Answer
The GO device obtains the latitude and longitude directly from the GPS engine. For a GPS position received from the GPS engine to be considered valid, the following conditions must apply:
3D fix (min. 4 SVs)
- We require a minimum of 4 satellites to be locked on to the device for a GPS record to be valid.
Position dilution of precision (PDOP) needs to be 6 or better
This threshold is programmed into the GPS engine. A lower PDOP value indicates a more precise GPS reading. A GPS record is marked as not valid if it doesn"t meet this requirement.
Time dilution of precision (TDOP) needs to be 10 or better
Similar to above but related to Time Geometry. This threshold is programmed into the GPS engine. A GPS record is marked as not valid if it doesn"t meet this requirement.
Speed Accuracy Estimate needs to be within 1 m/s
The GPS sends an estimate of the speed accuracy along with the GPS data.
The Speed Accuracy Estimate is how accurate the GPS module estimates the speed to be. This is received with every GPS log. The GPS record is marked as not valid if it doesn"t meet this requirement.
Ignore the first two valids.
Ignore GPS data that has a speed increase of over 30 km/h from the previous GPS data.
Ignore GPS data if the difference between the GPS speed and the calculated speed, using the latitude and longitude of the previous two seconds, is greater than 10 km/h.
Each bit of latitude and longitude has a precision of 0.0000256 of a degree (approx. 0.09216 arcseconds or 2.5 meters).