Representing a TIN in GeoJSON

Question

Regarding the GeoJSON representation of a TIN, are there

1. any specifications or
2. existing implementations I may not be aware of?

You could probably hack one together using the multipolygon feature type, but this seems inefficient.

Generally speaking, I don't see any surface types (regular or irregular) represented in the GeoJSON world, is there any existing or upcoming work in this area?

Answer 1

There doesn't appear to be a GeoJSON spec out for TIN, but there is one for WKT. Basically, TIN is a synonym for MultiPolygon, and Triangle is a synonym for Polygon.

Thus a four node, two element TIN can be encoded with the WKT:

TIN Z (((0 0 0, 0 0 1, 0 1 0, 0 0 0)), ((0 0 0, 0 1 0, 1 1 0, 0 0 0)))

Which should translate to:

{"type":"TIN","coordinates":[[[[0,0,0],[0,0,1],[0,1,0],[0,0,0]]],[[[0,0,0],[0,1,0],[1,1,0],[0,0,0]]]]}

With the OGC WKT specification, each triangle has one linear ring, with four vertices. (Rant: a triangle has only one linear ring and three vertices, and I'm unsure why OGC ignored these facts before inflating the storage size).