non-preset orientation - acceleration calibration

[Jordan]

Hi Harry,

I recently bought a GoPro 7 Black (got tired of dealing with the iPhone 4S) and have changed up where I'm mounting things. My new set up is to have the GoPro over the shoulder pointing forward with the main view, and the iPhone 7 in the upper right corner of the windshield pointing straight at me. This gives me the advantage of having it out of my field of view, in reach for initializing and stopping sessions, good view of the sky for GPS, and I use the front camera to record side-cockpit view of me. See this for a combined example video: https://youtu.be/1zKGJGnxE_4

However, because I did not calibrate the acceleration for HLT on the phone, the g-force data was way off. My fault, not yours. So now I want to make sure I understand the process to do for this weekend at the track. I read your Acceleration Handling documentation. Is this procedure correct and exactly what I need to do to get accurate acceleration data in HLT? It wasn't clear to me from the documentation whether I need to do both Pitch Calibration and Gear Calibration. I haven't tried it yet, so when I do, it might be more clear.

1. Mount the phone in the appropriate position with the car stopped
2. Go to prepare race -> Calibration
3. Make sure it shows 0 / 0 / 1G (is there a chance this doesn't happen automatically?)
4. Advance to gear calibration, hard accelerate straight for a few seconds and then brake hard for a second or two
5. Lock Calibration
6. Done

The very last paragraph in your PDF says:

The weak point of individual calibration is it may fail. This happens in case LapTimer does not interpret the “standing still” or “driving straight decelerating” correctly. This in turn will derive a wrong rotation and odd data as a consequence. The good news is: it is probably not necessary to run this calibration again and again (including a failure from time to time).

How can the user tell if the individual calibration worked correctly? Thank you in advance.

[Harry]

Hello,

You see individual calibration has succeeded if you get zero acceleration while standing still and get negative longitudinal acceleration with no or minimal lateral acceleration when braking. Acceleration is shown in real time in several views and you can certainly analyse recordings.

While the procedure to setup individual calibration is as described by you, I recommend to do it “unassisted”. It will run without looking into the acceleration view and fully automatically while in any view.

Once back in the pits, check if it succeeded (see last lap’s recordings) and lock calibration next. In case it failed, restart it for the next session.

The function to recalculate acceleration from GPS (for failed calibration) has moved in v23: select lap from Lap List, select Fixes, select the recalculate icon in the tool bar, select Acceleration.

Harry

[Jordan]

While the procedure to setup individual calibration is as described by you, I recommend to do it “unassisted”. It will run without looking into the acceleration view and fully automatically while in any view.

Not sure what you mean. Can you explain?

I tried doing the manual calibration last night. The first two steps were quick, and the acceleration step 3 worked okay. But I could not get the gear calibration to work. It kept going back to step 3. Then step 3 would work and go to step 4, and then back to step 3, etc. Eventually after several tries I hit the force calibration button and locked it. I don’t know if it’s correct or how to get the gear calibration to auto-finish.

[Harry]

It is not correct to force calibration. This has been added for testing and is an anachronism now that automatic presets are available.

What I wanted to say is that individual calibration is working automatically and without monitoring it in the Acceleration Assistant. Especially the last step is working on race tracks, but not on public roads where speeds and acceleration are below the level typically required.

In case you really want to work with individual calibration, please check the Acceleration Handling document available on www.gps-laptimer.de/documentation.

- Harry

[Jordan]

Thanks. How fast do I have to go to get the auto calibration to work?

[Harry]

There is no speed threshold, this is an indirect parameter: when driving fast, driving directions measured are getting smoother / smaller. To recognize a straight, LapTimer requires a number of fixes not differing by more the 1.3 degree.

- Harry

[Jordan]

I tried again last night on a highway and still couldn’t get it to auto finish the gear calibration. I was going I a straight line at 75mph and then medium braked down to around 30 or lower. Tried that a few times. Didn’t work. Not sure how to make it finish the right way.

[Harry]

Please use it on a race track as recommended a number of times. I do not see a reason it shouldn’t work for you. And please do not run such experiments on public roads.

Harry

[Jordan]

Please use it on a race track as recommended a number of times. I do not see a reason it shouldn’t work for you. And please do not run such experiments on public roads.

Obviously I was being very careful. However, I didn't do it on the track because it requires you to accelerate and brake in a straight line, which I can't do on the track. That's why I kept asking for more information. I don't understand how it's supposed to work if the highway doesn't work and the track has turns. I'm not ignoring your instructions- I don't understand how to follow them.

[Harry]

You will decelerate in a straight line at the end of every straight on a race track. On track, this step will happen during your introduction lap.

Harry