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Generally most manufacturers claim a 16m per kilometre tolerance with odometer readings, however some go as far to say a 80m per kilometre inaccuracy or more is possible. This means that over only 10,000 kilometres traveled, the manufacturer of the vehicle actually expects odometer inaccuracies of up to 160km or even up to 804km! This discrepancy means that the exact odometer reading the GPS device provides will differ from the inaccurate odometer on the vehicle.
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The GPS calculation is dependent, however, on GPS satellite signal quality (i.e vehicles may be unable to get signal accuracy due to travelling through underground tunnels, moving inside or under the eaves of buildings or similar structures or between tall buildings. These may all interrupt GPS signal) though with the use of moving average calculations errors are minimal.
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We highly advise and recommend fleet owners and operators of any GPS software using this information as a tool for notification for servicing alerts and RUC alerts based on mileage both on and off road, should do diligent checks on their vehicle fleets on a regular basis to avoid any large discrepancies and every 3 to 6 months to re-calibrate the mileage for their fleets. Re-calibration is an important function with all GPS tracking due to the discrepancies that can happen as described above.
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