4. Unit description and objectives

In this unit you will learn how multiple sources of error enter into the distance equations that affect our estimated distances between the GNSS satellites and the GNSS receivers on Earth. After completing this unit you should be able to:

  1. Describe different potential error sources in GNSS operation and how they are mitigated:
    • GPS satellite and receiver clock errors
    • Ionospheric delay
    • Satellite orbital errors
    • Tropospheric error
    • Multipath errors
  2. Explain how increased observation time increases the accuracy of GNSS-derived position.
  3. Explain how the mathematical process of double differencing is used to increase accuracy and reduce errors.
  4. Explain the role of continuous GNSS active-relative positioning systems such as NOAA’s CORS.