OARIS11 — Use of covariance versus accuracy attributes

The intended use Cartesian only full covariance classes and accuracy classes for each of the coordinate systems has caused some confusion amongst users of the specification. The intent needs to be more clearly described and explained.

Explain that covariance should be used as an alternative to accuracy values

Some sensors are able to provide a covariance matrix to describe uncertainty in position and velocity calculation as part of their processing. For other sensors accuracy values for each (or perhaps the only) measured quantity are more appropriate.
When constructing a sensor_track_type instance subsystems should use either one strategy or the other. This should be clearly specified in the notes for the covariance matrix, position and velocity accuracy attributes,.