[mkgmap-dev] DEM-file generation from geo-tiff sources ?

Thu Jan 4 20:13:32 GMT 2018

Hi Franco,

i have just downloaded all copernicus tiffs. The pure tiff data are round about 37GB. My short test was:

gdalbuildvrt all.vrt *.tif
gdalwarp -t_srs EPSG:4326 -r lanczos -ot Int16 -dstnodata -32768 -of GTiff -co "COMPRESS=LZW" -co "TILED=YES" -co "PREDICTOR=2" -ts 3601 3601 -te 11 
50 12 51 all.vrt N50E011.tif
gdal4hgt --raster=N50E011.tif --dstpath=.

The first command create a vrt file (virtual). This is only a xml file with links to the real tif's. It runs a few seconds.

The second command cut a the area with longitude 11..12 and latitude  50..51 (in EPSG:4326) from all.vrt and write it with3601x3601 pixel as lzw 
compressed geotif. A pixel is saved as int16. The resampling method is lanczos. It also runs a few seconds.

The last command is my own prog. It converts the tif in a few seconds to hgt.

It seem's to be ok.

If gdalwarp run in a loop, it create a lot of new tif's. With the new tif's can we create a new vrt. gdal4hgt should convert this new vrt to all 
nonempty hgt's in one run.

Frank

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