MPH delay on smartphone

[tetstang]

Hey - I know that many of you run Harry's Lap timer, and I wondered if the MPH reported on the iPhone is delayed. I have an AIM Solo and GoPro mounted to my roll bar, and want to mount my iPhone on the dash to capture real-time MPH in the video. I downloaded a GPS speedometer app (not Harry's Lap Timer) and notice that there can be a considerable delay in the MPH shown on the phone. On Harry's web page sample vids, I noticed this difference between the car's speedometer and the sample vid, suggesting that the MPH reported on the phone is not really synced with the car.

What is your experience? Is this delay the nature of GPS smartphones?

Thanks,
TS

 

[Fabman]

Hey - I know that many of you run Harry's Lap timer, and I wondered if the MPH reported on the iPhone is delayed. I have an AIM Solo and GoPro mounted to my roll bar, and want to mount my iPhone on the dash to capture real-time MPH in the video. I downloaded a GPS speedometer app (not Harry's Lap Timer) and notice that there can be a considerable delay in the MPH shown on the phone. On Harry's web page sample vids, I noticed this difference between the car's speedometer and the sample vid, suggesting that the MPH reported on the phone is not really synced with the car.

What is your experience? Is this delay the nature of GPS smartphones?

Thanks,
TS

I've been using track addict with iPhone 6 and the sync was perfect until I upgraded to an iPhone 7.
Now it seems to have multiple problems. Not sure if something went wrong with the upgrade or if it's something with the new software. Which version iPhone are you using?

 

[tetstang]

My iPhone is a 5s

 

[Fabman]

My iPhone is a 5s

Did you do the latest update?

 

[tetstang]

Always updated...

 

[Fabman]

I wonder if it's related to the new software?


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[tetstang]

Software technobabble is above my paygrade .....

 

[Fabman]

Mine too, guess that's why ours don't work


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[Fabman]

Then again, maybe it has nothing to do with it.
But, I have heard of folks having similar problems with the upgrade and timing software.

 

[Grant 302]

The phone's GPS sample rate is low. Once per second IIRC. An external GPS can increase the rate ten-fold, if memory serves. That's the main cause for delay in the data captured.

 

[barspen]

Even with an external GPS, I still get noticeable delay on my MPH info and Tach. Seems like a small delay in getting the info (from internal or external source) into the app causes a lag. iPhone 6, Dual XGPS 160 and GoPoint OBDII.

 

[Mad Hatter]

The phone's GPS sample rate is low. Once per second IIRC. An external GPS can increase the rate ten-fold, if memory serves. That's the main cause for delay in the data captured.

I have that problem with my samsung s5. Gps speed is always off as the cpu tries to process the info from rhe less then speedy gps. Steady state readings are fine but the more they vary,the bigger the delay. I just use the obd speed and then correct the data to the rpm taking into account gearing and tire size. Works fine as long as you assume the pcm rpm data is good!

Lap times are really close to transponder times though. Seldom more then 0.05s off with trackaddict

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[Flyboygsxr]

Buy an external GPS...it will make a huge difference. I use mine when flying and racing and the MPH is pretty accurate.