Acceleration Calibration

[R4SC4L]

Firstly, I'm really impressed with this App (GP edition) which I downloaded a few days ago. Using the supporting documentation I've been able to connect my GoPro Hero 3 to my iPhone 4S and love how the auto record feature works.

My intention, is to use my GoPro as my main camera and change the iPhone video to picture-in-picture using the App. Ideally, I want to have my iPhone mounted in landscape just away from my dash, tilted forward and to the side so I can record the footwell (and capture my poor heel and toe skills )

I've tested the iPhone in this position and had good GPS signal. However, from what I have read, am I correct in saying that the accelerometer pre-sets would not be suitable given the angle of tilt I'd have on the iPhone and I'd therefore need to undertake individual calibration?

If I do, I understand there are four stages to the calibration process but I'm not sure I completely understand how to complete them as described on the App. I'd be grateful if someone could help explain it to me.

Thanks

[Harry]

Correct, you need switch to individual calibration to measure acceleration in the scenario described. The basics are described in http://www.gps-laptimer.com/LapTimerDoc ... hapter.pdf, I assume you have seen this document already? The individual steps for individual calibration can be monitored and are described in LapTimer's Calibration Assistant. After switching to individual calibration, select LapTimer ‣ Analysis ‣ Realtime ‣ Acceleration and tap into the view. This will bring up the calibration assistant showing the calibration steps while they are performed.

- Harry

[R4SC4L]

Thanks Harry. Yes I'd read the documentation in your link above.

The first of the four calibration stages asks for the phone to be mounted in portrait. Bearing in mind I want to use the phone in landscape after calibration, does this that matter? Do I just need to have the phone in portrait but still at the tilted/angled I will be using it at to correctly complete this stage?
What is the instruction for the fourth stage (gear calibration) as I'd like to know what to do ahead of completing it in the car as opposed to trying to read the instruction whilst driving (perhaps there are some screen shots I can see?). Thanks again

[Harry]

Device orientation is not significant, LapTimer adds a rotation as required. Or in other words: in case you calibrate the device in portrait, you can rotate it to landscape later without the need to recalibrate. Tilt and yaw certainly need to remain the same.

Portrait is mentioned because the views (Acceleration View and the assistant) are available on or trait only.

For the snapshots: please start the app to see the screens. There are buttons available to force calibration steps usually done automatically. This will allow you to see all screens ahead of doing the calibration in reality.

Please note all this views are for illustration only. The whole calibration process is working automatically and in background.

Harry

[R4SC4L]

Thanks Harry. When you say the whole calibration process is working automatically in the background, does this I mean don't have to follow the four stage calibration process?

[Harry]

Yes, that's only in case you want to verify it actually worked and calibrated correctly. If e.g. the stand still calibration is performed when the car is not standing on flat surface, this step will generate wrong results. So checking acceleration is approximately zero before starting is a good idea.

Harry

[Harry]

Once calibration worked fine, you can lock it for future use. This makes sense provided you do not change the mounting.

Harry

[gplracerx]

You can fix yaw miscalibration in the G-G plot for any given lap. For any fixed calibration, you should check to see that lateral and lineal are zero when the car is level. Tweak the mount rather than recalibrate if they're not.

Which brings up the question, is there a way to apply a change in yaw in the G-G plot to all laps in a session? As an autocrosser running single laps, it doesn't mean much to me, but I'm curious.

[Harry]

No, you need to apply it to each lap individually.

Harry