Rule Name: Required Reference Vector Location

Definition

A Reference Vector is required to have a Location component whenever the Reference Vector is a component of a Polygon, Line, Infinite Light, Moving Light Behavior, or Union of Geometry.

Rationale

The SEDRIS API requires an appropriate Location to convert a Reference Vector to or from non-vector spatial reference frames, such as Geodetic. For most Reference Vector aggregators, the Location is supplied by the context inheritance mechanism. For the remaining classes covered by this rule, inheritance cannot be relied on to supply an appropriate Location component.

Example

1. A large Polygon with a Reference Vector component might use the "center" of the Polygon for the Reference Vector's Location component.
2. A Line with a Reference Vector component might use the Location of one of its component Vertices for the Reference Vector's Location component.
3. An Infinite Light is shining down on the local area. The "down" direction Reference Vector component must have a localizing Location component, since parallel translations of a "down" vector will not point down over most places on the Earth's (curved) surface.

FAQs

How does choice of Location component affect Reference Vectors in Models that have been specified in LSR spatial reference frames?

In the case of Models that use LSR, the choice has no effect at all. The LSR origin (0, 0, 0), for example, could always be used.