Originally Posted by
njkayaker
There's still no reason to expect that GPS will be more accurate (over longer distances).
Even though, it's "not a serious issue", it means GPS won't be more accurate.
You have to look at how errors accumulate. The errors for a speed sensor accumulate differently than the errors for GPS, and this gives GPS the advantage for long distances.
GPS also has issues with reception, which has more opportunity to happen over longer distances.
That's a bit like saying there are more opportunities for your sensor magnet to fall off over longer distances.
Garmin prefers the distance and speed from the sensor over that from GPS. They aren't doing that because the sensor is less accurate.
They use it mainly because it offers better speed measurements.