GPS accuracy and what affects it
When tracking a vehicle you want the position as accurate as possible. But GPS accuracy is not a constant – one moment the position is down to the metre, the next it jumps a few dozen metres. Let's look at what affects GPS accuracy and how a reliable position can be achieved even in difficult terrain.
What GPS accuracy is typically like
GPS accuracy with a modern receiver in open terrain is commonly on the order of a few metres. For vehicle tracking that is more than sufficient – you can tell without difficulty which street or car park the vehicle is standing in.
Accuracy is expressed as the deviation between the calculated and the actual position. It is not a fixed number but changes with current conditions – the number of visible satellites, the surroundings and the quality of the device used.
The influence of buildings and broken terrain
The greatest enemy of accuracy is an environment that blocks or reflects the signal. In dense urban development the satellite signal bounces off building façades and reaches the antenna by a detour. This phenomenon, called multipath propagation, can shift the position by tens of metres.
Tunnels, underground car parks and dense forest have a similar effect, where the signal is substantially weakened or lost entirely. Buildings, tunnels and broken terrain are therefore among the main factors that degrade GPS accuracy.
Weather, satellites and the atmosphere
The GPS signal has to cross the whole atmosphere, where it is affected by both the ionosphere and the troposphere. Strong storms and extreme weather conditions can degrade accuracy slightly, but ordinary weather such as rain or cloud has only a minimal effect on GPS.
The distribution of satellites across the sky also plays a big part. If the satellites are bunched into one part of the sky, the calculation is less accurate than when they are nicely spread out. The receiver therefore continually selects the most suitable combination of satellites.
The quality of the unit and the antenna
Not all GPS devices are alike. The quality of the receiver, the sensitivity of the antenna and its correct placement in the vehicle substantially affect how accurately and how stably the position is determined.
SaveTrack uses professional Teltonika units, which support several satellite systems at once. As a result they see more satellites, get a fix faster and hold an accurate position even where a cheaper device would fail.
How SaveTrack ensures a reliable position
Besides quality hardware, data processing on the server side helps too. The system can bridge short signal outages by interpolating the position from speed and heading, so the route stays continuous even in a tunnel or a garage.
Combined with a 60-second update rate while driving, you get a reliable and current vehicle position. For the mileage log, dispatching and checking vehicle utilisation, the resulting accuracy is entirely sufficient.
FAQ
How accurate is GPS when tracking a vehicle?
In open terrain the accuracy is commonly on the order of a few metres. In urban development or a tunnel it may temporarily degrade, but for vehicle tracking the accuracy is entirely sufficient.
Why is the position sometimes inaccurate in a city?
In densely built-up areas the GPS signal bounces off buildings and reaches the antenna by a detour. This phenomenon can temporarily shift the position by a few dozen metres.
Does weather affect GPS accuracy?
Ordinary weather such as rain or cloud has a minimal effect on GPS. Accuracy can be slightly affected only by extreme weather conditions and the state of the atmosphere.
How does SaveTrack handle signal outages?
During short outages the system interpolates the position from speed and heading, so the route stays continuous even in a tunnel or an underground car park.
Does a quality unit improve accuracy?
Yes. Professional Teltonika units support several satellite systems at once, see more satellites and hold an accurate position even in a demanding environment.
Want a reliable vehicle position even in the city? SaveTrack is built on professional Teltonika units – from €6 a month with no lock-in. Call +421 908 918 880 or write to info@savetrack.sk.
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