WI Coordinates

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WI Coordinates

WCCS (Wis County Coordinate System) &
WISCRS (Wis Coordinate Reference Systems)

Wisconsin County Coordinates - Then and Now

WLIA's Wisconsin Coordinate System Task Force was formed by the State Cartographer's Office in early 2004. The intent was to explore concerns raised by a number of GIS users over apparent errors and inconsistencies in data conversions to and from the Wisconsin County Coordinate System (WCCS). Material documenting the task force's activities are located at the State Cartographer's website at this link

In a nutshell

The problems arose from the WCCS use of "raised" ellipsoids to fit the grid to the ground. This in essence resulted in a different ellpsoid for each system. Since the semi-minor and semi-major ellipsoid axes were increased by the same amount the flattening (f) and eccentricity (e) for each elliposoid used was different.

Positional error would not be introduced when converting between coordinate systems if the user accounted for the semi-major and -minor axes increases. However many software packages assumed a datum-to-datum transformation was necessary when converting coordinates since each county ellipsoid differed from the GRS 80 ellipsoid used for all NAD 83 (19xx) positions. Different software handled the conversion differently resulting in different positions. Some of thesedifferences were pretty substantial (in the range of feet).

A summary of equations and parameters used for the WCCS are in the paper Equations and Parameters for Wisconsin Coordinate Systems.

WISCRS

It was decided to redesign the county systems using the standard GRS80 ellipsoid. Similar projections were used with different parameters to ensure positional differences of less than 5mm from that of WCCS. The redesign methodology is detailed in Al Vonderohe's paper WISCRS: Redesign of the WCCS, Final Report.

So how do you know if your software is converting correctly between County Coordinates and other systems (State Plane, UTM, Wis TM, Lat/Long) and vice versa?

An effort was made to contact software developers and provided them with the WISCRS county parameters and test data so the WISCRS could be incorporated into their packages. The "old" WCCS is still existent so a software package should make a distinction between it and WISCRS systems.

The parameters and test data are at the SCO website above. If all else fails, run some of the test data through your software.

BTW - WISCON correctly converts between WCCS County Coordinates and other coordinates systems and Lat/Long. However since its no longer being updated and supported it does not support WISCRS.

Tools For Do It Yourselfers

I've posted some Excel spreadsheet files here. These can be useful tools and you're welcome to use them but remember you do so at your own peril. If you do find an error in any of them please let me know

Notes:

WCCS and WISCRS systems are all based on the NAD 83 (xxx) datum.
State Plane, UTM, and WTM were defined for both the NAD 27 and NAD 83 (xxxx) datums.
None of the conversions here perform datum-to-datum transformations.

NAD 83 Tools

WCCS

Parameters

These are the parameters for the Lambert Conic and Transverse Mercator Cylindric equations for the original WCCS. This data is useful only if you plan on programming the equations yourself.

Spreadsheet

This spreadsheet allows you to convert between WCCS or State Plane or UTM or WI TM and Lat/Long. It only does one point at a time (no batch processing). It's useful if you want to test the accuracy of other conversion packages or if you have only a few positions to convert.
The spreadsheet uses macros and VBA routines so you must set Excel's security to low to accept these.
Be sure to read the first page of the spreadsheet for instructions.

WISCRS

Parameters

These are the parameters for the Lambert Conic and Transverse Mercator Cylindric equations defined in Al Vonderohe's paper. This data is useful only if you plan on programming the equations yourself or if you have a software package which allows user-defined coordinate systems.

coming soon...

This spreadsheet allows you to convert between WISCRS and Lat/Long. It only does one point at a time (no batch processing). It's useful if you want to test the accuracy of other conversion packages or if you have only a few positions to convert.
Be sure to read the first page of the spreadsheet for instructions.

NAD 27 Tools

coming soon...

These are the parameters for the Lambert Conic and Transverse Mercator Cylindric equations for the NAD 27 based State Plane, WI TM, and UTM systems.

coming soon...

This spreadsheet allows you to convert between State Plane or UTM or WI TM and Lat/Long. It only does one point at a time (no batch processing). It's useful if you want to test the accuracy of other conversion packages or if you have only a few positions to convert.
Be sure to read the first page of the spreadsheet for instructions.

Last update: 15 Aug 2010