Andrea Aime wrote:
> Ben Caradoc-Davies ha scritto:
>> Consulting with a knowledgeable stakeholder yielded these examples of 
>> interesting 3D geospatial data:
>> - 3-D line-string (wells and boreholes, atmospheric and ocean soundings)
> This is 2d+1, will be handled by the proposal
>> - TIN (geological horizons)
> This could be suported as a multipolygon made of triangular 3d faces
> which are 3d polygons, but it would be not explicity, and quite a bit
> hacky
>> - Tri-surface (other geology surfaces)
>> - Solid whose shell is a tri-surface (ore-body, grade-control-surface)
> This could be supported as well the way above. But not having a explicit
> class is annoying.

More remarks from Simon Cox:
1. 3D line strings are not 2D+1. They often turn back on themselves, so 
more than one z value for each x,y.
2. TIN and Triangulated Surface and Solid are explicit classes in ISO 
19107 and in GML

Ben (as Ben, again):

In 2D+1, is the main difference that the third dimension ignored by some 
operations, such as coordinate transforms? I suspect 2D+1 will be OK for 
line-strings, except when you try to change datum.

-- 
Ben Caradoc-Davies <[email protected]>
Software Engineer, CSIRO Exploration and Mining
Australian Resources Research Centre
26 Dick Perry Ave, Kensington WA 6151, Australia

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