Software for PDA to show 0-60 times, acceleration etc

[PThomas]

I have a HP iPAQ 6910 which has a built in GPS receiver.

Does anyone know of any free software that can give a 0-60mph, 0-100mph (Private road) reading?

I presume it would be fairly simple for some software to detect when you start moving and when you hit 60mph and record the time difference.

[philpugh]

There may be such s/w but the GPS unit in your handheld (and 99% of those sold) only updates the position every 1 second. This would lead to very poor timings. So you would be requiring units with much higher update rates (at least twice the resolution you wish to obtain) - and these aren't cheap. A friend sitting beside you with a stop watch is simpler !

You could try logging the position information and plotting the speed against time and trying to estimate the info you want - but your starting point could be upto one second out.

If you search the web you will find specialist suppliers of equipment used to do this. Prices start in the low thousands
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Phil

[PThomas]

Thanks

Any workarounds, such as sending data to a log file (Not sure how to do that) or having a button to press on the screen when you start off and then let it automatically detect when you reach 60mph?

Thsi would need to be free software as I can't afford/justify to pay for anything!

[philpugh]

Do a search for PDA s/w for GPS systems. Many should have a facility to log positions (sometimes called a tracklog) which may include speed. You could use Excel (or similar) to plot graphs allowing you to determine when 60mph is reached - but the problem remains that you won't get enough readings to get meaningful answers.

Take an averagely quick car 0-60 in 10 secs. You will only get between 9 and 11 points logged. Also you would need the GPS to have a clear view of the sky (i.e outside the car) to minimise satellite geometry positional errors, which at best are going to be around 5 meters for each point in any event. GPS systems measure speed by calculating the distance travelled between the current and last positional fix and dividing by time which will be 1 second (the timing is very accurate but the distance is inaccurate).

So the 0-60 in 10 secs car will get a result that is inaccurate by upto 1 second. You can't determine when it gives its positional information - this is internally controlled.

So the potential errors for this 10 sec car are...

Timing accurate to nearest second only. Distance error is 5 meters (best case) each second - giving erroneous speed calculations. Distance travelled over the 10 second period could be accumulative - but this is less likely due to the random nature of it. Assuming constant acceleration 0-60 in 10 seconds means you travel about 155 metres - so even 5 meters out gives you an error of 3%.

Faster cars will give you much worse percentage errors.

If what you are trying to do here is compare your car with others or if mods you make have made a difference then (and only try this on a closed road) set up a measured distance (say 100 meters) and do standing start over this distance. Record the finish line with a standard video camera. Denote the start with a loud sound - (registered on camera). Then examine the video frame by frame - you will be able to hear the start and see the finish accurate to 1/25 second - much better accuracy then you will obtain with GPS. To be accurate you will need to correct for the speed of sound. You will still only be able to calculate average accelerations and speed

But you could always use a stopwatch - it's going to be better accuracy than the GPS solution and is simpler to set up and use!
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Phil

[PThomas]

Thanks for the lengthy and informative reply.

Guess I'll have to go back to the boring stopwatch!

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