Hi Gerd I think there is still an issue when --x-dem searches for sea hgt files which by design don't exist . After splitting the UK with maxnodes at 160000 and selecting the far south west (Cornwall) tile I get an error - see below. Its looking for N49W008.hgt which is just sea. Would it be possible to ignore a .hgt if it doesn't exist or use Frank's dummyvalues idea? r Nick java.lang.RuntimeException: failed to open E:\Dem\europe/N49W008.hgt at uk.me.parabola.mkgmap.reader.hgt.HGTReader.<init>(HGTReader.java:45) at uk.me.parabola.mkgmap.reader.hgt.HGTConverter.<init>(HGTConverter.jav a:43) at uk.me.parabola.imgfmt.app.dem.DEMSection.<init>(DEMSection.java:51) at uk.me.parabola.imgfmt.app.dem.DEMFile.calc(DEMFile.java:44) at uk.me.parabola.mkgmap.build.MapBuilder.makeMap(MapBuilder.java:284) at uk.me.parabola.mkgmap.main.MapMaker.makeMap(MapMaker.java:107) at uk.me.parabola.mkgmap.main.MapMaker.makeMap(MapMaker.java:69) at uk.me.parabola.mkgmap.main.Main$1.call(Main.java:263) at uk.me.parabola.mkgmap.main.Main$1.call(Main.java:259) at java.util.concurrent.FutureTask.run(Unknown Source) at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source) at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source) at java.lang.Thread.run(Unknown Source) Caused by: java.io.FileNotFoundException: E:\Dem\europe\N49W008.hgt (The system cannot find the file specified) at java.io.FileInputStream.open0(Native Method) at java.io.FileInputStream.open(Unknown Source) at java.io.FileInputStream.<init>(Unknown Source) at java.io.FileInputStream.<init>(Unknown Source) at uk.me.parabola.mkgmap.reader.hgt.HGTReader.<init>(HGTReader.java:38) -- Sent from: http://gis.19327.n8.nabble.com/Mkgmap-Development-f5324443.html