8. Selecting CORS

The use of multi-frequency GNSS signals can typically eliminate over 99% of ionospheric delays. Additionally, post-processing GNSS data using simultaneous observations at known control points such as CORSs removes additional atmospheric influence, including tropospheric delays. It is crucial to select the best CORSs for session processing and network adjustments in order to ensure a successful outcome, including submission of the project to NGS. This is because the CORSs in your project will ultimately serve as the control for referencing your survey to the NSRS. Although OPUS had automatically selected a number of CORSs for the project based on post-processing each individual GNSS observation file (see How Does OPUS Processing Work?), these choices made through individual OPUS solutions are not necessarily the best choices for the entire project. This section steps you through a recommended selection process to determine the best set of CORSs for the project. While different processes can be developed for selecting CORSs, the most important takeaway is to analyze the CORSs to make informed decisions.

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• 8.1. Adding or Deleting CORSs
• 8.2. Selecting Appropriate CORSs for Successful Processing in OP
  • 8.2.1. Candidate CORSs
  • 8.2.2. Distance Considerations
  • 8.2.3. Data Quality Check
  • 8.2.4. Select the Hub
• 8.3. Add/Del CORS