Welcome to our new forum platform. We realize there is still some work to do and we appreciate your patience. Please let us know if you have any ideas or suggestions: email@example.com I have got some old maps to digitize. They are in unique and most probably unknown map projection and I georectified them in GM using just Ortographic projection. To tie the maps to the real world I got set of 60 points transformed by geodetic service from unknown projection to popular Transverse Mercator projection. I have got some home made software to convert corrdinates by affinite transformation based on the set of points. It is however very awkward to deal with it to transform big sets of digitized data. Let me know if it is possible to set affinite transformation of coordinates in GM to convert map projections (both rasters and vectors) using set of the points? I suppose it can be done easily as many other things in GM, but sometimes it is really hard to figure out how to do it. You can simply load the map with File->,Rectify Imagery menu command to provide control points to position the map. Global Mapper will warp to those points. Another option is to right-click on the loaded layer in the Control Center and select the option to shift/transform the file. With that you can choose to define a coordinate transformation for rotation, scale, and translate. Source.