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The SEDRIS Data Representation Model
APPENDIX A - Classes LTSE 3D Location |
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An instance of this DRM class specifies a 3D coordinate for an SRF based on the Local Tangent Space Euclidean SRFT.
See 8.5.6 Local tangent space Euclidean SRFT of ISO/IEC 18026 for a complete definition.
Consider a <Property Grid> instance that maps wind velocities along a coastline. The <Property Grid> instance uses an SRF derived from the Local Tangent Space Euclidean SRFT with the Y axis parallel to the coast.
An SRF derived from the Local Tangent Plane Space Euclidean SRFT may be used to specify a topocentric coordinate system to model a building.
The Local Tangent Euclidean SRF specifies a location in a georeferenced space. The Local Space Rectangular SRF specifies a location in a Cartesian, non-georeferenced "model" space.
Because the Local Tangent Euclidean references a Cartesian coordinate system to a curved surface, the two surfaces are not parallel (in particular, LTSE is not a projection-based SRF). When they are not parallel, a 2D coordinate in one SRF can map to a range of 2D coordinates in the other SRF. Specifying the third coordinate resolves this ambiguity.
If the data provider's grid is small enough or the ambiguity in location is unimportant, the data provider can specify a height as a global parameter of the <Property Grid>. Otherwise, the data provider should specify the height as a separate value in each grid cell, or use several grids of smaller extents.
The coordinate field specifies the set of coordinate-component values.
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