Just found this one. Decreasing tile size makes it go away. Requires sensible error message. -Wolfgang Exception in thread "main" java.lang.AssertionError: NET 1 offset too large at uk.me.parabola.imgfmt.app.net.RoadDef.writeRgnOffsets(RoadDef.java:24 4) at uk.me.parabola.imgfmt.app.net.NETFile.writePost(NETFile.java:64) at uk.me.parabola.mkgmap.build.MapBuilder.makeMap(MapBuilder.java:155) at uk.me.parabola.mkgmap.main.MapMaker.makeMap(MapMaker.java:87) at uk.me.parabola.mkgmap.main.MapMaker.makeMap(MapMaker.java:53) at uk.me.parabola.mkgmap.main.Main.processFilename(Main.java:150) at uk.me.parabola.mkgmap.CommandArgs$Filename.processArg(CommandArgs.jav a:329) at uk.me.parabola.mkgmap.CommandArgs.readArgs(CommandArgs.java:119) at uk.me.parabola.mkgmap.main.Main.main(Main.java:91)