Some instructions to work on digital terrain model data using gdal tool.

1. Convert .asc file to .geotiff:

   gdal_translate -of GTiff -a_srs "EPSG:9059" -co "COMPRESS=LZW" MDS05_REGCAN95_H28_1087_COB1.asc lp03.geotiff
   

   Data are downloaded from the CNIG; several files to cover one island.

2. Generate .vrt files:

   gdalbuildvrt geotiff.vrt *.tif
   

   The .vrt stands for Virtual Format, it allows a virtual dataset to be composer from other datasets.

3. Merge the geotiff:

   gdaltranslate -of GTiff -a_srs "EPSG:9059" -co "COMPRESS=LZW" geotiff.vrt master.tif
   

4. Change projection:

   gdalwarp -s_srs EPSG:9059 -t_srs EPSG:4326 in.tiff out.tiff
   

   • EPSG:9059: Geodetic coordinate system for Europe - onshore and offshore
   • EPSG:4326: Geodetic coordinate system for World.
5. Extract region of interest

   gdal_translate -projwin 5.6 50.6 5.9 50.4 out.tiff subset.tiff
   

   The bounding box is specified by the northwest and southeast corners.

Final result

After merging all the tiles, I extracted each municipality.
The figure shows Agaete (northwest of Gran Canaria) with a hill-shading plot.