GEOG 862
GPS and GNSS for Geospatial Professionals

Lesson 9 Overview



The configuration of the GPS Space Segment is well-known. A minimum of 24 GPS satellites ensure 24-hour worldwide coverage. But, today, there are more than that minimum on orbit. There are a few spares on hand in space. The redundancy is prudent. GPS, put in place with amazing speed considering the technological hurdles, is now critical to all sorts of positioning, navigation, and timing around the world. It’s that very criticality that requires the GPS modernization. The oldest satellites in the current constellation were launched in 1989. Imagine using a personal computer of that vintage today. It is not surprising that there are plans in place to alter the system substantially. What might be unexpected is many of those plans will be implemented entirely outside of the GPS system itself.


At the successful completion of this lesson, students should be able to:

  • recognize GPS Modernization;
  • explain the difference between Block I, Block II, Block IIR, Block IIR-M, BLock IIF and Block III satellites;
  • describe power spectral density diagrams;
  • identify the M Code;
  • define L2C;
  • recognize L5;


If you have any questions now or at any point during this week, please feel free to post them to the Lesson 9 Discussion Forum. (To access the forum, return to Canvas and navigate to the Lesson 9 Discussion Forum in the Lesson 9 module.) While you are there, feel free to post your own responses if you, too, are able to help out a classmate.