9. Selecting CORS

Typically over 99% of ionospheric delays GNSS signals experience can be removed by using multi-frequency GNSS signals. Post-processing GNSS data using simultaneous observations at known control points (CORSs) removes additional atmospheric influence including tropospheric delays. Selecting the best CORSs for session processing and network adjustments is one of the most critical steps in ensuring a successful outcome, including submission of the project to NGS. Selecting high-quality CORSs is important, because the CORSs in your project will ultimately serve as the control for referencing your survey to the NSRS. Your OP project will have a number of stations already selected, based on the choices OPUS has made in post-processing each individual GNSS observation file (see How Does OPUS Processing Work?). However, the choices made through individual OPUS solutions are rarely the best choices for the entire project. This section steps you through a recommended selection process. Of course, you can develop your own processes for selecting CORSs. The most important takeaway from this section of the manual is to analyze the CORSs to determine the best set for your project.

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• 9.1. Adding or Deleting CORSs
• 9.2. Selecting Appropriate CORSs for Successful Processing in OP
  • 9.2.1. Candidate CORSs
  • 9.2.2. Distance Considerations
  • 9.2.3. Data Quality Check
• 9.3. Add/Del CORS