Thanks, Charlie and Lambertus.

Lambertus, the only difference between the two images in my 10:49 post is that the lower one, which renders correctly, was done with r1173, which is the last mkgmap that I have found that fully supports my Polish format files. The image above was generated with r1625. I realize most of the effort in mkgmap is directed to supporting OSM, but I think that improved MapSource rendering is a concern we have in common.

Charlie, thanks for the tip. I’ll see if I can get GPSMapedit to modify the basemap.IMG files so they align correctly. And another question, right now I’m working in MP format because my data sources are USGS 10 meter DEMs and the US NHD data set. Is there a way to incorporate this data into OSM for compilation?