The consequences of this spec addition would be:

1. Inspectors like pmtiles.io can render and inspect Elevation tiles with real values, instead of showing the RGB raw tiles
2. tooling GDAL in the future can support PMTiles as an elevation source directly, although this would require changes within GDAL

Seeking additional comments, like if we should support encoding:mapbox?

Related: mapbox/tilejson-spec#28

@ingalls @wipfli per today's conversation, I've merged this into the spec.

Nice to hear the pmtiles spec now accepts specifying the encoding: terrarium metadata! Is it also made to accept encoding: terrain-rgb where elevation from rgb formula is elev = -10000 + ((R * 256 * 256 + G * 256 + B) * 0.1)? Thanks!

Can you provide a list of tile generation software and/or map rendering clients that use encoding: terrain-rgb right now?

We are encouraging encoding: "terrarium" to cover the happy path of using Mapzen Terrain, Mapterhorn and MapLibre together: https://maplibre.org/maplibre-style-spec/sources/#encoding_1

The only terrain sources I encountered using TerrainRGB encoding - available on terrain-viewer:

• MapTiler
• of course Mapbox
• and then some regional/local terrain DxMs like ESP - TerrainRGB Nuevo servicio XYZ del Modelo Digital de Elevaciones de España at this link or this one from gbank.gsj.jp
• also some commercial terrain sources like Nimbo
• LINZ was also exposing as TerrainRGB see mention but I cannot find it back.

Thanks, those seem to be tilesets with RGB encoding but they do not actually define a value in a tileset or renderer specification called encoding: terrain-rgb with a precise meaning.

Here is how the current Mapbox GL JS docs define encoding: https://docs.mapbox.com/style-spec/reference/sources/#raster-dem-encoding

In the case of tile generation projects like Mapterhorn, we have not observed a need for encoding: mapbox, since the sources available in that encoding are proprietary tile APIs and not static tilesets or pmtiles archives.

If you can provide some examples of places where encoding: mapbox is used with static tilesets we can consider adding that to the specification.

All the shared TMS/XYZ tilesets share the same underlying TerrainRGB encoding formula from mapbox indeed. When these terrain sources added to terrain-viewer via the BYOD Bring-Your-Own-Data panel, they all display correctly thanks to maplibre terrain-rgb decoding.

Terrarium encoding has many benefits over terrain-rgb (resolution, finer grained data, going beyond the -10km range etc), so it's great that the ecosystem is pushing towards terrarium encoding within pmiles containers, given that all existing global tilesets listed are proprietary.

There are some open-data national terrain tiled datasets that do use that mapbox encoding though, like that spanish example. Not sure if this is a living example of a static tileset, but I would assume so - it's also possible this terrain dataset is not only published as terrain-rgb but also as DSM COG. Hope this helps!

ESP - TerrainRGB Nuevo servicio XYZ del Modelo Digital de Elevaciones de España at this link