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

Sun Jan 7 00:10:12 GMT 2018

Hi Frank,

I tried to adapt your perl script to my Ubuntu System

I got the following warnings

Here's my Ubuntu-script

Frank Stinner-2 wrote
> Hi Franco,
> 
> i have little bit "played" with copernicus-files.
> 
> I have build a win-command-file with this perl-file:
> 
> -- cut ---
> 
> Yes, i was very lazy with the huge area. That are 2740 1°x1° tiles. But my
> computer is very diligent ;) . Have in mind the $delta. Hgt's have not 
> exact 1° width/height. It's 1 pixel more, that means a half pixel on each
> side.
> I have tested different interpolation methods. I believe "near" is the
> best (and fastest) method.
> My computer created in 65 min all the tif's. I'm sure, that is strong
> depend on the hardware.

Let's see how fast my machine will be -- still running

> Surprisingly the new tif's have only round about 4 GB.
> 
> Then i create with
> 
> gdalbuildvrt all.vrt *.tif
> gdal4hgt --raster=all.vrt --dstpath=..\hgt -O
> 
> the zipped hgt's. That is very easy but very slow (160 min). By the way,
> gdal4hgt create only hgt's with min. 1 non-nodata value. The resulting
> zipped 
> 1001 hgt's need 5,2 GB!
> 
> You wrote: "gdal_translate -strict -q -eco -of SRTMHGT -outsize 3601 3601
> "  should basically do the same job ...
> 
> The format SRTMHGT was new for me, but i think, you are right. I have not
> tested the speed.
> 
> Frank

Now I will have to find a way to identify the empty Tif-Files. 
I think gdal_translate will also create empty tiles, so I will have to
remove the empty Tifs before converting them to hgt

Ciao, Franco

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