The Tracking System object, represented by the icon in the Browser and in the ODTK toolbar, provides a convenient way of grouping one or more facilities and treating them as a unit for File and Edit operations such as Save, Delete, Cut, Copy and Paste.
You can also set tropospheric and ionospheric modeling options for the entire tracking system.
You can populate the tracking system with tracking stations manually by
Alternatively, you can select Import from the File menu and load a pre-defined tracking system that includes facilities (stored as an XML file) from the following location:
Tracking data is selected at the scenario level.
To import an STK facility (.f), place (.plc), or target (.t) object file, highlight the Tracking System in the Object Browser and select Import->Import Object from the File menu. Imported place and target objects are converted to facility objects.
Some formats such as the GEOSC format include flags to indicate whether or not the data has been corrected (for processing purposes). In other words, if whoever generated the tracking data file has already removed the effects of troposphere or ionosphere, they would set the flag indicating the measurements have been corrected.
Our generic simulation format also keeps track of these flags. From a simulation point of view, if troposphere or ionosphere is not included for a measurement, the flag is set to indicate the measurements have been corrected, or that the measurements do not contain unmodeled biases. If troposphere or ionosphere is enabled, then the flags are set indicating that the measurements do contain those effects.
When the filter processes measurements, if the tracking data flags are set to indicate that ionosphere or troposphere have already been corrected for, then the user settings for modeling those effects are ignored. However, if the tracking data does contain unmodeled biases, the user needs to make sure they model those effects if desired. Thus they have the choice to model or not model troposphere.
The exception to this discussion are the GPS CA, P1 and P2 pseudorange and phase measurements - the modeling of these effects is controlled entirely by user settings.
In the GEOSC format, a flag value of 0 means the data has been corrected and a value of 1 means the data contains the effects of troposphere/ionosphere.
If you want to simulate measurements and then be able to toggle on/off troposphere modeling and see the effects in the residuals, then simulate measurements with troposphere enabled, producing a flag of 1 in the tracking data file. Then when filtering, you can toggle the troposphere enabled flag and see the effects in the residuals.