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LOST IN TRANSFORMATION WVGIS 2014 Conference June 2-5, 2014 Christine Iksic

LOST IN TRANSFORMATION WVGIS 2014 Conference June 2-5, 2014 Christine Iksic. Coordinate Sytems Basics – WV SPC NAD 83 (what?) 3 Places Where Datums Matter Most Projections in ESRI Transformations in ESRI Datums & VRS Networks Checking In with NGS – DSWorld.

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LOST IN TRANSFORMATION WVGIS 2014 Conference June 2-5, 2014 Christine Iksic

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  1. LOST IN TRANSFORMATION WVGIS 2014 Conference June 2-5, 2014 Christine Iksic

  2. Coordinate SytemsBasics – WV SPC • NAD 83 (what?) • 3 Places Where Datums Matter Most • Projections in ESRI • Transformations in ESRI • Datums & VRS Networks • Checking In with NGS – DSWorld

  3. Coordinate systems are slippery… even if coordinates precise coordinates difficult to be certain • Coordinate systems assign a unique “address” to every point on Earth. • Coordinates are expressed relative to a datum.

  4. Projections Datums Unprojected Lat/Long Coordinate Systems UTM Projected State Plane Ellipsoids and Geoids Datums

  5. A datum specifies the earth-model (ellipsoid), and the origin associated with a particular set of coordinates. • It’s a function of a projection. • Datums provide the link between the earth and coordinate systems. • Without a datum, coordinates have no meaning. • There are many datums used worldwide. • Only one datum, WGS-84, is global, the rest are regional.

  6. What Language is your data speaking in? ITRF 00 NAD 27 GRS 80 WGS 84 NAVD 88 CORS NGVD 29 NAD 83

  7. NGS Datasheet

  8. Rostport, Pa

  9. Example - WVDOT Geo Spatial Policy “Henceforth, geospatial coordinates are to be collected utilizing technology capable of a 1-meter level of accuracy. .Techniques such as GPS or conventional surveying should be used to obtain positions at accuracies greater than 1 meter. GPS should be used to obtain positions at the highest possible accuracy.. The recommended standard for representing and reporting geospatial data is as follows” http://www.transportation.wv.gov/highways/programplanning/planning/grant_administration/wvtrails/Pages/gps.aspx

  10. 4790 4790 350m 150m 650m 4789 4789 610m Map Corner NAD27 541 542 541 542 Map Corner NAD83 NAD27 Coordinates = 350m, 650m NAD83 Coordinates = 150m, 610m

  11. WGS 84 NAD 83 (2011) NAD 27 10 – 120+ meters 1 meter

  12. WHY the difference, WHAT changed? Epochs = Adjustments • NAD83 or NAD83 CONUS = 1986 adjustment included NO GPS • NAD83 HARN = 1992-1993 adjustment were High Accuracy Reference Network (HARN); done state by state; differences between border areas • NAD83 CONUS CORS 96 - passive • NAD83 (NSRS2007) = 2007 adjustment GPS data only • NAD83 (2001)= 2011 adjustment CORS stations readjusted and held fixed as primary control

  13. NETWORK STATUS HPGN/HARN & STATEWIDE 1991 GPS222 1996 1992 1996 1991 GPS1048 GPS341 1991 GPS197 1996 GPS805 reos 7/96 GP S291 1993 1994 reos-1996 GPS941 GPS1047 reobs 9/97 1996 GPS730 GPS606 1994 1995 1992 1995 GPS1121 1997 1997 GPS404 GPS887 1994 1991 GPS394 GPS882 GPS GPS260 GPS1178 1997 1997 1995 1993 1200 GPS633 1992 GPS908 1992 1993 GPS1150 GPS1179 GPS610 reos-6/95-GPS904 GPS412 GPS611 1995 GPS419 1992 1990 -GPS120 1997 GPS852 1993 GPS376 GPS1133 1993 1994 1992 GPS725 GPS366 GPS721 1992 GPS585 1990 1992 GPS383 reos 1/96 GPS936 -GPS170 GPS450 1993 GPS667 1997 . GPS & CLASSICAL ADJUSTMENTS COMPLETED GPS ADJUSTMENT COMPLETED GPS577

  14. ESRI • Data Frame Properties • Geodatabase / Layers • Trimble (other GPS) 3. GPS a. Autonomous vs. Differential Correction ArcPad ArcMobile TerraSync, TerraFlex, others

  15. Esri provides form controls for selecting the coordinate system (geographic or projected) for a feature class and also for the data frame of a map document in ArcMap and ArcCatalog.  When the datums differ, you are prompted for a datum transformation in ArcMap. • Data Frame – select projection (prj) • Layers – define projection (prj)

  16. Projections – ESRI 10.1 newer

  17. Transformations What do you select, Yes, No, or Transformations?

  18. Transformations • Defined in one direction but are inversible – use in either direction. • _1, _2,_3, _4, _5 indicates ordered they were defined. • _5 most common to CONUS • Select correct transformation everytime. • Prior to 10.1 ESRI had no transformation available to NAD83 CORS 96 or 2011. NAD83 HARN was the closest. Today ESRI is current with NGS.

  19. Transformations From Layers Datum To Data Fram Datum

  20. Trimble (other GPS) 3. GPS - Autonomous, WAAS, or VRS each field software has slightly different workflow. a.ArcPad b.ArcMobile http://positionsblog.trimble.com/?p=234 c.TerraSync, TerraFlex, others Todays Demo / Instruction

  21. Autonomous GPS= WGS84 ITRF 00 • Differential Correction or VRS Real Time Correction will shift data to the reference frame and datum of correction source. Verify! • WVVRS and KeyNetGPS both NAD83 2011 VRS = NAD83 2011 WAAS or Autonomous GPS = WGS84

  22. Autonomous GPS= WGS84 ITRF 00 • No matter what you set coordinate system to in collector raw data in file is WGS84 ITRF00

  23. Differentially corrected GPS data are always in terms of the corrections source’s reference frame. • WVVRS and KeyNetGPS both NAD83 2011 • You can change the datum of your data depending on the settings under real time settings!! • In order to read NAD83 2011 from the collector both the Real Time Settings Datum & Coordinate System Datum must be NAD83 (CONUS) i.e a 0 transformation

  24. Live TerraSync Demo Setup Coordinate System Real-Time Settings

  25. Verification of accuracy is essential to gain confidence • DSWorld – NGS use this NGS software to find datasheets with Google Earth. • DSWorld– link to download • Know your coordinates • Know the language your data is speaking

  26. Differentially corrected GPS data are always in terms of the corrections source’s reference frame. • Verify reference frame of differential source • Two options • Base Provider Properties = WGS84 / ITRF00 • Base File (CORS) = NAD 83 (2011)

  27. Exporting a shapefile requires an ESRI .prj file be selected. • 10.1 prj files aren’t automatically accessible • Save prj file in ESRI to Favorites • Browse to ESRI Favorites in PFO to find prj file. • Select the correct datum! • A transformation can/typically occurs here on export based on datum selected • ITRF to NAD83 2011

  28. Common PP Workflow • Since our Reference Frame is CORS – Base Provider Properties • Our GPS data is corrected against a source that is in WGS84 or ITRF00 • Export to State Plane NAD83 (2011) / Select Correct prj file • And our GIS is in NAD83(1986) or CONUS or just NAD83 • We therefore define an NAD83 (2011) to NAD83 CONUS Transformation • If GIS is in WGS84 define a transformation from NAD 83 (2011) to WGS 84 (00)

  29. Pathfinder Office Differential Correction Base Provider or Base File Option Export to proper datum Select .prj file Save prj file to Favorites in ESRI 10.1 or 10.2

  30. Reference Frames Reference Frames • CORS Post Process = ITRF00 = WGS84 • Autonomous GPS = WGS84 = ITRF00 • WAAS = ITRF00 = WGS84 • NDGPS (Radio DGPS) = NAD83 (CORS96) • OMNISTAR (Satellite DGPS) = NAD83 (CORS96) • VRS (most) = NAD83 (2011)

  31. Review Review • Identify the proper reference frame for different differential sources – VRS and Post-Processing • Learn how to apply the correct datum transformation inside the GPS and back in the GIS. • Was there a correction or export, was there a transformation applied? • Does the prj file match the actual data (not always right.) • Tell ESRI what transformation to use. Don’t click YES. • Ask and Tell NAD 83 WHAT???!!!! • NAD83 (2011) ≠ WGS84 about 4.3 feet

  32. DON’T GET LOST in TRANSFORMATION Coordinate System? Datum?

  33. Questions Questions • Christine Iksic cmi@laserinst.com 412-512-5665

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