The section corners data tables have a field named TYPE...

If TYPE == SURVEY, the corner has been located by a certified surveyor, and its location has been collected with a professional-grade (sub-centimeter) GPS.

If TYPE == GPS, the corner has been located by a County or State forester, and its location has been collected with a recreational-grade (10m) GPS.

If TYPE == TOPO, the corner has not been located, and its location is from the Wisconsin DNR LandNet, which is based mostly off the USGS topo maps.

The shapefile is in WGS84.  A PRJ file is provided to allow reprojection to other coordinate systems. Since a shapefile is comprised of several files, they are combined and distributed in a ZIP file.

The text file is also distributed as a ZIP file to save bandwidth.

2012.01.24 -- CORNER ERRORS

I received a report that a number of corner locations were wrong.  It seems to be limited to the Survey corners, which can be as much as ten yards from the actual location.  I don't know yet what the error was...  Could be a projection error in the GIS program, or a floating-point operation or truncation/rounding error in the output shapefile.  I will post a new file as soon as I have the errors corrected.