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WCCS (Wis County Coordinate System) & 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:
NAD 83 Tools
NAD 27 Tools
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