My magelan GPS is not accurate for speed. I have done coastdown testing and once in neutral coasting (slowing down) the gps would sometimes go up in speed which would be improssible, not by much but still, i don't think it should be showing higher speed when there is no way i was accelerating...and sometimes when i'm crusing at a steady speed it would show me anywhere from 2 to 3 km/h difference when my speedometer/torque app is showing a steady speed.
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