True speed display with Columbus GPS

[jorgenr]

Tried everything, including RTFM, can anyone please tell me how to display the true speed obtained from the GPS unit in the maxidot or Columbus or whatever..?

-Jorgen

[jorgenr]

Tried everything, including RTFM, can anyone please tell me how to display the true speed obtained from the GPS unit in the maxidot or Columbus or whatever..?

Got The Answer from the dealer today - there is no such function with this setup. Wowsers, my good old $400 Garmin could do this, and I used it all the time on long trips in my previous car to make sure I was within speed limit++ since speedometers nowadays are pretty conservative.

Mumble.. lots of computers aboard that could have landed Apollo on the moon with no problem, and they cannot present the most basic data.. Looks like I have to get some velcro tape and charge the Garmin again.

Maybe a firmware update could do it - is there any place to file suggestions, something similar to Navteq feedback?

-Jorgen

[madfiddler]

Via a combination of button presses you can make the climate control display this. Quick search should find the info

I don't think this is taken from gps though, why is the Reading so important?

[G.K.]

Via a combination of button presses you can make the climate control display this. Quick search should find the info

I don't think this is taken from gps though, why is the Reading so important?

I was amazed that the Columbus unit did not have a true speed display.It ia a great tool on a stretch of dual carriagway where know that there are fixed cameras and you can set your sat nav at a true 74(ish) and know that you can sit with the cruise control on, speedo showng nearer 80, and pass all the plonkers who hit the brakes who slow down to about 60mphcause they are watching an in-accurate speedo. another own goal for an overpriced Skoda accessory.

N.B. update on the warranty claim on my Columbus... Now waited a month for a replacement unit due to poor audio performance. Still no replacement in sight, been offered a free meal at Skoda's expense (which I knocked back),,Rapidly regretting not settling for the portalble sat nav option and putting up with all the cables and wires!!!.

[jorgenr]

Via a combination of button presses you can make the climate control display this. Quick search should find the info

I don't think this is taken from gps though, why is the Reading so important?

Yes, I know all about this, but the point is that every speedometer is very conservative about speed, and now that I have spent some money on at least three computers aboard, at least one of them should be able to tell my true speed. Its all about the programmers that manage this thing, and being a senior programmer myself I find it, um, interesting that they didn't include this. As far as I know this is standard on most cheap GPS installations.

-Jorgen

[rurwin]

They are probably eager to avoid the thousands of complaints from customers that their two speed figures don't match. 99% of customers would not understand why, and would demand that one or other must be adjusted.

To put the boot on the other foot, car manufacturers get shirty when they only get 2999 hours and 40 minutes of data from a 3000 hour test because two time standards have been used that only match to 100ppm. (Which is better than most PC clocks.)

[Dodgy]

On the one hand you've got a potentially accurate GPS assisted speedo in the centre console, but you'd have to take your eyes off the road to see it (even though the columbus doesn't have one anyway). You've already identified that your car speedo is slightly inaccurate, but you'll also probably know that it's consistently inaccurate by the same margin. It's just a matter of knowing what that margin is and take it on board, even if it is sailing slightly closer to the wind

I routinely pass police cars on the motorway at 74mph ish without a care in the world, and I'm not looking at my sat nav (my MFD2 also doesn't show true speed).

Dave.

[Bagpuss]

I think rurwin is probably right on this one. It's simply a case of avoiding complaints form customers that the two displayed speeds don't match.

My last 5 company cars have all had factory fit satnav, and none of them has been able to display the GPS speed. However, the current Pioneer unit I'm using does.

Personally, it's interesting to look at once or twice, but I never bother with it in normal driving. Far more useful for me would be the ability of the savnav to warn me when I'm speeding. Sometimes, you enter a new speed limit and don't always realise it, either because the signs are poorly positioned or completely obscured by plants (as is the case around here during summer).

Bagpuss.

[rurwin]

It would probably fall foul of the rule that says the speedometer should not read low. There will always be an error, even if it is 0.1ppm, and on a GPS it is equally likely to be low as high.

That rule would not apply to an after-market GPS, but probably would apply to standard items.

[jorgenr]

On the one hand you've got a potentially accurate GPS assisted speedo in the centre console, but you'd have to take your eyes off the road to see it (even though the columbus doesn't have one anyway). You've already identified that your car speedo is slightly inaccurate, but you'll also probably know that it's consistently inaccurate by the same margin. It's just a matter of knowing what that margin is and take it on board, even if it is sailing slightly closer to the wind

I routinely pass police cars on the motorway at 74mph ish without a care in the world, and I'm not looking at my sat nav (my MFD2 also doesn't show true speed).

Dave.

I think most drivers know that the speedo is inaccurate, due to slightly varying wheel diameters, winter tires etc. But as I mentioned, there are a handful of computers in this car - one is sitting right in front of you! (Maxidot), and can display many inaccurate features, like average speed (too low), fuel consumption (too optimistic), and lots of data from the Columbus, so why not accurate speed?

-Jorgen

[madfiddler]

I think rurwin is probably right on this one. It's simply a case of avoiding complaints form customers that the two displayed speeds don't match.

My last 5 company cars have all had factory fit satnav, and none of them has been able to display the GPS speed. However, the current Pioneer unit I'm using does.

Personally, it's interesting to look at once or twice, but I never bother with it in normal driving. Far more useful for me would be the ability of the savnav to warn me when I'm speeding. Sometimes, you enter a new speed limit and don't always realise it, either because the signs are poorly positioned or completely obscured by plants (as is the case around here during summer).

Bagpuss.

I agree - I've had tomtom on a mobile unit with this feature for ages and in the end turned the display off.

I have some speed camera audible warnings based on POI but it would be good if based on these POI the warnign only was to sound if I was within + or - x% of the speed limit.

as far as I know the rule on speedos has been for many years in the UK that the reading only has to be within 10%, many people would drive therefore up to 10% higher than the allowed speed limit according to their speedo.....

....not that I advocate speeding but it seems the police are much more interested in dangerous drivers than speeding drivers at the moment, particularly on the UK motorways

[VRStu]

Columbus does have a true speed indication but only in the hidden menu so not really for everyday use.

[scouter2]

Tried everything, including RTFM, can anyone please tell me how to display the true speed obtained from the GPS unit in the maxidot or Columbus or whatever..?

-Jorgen

Another good use of true speed on the portable GPS unist is that I can easily change it to show km/h when driving abroad, as I find the km/h reading pretty rubbish on the speedo... Particularly handy to double check speed when apporaching a speed cam.

Does the Columbus show the speed limit for the road?

[VRStu]

Does the Columbus show the speed limit for the road?

No, that is something that is normally driven by Speed Camera software.

[jorgenr]

Columbus does have a true speed indication but only in the hidden menu so not really for everyday use.

Well, at least I can "calibrate" the speed once in a while without bringing with me the Garmin. Thanks, this must be investigated... :holmes:

-Jorgen

[jorgenr]

Well, at least I can "calibrate" the speed once in a while without bringing with me the Garmin. Thanks, this must be investigated... :holmes:

Done. Door close, key in, [<-][->] and then hold setup seems to work well most times, then you can find accurate speed on the gps and work out the offset on the speedometer, in my case about 7-10%, a lot more than my old Citroën.

-Jorgen

[Mac1961]

I think that showing the GPS speed is down to the actual program in use and not the unit. I have a mobile sat-nav with two programs loaded, Mio and Tom-Tom 6, the former does not show speed, but the latter does, probably because it has speed camera software as VRStu mentioned.

I only use the Tom-Tom in the UK as it does not have street level mapping for the Continent (I'm too tight-fisted to upgrade) and that is where I use the Mio.

Drive carefully, Mac

[_ZS_]

Cop cars tend to have calibrated speedos. Over here the local Iveco dealer calibrates speedos on all sorts of cars (they do all the cop cars over here unless they're supplied with calibrated speedos like the Vauxhalls).

[DurleyDave]

When first delivered my Superb Elegance was without the satnav dvd so I used my old Garmin stick on screen job. GPS speed very easy to check on this unit and I was surprised to find my car speedo over-read by only just over 1 MPH. This will undoubtedly change as the tyres wear but it will be very easy to calibrate in the future.

Of course, the Columbus unit should have this facility as standard. As G.K. said it is very good for setting the cruise control to the correct speed especially with the average speed cameras. I get the impression that the latter do not give much latitude on max. speed but I may be wrong.

[Guest]

This is some thread revival!

[Timmyboy]

And.... the Columbus does indeed now show the speed limit!

[DurleyDave]

This is some thread revival!

[DurleyDave]

Sorry, I'm a 'Johnny come lately'. Having spent half the morning trying to feed addresses into the memory I can fully understand the comment that the Columbus is not very intuitive. At least it doesn't appear to get too upset when I choose to ignore directions!

[skodacarman]

I wouldn't worry about a speedo v. GPS reading difference of 1 MPH. There's no 'true speed' anyway.

GPS speed is the speed your car is doing between successive fixes as you travel over the surface of the imaginary WG84 geoid, which is only an approximation to the real earth's surface over which you are actually travelling. So you could seem to travel by GPS reckoning further or shorter, i.e. faster or slower in any given time, than is the case of actual speed over the ground, depending on wether the geoid is smoother or bumpier than the real earth's surface where you do the measurements. The geoid is mostly smoother than the actual ground surface, so it mostly makes the speedo reading look too high. Check it out on a really steep hill. For a speed ticket, GPS doesn't count as edvidence.

Road wheel speed, as shown on the speedo, is usually too optimistic, i.e. it will read 70mph when you are doing 68mph. Apart from all sorts of problems arising, like variations in tyre inflation and hence wheel diameter and the like, speedos will generally read too high because the speedo makers have to get a 'yield' from their production lines of, say, around 95% of units working properly within the natural variations of maufacture. If the average speed of a production sample was spot on, they would only get a 50% yield. For obvious reasons, the law says they can read too high within a given tolerance, but they must never read too low. Since they can't read too low, the average reading has to shift down to the 'reading high' side of the yield curve, and on average they will, as a result, read too high. For a speed ticket, again it doesn't count as edvidence.

Police car speedo don't have to be constrained by the pressures of high yields, the people who make them will cheerfully throw half of them away, or make them adjustable and subject them to continual expensive and time-consuming checks and re-calibrations, so they're better than yours, and they do count as evidence ("Er, yes sir, that extra £250 on your car's annual service bill is for the compulsory annual speedo re-calibration"). If the cops are chasing behind you, it's probably the closet thing to a measure of your 'true speed' that you will get, and good evidence of course. But I wouldn't recommend it as a way of checking your speedo.

Best of all, as far as courts are concerned, is radar gun speed measurement. This is in truth just a measure of how fast you are closing on the radar gun over an imaginary surface that you could draw as a straight line between you and the gun, which may or may not bear a close relationship to the ground over which you are in fact travelling! In fact, you are more likely to be travelling faster over the ground than the actual radar gun reading, unless you happen to be speeding on a billiard table. That said, the wielder of the gun will usually give the benefit of the doubt if you are just a shade over, as the maths and geometry get a bit fraught. But it's good evidence - unless you can prove that the radar beam did in fact bounce off something else, not you, or that it got defelected in someway in its path there and back.

So don't worry about 'true speed' - it doesn't really exist! The only type of speed that matters is the one that you get booked for, all the rest are just rough guesses.

[PhilP1903]

I wouldn't worry about a speedo v. GPS reading difference of 1 MPH. There's no 'true speed' anyway.

GPS speed is the speed your car is doing between successive fixes as you travel over the surface of the imaginary WG84 geoid, which is only an approximation to the real earth's surface over which you are actually travelling. So you could seem to travel by GPS reckoning further or shorter, i.e. faster or slower in any given time, than is the case of actual speed over the ground, depending on wether the geoid is smoother or bumpier than the real earth's surface where you do the measurements. The geoid is mostly smoother than the actual ground surface, so it mostly makes the speedo reading look too high. Check it out on a really steep hill. For a speed ticket, GPS doesn't count as edvidence.

Road wheel speed, as shown on the speedo, is usually too optimistic, i.e. it will read 70mph when you are doing 68mph. Apart from all sorts of problems arising, like variations in tyre inflation and hence wheel diameter and the like, speedos will generally read too high because the speedo makers have to get a 'yield' from their production lines of, say, around 95% of units working properly within the natural variations of maufacture. If the average speed of a production sample was spot on, they would only get a 50% yield. For obvious reasons, the law says they can read too high within a given tolerance, but they must never read too low. Since they can't read too low, the average reading has to shift down to the 'reading high' side of the yield curve, and on average they will, as a result, read too high. For a speed ticket, again it doesn't count as edvidence.

Police car speedo don't have to be constrained by the pressures of high yields, the people who make them will cheerfully throw half of them away, or make them adjustable and subject them to continual expensive and time-consuming checks and re-calibrations, so they're better than yours, and they do count as evidence ("Er, yes sir, that extra £250 on your car's annual service bill is for the compulsory annual speedo re-calibration"). If the cops are chasing behind you, it's probably the closet thing to a measure of your 'true speed' that you will get, and good evidence of course. But I wouldn't recommend it as a way of checking your speedo.

Best of all, as far as courts are concerned, is radar gun speed measurement. This is in truth just a measure of how fast you are closing on the radar gun over an imaginary surface that you could draw as a straight line between you and the gun, which may or may not bear a close relationship to the ground over which you are in fact travelling! In fact, you are more likely to be travelling faster over the ground than the actual radar gun reading, unless you happen to be speeding on a billiard table. That said, the wielder of the gun will usually give the benefit of the doubt if you are just a shade over, as the maths and geometry get a bit fraught. But it's good evidence - unless you can prove that the radar beam did in fact bounce off something else, not you, or that it got defelected in someway in its path there and back.

So don't worry about 'true speed' - it doesn't really exist! The only type of speed that matters is the one that you get booked for, all the rest are just rough guesses.

Erm Nuff said, dead thread LOL