The Perils of Unapproved GPS

by Shawn Coyle, Engineering Test Pilot, Transport Canada

Recently one of our readers sent a letter outlining problems with a hand-held global positioning system (GPS). Basically the problems were with the map display. It appears this particular model showed highways in the incorrect location, and the Toronto Island airport was shown far out into the lake. The manufacturer of the equipment blamed the database (which they obtain from another supplier), but other hand-held GPSs that use the same database were correct. What lessons are to be learned from this? For those who supplement their IFR navigation with hand-held GPS units, remember they are very different from IFR-approved GPS receivers. Hand-held GPSs are not subject to any certification process, and while they are useful, they are not a substitute for standard IFR navigation instruments or proper VFR map reading. Hand-held GPSs have no self-monitoring to tell you that the satellite geometry may be less than optimum. There have been reports of errors of up to 80 NM with hand-held GPSs. GPS is a very useful tool, but it is not without its pitfalls.