mx5cartalk.com

I'm curious...Are there any Iphone apps that would be useful on track? I just got an Iphone and hunting around the app store found a few 'performance meters' and found an Aston Martin app that will overlay speed on to video taken with the phone. Is there anything a bit more advanced that or anything that uses the phones GPS to build an image of the circuit and its G sensor gubbins to build a bit of telemetry?

Race Chrono.

I've found the internal GPS on phones is not accurate enough to work effectively. Racechrono is a great program but they recommend an external GPS unit and I don't believe theres and iOS version of it yet.

I just found one called 'lap timer data acquisition' which claims to do some funky drawings of the circuit with data overlay. It also does video with long/lat g forces, speed, time etc. You can also have it just displaying a lap timer with last lap, current time running and predicted time. This can be all exported to a free Mac (Im a mac user anyway) program to be stored and used later or to edit / share the videos and data. Promises a lot for $14.99!!!

Interesting that phone GPS is not very accurate, I'm guessing only to 50 feet or something?

I will take a look at Racechrono to.

It's more the update time of the GPS is to slow. I've tried racechrono on nokia phones and a few different ones on the iphone but the GPS was always the big letdown.

Buy the Qstarz Bluetooth GPS receivers... the one I have works at 10Hz, locks on quickly and has worked very well with RaceChrono. Given new life to my useless N73 http://www.qstarz.com/Products/GPS%20Products/BT-Q1000EXQR-F.htm

Think it cost me about 100-120 on ebay.. + $20/- for the donation to RaceChrono (why are all the truly cool programs cheap or free??)

Racechrono is not available for the iPhone and most if not all the alternative apps are not worth paying for. The problem is that the iPhone GPS has a sampling rate of only 1Hz (I believe), which is far too slow for datalogging at the track. You need at least 5Hz and preferably more than 10Hz. A 10Hz receiver will only allow laptimes to the nearest 0.1s while you're on track although afterwards you can use PC software to estimate times to nearest 0.01s (they're usually within 0.02s of the true time measured via transponder). Plus the iPhone will not accept plug in of external GPS receivers, as far as I'm aware.

If you want a cheap GPS laptimer, get yourself a suitable used Nokia mobile, an external GPS receiver and download Racechrono. It works extremely well.

As for iPhone apps for MX-5s, it's hard to go past YouCruise by Mazda!

I wondered why I could not find Race Chrono

So around 1hz is only going to be accurate to <1sec or something like that. Without the external GPS receiver we can say that it is for novelty use only!

Correct, I did log speeds in excess of 300km's with the internal GPS on the phone so maybe it's not all that bad

harrys laptimer pro

Datalogging at 10Hz


Datalogging at 1Hz


The best you'll get out of 1Hz sampling frequency is plus/minus one second per lap! If you're running a marathon, that's fine. But it's absolutely useless for track days.

Having said all that though, there MIGHT be some iPhone laptiming apps that also utilise the gyro sensor to improve the position sensing. Haven't looked into those ones, since I have no need (Performance Box does 10Hz!).

Thanks for those images Guran.

Harrys lap timer pro looks quite advanced and supports an external GPS sensor and can be interfaced with google earth, I assume to use an image of the circuit. I don't think it does video with info overlaid on it.

Guran wrote:Datalogging at 1Hz

That's the oldest trick in the book Bryan; blaming the sampling rate when your lines turn to sh!t !!

Actually looking at those images....Is the 10hz one representing a single lap or a multiple of really consistant laps? Is the 1hz one lots of bad laps or is it a bit like when you have bad reception on your satnav and the picture of your car is driving on a road or in a field 500 meters to your left...so it is drawing lines that are either side of where you really are?

10Hz == lots of quite consistent laps... you'd see the different lines if the image was zoomed in...

Hey Guran, picked up a shift light today ... hanging out to do the next trackday and put your circuit analysis to use!