Supposedly, the Dynolicious Log Box app for an iPhone will provide basic track timing function. Has anyone tried this? The missing part seems to be overlay with the actual track. I was considering an iPhone and this could seal the deal.

http://www.bunsentech.com/projects/dynolicious-log-box/

 

I have both LogBox and G-Tac Pro... I find that G-Tac Pro is well worth the extra money. It samples the accelerometer at 30Hz, the GPS whenever it can (reception is an issue with the iPhone hardware), and it produces the data in two simple CSV segments. It also will patiently sit there and wait for you to accelerate to start recording, which is very useful when sitting in grid. It allows you to play back the session on the phone with a map, and it has some other features as well (such as drag racing mode).

LogBox kept allowing the iPhone to go to sleep while I was sitting in grid, which was quite irritating when strapped into a race car and barely able to move. I could have avoided that by telling it to start recording early, but then I wouldn't have enough space to record my entire session... when you have it set to 20Hz sample rate, it only gives you 25 minutes of recording. The default 100Hz rate only gives you 5 minutes, which is just silly, especially since the app can't even reliably sample at 20Hz let alone 100Hz. The data it exports isn't very useful... it doesn't sample at a reliable rate, nor does it give you unique timestamps on the individual accelerometer samples, so you basically have to just guess. The app itself is really just a logger and nothing else. It does not allow you to play the session back on the phone. So, the price is good, but you get what you pay for. It could have a lot of potential if they release an update that corrects these issues, but until then my recommendation is to spend a few bucks more on G-Tac Pro.

Both apps have the same GPS reception issues, because that's really caused by the iPhone hardware, so it will take some trial and error to find a good mounting location. The best I've seen from the GPS is 9 meter precision and 2 Hz sample rate, which isn't too bad, and you could possibly interpolate it with the accelerometer data to turn that GPS position and speed into a 30Hz sample rate. However, typical conditions are 17 meter precision and one sample every 1-2 seconds. It obviously doesn't compete with Traqmate and other real dataloggers in this category, but it still has the potential to be pretty good for its price.

Here is my experience comparing accelerometer data from the iPhone 3G (using G-Tac Pro) vs Traqmate... http://www.rm944.com/weston/iPhone/G...%20090419.html

 

I just downloaded this for $12. Going to go give it a try. Looks like it could be pretty sweet for the price. There's download software and live playback for your laps. Check it out.

http://www.firstclass.com/~ron/Lap_Timer/Lap_Timer.html