Working with the Wisconsin County Coordinate Systems (WCCS) A.J. Wortley, Jay Yearwood

1. Working with the Wisconsin County Coordinate Systems (WCCS)A.J. Wortley, Jay Yearwood

2. Wisconsin County Coordinate Systems • Who is using the County Coordinate Systems? • Who is confident that their data is defined correctly?

3. What are the Wisconsin County Coordinate Systems? • Individual counties began developing their own coordinate systems in the 1980s to support large-scale local mapping • Designed to minimize ground-to-projected-grid differentials • WisDOT contracted for development of county-based coordinate systems in 1993

4. More on the Wisconsin County Coordinate Systems (WCCS) • Based on a mathematical technique that modifies the underlying GRS80 spheroid for each county • Documented in “Wisconsin Coordinate Systems” handbook published by State Cartographer’s Office

5. Why Project Data to or from WCCS? • Not necessarily a problem if you always work inside a particular county • May be an issue if you are trying to use GIS data from more than one county • Locally-produced data is becoming more widely available and need to be integrated on a regional or statewide basis

6. How is Projecting Data to or from WCCS a Problem? • GIS users often expect projection of WCCS-referenced data to be quick and easy • Most GIS software lack tools that handle WCCS projection in a reliable & straightforward manner • Little or no documentation of best practices exists

7. How is Projecting Data to or from WCCS a Problem? (continued) • Finding a method for projecting WCCS-referenced data can be time-consuming & frustrating • Users (including consultants AND software) can easily define or project WCCS data incorrectly, resulting in positional offsets

8. Defining Terms Used in Projecting Data • First, a few caveats… • This is not a complete or rigorous discussion of projection-related issues (not enough time) • For convenience, we take “Projection” (noun) to be any combination of coordinate system, map projection, and reference datum or spheroid • For more technical info, refer to “Wisconsin Coordinate Systems” handbook...

9. Defining Terms Used in Projecting Data (continued) • Projection Definition: Assigning a projection to a spatial data set • Projection Transformation: Physically transforming spatial data from one projection to another projection (“hard” projection) • Projection On-the-Fly: Data stored in different projections are temporarily presented in a single projection for display purposes (“virtual projection”)

10. How are Projection Functions Handled in ArcGIS? Projection Definition • ArcGIS version 8 • Users must enter WCCS parameters • Problems arise because parameters for both a custom spheroid and datum are required • ArcGIS version 9 • Includes WCCS parameters • Not all WCCS parameters have been tested and verified

11. How are Projection Functions Handled in ArcGIS? (continued) Projection Transformation • Note:Projection of source data must be defined prior to the actual projection! • ArcGIS version 8 • Offers users a drop-down list of transformation methods when using WCCS...

12. How are Projection Functions Handled in ArcGIS? (continued) Projection Transformation • ArcGIS version 8- suggested transformation methods: Best: • Use “Geocentric Translation” with “0” (zero) for all parameters Alternate: • Use NADCON transformation when going from NAD27 to WCCS • Use HARN transformation when going from WCCS to DD, WCCS to NAD83, or NAD83 to WCCS

13. How are Projection Functions Handled in ArcGIS? (continued) Projection Transformation • ArcGIS version 9 - first the bad news… • No drop-down list of transformation methods when using WCCS • Transformation must be typed manually from a list of “valid transformation methods”

14. How are Projection Functions Handled in ArcGIS? (continued) Projection Transformation • ArcGIS version 9 - the good news… • Projection wizard supports projection from WCCS to regional/statewide systems such as WTM83/91 • ...but not the reverse, nor from WCCS to WCCS • Better news about projection on-the-fly

15. How are Projection Functions Handled in ArcGIS? (continued) Projection Transformation • Workstation ArcInfo • Has been used successfully for years to project to or from WCCS • Different organizations use different approaches • Procedures not agreed upon or well documented • Most orgs are migrating to ArcGIS for these tasks

16. How are Projection Functions Handled in ArcGIS? (continued) Projection Transformation • Verify your projection methodology! • Always recommended when using new methods • Verify by comparing your projected data to the same data projected using an established method • Compare to sample test data, or • Compare with sample points projected using WISCON (point data only) • DON’T rely on results from other CAD/GIS software • Turn off on-the-fly projection

17. How are Projection Functions Handled in ArcGIS? (continued) Projection On-the-Fly • ArcGIS version 9 • On-the-fly projectionappears to work for vector WCCS data • On-the-fly projectionof raster data from WCCS to regional/statewide systems works... • ...but not the reverse

18. How are Projection Functions Handled in ArcGIS? (continued) Projection On-the-Fly • ArcGIS version 9 • Use with caution!! • All data must first be properly defined • If not, erroneous projection on-the-fly may result • ...despite the appearance that all is working fine!

19. Other Projection Frontiersto be Explored • Further testing and documentation of projection tools is needed! • Differences in projection functionality between ArcInfo, ArcView & ArcGIS versions 8 or 9 and other software are not well documented • Geodatabase “Spatial Layer Definitions” are not well understood, tested or documented

20. Wisconsin Land Information Association WCCS Task Force • Mission: “investigate, analyze, and document…software implementations of data conversions to and from the WCCS” • Task Force to make recommendations to simplify these conversions • Includes representatives from academic, government & private sectors • For info about the work of the Task Force, see: http://www.geography.wisc.edu/sco/coordsys/index.php

21. Wisconsin Land Information Association WCCS Task Force (cont.) • Based on user frustration and inconsistent software definitions, Task Force recommended the redesign of the WCCS. • Redesign was endorsed by WLIA, WLIB, WSLS, WCSA, LION • Grant obtained for funding of redesign. • Work began Summer 2005 • Redesign done, in QC phase

22. WCCS Redesign • To simplify use of the Wisconsin County Coordinate Systems (WCCS), the WLIA Task Force on Wisconsin Coordinate Systems has recommended their re-design. The re-designed systems are all to be based upon the GRS 80 reference ellipsoid, without the need to change any ellipsoid parameters during coordinate transformations. In addition, coordinate shifts between the original and re-designed systems are to be negligible so that legacy databases can be integrated with new data without concern for positional discrepancies. The target maximum absolute value in any coordinate shift (easting (X) or northing (Y)) is five millimeters. -A Methodology for Re-Design of the Wisconsin County Coordinate Systems Draft Report

23. What to Expect? • More complete info at WSLS, WLIA (better timeframe) • Redesign to be complete on April 2006. • Parameters will be submitted to software vendors to be incorporated into next releases. • Regional presentations to be done around the state. • Follow-up presentations at major conferences.

24. What YOU will need to do • Remember to verify new projection transformation methods AND your data! • Check the WCCS Task Force website for sample test coordinate data • Use multiple conversion software for comparison. • Use WISCON (this is not an endorsement) • Desktop point data projection utility • Developed under contract to WisDOT • May order from private vendor; contact info on SCO site • Cost approximately $200 per copy • Vendor is not known for prompt replies or for support...

25. What YOU need to do now • Verify your data • Verify your data • Verify your data

26. Question-and-Answer