GPS For Sole-Means Navigation?

For many years Canadian pilots have been relying more and more on GPS for both VFR and IFR navigation. There are even pilots who are using it as their sole-means, especially VFR and have stopped buying paper maps. With very few problems the GPS satellite constellation has proven itself up to the task, at least since it was declared operationally ready on 27 April 1995, but that could be changing very soon.

The U.S. Government Accountability Office has identified that the USAF-run GPS satellite constellation is in trouble. There are currently 30 satellites in orbit, the 24 needed for the system and six spares, which sounds like enough to run the system. The problem is that many of the satellites are getting old and will need replacing soon or will fail. The USAF has a program to replace the satellites, but it is US$1B over budget and almost three years behind schedule.

U.S. Government Accountability Office recently said that it "is uncertain whether the air force will be able to acquire new satellites in time to maintain current GPS service without interruption...there will be an increased likelihood that in 2010, as old satellites begin to fail, the overall GPS constellation will fall below the number of satellites required to provide the level of GPS service that the U.S. government commits to."

Because of the orbits involved, Canada is one nation that may see greater periods of no-usable-GPS signals, starting in 2010. If the USAF is not able to catch up its replacement program or if the older satellites fail at an increased rate than expected then GPS signals may not be reliable enough for navigation over Canada next year.

There are replacements available, such as the Russian GLONASS satellite system that is currently semi-operational, having not completely recovered from the fall of the USSR. To use it though, you will require a different receiver that works on the GLONASS frequencies, something most current receivers do not currently do. There are two other systems, the European Galileo system and the Chinese COMPASS system. Galileo is expected to be operational in 2013 and COMPASS is still in the planning stages.

These three alternate systems will probably mean that starting in 2013 reliability will be improved and you will be able to buy new hardware that will use two of more of the available systems.

So what to do for aviation navigation in 2010? Probably the obvious solution is to ensure that you have the "traditional" methods of navigation available, this includes paper maps for flying VFR and VOR/ADF for IFR flight. Losing GPS signals while VFR is a nuisance, but it can be a "show stopper" while in cloud IFR.

The warning has been sounded, now we all have to take advice from the Boy Scouts and "Be Prepared".