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.

If a data provider has a 2D grid, why is the data provider required 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 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.

Constraints

Component of (two-way)(inherited)

Inherited Field Elements

This class has no inherited field elements.

Field Elements

SRM_LTP_Coordinate_3D coordinate;
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Last updated: May 15, 2003 Copyright © 2003 SEDRIS™