Anyone understand GPS vehicle trackers?

[Migmac]

Son had tracker in his first car, insurance required it. I had access to all the data. It continually said he was speeding. I’ve no doubt he was on some occasions. I was in the car and decided to look at the data. We were doing 70mph apparently! No we weren’t, we were in town coming to a stop at a round about. I use a personal tracker at work, it is extremely accurate as long as Uncle Sam doesn’t muck about with the satellites. I have been over thirty miles from my actual position! Perhaps when your speeding the satellites are being played with

 

[James1979]

Green road. It also doesn’t reset with each driver. If I Chuck the bus about for 3 hours then we swap drivers it takes you anothe 3/4 hours to bring the average back up.

She previously worked for a council and it was an inter team competition to see who could keep it red for longest....

 

[voipio]

There are issues with GPS-based monitoring, as many of us have noticed. The problem sources are 1) multipath signals in built up areas, where the apparent distances to each of the satellites are constantly and "randomly" varying as a result of changing reflections from buldings, buses, and other metalwork, 2) screening/shielding of individual satellite signals by stuff, like bridges, trees, people, pylons, van metalwork and suchlike, plus 3) effects of interference that can occasionally appear like genuine GPS but are spoof signals or, more frequently, interference that causes loss of reception.

Any of the above can result in positional solutions that jump around from the actual real world position, leading to excessively high speeds and, less frequently, excessively low speeds, being calculated based on the "position to position" method. The second problem is how the tracker software deals with these. Ideally, GPS position-derived info like speed should really be averaged over several seconds, together with a method in the software for removing obvious outlier values by a robust filtering algorithm. Vehicle tachometer data should also be factored in. If the tacho pulse rate is nearly constant, but GPS-derived speed is all over the place, and the positional fix is in a built up area, then the software should place more trust on the tacho data. Equally, the software should avoid issuing "penalties" for momentary changes in speed limits

The average trackers are obviously falling by a country mile, if they continue to produce false "positives" by over aggressive and unrefined computation methods.

 

[Cobbler]

Not with a tracker, but a satnav, coming down the M4, somewhere about the Reading area, the speed showing suddenly drops from 70ish to a fluctuating 40ish. Haven’t been that way for a while, but it always did it, no idea why.

 

[m_c]

There are issues with GPS-based monitoring, as many of us have noticed. The problem sources are 1) multipath signals in built up areas, where the apparent distances to each of the satellites are constantly and "randomly" varying as a result of changing reflections from buldings, buses, and other metalwork, 2) screening/shielding of individual satellite signals by stuff, like bridges, trees, people, pylons, van metalwork and suchlike, plus 3) effects of interference that can occasionally appear like genuine GPS but are spoof signals or, more frequently, interference that causes loss of reception.

Any of the above can result in positional solutions that jump around from the actual real world position, leading to excessively high speeds and, less frequently, excessively low speeds, being calculated based on the "position to position" method. The second problem is how the tracker software deals with these. Ideally, GPS position-derived info like speed should really be averaged over several seconds, together with a method in the software for removing obvious outlier values by a robust filtering algorithm. Vehicle tachometer data should also be factored in. If the tacho pulse rate is nearly constant, but GPS-derived speed is all over the place, and the positional fix is in a built up area, then the software should place more trust on the tacho data. Equally, the software should avoid issuing "penalties" for momentary changes in speed limits

The average trackers are obviously falling by a country mile, if they continue to produce false "positives" by over aggressive and unrefined computation methods.

It all depends on what kind of system is installed.
Some are purely GPS trackers. Some rely on having a standalone accelerometer as part of the system to detect g-forces from acceleration/braking/steering, and some read live data from the vehicle.

They all have weaknesses, but any sensible person can spot spurious data and act accordingly, however the people who often implement these systems think they're infallible and expect drivers warned without any context being considered.
There is a big difference between someone who just done a nightshift run averaging 90mph on the motorway sections and over 70 mph on the single carriageway through various towns and villages, than somebody who rarely gets flagged up but has got a couple obviously spurious implausible speed warnings.

 

[Ali]

Thanks all, good to know it’s not just me! Might have a look and see if I can find a phone app to track your journey avg. speed / max speed etc, but then it would probably be GPS too...

 

[James1979]

The black boxes for the young drivers can be really bad as well.

There is a stretch of road where I used to live which is a 40 but there's 200m of 20 outside a school, but only during school hours. The boxes aren't intelligent enough to know this and flag up an infringement if you do over 20 in that stretch :/

Mates boy has a rubbish deal on a black box. For every infringement it fines him. Straight out of his bank. His dad (my mate) is a traffic officer. He borrowed the boys car once to get to work, highly trained police driver, but running late - "making progress where available" as they say. Not necessarily speed, just using the road and a bit of hard braking / acceleration. Cost the poor little bugger a fortune

 

[tlovatt]

Our work vehicles are tracked, and the driver + boss get a notification if they exceed 70mph.
I had a telling off a while ago for an email showing I was driving at 90+ mph, and I was shocked as the weather was appalling on that trip and I’m not that type of driver anyway. It was in a Renault Trafic, I’m not even sure they’ll do 90? I just apologised and assumed I must have had a lapse of concentration going downhill with a tailwind. The location was roughly correct.

I normally use the speed limiter anyway, but I’ve been religious about it since then. Then I got another one this morning 90.8mph and another one 1s later 68mph. I didn’t jam the brakes on like that at any point in the journey as I was fully loaded with expensive kit. Location roughly correct again.

No idea how these work but something isn’t right, unless I’m Dr Jekyll & Mr Hyde.

You need to ask your boss for the duration of your speeding, you can on most trackers get glitches but these are easy to spot as the duration of the speeding will be a few seconds or less. Generally only give people a talking to if the speed shows for half a minute or more is the rule we generally work to.

I would say that mostly the trackers are very accurate and if you look at average speeds and accident data you will see the frequent flyers are the frequent crashers!

 

[premmington]

I don't fit trackers to our vans. Not into micromanaging staff. None of them have got speeding tickets (yet).

Courtessy cars is another ball game - I am always having to redirect speeding tickets to customers addresses - then they ring up moaning (do they expect me to take thier points for them?)

My brother in law has an electrical contracting bussiness - about 30 vans - he has had to stop signwritting the backs of the vans up - because he is fed up with the general public keeping ringing him up - moaning about his staff driving like idiots.

 

[brightspark]

I don't fit trackers to our vans. Not into micromanaging staff. None of them have got speeding tickets (yet).

Courtessy cars is another ball game - I am always having to redirect speeding tickets to customers addresses - then they ring up moaning (do they expect me to take thier points for them?)

My brother in law has an electrical contracting bussiness - about 30 vans - he has had to stop signwritting the backs of the vans up - because he is fed up with the general public keeping ringing him up - moaning about his staff driving like idiots.

best laugh is i had a hire business and a ******** in a car cut me up so at traffic lights i pulled level and threatened him through the window later that night someone rang me up and said the guy that works for you threatened me ohh aye yea it was me so il tell u again and listen good this time i just have a white van now no names or anything distinguishing on it

 

[Ashley Burton]

I would never have a job where I'm micromanaged

I would say there's the keys, See you!