How Accurate is Dash Cam Speed Recording?

8th December, 2022 | Dashcam, Road safety

Having a dash cam to record the speed of your car could potentially help to get you out of a speeding ticket, fines and points on your licence. The footage it can record could even help provide evidence for someone else if your camera happened to capture an accident in front of you.

There have been multiple examples of video footage being used as evidence in court. As such, dash cams are a real investment when it comes to preventing an irritating court case, if you can produce the evidence that the speeding ticket wasn’t merited.


Why is recording speed from a dash cam a good idea?

Speed cameras in the UK are generally calibrated to an accuracy of 2%. Gatso cameras record the speed of passing vehicles by taking two photos over markings on the road. Mobile speed cameras, on the other hand, are usually gun-type, like those that the police use in speed traps are usually more accurate, as they use the Doppler effect to measure speed. ‘Red-light’ cameras tend to track vehicles using radar or electric detectors buried in the road’s surface. All of these methods depend on accurate calibration, which can sometimes be ‘off’, and an accurate dash cam reading has been known to overturn speeding tickets in court, especially if investigators find that the speed camera hasn’t been recalibrated in a while.


Is a dash cam more accurate than the car’s speedometer?

A car’s speedometer tends to be slightly more accurate at lower speeds, as it works from some of the physical sources of the car, such as tyres and the drive shaft. A dash cam with GPS works from a satellite, so as long as there isn’t too much tree or building cover to interfere with the satellite reception, dash cams can be incredibly accurate. That being said, both methods of measuring speed are quite accurate and will only have one or two miles per hour difference in result.


How does a dash cam measure speed?

There are a few different ways that a dash cam can measure speed:

  1. One common method is to use the recorded footage and, with software that can track objects within the video, measure their speed by the movement across the frame.
  2. Another method is by using optical flow algorithms, which is similar but tracks objects in the video through multiple frames. Both of these methods require good video quality, as if the picture is blurred, then it might not be admissible as evidence.
  3. The third and most accurate method is via the dash cam GPS. This uses satellite reception and can ensure the most precise recording of how fast the car is travelling, so long as there isn’t too much interference in the reception.


So, the answer to the question on ‘how accurate is dash cam speed recording?’ is – pretty accurate! At Viofo, our cameras all provide clear imaging and GPS tracking to ensure that, should you need it, the camera records accurate speed tracking. The best way, obviously, to ensure you don’t need to use the evidence in a court situation – is to obey the speed limit on the roads. Although, you could come to the aid of another driver with vital evidence to help prove who was at fault in an accident – making you a modern-day hero!

For our extensive range of superb, quality cameras, and for advice on what is the best fit for your personal dash cam requirements, chat to us today.

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