Hi, The 0x4a/0x4b polygon shouldn't be a problem as long as the upper map is transparent. But there are more issues with combining two map layers on top of each other, I noticed that merging img layers that were made with a different versions of mkgmap also leads to rendering problems. Don't know why this happens but you will see that contour lines appear/disappear at certain zoomlevels if it is made with another version of mkgmap. Only if I make the contour lines every time again with the same version, it renders ok. For my Benelux map I always use an already prepared mp file with contour lines, but for newer maps I start to merge the contour data with the geofabrik data before splitting, the outcome is more consistent.
is there a way to recognize this situation in mkgmap and issue a warning? I guess there should be no type 0x4a or 0x4b polygon in the input files when creating the gmapsupp?
Gerd