The SEDRIS Data Representation Model
APPENDIX A - Classes
LTP Location 3D

Class Name: LTP Location 3D

Superclass - <Location 3D>

Subclasses

This DRM class is concrete and has no subclasses.

Definition

An instance of this DRM class specifies a coordinate within the Local Tangent Plane (LTP) 3D Spatial Reference Frame (SRF).

See [I18026] for a complete definition.

Primary Page in DRM Diagram:

Secondary Pages in DRM Diagram:

This class appears on only one page of the DRM class diagram.

Example

  1. A <Property Grid> maps wind velocities along a coastline. The <Property Grid> uses a Local Tangent Plane spatial reference frame with the Y axis parallel to the coast.

FAQs

How does the Local Tangent Plane (LTP) SRF differ from the Local Space Rectangular (LSR) SRF?
The Local Tangent Plane SRF specifies a location in a georeferenced space. The Local Space Rectangular SRF specifies a location in a Cartesian, non-georeferenced "model" space.

I have a 2D grid. Why do I have to specify a height?
Because the Local Tangent Plane references a Cartesian coordinate system to a curved surface, the two surfaces are not parallel (in particular, LTP 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 your grid is small enough or the ambiguity in location is unimportant, you can specify a height as a global parameter of the <Property Grid>. Otherwise, you should specify the height as a separate value in each grid cell, or use several grids of smaller extents.

Constraints

Component of (two-way)(inherited)

Inherited Field Elements

This class has no inherited field elements.

Field Elements

SRM_LTP_Coordinate_3D coordinate;
Prev: LTP Location 2D. Next: M Location 2D. Up:Index.

Last updated: October 1, 2002 Copyright © 2002 SEDRIS™