Reference Vector Transformations
A reference vector is a unit vector associated with a point P in a spatial reference frame
If the point P and the reference vector are in a projection-based SRF, the inverse transformation is used to find the origin of the canonical LTP system on the ORS
- e.g., locate the LTP origin at T-1(P(x, y)), where T is the projection transformation
The z-component of a reference vector in a CLTP is always perpendicular to the LTP plane
A reference vector in an (augmented) projection-based SRF is referenced to grid north (the Y-axis) and generally not to true north
- By definition, the CLTP has its Y-axis pointing to true north
- This means that the vector must be rotated with respect to the CLTP Y-axis
The required rotation angle is the convergence of the meridian (COM)
- This is an angle whose value depends on P