USING GPS IN ROAD RUNNING
GPS units are NOT accurate and consistent enough to measure a course for certification.
Course measurers need to use their calibrated bikes in order to guarantee to get 10km course within 10 metres (0.1%) of its advertised length. In the links on the right we report tests by measurers of GPS which give results that are sometimes in error by 30 to 50m for a 10k, even when satellite visibility is good. When obstructions block the view of the sky the results can be much worse.
Analysis of results from runners' GPSs often give even poorer results, for a variety of reasons. In one race average result from 26 runners GPSs was 220 m long per 10km (2.2%). (See on right)
There is no doubt that, despite its inaccuracies, a GPS is very useful for approximate measurements of training routes, and splits, and for race directors trying to plan a course before calling in a course measurer for an accurate measurement for certification purposes. We will be preparing a list of tips about getting the best out of your GPS.
Tracks from runners' GPSs are occasional helpful to measurers investigating whther a course has been run as measured, and that major short cuts have not be taken., e.g. GPSs showed that a turning point might have been accidentally wrongly located by the race organiser , this was confirmed by a course reameasurement. On another occasion the tracks from 4 runners showed that a race route had been changed by the race director without seeking a remeasurement and certification. So it may be useful to send in a GPS track if you think the wrong route may have used.
There are alternative procedures for rough course measurement using maps, or online mapping software. With care these can be accurate to better than 1%. This was the way we used to estimate distances before GPS became widely available. Even today a race director or a measurer may make a rough estimate for planning purposes using a map techniques, before a measurement with a calibrated bicycle is undertaken.