • 15 Prime Meridians • 44 Parameters • 3567 PCS • 14 Geographic methods • 117 Vertical Datums • 2 Horizontal methods • 124 VCS • 9 Vertical methods • • 74 Projections • 47 Vertical Transformations 17 Horizontal/Vertical CS Total = 6796 at 10.0 Number of Objects in PE Factory • 10 Angular Unit • 644 Datums • 59 Linear units • 671 GCS • 218 Spheroids • 1375 Geographic Transforms • 15 Prime Meridians • 44 Parameters • 4289 PCS • 14 Geographic methods • 126 Vertical Datums • 2 Horizontal methods • 133 VCS • 9 Vertical methods • • 76 Projections • 69 Vertical Transformations 17 Horizontal/Vertical CS Total = 7771 at 10.1.1 Coordinate Systems 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 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 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 spatial filter favorites create or import coordinate system search well-known ID 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 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 Coordinate System Demonstration Transformations Geographic transformations • ‘Datum’ transformations • Convert between GCS • Includes unit, prime meridian, and spheroid changes • Defined in a particular direction • All are reversible 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 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 Combined transformations ArcMap 10.1.1 transformations • • NAD_1927_To_NAD_1983_NADCON - ArcMap default - Until 10.1.1 No more default transformations! 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 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 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 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 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 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 NGS CORS coordinates website http://www.ngs.noaa.gov/CORS/coords.shtml 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 Geographic Transformation Demonstration Current and Future Work 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 Geodetic features • • Types - Geodesic - Great circle / great elliptic - Rhumb line / loxodrome - Normal section Measure tool Future work • Vertical transformations • Customizable ‘factory’ - • Limited selection of coordinate systems and transformations 14 parameter (time-based) datum transformations 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 14 parameter time-based transformation • Base 7 parameters are updated based on velocity values Review Review:Datums Change WGS84/ITRF Sats ITRF00 Base Provider Export Using NAD83(CONUS)CORS96 GIS SSF COR SHP How to Do it • In Garmin Workflows with DNRGPS (Formerly DNRGarmin)… • Tag all your data as “plain vanilla” “NAD83” Exported Coordinate System: Use this POSC Code: Use this PRJ Alaska Albers 3338 NAD 1983 Alaska Albers (Meters).prj UTM Zone 8 26908 NAD 1983 UTM Zone 8N.prj GCS NAD83 4269 (no projection GCS NAD 1983.prj 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 Exported Coordinate System: Use this PRJ File: Alaska Albers NAD 1983 (CORS96) Alaska Albers (Meters).prj UTM Zone 8 NAD 1983 (CORS96) UTM Zone 8N.prj GCS NAD83 NAD 1983 (CORS96) prj How to Do it • In ArcGIS *Assuming the standards of how the data “got to NAD83” were followed… Convert from: Into GCS_NAD_1983_CORS96 use: GCS_North_American_1983 None GCS_WGS_1984 Garmin/DNRGPS: Go Into GCS_NAD83 only Mapping Grade: WGS_1984_(ITRF00)_To_NAD_1983_CORS96 GCS_North_American_1983_HARN NAD_1983_CORS96_To_NAD_1983_HARN 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. 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/Document170369/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 Questions? Thank you!