Most software, like Strava or Garmin Connect, can correct to follow known roads, but if your sampling interval isn’t fast enough, the path can incorrectly account for distance.
RIDE WITH GPS VS MAP MY RIDE SOFTWARE
Software typically connects those points with straight lines even if your route is curved. GPS devices only measure your location at intervals, so your path ends up being a series of discrete points. Interpolation Error: If you’ve ever downloaded a GPS file that renders your path around a curve as a weird series of jerky straight lines, you’ve experienced interpolation error. GPS device makers compensate for that with algorithms, but even then, the most advanced among them can only approximate your position within three to five horizontal meters most are only accurate to within a diameter of 10 meters. Satellite signals travel through our atmosphere, which slows them down slightly. The Flagstaff Summit Road is an out-and-back, but notice how the part of the route with the black circle is some 50 meters off the road itself. fit file from a Garmin Edge 500 with older firmware, shows measurement error. Measurement Error: If you’ve ever downloaded a GPS file only to find your path on the map is parallel to a road but not actually on it, that’s measurement error, as shown in this Garmin Connect file from a recent ride to test GPS accuracy. Based on the time difference between when the wave was sent and received, a GPS unit figures out how far away each satellite is and uses that info to pinpoint your location-a process known as trilateration. Those satellites send out radio wave signals picked up by your device.
GPS devices gather data from a group of 27 satellites that orbit Earth twice a day, following exact trajectories such that, at any given time at any given location on earth, at least four are visible. Understanding the reasons why GPS discrepancies happen might help you eliminate some error, or learn to live with it until a better alternative arrives. By using GPS, “we operate on a system that’s inaccurate to some degree,” she says.
RIDE WITH GPS VS MAP MY RIDE PRO
“Each difference has a different driver,” explains pro cyclocross racer Elle Anderson, who, as part of Strava’s customer support team, deals with these questions every day. GPS lies, if we want to call them that, derive from a number of issues and affect metrics from distance to average speed to elevation gain. Play icon The triangle icon that indicates to play
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