topotiles

Convert Topopgraphy Raster to Tiles with Hillshade

Steps

./get_gmrt.sh - Downloads topography data from https://www.gmrt.org in tiles of approximately 30 degres
- These files are about 200 MB a piece
./fix_180.sh - Shift tiles into -180/180 longitude if necessary
./make_tiles.sh - Create hillshaded topography and create tiles for a leaflet tilelayer / slippy map
./png2webp.sh - Convert and shrink all png files to webp using cwebp

Any raster topography can be used for this process
Processing is done using https://gdal.org/
Rasters with longitude values outside of -180/180 appear to be lost in the procedure in gdal2tiles.py
Hillshaded topography is accomplished by creating
- a color-relief using gdal2dem
- a hillshade using gdal2dem with a multidirectional shading
  - scale values -s and -z can be changed depending on the data units and desired output
- a gamma correction is applied to the hillshade using gdal_calc.py
- the gamma corrected hillshade and color-relief are combined using an overlay function
- Reference: https://gis.stackexchange.com/a/255574
Creating of the tiles can take a long time
The output tiles directory should have leaflet.html and other various html files to easily view the output
Any artifacts in the color-relief image will propagate into the resulting tiles.
Colormap is taken from GeoMapApp and the default GMRT colorscale
- The land and ocean scales were merged
- Colored at shallow water depths were changed from a dark green to very light/almost white

BSD 2-Clause Simplified License