Originally Posted by
Wildwood
I'm worried that GPS is vulnerable to electro-magnetic disruptions; thereby, interfering with my cycling & fitness statistics. Odometer, and I do a roll-out every day for calibration accuracy, after filling tires to properly recommended pressure.
Unwarranted concern, and wasted effort. Technology has addressed both of these problems.
Most GPS bike computers will also take speed and distance readings from a wheel sensor. The well sensor reading is a "back up" for when the GPS signal drops out.
The Garmin unit will auto-calibrate the speed/distance sensor by comparing it to GPS readings.