tsc_EcefObservation

This a subclass of tsc_GnssObservation, and contains a tsc_Ecef coordinate.  This type of observation is used to store measurements taken by a position-storing GNSS survey.

The ECEF coordinate should be in terms of the raw ECEF supplied by the instrument (i.e. in the case of mixed RTK-RTX surveys use the native ECEF).

Such an observation can only be appended to the database while a current survey is running.

Each GNSS observation requires context information - the environment and the precisions - which are supplied by the measurement code and can be sourced from the database or the tsc_GnssModes object.  This context information must be set on the observation object to ensure that the point is stored correctly.