Defining an ORM
1. Identification of the object, e.g., the Earth, International Space Station (ISS), or survey site
2. Specification of a distinguished location, e.g., the mass center of the Earth, a surface crater on a planetoid, or the barycenter of the solar system
3. Specification of an orientation at that location with respect to the object, e.g., a rotational axis and meridian
- Where n is the dimensionality of the object, the equivalent to n-1 distinguished orthogonal directions are specified
- In some cases, the orientation, or directions, may be purely conceptual, and the specification of orientation may be simply “up” or “forward” along specific directions
4. A system of time, and an epoch
5. Optionally, one or more Object Reference Surfaces (ORS), e.g., the surface of an ellipsoid of revolution or a gravity equipotential surface