These don’t exist in master, only the terrain branch and other related branches. Are you using them? I’m thinking about getting rid of them (at least for now) in preparation for getting terrain into master. I don’t think they’re very useful, because…
WebMapServiceTerrainProvider theoretically lets you serve terrain from a WMS server, which sounds useful. But in practice the only WMS server it works with is GeoServer, and even then only when the BIL plugin is installed. And you may even need some wacky customizations to the BIL plugin to get it to work.
TileMapServiceTerrainProvider expects the server to produce PNGs using the TMS tile layout, which seems standard enough. But the PNGs have to use the unusual format where each height is expressed in millimeters above -1000 meters and stored as a 3 byte integer, where the red channel is the high byte, the blue channel is mid byte, and the green channel is the low byte. Since this isn’t exactly a standard format, it’s unlikely anyone already has terrain data in this format. And if you’re creating a new dataset for use with Cesium, you would be much better served by the CesiumTerrainProvider instead of using this one.
So I’d like to get rid of these. Any objections?