Hi All I offer one possible solution for installing a DEM map on a GPS using Garmin's Mapinstall. Its not ideal but it works once you take account of the following: After much frustration, I think I have resolved the problem with Mapinstall. It seems that Mapinstall ,more often than not, detects an issue with one of the files created using mkgmap's -gmapi option. I have not tried to work out which one but I can say that ,so far, all gmaps created using Javawa Mapconverter have formed a successful basis for uploading dem maps to a gps device. 1) Create your Mapsource/Basecamp map using mkgmap Ignore the gmap if created by mkgmap drag your mapfolder onto Javawa's mapconcerter to create a new gmap - place this in c:\programdata\garmin\maps 2) I use Franks excellent program to create & add dem files 3) I add DEM file sizes to the .tdb file - I have presumed that all dem file sizes require a maximum of 4 bytes - I have not encountered files which require 5 bytes - please let me know if is a DEM file which needs 5 byte. 4) I have not had to add or replace separate bytes in the tdb file to make it work apart from setting the DEM flag 5) If some maps have no dem then no dem height or ref to a DEM is added to the tdb 6) I now use Mapinstall and upload map to my GPS. This is one solution which now seems to work. As this is rather long winded, you don't really want to do this each time you update a map! Perhaps we need to look at ways of creating 'empty' maps with just DEM as a separate gmapsupp. examples on Oregon: Greece : <http://gis.19327.n8.nabble.com/file/t339487/241.bmp> <http://gis.19327.n8.nabble.com/file/t339487/265.bmp> <http://gis.19327.n8.nabble.com/file/t339487/350.bmp> -- Sent from: http://gis.19327.n8.nabble.com/Mkgmap-Development-f5324443.html