tsc_GnssObservation

This an abstract subclass of tsc_PointObservation, and contains a GNSS coordinate.  The type of the coordinate depends on the base class and should be appropriate for the GNSS survey type (Store fixed positions or Store vectors from base).

Such an observation can be appended to the database only while the survey that observed the coordinate is still running.

Each observation requires environment information - the survey and the antenna - which are supplied by the tsc_GnssEnvironment class.  An instance of tsc_GnssEnvironment should be passed in when setting the coordinate on the tsc_GnssObservation subclass to ensure the correct environment information is stored with the point.

The precisions and quality information is also required before storage.  See tsc_GnssPrecisions for details.

The read only GNSSVerticalOffset value is available on this subclass in case there is a need to determine and display the height or elevation of the observed point prior to appending the observation to the database (eg. for interim display of a point height or elevation, or results of a computation based on one of these values, prior to storage).