When working with geospatial data and maps, an effective way to communicate in email is to send images highlighting the specific thing one wants to point out. For example, showing areas where the dominant land cover is lichens:
gdaldem, though named for its role in processing Digital Elevation Maps, is a useful tool even for things which have nothing to do with elevation. It has a color-relief subcommand intended for color gradients of terrain but which can be used for lots of purposes. It takes a simple text file mapping pixel values in the original to colors in the output. For example, my lichen image above used:
0 black 1 grey 139 grey 140 red 141 grey 209 grey 210 black 211 grey
This means:
- pixel value of zero (NoData in the original image) should be colored black.
- water is pixel value 210 in the original image, so make it black as well.
- the land cover class for lichen in the original image is 140, so color it red.
- we set grey for 1 and 139, for 141 and 209, and for 211 because by default, gdaldem color-relief would create a gradient of colors between those specified. We want those areas to be solid grey.
The original image was:
