What device/s can u use in/on your car to record your vehicle speed accurately?

[Symo Advanced Member Find all posts View Profile Close Symo]

I'm guessing you guys have now idea how a GPS measures speed...

An iPhone can measure speed to 1/10th of a kmh let alone any other dedicated device. Ever heard of v-box? It's the brand that uses g sensors and GPS to measure acceleration and speed to a fraction of a kmh.

There is nothing special about it, and it has nothing to do with gps in particular. To record a speed using any radio wave GPS in particular you use the Doppler principle. The code in the GPS signal is timed, the length of the code is specific, when moving the code compresses and this compression can be measured using software, it is then a simple physics calculation to determine the missing component, speed.

All GPS devices, performance measuring equipment etc just use the Doppler effect on the code and it knows how fast you are going without even trying to 1/10th of a kmh. It's child's play, and no calibration is necessary as the software automatically compares one satellite with at least 10-15 others for redundancy.

The law enforcement are just using excuses to prevent such a simple device from clearing some people from rightful dismissal.


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[rob_macca67 Avid PP Poster! Find all posts View Profile Close rob_macca67]

I thought the GPS can only read a horizontal speed and therefore when heading up/down hills, then the speed travelling is not that accurate... ?

I'm guessing you guys have now idea how a GPS measures speed...

An iPhone can measure speed to 1/10th of a kmh let alone any other dedicated device. Ever heard of v-box? It's the brand that uses g sensors and GPS to measure acceleration and speed to a fraction of a kmh.

There is nothing special about it, and it has nothing to do with gps in particular. To record a speed using any radio wave GPS in particular you use the Doppler principle. The code in the GPS signal is timed, the length of the code is specific, when moving the code compresses and this compression can be measured using software, it is then a simple physics calculation to determine the missing component, speed.

All GPS devices, performance measuring equipment etc just use the Doppler effect on the code and it knows how fast you are going without even trying to 1/10th of a kmh. It's child's play, and no calibration is necessary as the software automatically compares one satellite with at least 10-15 others for redundancy.

The law enforcement are just using excuses to prevent such a simple device from clearing some people from rightful dismissal.


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[Beach Advanced Member Find all posts View Profile Close Beach]

I'm guessing you guys have now idea how a GPS measures speed...

An iPhone can measure speed to 1/10th of a kmh let alone any other dedicated device. Ever heard of v-box? It's the brand that uses g sensors and GPS to measure acceleration and speed to a fraction of a kmh.

There is nothing special about it, and it has nothing to do with gps in particular. To record a speed using any radio wave GPS in particular you use the Doppler principle. The code in the GPS signal is timed, the length of the code is specific, when moving the code compresses and this compression can be measured using software, it is then a simple physics calculation to determine the missing component, speed.

All GPS devices, performance measuring equipment etc just use the Doppler effect on the code and it knows how fast you are going without even trying to 1/10th of a kmh. It's child's play, and no calibration is necessary as the software automatically compares one satellite with at least 10-15 others for redundancy.

The law enforcement are just using excuses to prevent such a simple device from clearing some people from rightful dismissal.


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None of this is admissible in court. Its been tried before. You can quote the Doppler effect as much as you like. You must have a recognised certification on the device you are relying on to prove the speed you were traveling at. If your evidence has a good chance of showing the police device or speed camera to be in any way fallible, the case against you will be dropped.

[Bushbasher Out of control poster! Find all posts View Profile Close Bushbasher]

they must think the data reasonably is accurate.

In the absence of any other evidence to prove otherwise, the court may admit into evidence any information which may or may not help go towards proving a fact beyond reasonable doubt. They would say in the case you describe that the GPS indicates a speed of X which is, or isn't, in line with the wreckage/scene.

Also, if you want to take on the authorities by claiming their technology is faulty (radar/laser) then you will find yourself up against the manufacturer's expert. His attendance will cost you minimum $10K. Cheaper to pay the fine.

[Steve M Addicted PP Member Find all posts View Profile Close Steve M]

That's the problem Dave it cost so much to prove you were in the right so majority of people just pay the fine. Would piss me off if I got pinged knowing I was in the right. If they can use the camera using GPS for evidence then how do they allow that but not the other way round. Very one sided and extremely unfair.... Cheers

[Guest Close Guest]

What about that story of the guy who got pinged by a policeman who didn't use any instrument to detect speeding? He only used his expert judgement.

[Bushbasher Out of control poster! Find all posts View Profile Close Bushbasher]

Don't speed. I've worked that out over here, especially on the freeways and main arterial roads. I always seem to keep up with the lead-foots, catch them at the next set of lights.

[Beach Advanced Member Find all posts View Profile Close Beach]

Don't speed.

If you're not doing anything wrong, you have nothing to fear. Right?

Just because you're not doing anything wrong, doesn't mean you have nothing to fear. Hence the discussion we are having now.

[Bushbasher Out of control poster! Find all posts View Profile Close Bushbasher]

Yeah, I agree. Gotta watch out for all the lunatics out there, running red lights, speeding on speed, texting, eating breakfast, doing their make-up. Somebody needs to invent a device that will scan and point them out whilst you're mobile.

[Beach Advanced Member Find all posts View Profile Close Beach]

Yeah, I agree. Gotta watch out for all the lunatics out there, running red lights, speeding on speed, texting, eating breakfast, doing their make-up. Somebody needs to invent a device that will scan and point them out whilst you're mobile.

All that and more. In car cameras are providing a lot of evidence and catching negligent drivers.

If my camera records someone committing a driving offence and I take the footage to the police, can they act upon it?

Additionally, a certified in car speed recording device is a good idea to guard against those in authority who would have you pay fines for offences you did not commit.

[rwo Advanced Member Find all posts View Profile Close rwo]

All that and more. In car cameras are providing a lot of evidence and catching negligent drivers.

If my camera records someone committing a driving offence and I take the footage to the police, can they act upon it?

Additionally, a certified in car speed recording device is a good idea to guard against those in authority who would have you pay fines for offences you did not commit.

I believe your in-car footage is admissible evidence and seem to recall the laws on this changed a few years ago, as this was not the case previously. I think it was all to do with providing the police a means to track down and prosecute "hoon" drivers, when all they had to go on is video evidence or photo's sent to them by members of the public. I also believe there have been a number of drivers prosecuted after posting their own reckless acts on social media...

I know very little about speed detection used by the police and the certification of it, but would love to get hold of a copy of their (or the manufacturers) official "speed camera" guidelines that says where they can and can't use speed camera's to accurately detect speed. It's always got me buggered how they can simply pull up an X-trail or Territory (or what ever else they use) on the side of the road with a camera fitted in the back, start snapping accurate, calibrated and credible speed photo's and then dish out fines accordingly.

Don't get me wrong, I'm not an advocate for speeding and do think it's best to not speed at all, I'm just still a bit dark by the last fine I got which was snapped by one of these cars about 100km north of Geraldton, WA, literally the middle of nowhere. Obvious road black spot that one, they must be looking out for the well being of our Kangaroo population, not used for revenue raising my arse!

Anyway, I would buy this certified speed device in an instant if it existed and was admissible as a defense, but something tells me the government would bend over backwards to stop the sale of them. It would give the average Joe Blow the means to defend himself against incorrect speed fines and may even start to change the culture of "I don't agree with this fine, but it's too hard/expensive to defend so I will just pay the bloody thing", imagine how much that will cost them...

[Bushbasher Out of control poster! Find all posts View Profile Close Bushbasher]

We had a guy who wanted to complain about somebody throwing a beer bottle at his car. Looked at the dash cam footage and it was shite. I witnessed an incident. Had it all on my dash cam I thought. Checked the video and the bloody thing kept dropping out at the very bit that I needed. Sure they can be useful - when they work.

[Bushbasher Out of control poster! Find all posts View Profile Close Bushbasher]

And how many states ban radar detectors? Number plate disguisers/rotators? Don't get caught.

[Steve M Addicted PP Member Find all posts View Profile Close Steve M]

Hi Dave, I think the only state that still allow detectors is WA isn't it ?? I remember in my foolish days I use to run two of them. One mounted on the sun visor the other on the windscreen. Saved me numerous times. Then they become illegal so the one on the windscreen went and the one on the sunvisor went into the sunvisor (pulled the visor apart) drilled a hole through the arm supporting it and ran power wire with external speaker which I mounted right near the seat belt near my right ear. Used it for about 12 months till my boss got pinged using his, for memory was some thing like $800 fine plus they took the detector. (Got pinged on pennant hills rd).. So after that pulled the fuse but was still in there when I sold the car..... Still hate those mobile cameras though,(cops I don't mind them, they use there discretion, most times fairly) the mobile ones on the side of the road, anybody who thinks there not revenue raising has their head up their ar#e

[B.Col Lurker Find all posts View Profile Close B.Col]

Folks, I don't think we are going to get what rob_macca67 set out to achieve. Despite what symo tells us about GPS accuracy, there is no way Police will accept it. If symo is correct, at 60kmph the GPS COULD be out by 6kmph. More than enough for police to distrust your GPS.
I suggest an alternative. If you have a dash cam that shows the time accurately on its recording, and you can accurately record the time it takes to travel between 2 points, then you can accurately determine the speed you were doing. I recon you would need to have relatively high definition in order to pin point distance traveled in order for a court to accept it.
Aside from that, it's probably good practice to know exactly what you odo and speedo is reading. Does your odo accurately record how far you've gone? At a given speed on your speedo, how long does it take to travel a km? Don't rely on the GPS. It's possibly out by 100m. You can't argue with time and distance.