GPS Satellite Outages

This page no longer shows GPS Outages, and will be removed in the coming weeks.

I have put GPS satellite outages on a new site, check there from now on.


Navigation blog entries

Gps Basics
The basics of how GPS works with some technical content.

How Long Can You Use an Almanac?
GPS position data is contained in almanac files. Learn how long you can use these for analysis.

Selection of my published papers

Quantitative Analytics for BVLOS Operational Risk Assessments
Using quantitative analytics, we show that functions describing metrics of interest in BVLOS ORAs can be used to define risk likelihood. This leads to a way to automate operational risk assessments, and visually display risk likelihood for faster, more accurate UAV operator decision making.

Understanding GPS Navigation in Contested Environments
Review of GPS errors, their source and how we can mitigate them. Review of terrain datums and their operational usage and an overview of alternative navigation techniques.

Operational Considerations for Improved Accuracy with an IOC Galileo Constellation
This paper looks at how the Galileo operators can improve the performance of an initial Galileo constellation by managing their ephemeris and clock errors. Keeping those errors small can help keep initial positioning errors small, even when large DOPs are present.

Long term prediction of GPS accuracy - Understanding the Fundamentals
Topics on prediction methods for GPS and how long GPS errors can be predicted. Starting from an understanding of the elements of prediction, including almanac use and ephemeris and clock errors, I look at the statistics of GPS position error predictions under various scenarios.

Statistical Analysis of Military and Civilian Navigation Error Data Services
This paper examines the difference between ephemeris and clock errors generated using civilian data versus those generated using military data. The different data sources result from civilian GPS receiver and military GPS receiver.