11. Session Processing

Session processing is the critical step in which the processor implements the GNSS survey network design. Session Processing calculates the baselines between the hub(s) and the user marks. In addition, a variance-covariance matrix is produced estimating the errors associated with the baselines, and their correlations. Finally, a minimally-constrained adjustment is applied to align the baselines to the NSRS at the hubs.

The Session Network Design default can be changed at processing and, to a limited extent, modified by selecting user marks to be excluded from the processing or to be assigned as hubs. You can only process baselines for marks or hubs that have been simultaneously occupied. The term “hub” means a mark that is preferentially selected for inclusion in baselines. In other words, all marks that are not hubs will have a direct baseline connection to the nearest hub.

Session processing leverages common satellite observations and error estimations. As a result, some marks that did not meet project preferences in the initial OPUS solution, may now meet project preferences under session processing. However, care should be taken in including poor observations, as they are likely to degrade the quality of the overall session processing. See Section 4.3 for more information on project preferences.

Session processing can be done as soon as all the data for a given session have been loaded. If additional data for a session comes in after that session has already been processed, the session will have to be reprocessed with all of the data. You may want to process the first session and review the results before processing subsequent sessions. This can help avoid confusion regarding which session is being analyzed.

Caution

For publication, NGS required that the “final precise” ephemerides be used in processing