Crazy G-force Readings - IOS

[jbeachy]

I used Harry's for a track event one month ago and everything worked perfectly. The last two track events the g-force readings have been very screwy.
[youtube]http://www.youtube.com/watch?v=9Syt1lB8BDw[/youtube]

I have the phone in the mount when I launch Harry's and click through to video. Any ideas on how I can correct this?

Thanks!

[Harry]

Starting with LapTimer v19, acceleration presets are used instead of the former individual calibration. Individual calibration is still available for those using a special mounting approach (or those who want to optimize acceleration calibration). Using presets means LapTimer expects you to mount the device in a certain way. 4 presets are available and are selected automatically: LHT, RHT, video, motorbike. LHT and RHT assume you have the device centered in your windscreen pointing slightly to the driver's side and slightly tilted to the front. Video means the smartphone points to the front (no yaw) and again, is slightly tilted to the front. Motorbike means nearly flat and mounted to the steering rod. You can check animation #4 in Quick Reference to see the options.

In case acceleration measurement does not work right for any reason (like in your case), you may either rotate / flip values in LapTimer ‣ Lap List ‣ Lap ‣ Data Recordings ‣ Preview ‣ Charts ‣ G-G, or let LapTimer calculate new values from GPS: Lap List ‣ Lap ‣ Recalculate ‣ Acceleration.

- Harry

[captaindave]

I am having problems, also. I did the recalculation and it corrected some of the data, but there are spikes all along the track line. I was using an XGPS150 for my GPS signal. Next time I will try to align everything as suggested in the quick help and be more careful about lining up the GPS unit with the Iphone in the mount. I know that the XGPS was about 1 ft to the left of the IPhone. Would that make a difference?

CaptainDave

[Harry]

The GPS (either external or smartphone) should be positioned on the motorbike's vertical axis. In case it is positioned to the left or right, there will be an impact - but I doubt it is too critical (but haven't done the math). Spikes are from GPS inaccuracies / noise. When calculating lean / lateral from GPS, you get a dialog that allows you to smooth the calculation - to work around this noise effects. Just repeat the process, you don't lose anything the second time.

- Harald