Harry's GPS Suite Forum

Hey all, new on here.

I purchased Harry's Laptimer Rookie on my iPhone 4s a few months back intending to use it to record data on track, then sync it up with GoPro on Dashware software. I did this as I didn't want to fill my iPhone with GoPro videos.

We used it a few days after I purchased it and it didn't seem to be particularly accurate. Me and my dad were using it to compare laptimes.

The laptimer seemed to show that he was faster through the first sector by .5 seconds, I was faster through the next sector by 1.4 seconds, he was faster through sector three by 1 second and I was minorly faster through the final (4th) sector (about .05).

The end time meant he was minorly faster which I'm not bothered about at all, but I seem to think the app results are inaccurate. (Not the fact he was faster whatsoever. For my below reasoning.)

The iPhone was mounted the same for both sessions, on the inside of the windscreen with a cheap sucker mount (which worked well and held on the entire day!).

My reason behind my thoughts on the accuracy is that it is only a 1:08 laptime, and the track is fairly straightforward. Fair enough if it was 2+ minutes a lap, then it wouldn't seem out of turn, but I seriously doubt I was 1.4 seconds faster through one of the sectors than him and I also don't see him being 1 second faster through another than me. We run almost identical the whole track so something isn't right.

Could this be down to the internal GPS on my iPhone 4s giving inaccurate results? This isn't even the fastest lap that was in my dad's session. I selected his second fastest lap and my fastest. The reason behind this is that the iPhone didn't register a 4th sector on his fastest lap and just one longer sector 3. That's another reason I'm unsure on accuracy...

Thanks in advance, Sam.

Please export one lap you doubt is correct to .hlptrl and send it to me (Harry@gps-laptimer.de).Timing accuracy depends on GPS accuracy, I will check that. For a 4S's internal sensor, timing accuracy should be better than 0.1 seconds.

Harry

If a split is missed, one can move the POI a little and recalculate that lap. You can even add split triggers after the fact and recalculate all the laps. The internal GPS has two problems. The first is that the update rate is only 1Hz. The second is that Location Services can mess with the data, which will degrade transient response and give you fixes that are not at the actual location. There's a post here somewhere in the GPS accessory section that shows what that looks like.