Wrong average speed

peterc10 · Posted: Tue Nov 15, 2011 7:40 pm Post subject: Wrong average speed

Have been meaning to report this for a while. I thought somebody else did but could not find the post.

I am now the proud owner of the world land speed record. According to CamerAlert I managed 945mph average on the SPECS section of the M25 (M1 slightly slower). The instantaneous speed was telling me I was only doing 50mph, but I am told that it is the average that counts. Should I write into the Guinness Book of Records?

Or maybe there is a problem with the average speed calculation? Wink

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HTC Sensation
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CAA_0824011705 · Occasional Visitor Joined: Aug 24, 2011 Posts: 1

i was also having this problem to day tn the a 419 & m4
is is possable to have a fix for this

adm143 · Occasional Visitor Joined: Jan 20, 2009 Posts: 9

lbendlin · Posted: Sat Jan 14, 2012 1:54 am Post subject:

The GPS doesn't have a concept of "forward" or "backward". It only thinks in headings. So any distance value that we get back from the GPS is always an absolute distance. However we have seen quite a few chipsets that are, let's say, rather inventive about the distance they claim to have traveled in a second. That is a much more likely cause.

A klutzy workaround in such a situation is to stop and restart the averaging manually by tapping on the speed icon twice.
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CAA_0511165900 · Occasional Visitor Joined: May 11, 2012 Posts: 2

Clearly CP still has a problem with SPECS, any chance it will ever get fixed?

PaulB2005 · Posted: Mon Jul 23, 2012 1:36 pm Post subject:

Please feel free to elaborate.

CAA_0511165900 · Occasional Visitor Joined: May 11, 2012 Posts: 2

Of Course!

Travelling along the A14 towards Cambridge at the first SPECS camera it showed my speed and average as expected and at the next, then suddenly the average speed showed red and displayed crazy numbers changing constantly! I pressed the screen and the display recovered and then immediately did the same!

I had CoPilot Live on a Samsung Galaxy SII and on entering the SPECS zone brought CameraAlert to the front.

Chris

peterc10 · Posted: Tue Jul 24, 2012 11:22 am Post subject:

All of us appear to be reporting the same problem - the instant speed is correct, it is the average speed that is wrong. In those circumstances I am struggling to see how it can be the chipset getting the distance it travelled in a second wrong, otherwise the instant speed (or both speeds) would be wrong. Or have I misunderstood how it all works?

And we all three have different phones - Desire, Sensation and Galaxy.
_________________
Peter
HTC Sensation
Sygic GPS for Europe (No more TT "support"!)
Copilot for USA
Bury CC9060 bluetooth car kit & Brodit mount

AliOnHols · Pocket GPS Verifier Joined: Oct 15, 2008 Posts: 1936

I'm no mathematician or scientist but I think that this is how it works -

Let's say that you are traveling in a straight line at 90kmh (25m/sec). Now, while everything is TicketyBoo, every second the chipset is calculating that your position is 25m further along the road than the last time it checked. Your average speed remains 90kmh.
If there is a glitch for a second and for some reason the chipset calculates that you are 100m away from your actual position, it shall report that you will have traveled at 100m/sec or 360kmh and the average speed shall be affected accordingly. If in the next second it accurately records your location, you have now traveled 100m+25m+25m in the last second at a speed of 540kmh. Your average speed is now WAY OUT and shall take a very, very long time, if at all, to get back to anything meaningful, so best to stop the app and restart.

CamerAlert only takes the information given to it by the chipset and performs the calculation to give the average speed. If the information is wrong, the calculation is wrong. RiRo.

The mathematicians amongst us shall say that the above example is only true at times when Pythagoras-Sees Old Harry-Catch A Herring-Trawling Off America correctly, but I don't care. I know what I mean, I hope you do too.
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peterc10 · Posted: Tue Jul 24, 2012 2:49 pm Post subject:

Alionhols

But that means that the instant speed reading would change too, albeit for a second, but it doesn't. And it would also mean that the speed would increase by a small amount if you were half way along a section, because the error would be mathematically less significant than at the beginning of the section, but that does not happen either. And finally it also means that the readings of average speed would start to fall each second (as the error became mathematically less significant) until the problem occurs again, but they don't.

It seems to have no rhyme or reason to it. Half way between cameras it will suddenly leap from 50mph to 900mph, suggesting a huge error in distance, then a couple of seconds drop to 500mph, suggesting it was not so huge, then a couple of seconds back up to 750mph! And during the whole time the instant speed will remain a steady 50mph.
_________________
Peter
HTC Sensation
Sygic GPS for Europe (No more TT "support"!)
Copilot for USA
Bury CC9060 bluetooth car kit & Brodit mount

M8TJT · Posted: Tue Jul 24, 2012 2:56 pm Post subject:

I've been through the specs on the A14 between A1 and M11 4 times over the last couple of days and CA behaved perfectly. But that does not really help those for whom it isn't behaving perfectly Confused

Galaxy Ace2

AliOnHols · Pocket GPS Verifier Joined: Oct 15, 2008 Posts: 1936

peterc10
Like M8TJT's, my CamerAlert also performed perfectly when in the Uk recently so I believe that there is nothing wrong with the software or the formulas employed.

Sorry, I don't have an alternative suggestion other than the chipset/gps receiver on your phone giving the occasional false reading.
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Garmin Nuvi 2599
Android with CamerAlert, OsmAnd+, Waze & TT Europe.
TomTom GO 730, GO 930, GO 940 & Rider2.
SatMap Active 10 & 20.

peterc10 · Posted: Tue Jul 24, 2012 3:10 pm Post subject:

M8TJT · Posted: Tue Jul 24, 2012 4:23 pm Post subject:

lbendlin · Posted: Tue Jul 24, 2012 5:10 pm Post subject:

The overspeed warning is for the current speed, not the average speed/
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