Tom Tom and speeding tickets.

Lum

dreem wrote: »

I was surprised to find on a Google when i got home that the satnav would be accurate! The rules state an allowable car speedo tollerance of +/- 10% at 30 mph... Manufactures, for fear of the concequences I guess always duck slightly under... You would think in this digital age a car (Mercedes) would be able to give a near 100% accurate reading...

"Yes officer I was doing 30mph give or take 10%!"

Speedo is allowed to overread by up to 10% + 6.25mph. I.e. in a 30 limit it can read anything betweeo 30 and 39.25 mph and still valid.

It doesn't matter what make of car you have or how expensive it is, your speedo is always going to overread, even if it's absolutely perfect when your car leaves the factory. This is because of the simple fact that they work by measuring how quickly the wheels rotate and as you wear down your tyres you cover less distance per rotation so the indicated speed rises.

In practice most manufacturers aim for around 5% +3 as there will always be some variation in either direction and this allows for more of them to be legal. Premium manufacturers may well aim for closer to zero, which probably goes some way towards explaining the stereotype of a !!!! in an Audi A4 getting wound up by someone going too slowly in a Nissan Micra.

Also satnav speed readings are only accurate if you take the reading while traveling in a straight line on a flat road with a good view of the sky and no tall buildings at the edge of the road. Best thing to do is once you find such a road, compare the too and then you'll know what indicated speed on your speedo you can do while still remaining legal. Just remember to re-check it every so often.

mikey72

Satnavs are accurate in 3d, using doppler shift.

dacouch

mikey72 wrote: »

Satnavs are accurate in 3d, using doppler shift.

Laymans terms please

mikey72

When the sat nav recieves the satellite signal, it recieves all the information on where it is, and what frequency it's transmitting on. If the car is moving towards it, the measured frequency is slightly higher, away and it's slightly lower.
With enough different satellites, in different directions, the sat nav can accurately calculate the speed the car is moving at.

Even when moving straight up, as it is getting closer, so there is a frequency change which can be measured.

newfoundglory

In reference to the Police in the Netherlands using the data to identify where on average people are driving too fast and putting up speed cameras and traps, the CEO says:

We don't like that, because our customers don't like that

:rotfl:

Don't bite the hand which feeds you, Tomtom

Customers are unforgiving on this sort of thing, and Tomtom knows it.

I think you'll find most satnavs with decent hardware and software will be good at calculating speed over short distances.

Stephen_Leak

Strider590 wrote: »

I know this sort of guy, big mouth, large vocabulary, probably laughs annoying at the slightest thing, but has noooooo brain.

Some years ago the govt was hinting at fitting GPS tracking devices to ALL new cars, the idea was to do away with speed camera's, connect to your GPS "black box" at MOT centre's, download your data and issue fines automatically, all at the same time.
They would of course have had to do away with the licence points else 95% of the population would lose their licence within 12 months.... Leaving just the doddery old farts and tractors on the roads.

Though if it get's "Mr/Mrs Constant 41mph" off the road, i'd be well impressed

If they get around the human rights issue they might be able to do this in future, BUT your Tom Tom is not spying on you and never will:rotfl:

The worrying thing is that all the technologies required to do this already exist. All you have to do is link them together, and that's not rocket science. Even someone working in IT at the HMRC ought to be able to do it, albeit with the aid of a "Networking For Dummies" book.

And since when have human rights ever applied to drivers? As soon as you get into a car, you're guilty. The only question is of what?

newfoundglory

I don't think the govt would ever be able to pull this off... despite my tomtom having the latest map and corrections there are still a load of speed limits it gets wrong.

Can you imagine how many people would be wrongly fined for driving down roads correctly at 40mph where the limit on the central database is incorrectly listed as 30? Or like around here where a national speed limit dual carriageway was reduced from 60 to 50?

The logistics of this could cost a fortune, as well as people suing the govt department responsible for administering it.

Governments which have an interest in doing this sort of thing generally don't last in government very long (remember the labour party identity card fiasco? :rotfl:)

[Labour are now where they belong for the next 10 years = not in power]

Stephen_Leak

Permit me some fun, playing devil's advocate.

If you have more than one source of information, you will have discrepancies. So, do away with the roadside speed limit signs. If the database says 30mph, show that on the device in the car, and that's what the driver should keep below. Just like a satnav can do now.

Fewer road signs would mean both a financial and environmental benefit and a reduction in the "information overload" for drivers.

Of course, it would cost a fortune. Government money saving schemes always do.

Lum

newfoundglory wrote: »

I don't think the govt would ever be able to pull this off... despite my tomtom having the latest map and corrections there are still a load of speed limits it gets wrong.

Can you imagine how many people would be wrongly fined for driving down roads correctly at 40mph where the limit on the central database is incorrectly listed as 30? Or like around here where a national speed limit dual carriageway was reduced from 60 to 50?

That isn't how you would do something like this. Satnav databases are permanently out of date simply because of the way maps are created from old fashioned surveys and then converted to an electronic form.

If you were to implement this sort of system, you'd assign each tomtom a unique ID, e.g. the serial number and then make sure that this data is preserved when the data is collected. It would be as simple as just storing all the NMEA strings from the GPS chipset (which contain date, time, location and speed) somewhere, though in reality you'd want to put them into a database for easy searching.

Matching this data up to an offence would be done by the police, not by your device, they would should have up to date records of speed limits at every location, and from there you would just be running queries for all speeds above a certain threshold in certain locations.

You can get blips in satnav data so once a potential offence had been found you'd need to pull 5 or 10 minutes of location/speed data and take an average.

You would also need to avoid processing any road that is within about 40 metres of another road. I'd probably go for more like 100 to be safe. Anyone who has driven with a satnav on that bit of the M4 that has an A road running underneath it will know why. Likewise you couldn't do it in areas with tall buildings such as Glasgow city centre.

It would definitely be feasible for motorways and NSL A and B roads, and probably quite a lot of rural roads too. If you did want to process offences on more dense road systems, you'd only safely be able to process on whichever of the roads is the higher speed limit, such as an urban dual carriageway. The North Circular in central London would be a good candidate.

The amount of computing power needed to do this is the only thing that makes it infeasible, any initial implementation would likely concentrate on speeds over 96mph because once you go above 70 mph you don't even need to cross reference it with the location to get potential offences.


It would also need legislative change, TomToms would have to be type approved for the purpose, and Section 172 would have to be amended to require people to know where their TomToms are and who was using it, in the same way it currently requires you to know who is driving your car.

It's not something they could sneak in the back door and all the people they're likely to catch would be throwing away their TomToms should anything like this come in.


If anything like this is going to happen it will be using the in-car GPS (or more likely Galileo) systems that they are proposing to use for road use charging. The black boxes they use for certain young driver insurance policies would also be capable of this.

The most likely route is they'd advocate a data-sharing agreement between the road user charging quango and the police and claim that it's for crime prevention, or that old standby "to catch terrorists" because we all know that criminals and terrorists all own legitimately purchased cars that are correctly registered in their own name and with a valid postal address where they actually live.

Once the data sharing is in place, it would simply be a case of building the system I just described and running queries.

If they do start mandating that everyone have this equipment fitted, I think I shall be purchasing a car with a 6V positive earth electrical system.

Stephen_Leak

Integrate GPS and a mobile phone technology - my mobile has both, and it isn't a new one - and use the IMEI.

I doubt that they would need to play the "terrorist" card, but it's good to have a "Plan B". It is a fact that ANPR technology has led to lots of uninsured drivers being stopped, who then turn out to be involved in other criminal activities. Well, at least it says so on every episode of "Strictly Police Pursuit Cameras on Ice" or whatever I've seen.

Now, as a law-abiding citizen, I have no problem with this. Which, of course, means that I should be punished for this heresy.

I know that there would be obstacles to overcome to fully implement this scheme to its awful full potential. But, they'e done worse before.