Satnav and speed limits

elsie
Posts: 371
Joined: Fri Mar 02, 2018 8:47 pm
Has thanked: 2 times
Been thanked: 52 times

Re: Satnav and speed limits

Post by elsie » Thu Mar 14, 2019 9:36 am

FF: you might wish to reconsider what is happening/likely to happen in the coming years. All new cars registered after 31 Mar 2018 have to be fitted with a GPS system. At present, it is only used for automatic emergency calls in the case of an accident.

Now the European Galileo global navigation satellite system is complete it will be used for a lot more assistance, control and other projects in our daily lives.

From https://etsc.eu/automated-emergency-cal ... ar-models/
Inclusion of the system means that all new models of car sold in the EU are fitted with GPS devices and are capable of communication over the GSM phone network. This will facilitate the introduction of future safety systems such as Intelligent Speed Assistance, which can use GPS to locate speed limits on digital maps, and could use the GSM connection to download regular map updates. The fact that eCall technology is already fitted as standard will make introduction of the technology considerably cheaper.

User avatar
DominicBest
Posts: 2132
Joined: Thu Mar 01, 2018 8:13 pm
Has thanked: 104 times
Been thanked: 427 times

Re: Satnav and speed limits

Post by DominicBest » Thu Mar 14, 2019 9:50 am

F Flinstone wrote:
Thu Mar 14, 2019 8:58 am
According to a lot of you, Satnav speed detection systems are very good, if they are so good then,why are they not fitted as standard to all new cars ;) Because you need a mechanical/electronic back up for when you loose the signal, so they may be good but not perfect, if your car is not fitted with such a system, then I assume you have to bring the Satnav with you, or are all phones now fitted with them? At the end of the day, they may tell you your speed, but not the speed limit in force at that time, unless you have a car with road sign recognition software, which on my Brontosaurus V8 Mk2 has. :D
Satnavs do not drive the car, they give the driver access to up to date, accurate information with minimal distraction. Individuals are allowed to like them or dislike them but I really miss travelling on the roads or the sea without them. I am going out in the car today and I have just put my map book in it, the one I used to plan my journey, the route that is now in my satnav. When I’m on my boat I always have charts and pilotage books for backup but as an everyday tool the satnav is great.
I meant to reply to Chancer’s comment about the inaccuracy of his Garmin watch. That goes without saying; as he is running forward at 8kmh the wrist with his watch on might well be moving in the opposite direction at the same speed or in the same direction at twice his speed. That will make a spot speed impossible to record, average speed based on distance travelled and time taken will be unaffected.
These users thanked the author DominicBest for the post:
Le Démerdeur (Thu Mar 14, 2019 10:21 am)
Rating: 11.11%

Hereford
Posts: 35
Joined: Mon Mar 12, 2018 12:37 pm
Has thanked: 0
Been thanked: 3 times

Re: Satnav and speed limits

Post by Hereford » Thu Mar 14, 2019 10:26 am

Thanks for the responses. I do not rely on my satnav for the speed limits (my OH noticed the differences not me). None of the places it happens had any 90 signs but I can see that they may not need them.
I suspect I will keep to a max of 80 on such roads - I am used to that now unless on a motorway. On the smaller roads 80 max would be ambitious anyway so is ignored.
We usually have the satnav on silent unless going through a complicated section and always have maps too.
Good to learn though,
thanks again.

Le Démerdeur
Posts: 4775
Joined: Thu Mar 01, 2018 11:22 pm
Location: Picardie and occasionally Sussex
Has thanked: 607 times
Been thanked: 545 times

Re: Satnav and speed limits

Post by Le Démerdeur » Thu Mar 14, 2019 11:53 am

DominicBest wrote:
Thu Mar 14, 2019 9:50 am
I meant to reply to Chancer’s comment about the inaccuracy of his Garmin watch. That goes without saying; as he is running forward at 8kmh the wrist with his watch on might well be moving in the opposite direction at the same speed or in the same direction at twice his speed. That will make a spot speed impossible to record, average speed based on distance travelled and time taken will be unaffected.
It doesnt work in that way and if it did my arms dont swing back and forwards 10m at a time :D

There are several accelerometers which detect the footfall and the arms definitely dont need to be swinging as the accuracy when walking is excellent I can be reading a map or simply looking at the display holding it close to my eyes and it instantly records changes in my pace. There is an initial period of calibration where it guesses the stride length and compares it with how many paces between GPS fixes, it is constantly refining that and even shows the correct speed when I am injured, limping/hopping, it knows the stride length for walking, running and at each speed and when we train on varying the stride length it accurately displays it, I am very impressed with it.

I'm sure if I bought a modern replacement for my 2007 Tom Tom it would be a lot better, however I recently bought a widescreen Grundig one (looks like a smartphone) which is app based and its a complete chocolate teapot, it will only ever get used if/when mine breaks and while waiting for a proper one to arrive

b33jay
Posts: 182
Joined: Fri Mar 02, 2018 2:35 pm
Has thanked: 6 times
Been thanked: 22 times

Re: Satnav and speed limits

Post by b33jay » Thu Mar 14, 2019 2:36 pm

F Flinstone wrote:
Thu Mar 14, 2019 8:58 am
According to a lot of you, Satnav speed detection systems are very good, if they are so good then,why are they not fitted as standard to all new cars ;) Because you need a mechanical/electronic back up for when you loose the signal, so they may be good but not perfect, if your car is not fitted with such a system, then I assume you have to bring the Satnav with you, or are all phones now fitted with them? At the end of the day, they may tell you your speed, but not the speed limit in force at that time, unless you have a car with road sign recognition software, which on my Brontosaurus V8 Mk2 has. :D
My sat nav "knows" the speed limit for the road as it's included in the mappping and will bleep if the limit is exceeded. An app that I have added to the sat nav also knows the speed limit for the road and where the fixed speed cameras are located as well as possible mobile camera sites and all can be updated on a daily basis. The latest models of some cars have recognition of speed limit signs built in. Most mobile phones have a mapping system included such as Google which is very good and can even indicate which roads currently have delays.

User avatar
DominicBest
Posts: 2132
Joined: Thu Mar 01, 2018 8:13 pm
Has thanked: 104 times
Been thanked: 427 times

Re: Satnav and speed limits

Post by DominicBest » Thu Mar 14, 2019 7:13 pm

Le Démerdeur wrote:
Thu Mar 14, 2019 11:53 am
DominicBest wrote:
Thu Mar 14, 2019 9:50 am
I meant to reply to Chancer’s comment about the inaccuracy of his Garmin watch. That goes without saying; as he is running forward at 8kmh the wrist with his watch on might well be moving in the opposite direction at the same speed or in the same direction at twice his speed. That will make a spot speed impossible to record, average speed based on distance travelled and time taken will be unaffected.
It doesnt work in that way and if it did my arms dont swing back and forwards 10m at a time :D

There are several accelerometers which detect the footfall and the arms definitely dont need to be swinging as the accuracy when walking is excellent I can be reading a map or simply looking at the display holding it close to my eyes and it instantly records changes in my pace. There is an initial period of calibration where it guesses the stride length and compares it with how many paces between GPS fixes, it is constantly refining that and even shows the correct speed when I am injured, limping/hopping, it knows the stride length for walking, running and at each speed and when we train on varying the stride length it accurately displays it, I am very impressed with it.

I'm sure if I bought a modern replacement for my 2007 Tom Tom it would be a lot better, however I recently bought a widescreen Grundig one (looks like a smartphone) which is app based and its a complete chocolate teapot, it will only ever get used if/when mine breaks and while waiting for a proper one to arrive
If it’s a GPS watch it works using GPS. When you run you use your arms, every efficient runner does, so it dramatically affects the movement of the GPS device on your wrist. I really don’t understand your comment about 10m, I can only presume your are misusing a manufacturer’s advice that the device is only accurate to 10m, in fact with normal signals the level of accuracy is far, far tighter than that. If you want something that works on stride length look no further than a pretty basic pedometer, a GPS device works on three dimensional position.

Le Démerdeur
Posts: 4775
Joined: Thu Mar 01, 2018 11:22 pm
Location: Picardie and occasionally Sussex
Has thanked: 607 times
Been thanked: 545 times

Re: Satnav and speed limits

Post by Le Démerdeur » Thu Mar 14, 2019 8:37 pm

I have what I want thanks Dominic and I know how it works.

Le Démerdeur
Posts: 4775
Joined: Thu Mar 01, 2018 11:22 pm
Location: Picardie and occasionally Sussex
Has thanked: 607 times
Been thanked: 545 times

Re: Satnav and speed limits

Post by Le Démerdeur » Thu Mar 14, 2019 10:14 pm

From the Ordonance Survey but the same info as all the sites I checked:

Positional accuracy with a single receiver, to civilian users approximately equals 5m to 10m, 95% of the time, and the height accuracy is generally 15m to 20m 95% of the time.

User avatar
DominicBest
Posts: 2132
Joined: Thu Mar 01, 2018 8:13 pm
Has thanked: 104 times
Been thanked: 427 times

Re: Satnav and speed limits

Post by DominicBest » Thu Mar 14, 2019 10:43 pm

You are still misrepresenting the data when you talked the about the length of your arm. My cheap, old, handheld Garmin GPS loaded with west coast of France charts places my boat in the correct marina berth when stationary. That’s a lot better than 10% accuracy given that the double berth is only just over 5m wide. The accuracy also makes no difference to the velocity displayed as that is giving the speed between the first presumed position and the second. I gather that you don’t trust modern technology but some of us use it very successfully all the time.

Le Démerdeur
Posts: 4775
Joined: Thu Mar 01, 2018 11:22 pm
Location: Picardie and occasionally Sussex
Has thanked: 607 times
Been thanked: 545 times

Re: Satnav and speed limits

Post by Le Démerdeur » Thu Mar 14, 2019 11:07 pm

Then you have completely misunderstood, I have bought a runners GPS watch and very much like using it, I bought a GPS satnav after losing the use of one eye and no longer being able to read or follow maps while driving, I still use it for that purpose.

The GPS watch uses several different accelerometers together with learned data to estimate speed, cadence etc via varying stride lengths, the same accelerometers are used to detect and calculate sleep rythms. As it picks up GPS data along the route it will correct and overwrite what it has recorded and displayed, I can see this happening myself, its a lot easier when walking to do so. It will also recalculate and change the data when its uploaded to the phone or computer because at that time it has the elevation and gradient data.

The watch 100% does not measure its speed or pace from the fore and aft movement of the arm that it is worn on, nor does it do so as a simple GPS device so the arm swinging backward and forward will have no bearing on the speed it displays or its accuracy.

Anyway this all started by me saying that a GPS will not be as accurate as a calibrated speedometer (OK I did not use the word calibrated) especially when travelling up or down hill and I dont think they will ever be homologated to do so.

Nowhere in my response did I say or give the impression that I dont trust modern technology, I have used my satnav since 2007 and now use the GPS watch 24/7, when I get my boat I will definitely welcome your advice on the best electronic and navigation systems to use.

PS, Where does the talk of 10% accuracy come from?

Post Reply