AP Wire | 09/13/2004 | Expert: Problems With Peterson GPS Device

The glitch that plotted Scott Peterson's car traveling in excess of 30,000 mph is inherent to many GPS devices and associated software. GPS velocity calculations work by taking a location measurement at a precise instant and comparing it to the previous measurement. Thus, a vehicle's speed can be extrapolated, and usually very accurately. However, when environmental issues are thrown in such as poor GPS coverage caused by driving under trees, overpasses, or through tunnels, inncaccurate readings can occur.

The uproar over the GPS reliability in the Scott Peterson case is unfounded. It simply points out that most people do not understand and have little experience with the technology. The issue at hand is not how fast he drove, but where he was at a given time. This can be accurately determined.