Monday, March 5, 2012

What to Do When a GeoRef Shapefile is Missing a *.prj File --- a new tutorial

A couple of weeks ago, Michigan professional forester Lee Mueller sent me an e-mail asking if it were possible to use uDig to assign a projection to a shapefile. Lee had been given a shapefile that was missing the all-important *.prj file, which defines the map projection to which the shapefile has been projected. The supplier, however, assured him that the shapefile had been projected to Michigan GeoRef.

Lee needed a method whereby a *.prj file could be created for the problem shapefile; without the *.prj file, uDig cannot reproject it to State Plane.

We pondered this question by e-mail over a couple of days, and in the end both he and I came up with different, but equally valid and elegant, solutions. I figured out how to do it using uDig, and Lee figured out how to do it using QGIS. Lee's solution takes advantage of the fact that even though QGIS can't handle GeoRef very well, it still can recognize that two GeoRef-projected files are in the same projection, and can plot both files correctly, relative to each other.

There is a new tutorial in our Township GIS site that presents these two methods. Check out

You folks may find other methods and/or uses for these work-arounds. Be sure to share them with us when you do!

No comments:

Post a Comment