The data reported by the Airmax Telematics Unit is based on data if collects from three sources; the vehicle, GPS, plus an internal accelerometer:-
1. Data such as vehicle speed and engine speed and odometer (where available), is read directly from one or more of the vehicle’s ECUs and the overall accuracy is determined by the vehicle itself. For example, the speed value from a vehicle ECU speed is normally the same speed value used to drive the speedometer on the vehicle’s display / dashboard, this is generally accurate to required legislation, but may not agree with the speed shown on that speedometer, as vehicle manufacturers are required, by legislation, to ensure the speed shown on the speedometer is never less than the actual speed of the vehicle, but can indicate up to 10% + 6 kph higher than actual speed. For Blue Light applications, other data, such as blue lights active and sirens on/off, is derived via connections to vehicle systems and is simply a status indication and no calibration is possible.
2. Data used from GPS is predominantly location and time. The location accuracy is determined by many factors including the GPS network, the GPS receiver, but more often by the number satellites in view at any one time and the signal obscuration and multipath effects, all of which is outside of our control.
3. The internal accelerometer is factory calibrated and no further in-vehicle calibration is possible.
Manufacturers and system accuracy statements can be provided for GPS and accelerometers, as can the results of our on-track testing for vehicle speed. Time provided by our telematics unit is via an internal rea-time clock which is synchronised to GPS time.
To confirm continuing operation, the unit sends regular “heartbeat” messages, when it has no other messages to send and will send status message should it detect any operating errors.