Here is my workflow for importing individual SRTM tiles into postgis using the GDAL utils and rendering a png using mapnik:
- gdal_fillnodata.py -srcnodata -32768
- gdal_contour -i 10 -a ele -snodata -32768
- ogr2ogr -f PostgreSQL -nln srtm3 -append -t_srs 'EPSG:900913'
- (some SQL to split the data into 10m, 50m and 250m tables)
- nik2img.py [stylesheet] [file] --srs 900913 -d [width] [height] --no-open -f png -v --center [center] --zoom [zoom]"
Most of the time this works perfectly. However, large areas with mountainous terrain are often completely distorted:
Huge swaths of landscape are covered with strange (often linear) patterns that shouldn't be there. No way the SRTM data is that messed up.
What am I doing wrong and how can I avoid this?
Ideally there should be a command-line solution.