5. Unit description and objectives

In this unit you will learn how GNSS-based coordinates are fundamentally tied to a Cartesian coordinate system with its center at the center of mass of Earth, and how mathematical equations are needed to convert these coordinates into more the easily understandable positional units of latitude, longitude, and height. After completing this unit you should be able to:

  1. Describe a reference frame (or datum) and how it is used in GNSS.
  2. Describe the process of converting between Cartesian coordinates (X,Y,Z) and positions (latitude, longitude, ellipsoid height).
  3. Explain why, for most applications, heights should be converted from an ellipsoid to an orthometric reference frame.