Slow Ramp-Up on G-Data

[NESMotorsports]

Hi Harry,

I think the general issue has been mentioned before, however I don't think it was explained clear enough to sort out an answer. While I love using the LapTimer files with DashWare and GoPro video, I have found the just as I see in the app while using it, the G data derived from the iPhone's built in G sensor seems not only slow to respond in the app, but also take a couple seconds to ramp up and show the actual G value even when it is instantaneous G. I thought this was just native over smoothing from iOS itself and I was going to buy the logging version of the Bluetooth GPS Dongle I currently use since it has a built in G Meter instead and use the files from it for DashWare overlay, but I just saw tonight in another app I downloaded (DashCommand), which has a similar G circle display (even if it is very primitive in comparison to LapTimer), it's G Dot responded instantly!!! I have tried removing all delay in the advanced functions of LapTimer Pro to try and replicate this, but to no avail. Is there a way to get LapTimer to work with this G data completely unfiltered like that?! It is a very important requirement I have found for reading how the car and driver is handling through the corner (specifically looking at g circles) and very important for some math channels I am trying to use after the fact when analysing the laps. Can you help me with getting LapTimer's G recording to work this way?

Thank you in advance,

[Harry]

First of all, please do not look into the acceleration view while cornering - LT keeps the max some time and allows you to have a look into it afterwards.

The delays are relevant for GPS / acceleration alignment only. Please note that reducing the acceleration delay to e.g. 0 will shift the acceleration fix 'forward' compared to the GPS fix. So in case it seems 'late' in the recording, increase the delay to move it forward.

On the 'instantness': on screen, LT always displays the latest information available; so this is not related to the delay setting. The reason it appears late is probably the following: I have reduced acceleration sampling to 10Hz to save energy. It is easy to raise this again. In addition, LapTimer needs to 'filter' the values as they are very noisy. The so called lowpass filter applied in effect smoothens the value and makes it less instant. So what I can try is raising the sampling rate again (or make it a preference). Applying the same filter, this will make the reaction faster.

- Harry

[NESMotorsports]

Haha, I certainly never can look at it while I am driving.

Faster certainly would be preferred, I know in my application, since it is plugged into the dash, I have no huge concern for power usage. An option in the preference between the current 10Hz setting and full speed (at least as high as your recording rate would allow) would be perfect! As for what is effectively a lowpass filter on the G values, I can understand why you want to smooth out what could be an extremely noisy reading depending on how the phone is mounted, could you however include a simple checkbox to disable this filter in the settings, or a slider to vary it's strength from what it currently is to off? I realize I may be opening a bit of a can of worms by not running any filter on the G value, but for those of us (I will be running it in a number of our car club cars this year) that have the phone very solidly mounted in the car and those that want to use the data to create traction circles and for math channels in post analysis, it is kind of a needed option from what I have seen after trying to use the data.

My only other question on the G data front is, is there a way to lock in a calibration for the app to use each time it is launched? Since the phone is always mounted in the same location in the car, in the same orientation, being able to retain that setting from previous use would be ideal, since doing a calibration run at the track is not always feasible.

Honestly, as I have said before, I find your software amazing and the G data is the only real issue I have run into in using the recorded data. Sorry also if this all really should have ended up in the requested features section, since as I read through it now, it makes more sense there.

Thanks again,

[Harry]

Even for an iPhone, without any movement, the sensor generates a noisy stream of values. So you will always apply a lowpass filter. But as stated above, you can minimize the latency introduced by this the filter by raising the update rate.

Currently, there is no option for a locked calibration. I have other plans that will make this obsolete

- Harry

[NESMotorsports]

Ok, that makes sense, and honestly not that surprising. Is this update rate for the G sensor currently in the expert settings? I didn't see it in there, only a system refresh rate, which I did increase to full 10Hz and seems to be running well. If you have access to see what I mean by DashCommand's Skid Pad view, it seems to be quite smooth in terms of lack erroneous values, but much more along the lines of how I need the G data to react to create a usable Traction Circle and use the values for math channels. If the increased rate is not enough (10Hz seems perfectly reasonable, though perhaps if something closer to 30Hz is achievable it may help) a reduction in the strength of the filter may be needed.

Awesome news on making the calibration bit obsolete, I look forward to every update you put out for this app. It just gets better and better!!!

[Harry]

The 5 Hz in the expert settings are a kind of refresh rate for the screen - 10 Hz will not increase data quality, but generate more load. The accelerator update rate is not configurable yet, you remember, we started the discussion just some posts ago

- Harry

[NESMotorsports]

HAHAHAHA, you just seemed to talk about it like it was already there.

[Harry]

No no, ideas develop in this forum, I get a lot back here!

- Harry

[NESMotorsports]

I bet Harry, and we love that about you. You really listen to us lowly track guys that use your awesome app.