Digital Odometer Accuracy

Digital Odometers are incorporated into some Raveon GPS transponders such as the M7-GX.  They work very well, but you will see a difference in reading between the digital odometer reported by a GPS transponder and the odometer on the dashboard.

  1. A GPS transponder with GPS uses its GPS location to calculate distance .  Every second it computes how far it moved, and adds this up to accumulate the odometer reading.
  2. At any time, you can type a command into the radio to force the Odometer reading to be any reading you want.  Because this can be set anytime to any value, the GPS odometer should not be the sole mechanism for determining maintenance intervals.
  3. The digital odometer in the GPS transponder will vary from the dash-board reading. Typically we see 1-5%.
  4. Reasons for the difference between the dashboard and the GPS transponder reading are:
    1. The GPS Signal itself is only accurate to about 30 feet typically. Sometimes 10 feet sometimes 100 feet.
    2. Near tall building, tree, canyons, down-town cities, GPS accuracy may only be 100 feet.  Adding 100 feet of error every seconds adds up quickly.
    3. If a car drives in a tight circle, the dashboard odometer climbs, but the GPS odometer reading sees little distance change.
    4. If a vehicle drives in reverse, the odometer reading may go backwards.  The GPS odometer will not.
    5. The resolution of the GPS signal is about 1 meter.
  5. Raveon recommends using the digital odometer to determine changes in odometer readings not absolute numbers.
    1. To see how many miles a vehicle has on it, use the dashboard odometer.
    2. To track how many miles a day  vehicle travels, use the GPS.
    3. To see how far a vehicle drove between events or rule alerts, use the digital odometer in the GPS transponder.
    4. To track intervals between maintenance, use the GPS and dashboard.

Digital odometers based on GPS location are great for monitoring vehicle activity and tracking usage.  If you want to keep them in sync with the dashboard, you’ve got a big challenge and a lot of updating to do.