| View previous topic :: View next topic |
| Author |
Message |
spot
Occasional Visitor
Joined: Jun 05, 2005
Posts: 45
|
 Posted: Mon Oct 08, 2007 2:21 pm Post subject: The Empire Strikes Back |
 |
|
Colleagues may be interested in this news!
http://news.bbc.co.uk/1/hi/england/wear/7033353.stm
Sorry if this is off topic - I normally only visit TTG pages of this site.
Drive safely!!
Cheers
Spot |
|
| Back to top |
|
 |
Darren
Frequent Visitor
Joined: 11/07/2002 14:36:40
Posts: 23848
Location: Hampshire, UK
|
| Posted: Mon Oct 08, 2007 2:37 pm Post subject: |
|
|
Interesting, nothing unique in the logging functionality but it would be interesting to know how the additional accuracy is obtained, something to do with the GSM phone perhaps?
_________________
Darren Griffin |
|
| Back to top |
|
|
gardenshed
Frequent Visitor
Joined: Jul 05, 2007
Posts: 466
|
| Posted: Mon Oct 08, 2007 3:37 pm Post subject: |
|
|
i wonder if the data logs from trripmaster would stand up in court  |
|
| Back to top |
|
|
zardoz
Lifetime Member
Joined: Jan 03, 2006
Posts: 76
|
| Posted: Tue Oct 09, 2007 11:25 am Post subject: |
|
|
| gardenshed wrote: | | i wonder if the data logs from trripmaster would stand up in court |
If I was being prosecuted for speeding and I was convinced that the detector was at fault, I would certainly offer them in my defence and allow the magistrates to decide. You would have to be pretty sure of your ground though... You might however be able to persuade the CPS to drop the case if you had good evidence that they might have a fight on their hands.
It might also be of use if your car was cloned, in that you could offer evidence that you were elsewhere at the time.
Z. |
|
| Back to top |
|
|
mikealder
Pocket GPS Moderator
Joined: Jan 14, 2005
Posts: 19638
Location: Blackpool , Lancs
|
| Posted: Tue Oct 09, 2007 6:05 pm Post subject: |
|
|
If you take the wheel speed sensor signal from a car equipped with ABS it will generate a square wave pulse train, the frequency of this square wave is directly proportional to vehicle speed. If you then ''callibrate'' the wheel frequency against the GPS speed which is easy in software you can have an accurate speed record far more frequently updated than the 1Hz GPS derived speed, using this method removes any inaccuracy due to tyre wear or temperature and pressure changes.
Getting the wheel speed frequency into the PC is easy using an AtoD converter. The GPS data can be easily recorded on the PC from either a Bluetooth receiver or direct connection to the PC serial port.
The device pictures I have seen appear to resemble an EPIA mini / micro ATX board which is regularly used for car based projects as they are cheap cost effective and can be equipped with a power supply that feeds direct from the 12V DC in the vehicle.
The key to this being usable data must reside with the GSM connection being used to store the data in a secure way to prevent it being altered, it is certainly not rocket science to alter the NMEA data in a trip log making the data display any speed you want, even altering the check sum value is easy when you know how.
Perhaps the CPS decided they were on sticky ground and threw the case to prevent the advertising a case dismissed verdict would have made - Mike |
|
| Back to top |
|
|
Skippy
Pocket GPS Verifier
Joined: 24/06/2003 00:22:12
Posts: 2946
Location: Escaped to the Antipodies! 36.83°S 174.75°E
|
| Posted: Tue Oct 09, 2007 8:39 pm Post subject: |
|
|
| mikealder wrote: | | Perhaps the CPS decided they were on sticky ground and threw the case to prevent the advertising a case dismissed verdict would have made - Mike |
Well, that's what Phillip Tann and Autopoietic Systems would like us to believe anyway.
| bbc wrote: | | A spokesman for the Crown Prosecution Service (CPS) said: The officer who operated the camera has since retired. |
The way I read it, the case was dropped because the officer involved was not available to give evidence because he had retired. This would hold true for ANY alleged speeding offence recorded by that officer if the defendant elected to defend the case in court.
Having a data logger sounds like a great theory, but despite what Autopoietic Systems would have us believe, this wasn't a test case of their system and I think they would have a real hard time proving that the evidence hadn't been tampered with and having it accepted in court.
Even if the court did accept that the tracklog was an accurate log of the journey, what would stop the prosecution demanding that the company holding the data to produce the complete log ALL the data recorded by the system. 
No problem if you never, ever, ever exceeded the speed limit..... 
Anyway, let's hear what this guy has to say:
| Quote: | | "My system can track a GPS phone within half-a-metre of where it is, whereas devices currently on the market can, at best, only track a phone within five metres." |
He goes on to claim he was doing "29.717 MPH, it's accurate to 15 decimal places". The reporter goes on to claim that the location and speed are "up to 20 times more accurate that existing systems".
A consumer GPS unit typically quotes an accuracy to about .1 MPH. Even using some sort of dead reckoning like a gyroscope and wheel speed sensor, he isn't going to improve on that accuracy much. Certainly not to 15 decimal places like he claims.
And improve accuracy to half a meter? How does that work then? If such a thing was possible in a unit retailing for £60 don't you thing that the likes of SiRF and Garmin would have integrated the technology into their GPS units?
Now I don't know about you guys but my BS detector is going off like crazy. This is more like something you would read in the Daily Mail - pretty crap reporting and an obvious plug for someone's product by the BBC.
_________________
Gone fishing! |
|
| Back to top |
|
|
Darren
Frequent Visitor
Joined: 11/07/2002 14:36:40
Posts: 23848
Location: Hampshire, UK
|
| Posted: Tue Oct 09, 2007 9:11 pm Post subject: |
|
|
| Skippy wrote: | | The way I read it, the case was dropped because the officer involved was not available to give evidence because he had retired. This would hold true for ANY alleged speeding offence recorded by that officer if the defendant elected to defend the case in court. |
Precisely. We do not know if the CPS would have defended the case if the camera operator had been available.
I'm trying to seek more information on the claimed accuracy of his software which I find hard to believe.
_________________
Darren Griffin |
|
| Back to top |
|
|
nivek22
Lifetime Member
Joined: Mar 09, 2006
Posts: 194
Location: Barnsley, South Yorkshire.
|
| Posted: Wed Oct 10, 2007 8:14 am Post subject: |
|
|
| mikealder wrote: | | using this method removes any inaccuracy due to tyre wear or temperature and pressure changes. |
Am I missing something here?
Assuming that the square wave is generated by the rotation of the wheel, then changing the circumference of the wheel WILL change the speed of the vehicle while the the wheel rotates at the same speed. |
|
| Back to top |
|
|
Skippy
Pocket GPS Verifier
Joined: 24/06/2003 00:22:12
Posts: 2946
Location: Escaped to the Antipodies! 36.83°S 174.75°E
|
| Posted: Wed Oct 10, 2007 9:01 am Post subject: |
|
|
| nivek22 wrote: | | Assuming that the square wave is generated by the rotation of the wheel, then changing the circumference of the wheel WILL change the speed of the vehicle while the the wheel rotates at the same speed. |
These systems are called "dead reckoning". What they do is use the GPS to dynamically calibrate the speed sensor from the wheel.
So, if the system detects that you are traveling in a straight line with a good GPS reception for several seconds then it can be fairly confident that it has an accurate speed reading from the GPS. It now uses this data to figure out how many pulses it gets from the wheel over a particular distance.
It can now augment the GPS data with the data from the wheel speed and use this when the GPS reception is poor or to enable the system to log data at a faster rate than the one sample per second provided by the GPS.
Really clever systems add a gyroscope, electronic compass or accelerometer to detect changes in direction too.
_________________
Gone fishing! |
|
| Back to top |
|
|
nivek22
Lifetime Member
Joined: Mar 09, 2006
Posts: 194
Location: Barnsley, South Yorkshire.
|
| Posted: Wed Oct 10, 2007 12:18 pm Post subject: |
|
|
I knew I was missing something  thanks for that. |
|
| Back to top |
|
|
FazerUK
Lifetime Member
Joined: Nov 18, 2004
Posts: 242
Location: Wrexhaml, UK
|
| Posted: Wed Oct 10, 2007 7:15 pm Post subject: |
|
|
The big problem would of been, if this guy got off with his case because of that device, then the government would have all new cars fitted with a device like it and every time someone goes over 30 mph in a 30 zone, you automatically get fined
_________________
TomTom Go 700,
with External Antenna, External Mike
App v7.160, OS:2324, GPS v1.21, Boot 5.4201
Western_Europe-Map v650.1127 |
|
| Back to top |
|
|
|
![]() Posted: Today Post subject: Pocket GPS Advertising |
|
|
We see you’re using an ad-blocker. We’re fine with that and won’t stop you visiting the site.
Have you considered making a donation towards website running costs?. Or you could disable your ad-blocker for this site. We think you’ll find our adverts are not overbearing!
|
|
| Back to top |
|
|
|
Forum FAQ
Search
Usergroups
Profile
Log in for private messages
Log in
