Hello guys

I don't know if this is the right place to ask: please forgive me if not and delete my request.

I have a problem with contours, generated from DEM HGT files, downloaded both from Nasa and Viewfinder, and tried with different Douglas-Peucker values.

I get empty spaces in some areas of the map, close to the state/region border, and squares with no DEM data, as you can see in this picture (this is the north part of Trentino Alto Adige, north of Italy):

I use HGT2OSM and OSMCONVERT to process all HGTs and obtain a single OSM file, the I split it with the Splitter.

Then I merge everything in a single IMG file with MKGMAP.

Do you know what could be the reason of this problem and how to solve ?

Thank you in advance for all your help

Regards,

Diego