Fleet GPS tracker accuracy: what to measure and accept
Accuracy is three questions: where was it, how old is that position, and how far did it go. Each has its own error and its own test. ReWheel FMS connects supported vehicle information with equipment and operational records for field and institutional operations. Agree what you will accept for each question before you read a report, not after.
Three kinds of error
Keep these apart
- Position error: the reported point differs from where the vehicle was.
- Freshness: the position is correct but old, so it is not where the vehicle is now.
- Distance error: positions are individually fine but the summed trip distance is off.
A vehicle can pass one test and fail another. A fresh point can be several metres off, and an accurate point can be minutes old.
A simple acceptance test on known routes
Run this on a route you know
- Drive a known route that includes open road, a yard and a stop.
- Note the true start time, stop time and odometer reading.
- Compare the reported positions, report times and trip distance with your notes.
- Record the difference for each of the three questions and decide whether it is acceptable for the decision the report supports.
Where error grows
Test in the conditions you work in: tall buildings, covered yards, remote sites and areas with weak coverage. These are test conditions, not claims about any device. GPS receiver accuracy depends on local conditions, as the public GPS.gov guidance explains.
When a speed alert looks wrong
Check these two causes first
- A wrong unit label: a speed recorded in km/h but exported as mph makes a normal speed look high or low.
- An out-of-date or mismatched map limit: the limit may belong to a different road or an older speed zone.
Accuracy acceptance test table
Write your own acceptance rule in the third column before the test, and fill the result from your own route.
On a small screen, scroll this table horizontally. Keyboard users can focus the table region and use arrow keys.
| Question | What to compare | Your acceptance rule | Example result |
|---|---|---|---|
| Where was it? | Reported point against a known landmark | Decide the largest acceptable offset for the decision | Offset noted for two yard reports |
| How old is it? | Report time against true time | Decide the oldest acceptable position | Last report 4 minutes old |
| How far did it go? | Reported trip distance against the odometer | Decide the largest acceptable difference | 38.2 against 40.0 |
Sources and review context
What ReWheel provides
ReWheel FMS connects supported vehicle information with equipment and operational records for field and institutional operations. Vehicle compatibility, data-access requirements, connectivity and installation are assessed per deployment, never assumed.
Continue with ReWheel: OBD, hardwired and battery GPS trackers compared
Discuss your workflow