iPhone 4 questions: accelerometers, incoming calls, etc.

[chorrell]

A couple of questions have come to mind as I've been using the LapTimer Pro app on my shifter kart (iPhone 4, Dual XGPS150):

1 - From the layout of the track with the lateral acceleration overlay it looks like there is a bit of a delay on the lateral acceleration. This shows up as having a fair amount of lateral acceleration tapering off even after I've completed the curve and am driving down the following straight. I noticed in one of the settings an accelerometer delay of 1.5 seconds - would it be OK for me to reduce this, and would doing so have the desired effect?

2. - Is there a way to set my phone to where it won't receive incoming calls or texts or anything while I'm driving? I haven't had any experience with it yet, but it seems like it could mess up the data acquisition. I thought about putting it in airplane mode, but figured that might turn off the bluetooth or GPS signals.

Thanks,
Chuck

[Harry]

On #1: Yes, changing the delay will change the timing between acceleration and GPS for the next run. However, it will not change the data for recorded runs. Please first check if your acceleration calibration has been setup correctly. You can easily see this if you have lateral acceleration while driving a straight. It should be nearly 0 here. You can repair this 'after the fact' by pressing the 'Recalculate' button in Lap Details. This will derive acceleration from the GPS slot - not as accurate, but it works.

On #2: Flightmode will turn off the location service, so this is no option. You may redirect incoming calls to your mailbox, or remove the SIM.

- Harry

[chorrell]

Great - thanks for the feedback. As I was in the settings reducing that accelerometer delay I saw that there are delays for other things as well - the Dual X150 that I'm using and for the video overlay among other things. Do you have documentation somewhere that describes what these delays are for and how changing them might affect things?

One other question - is there a way to turn down the scale of the overlaid lateral acceleration on the map view? A sprint track for shifter karts is pretty small and there can be a lot of overlap of the lateral acceleration graphics of nearby corners.

Thanks,
Chuck

[Harry]

The delays simple document an estimate for the time gap or delay between the 'real' event and the time this 'real' event is available in LapTimer. Take e.g. GPS: the satellites send a signal (+time to reach earth), the GPS chips makes a position from this (+processing time), there is a given update rate (+ half the time between two fixes in average, e.g. 0.5s for a 1Hz device), finally time from the sensor to LapTimer's logic (+time again). As not all sensors come with a real time stamp (like GPS does), one needs to work with this kind of heuristics. Finally, if your acceleration data is 'behind' GPS, decrease the delay - and vice versa. Same for all other sensors. GPS serves as a kind of reference here.

Currently, there is no customization possible except leaving away some items - like the time or speed. I have nothing planed here as you may opt for external overlaying software in case you want to tweaks this.

- Harry