Harry's GPS Suite Forum

Hello all,

I bought the ProVersion this week and I'm very happy with the functionality, but I'm having problems getting a correct calibration of the accelerometer.

My Iphone is mounted in my car right of the gear shifter, with the screen pointing slightly to the left side towards the driver's seat. When I put the Iphone in the holder and start the calibration process during the standstill of the car, the first two items ("Correct mounting" and "Pitch calibration") are readily checked green. When I then start driving in a straight line for the third item, I constantly keep getting the "circle" icon, but no green checkmark. I tried going straight for a few hundred meters, I tried accelerating/braking on a straight line, but neither of these worked. So finally, I pressed the "Force calibration" button during straight driving at constant speed, which triggered the "Drive straight line" and the "Gear calibration" to be checkmarked green and the calibration to be completed.

However, it seems to me that this is not the correct way to finish the "Drive straight line" item. When I look at the accelerometer display, I see that during straight line accelaration, the acceleration vector is pointing downwards and to the right, while during braking, it is pointing upwards and to te left. In my opinion, this shows that the straight line calibration wasn't performed correctly, and the sideway components during acceleration/braking are displayed because of the way the Iphone is mounted.

How do I perform the calibration correctly so that I do not get these sideway components of acceleration displayed during straight line acceleration (without changing the position of my holder)?

Best regards,
MIchael

Hi,

The very simple answer to this question is "go to track". The last step in calibration is to turn the acceleration vector in way that the effect of "with the screen pointing slightly to the left side towards the driver's seat" is eliminated. To do this in a reliable way, LapTimer requires you to really accelerate (with most cars - decelerate) hard. You will find that once you've been down the start / finish line braking into the first corner, everything is fine.

By the way - I will remove the Calibration Assistant from the Assistant View in the next version. This automatic calibration (and even the Calibration Assistant) is around for now 10 versions of LapTimer and little was changed over time. But - I never had so many questions on it like I currently get!

Hope that helps,

- Harry

Hi Harry,

thanks for the reply!

You are writing "Go to track!" - does this mean that the automatic calibration is triggered when you pass one of the POIs out of a trackset? Or is triggered everytime that I start-up Laptimer? I did not load/race a pre-defined track yet, I only used Laptimer during "cruising" around, but despite some decent braking and accelerating on an empty parking lot, I still seem to be getting the "skew" calibration of the accelerometer. Therefore I wonder when and under whic conditions the automatic calibration is performed.

Best regards,
Michael

Hi,

This means for the last step in acceleration, LapTimer requires acceleration values achieved typically on track only.

- Harry

Hi,

it worked! Thanks for the support!