Originally Posted by
tomato coupe
No. Speed sensors that are meant to be used with GPS computers offer better speed measurements at short times/distance where GPS doesn't work as well. At longer distances, GPS computers rely on GPS positions to determine distance more accurately.
I've found nothing that indicates distance from a well-calibrated rotation sensor is less accurate (for the usage being discussed). Using GPS is easier (no calibration) and it's clearly "good enough" (generally).
The early GPS units might not have been that good at measuring distance. (They still aren't great at measuring short-term speed.)
The distinctive thing GPS provided was the location of where you were riding (and recording data). GPS didn't improve much on the results (distance and speed) of using rotation detectors and were more expensive.
GPS has improved such that it might now be fine or better for distance
generally. There are still situations where GPS doesn't work well at all.
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https://support.garmin.com/en-US/?fa...623Z535geTx2e9
The Garmin Speed/Cadence Sensor (GSC10), Bike Speed Sensor (BSS), and
Speed Sensor 2 override the speed and distance data from the GPS satellites when used during an outdoor timed activity.
The GSC10 uses a magnet on the wheel and the bike profile's wheel size to calculate distance and speed with improved accuracy, while the BSS and Speed Sensor 2 use a magnetometer and orientation to accomplish the same thing.
These sensors are useful when traveling through tunnels, areas with heavy tree cover, and on rides with substantial changes in elevation where GPS is limited. When the device is recording distance with GPS, it is recording the distance from one point to the next, and may not be factoring in the elevation ascent or descent.
The sensors give a more accurate reading by recording distance based on wheel rotation.