In April 2020, I presented a talk on understanding GPS in contested environments. Topics included the following:Understanding GPS position error, dilution of precision and user range errors, physical and radio visibility, terrain heights and field results, mitigation techniques and alternative navigation technologies.

When you turn on your GPS receiver - what happens? Well, lots of stuff. But primarily, GPS receivers work in a two stage process: 1) Look for available satellites to track 2) Do everything else. In this article, I want to focus on step 1, we'll get to step 2 later.