[gdal-dev] Support for Terrain-RGB

[Lars Ahlzen]

On 05/01/2026 19:47, rayg wrote:
> Strange encoding, -10000 meters isn't deep enough for the Marianas 
> Trench. You could borrow another 10 km from the 1.6 million meters 
> still available on the positive side.
>
> Scaling by 0.1 also means a 10 cm vertical resolution., which is 
> useless for some use cases. The 24 bits per pixel could be much better 
> allocated.

I kind of agree with both points, but I guess the format is what it is.

I don't think it's supposed to be a general-purpose storage format. It's 
encoding just enough data to do good enough real-time visualization of 
elevation, like hillshading or hypsometric tints, client side.

Looks like at least rio-rgbify [1] allows setting a custom base value 
and interval. That might be something we want to emulate as well, 
perhaps as creation options (if a raster format driver) or command line 
options (if part of gdaldem).

- Lars

[1] https://github.com/mapbox/rio-rgbify