Starting January 1st, 2016 speed detection has fundamentally and dramatically improved for 4th-generation devices. For several years, the reported speed of a vehicle was determined entirely by the GPS device. The result was that sometimes, due to poor GPS reception quality, an event such as Driving or Speeding could display an incorrect speed. Although we made a lot of progress improving speed accuracy, false alarms still occasionally got through. So we went back to the drawing board.
There are two things to know about things. You can know where something is, or how fast it's moving... not both... at least not at the same time. This is a fundamental truth of physics.
GPS provides location; not speed. GPS speed is inferred by a small sample of locations over a short period of time. The more accurate you monitor speed, the less you can know about where it happened. We finally realized that the GPS device can only do so much and we have repurposed them with a simpler task to only provide location; accurate location.
How did we calculate speed before?
2nd and 3rd generation equipment
The GPS device was programmed to analyze it's speed by looking at a few seconds worth of high-resolution GPS data. This worked. In fact 99.9999% of the time this is more than sufficient. When the GPS fix was invalid (not perfect) we would scrap the speed. But sometimes invalid data leaked through.
How do we calculate speed now?
current 4th generation equipment
The GPS device will report it's location (and time of course) and our data centre will crunch the data and deduct the speed travelled between two events and bind it to the later of two points. This is a magic bullet of identifying true speed. It's the natural improvement of increasing the sample rate to get better date. But now the question is how often will the GPS device report?
PING/LINK/SAFELINK autonomously report their location based on four conditions calculated on the device. It will report a location when one of the four events happens first:
1. Speed – increase or decrease by 15kph
2. Course – change in heading by 15 degrees
3. Distance – travel 0.5km
4. Time – elapsed 60 seconds
On average we see that devices (4th generation) report their location between 10-30 seconds. If a vehicle increases it's speed to pass, you'll know. Ultimately you'll have a better picture of your fleets speed with our improved method of speed detection.