Speed limits speedometers vs GPS speed

[Gareth79]

OutInTheShed said:

Teem50 said:

Not true, I'm afraid. GPS speed measurement is based on dopplering the carrier signal from the satellites and produces an instantaneous measurement. If you have access to all the information produced by the GPS receiver (such as I get on my race car's data logger) then you get another channel which tells you the instantaneous accuracy of the speed measurement. It varies quite a lot.

https://www.vboxautomotive.co.uk/index.php/en/how-...

As your own link says, that's only the case for certain specific 'GPS Engines'.

Probably wvery GPS 'engine' made in the past 20 years, and certainly everything being made today.

OutInTheShed said:

It's something of a simplification anyway, because GPS doesn't actually transmit a 'carrier' and the signal's doppler is kind of dominated by the satellite doing something like 9000mph. Add in some signals bouncing off buildings in town, or losing the signal under a wet tree

The doppler shift is used as part of the position calculation. Bouncing around at street level will not affect the speed.

OutInTheShed said:

The GPS in a phone or a Tom-Tom sat nav will have quite a lot of processing between the 'GPS engine' and the display.

Not really. The speed will be averaged a bit, which is where people see a speed still dropping when they have stopped.

[Super Sonic]

MustangGT said:

How about proving it by posting a personal detail redacted copy of the 'ticket'?

The notice of intended prosecution letter has to be sent back w the relevant box ticked or name filled in.

[Super Sonic]

Craig_suke said:

Cool story…Or looking at data provided by said police forces and their own guidelines prove he is probably talking rubbish. It’s all publicly available to see the guidelines….

Only probably? So not definitive? 'Guidelines'!

Edited by Super Sonic on Thursday 23 March 18:30

[JimbobVFR]

catso said:

In my experience, modern car speedos seem to be much more accurate, so much so that I wonder if they might use some kind of GPS 'correction'?

My old Audi A2 had a key combination on the AC panel that showed various diagnostic info including the cars speed in KM/H. This was pretty much spot on when compared to GPS but the Speedo was a few MPH over.

[OutInTheShed]

JimbobVFR said:

My old Audi A2 had a key combination on the AC panel that showed various diagnostic info including the cars speed in KM/H. This was pretty much spot on when compared to GPS but the Speedo was a few MPH over.

The 'car will know' its speed fairly accurately, give or take only the variation in effective diameter of the tyres.
It knows the engine rpm to within a few parts per million.
If it knows the gear ratios and what gear you are in, it's easy.
Tyres obviously lose 5mm in wear and vary a bit with inflation.

[James6112]

Stick to the speed limit on Waze & you’ll be fine.
Set the alert to ping when you go over.
Can’t go wrong.

[Craig_suke]

Super Sonic said:

Only probably? So not definitive? 'Guidelines'!

Edited by Super Sonic on Thursday 23 March 18:30

Again his story is a good one. But unless there is any proof it is just that…..a story which some idiots will believe.

[E-bmw]

Why is it that so many people on here get all hung up on whether anyone did or didn't get a ticket for doing under or over the "guidelines" stated?

I personally couldn't give 2 sh!ts what speed anyone did or didn't get done for or whether it is concocted or not, and I certainly couldn't be bothered with giving the claimant any grief or need for proof.

If it happened it happened, if it didn't it didn't what is the point in arguing the point?

Build a bridge & get over it.

[BertBert]

to take a different view, it's a huge curiosity. The guidelines have been in place for ages of 10%+2 (or similar, but none lower as far as I know). Of the instances of tickets that are claimed to be below the threshold none have been able to show the docs. It's not a personal slight, just that we've not seen one yet.

[E-bmw]

BertBert said:

It's not a personal slight, just that we've not seen one yet.

Yes, but why is it a problem that you haven't seen one?

[anonymous-user]

E-bmw said:

Why is it that so many people on here get all hung up on whether anyone did or didn't get a ticket for doing under or over the "guidelines" stated?

I personally couldn't give 2 sh!ts what speed anyone did or didn't get done for or whether it is concocted or not, and I certainly couldn't be bothered with giving the claimant any grief or need for proof.

If it happened it happened, if it didn't it didn't what is the point in arguing the point?

Build a bridge & get over it.

Because if someone actually did get a ticket for 43 in a 40, or 75 in a 70, or whatever, then it really does change the way many of us manage our speed. It is of interest to us all as motorists. It would be a significant change in Police policy or standard practice.

The reason the poster is getting so much stick is because in the 19 years I have been on this forum (14 with this username and 5 with an earlier one) no one has ever managed to provide proof of these speeding offences, despite countless people claiming they have been 'done' for such an offence.

When someone pops up and claims they were ticketed for an offence of less than 10% over the speed limit, people ask them to photograph/scan the ticket and post it. When that happens, one of three things happens in every single case:

1) They state it was a long time ago. They can't quite remember. The ticket is long gone. Their memory is a little hazy. It was years ago. But they are fairly certain it was 44 in a 40, or something. Maybe. Possibly.

2) They come back to the thread and confess that actually, they have re-read the ticket and it was 49 in a 40. Or they got done for doing 32 and were annoyed, but it turns out that it was actually a 20 zone and they were 12 mph over.

3) They disappear and are never heard form again, presumably because they made it up.

Every single time. No one has ever shown a ticket for a 10% over speeding offence. No one can find any proof anywhere else on other forums that it has happened either. Just lots of 'My mate got done for 33 in a 30 once'.

I'm not saying the poster in this thread was making it up, but I am suggesting he may have mis-remembered, as in his own words, it was years ago. It is just an old wives tales. Even the Police themselves and Safer Roads have confirmed they do not ticket for below this threshold.

But, and here's the but, it is worth remembering that there are official variations in Wales and in Scotland, plus in specific areas in England. For example, a few months ago, the Met said it was reducing tolerance form 10%+3 to 10%+2, which to be honest, just brings them in line with most other counties/forces.

[MustangGT]

Super Sonic said:

MustangGT said:

How about proving it by posting a personal detail redacted copy of the 'ticket'?

The notice of intended prosecution letter has to be sent back w the relevant box ticked or name filled in.

Anything like that would be scanned or copied before return, certainly in my household.

[Cat]

Lord Marylebone said:

But, and here's the but, it is worth remembering that there are official variations in Wales and in Scotland, plus in specific areas in England. For example, a few months ago, the Met said it was reducing tolerance form 10%+3 to 10%+2, which to be honest, just brings them in line with most other counties/forces.

What is the official variation in Scotland?

Cat

[Craig_suke]

E-bmw said:

Why is it that so many people on here get all hung up on whether anyone did or didn't get a ticket for doing under or over the "guidelines" stated?

I personally couldn't give 2 sh!ts what speed anyone did or didn't get done for or whether it is concocted or not, and I certainly couldn't be bothered with giving the claimant any grief or need for proof.

If it happened it happened, if it didn't it didn't what is the point in arguing the point?

Build a bridge & get over it.

Personally find it’s funny that people will try to pass around false information, these people need to be called out about it

I’ll put it out there that no forces ticket office (the ones who would issue the ticket or offer a course) would accept a ticket for less than their own stated guidelines as it would be an easy argument in court. The officers, camera’s and vans all operate to these guidelines.

As mentioned many times people claim it to get some attention but then could strangely prove it.

[E-bmw]

Craig_suke said:

E-bmw said:

Why is it that so many people on here get all hung up on whether anyone did or didn't get a ticket for doing under or over the "guidelines" stated?

I personally couldn't give 2 sh!ts what speed anyone did or didn't get done for or whether it is concocted or not, and I certainly couldn't be bothered with giving the claimant any grief or need for proof.

If it happened it happened, if it didn't it didn't what is the point in arguing the point?

Build a bridge & get over it.

Personally find it’s funny that people will try to pass around false information, these people need to be called out about it

Personally, I think if someone wants to claim something did/didn't happen, I couldn't care less if I tried.

Craig_suke said:

As mentioned many times people claim it to get some attention but then could strangely prove it.

But, the only attention they get is from those who claim it didn't happen until they see proof, so you are encouraging it in your denial.

Don't forget that the veil of the internet is the easiest thing in the world to hide behind & it can never be removed, unless willingly done so.

[anonymous-user]

Cat said:

Lord Marylebone said:

But, and here's the but, it is worth remembering that there are official variations in Wales and in Scotland, plus in specific areas in England. For example, a few months ago, the Met said it was reducing tolerance form 10%+3 to 10%+2, which to be honest, just brings them in line with most other counties/forces.

What is the official variation in Scotland?

Cat

Sorry, to be clearer, I should have said:

"This is what I understand to be the case in England and tolerances may differ elsewhere, and I do not know what they are, so do your own reading of the law before speeding"

I mentioned Scotland because the last I heard was this from a few years ago (from The Times, and Police Scotland):

"Police in Scotland have announced that they are axeing the thresholds. From this autumn Scottish drivers going fractionally over the limit will receive formal warning letters. If they are stopped a second time, they will receive a £100 penalty notice and three penalty points or be reported for prosecution.
The new procedures, approved by the Scottish government, will be tested in a six-month pilot project. Scottish police — unlike those in England and Wales — have never disclosed the margin of error they use"

"According to Superintendent Iain Murray, head of road policing in Scotland, the change is being driven by safety considerations. “We are talking about people who might be law-abiding in every other respect but fail to realise the risk they pose by driving on autopilot or failing to pay enough attention to what is going on around them"

"a spokesman for Police Scotland confirmed that repeat offenders would be penalised. “If you were just fractionally over the first time, you would be given a warning, but if you were to again just be fractionally over, you would be given a fixed penalty or it would be reported to the procurator fiscal,” he said.

As mentioned in the article, Scotland will not say what threshold they operate to, and I do not know what it is, but officially they have claimed to have zero tolerance. Maybe they do, maybe they don't, which is why I said I was only aware of the rules in England.

[donkmeister]

If you are going to drive at GPS speed +10%+1mph to get your money's worth, just don't get annoyed that most people aren't following the same strategy. Especially if you are driving in built up areas, where 23 or 34mph might be too fast for the conditions.

Blindly trying to achieve a particular speed simply because it's not technically speeding is the first step to becoming a member of the 40mph everywhere club

[Cat]

Lord Marylebone said:

Sorry, to be clearer, I should have said:

"This is what I understand to be the case in England and tolerances may differ elsewhere, and I do not know what they are, so do your own reading of the law before speeding"

I mentioned Scotland because the last I heard was this from a few years ago (from The Times, and Police Scotland):

"Police in Scotland have announced that they are axeing the thresholds. From this autumn Scottish drivers going fractionally over the limit will receive formal warning letters. If they are stopped a second time, they will receive a £100 penalty notice and three penalty points or be reported for prosecution.
The new procedures, approved by the Scottish government, will be tested in a six-month pilot project. Scottish police — unlike those in England and Wales — have never disclosed the margin of error they use"

"According to Superintendent Iain Murray, head of road policing in Scotland, the change is being driven by safety considerations. “We are talking about people who might be law-abiding in every other respect but fail to realise the risk they pose by driving on autopilot or failing to pay enough attention to what is going on around them"

"a spokesman for Police Scotland confirmed that repeat offenders would be penalised. “If you were just fractionally over the first time, you would be given a warning, but if you were to again just be fractionally over, you would be given a fixed penalty or it would be reported to the procurator fiscal,” he said.

As mentioned in the article, Scotland will not say what threshold they operate to, and I do not know what it is, but officially they have claimed to have zero tolerance. Maybe they do, maybe they don't, which is why I said I was only aware of the rules in England.

There is no zero tolerance policy in Scotland. The scheme refered to above never went beyond the pilot (if it actually lasted that long).

Cat

[Craig_suke]

E-bmw said:

But, the only attention they get is from those who claim it didn't happen until they see proof, so you are encouraging it in your denial.

Don't forget that the veil of the internet is the easiest thing in the world to hide behind & it can never be removed, unless willingly done so.

Crack on then buddy, each have our own opinions on the matter. If stupid goes on unchallenged then it’ll multiply, just look at Facebook to confirm this.

[E-bmw]

Craig_suke said:

E-bmw said:

But, the only attention they get is from those who claim it didn't happen until they see proof, so you are encouraging it in your denial.

Don't forget that the veil of the internet is the easiest thing in the world to hide behind & it can never be removed, unless willingly done so.

If stupid goes on unchallenged then it’ll multiply, just look at Facebook to confirm this.

I agree about faceberk, which is why I never use it, however in the posts where I see things like this being challenged it just adds fuel to the fire, ignoring it stops it dead, hence my stand on it, but as you quite rightly (if not actually) say different opinions are what makes the world go round.