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I've finally found a way to get high quality GPS lap timing data into an iPhone. The iPhone's built-in GPS is useless - it updates at 1 Hz, and sometimes it positions you 500 feet off the track! There is now an Apple-approved GPS, called the Emprum Ultimate, which plugs into the iPhone and updates at 5 Hz, and is accurate to around 10-20 feet. Combined with Harry's Lap Timer app, it can generate data like this (I acquired this today at Thunderbolt Raceway in New Jersey Motorsports Park).

First image is a graph of speed (y-axis) against lap distance (x-axis). The red line is my fastest lap, compared against the white line (where I was being held up by another car). The gray histogram in the background is the cumulative time difference between the two laps.


Second image is zoomed in to a smaller section, which is shown highlighted on the track map behind the graph.



Third image is the lateral g-forces recorded around the track map, color-coded from green, to yellow, to red (> 1g).



The really cool thing about this is you can transfer the data from the iPhone to an iPad via bluetooth, then analyze it in detail immediately after the session. It'll do a lot more too - it also acquires OBDII data via a wireless device (e.g. Kiwi wifi), so you can overlay engine parameters (e.g. rpm) on to GPS data.
 

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Discussion Starter #3
Oh, and I forgot to mention it will acquire video from the iPhone too, and overlay the GPS and OBDII data on the video. Didn't test that - it's too much for my aging iPhone 3GS to handle!
 

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Discussion Starter #6
I use it. Harry's Laptimer. Good stuff.

Here's a lap that I filmed using it on iPhone 4.
Did you use the iPhone's built-in GPS, or do you have the Emprum UltiMate?
 

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Did you use the iPhone's built-in GPS, or do you have the Emprum UltiMate?
I used the built-in GPS. The accuracy is pretty good - the draw back is the update rate is not as good. You'll notice that in the video the speed refresh rate is sometimes jerky or delayed because of this. Actual top speeds on the straights were higher than it actually shows.

Harry has mentioned that the iPhone 4 has a better GPS implementation than the older iPhones and it has improved with each generation.

I even used this at a much smaller autocross track and it was very accurate down to a couple of feet - this is not a predefined course and I mapped it in real time.
 

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The built-in GPS on the iphone4 is not accurate enough for road courses. The speeds are too high. My buddy with a GTR was getting 70mph down the straightaway when in reality he was going 130mph. External gps is definitely the way to go. I havent switched over to harry's laptimer for 2 reasons
1) video overlay is only one lap at a time, you skip every other for some reason
2) no support for obd-key (bluetooth) yet
3) unable to link to 2 bluetooth sources at a time (GPS and obdII)
4) need to jailbreak for for certain uses

correct me if I'm wrong on any of these issues
 

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Discussion Starter #10
The built-in GPS on the iphone4 is not accurate enough for road courses. The speeds are too high. My buddy with a GTR was getting 70mph down the straightaway when in reality he was going 130mph. External gps is definitely the way to go. I havent switched over to harry's laptimer for 2 reasons
1) video overlay is only one lap at a time, you skip every other for some reason
2) no support for obd-key (bluetooth) yet
3) unable to link to 2 bluetooth sources at a time (GPS and obdII)
4) need to jailbreak for for certain uses

correct me if I'm wrong on any of these issues
You should try the new Emprum Ultimate GPS - it's tiny, plugs into the iPhone, has a 5 Hz update rate, and is MUCH more accurate than the built-in GPS. No need to jailbreak - it's Apple-approved, and only $90. Makes Harrys Lap Timer a viable option. I compared the GPS speed with my OBDII logged speed and they were within 1-2 mph of each other, even at 120+ mph.

I haven't tried obd-key, but it works great with Kiwi wifi. Also haven't tried video - that will have to wait until I upgrade my old iPhone 3GS to a iPhone 5!
 

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Do they make something like this for android?
Yes they do. It's called trackmaster by trackaroo. Also has an optional module which allows you to use external gps (I use qstarz 818xt)

It is awesome, does all the same things as harry's
 

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Bumping pu this thread, I just got my hands on a i phone 4s yesterday. I'm going to download the appt tonight was wondering if i still needed to get the Emprum GPS attachment for better results? I'm really looking forward to start logging.

Are you guys using lap time Pro or just the Normal lap timer

Matt.
 

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Discussion Starter #13
Bumping pu this thread, I just got my hands on a i phone 4s yesterday. I'm going to download the appt tonight was wondering if i still needed to get the Emprum GPS attachment for better results? I'm really looking forward to start logging.

Are you guys using lap time Pro or just the Normal lap timer

Matt.
Yes, you do need the Emprum - the iPhone's internal GPS is only 1 Hz, which is not good enough for proper timing. Emprum is 5 Hz - still a little low, but anything better costs a lot more. I use the Pro version. I also tried the latest version of Harrys Lap Timer with my Kiwi Wifi at VIR last weekend, and got no dropouts at all - looks like the issues with the Kiwi wifi dropping the signal are gone.
 

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Yes, you do need the Emprum - the iPhone's internal GPS is only 1 Hz, which is not good enough for proper timing. Emprum is 5 Hz - still a little low, but anything better costs a lot more. I use the Pro version. I also tried the latest version of Harrys Lap Timer with my Kiwi Wifi at VIR last weekend, and got no dropouts at all - looks like the issues with the Kiwi wifi dropping the signal are gone.
So the 4s is still only 1Hz, What the heck is Kiwi wifi? Is that like a different app to gain data from your ecu?
 

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I have the Bad Elf GPS for my flying applications. It was accurate at 36,000ft and ~470+ kts... I bet it would work wonders for a lap timer.

Have you heard of anyone using the Bad Elf for a lap timer?

EDIT: Just looked up the specs... let's just say it will get the job done.

"GPS Technical Specs:
Fast GPS lock times (45 seconds or less)
2.5 meter accuracy
60k feet maximum altitude
1000 MPH maximum speed
Up to 10Hz position update rate
66-channel MTK GPS chipset
SBAS/WAAS/EGNOS/MSAS"
 

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Discussion Starter #16
So the 4s is still only 1Hz, What the heck is Kiwi wifi? Is that like a different app to gain data from your ecu?
It's a OBDII reader that transmits the data via wifi to various iPhone and Android apps. Harrys Lap Timer reads it, and stores the data alongside the GPS data.
 

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Matt, I've been doing the datalogger 'dance' for the past few months. I ditched my racechrono setup because I have having problems with dropping data, and the data analysis software was horrible. Then I switched to Harry's. You need the emprum GPS unit to get decent accuracy. Internal 1Hz updates at one reading per second. Not ideal. At 5Hz you get 5 points per second (every .2 seconds). If you get the Kiwi unit, don't cheap out like I did because the knockoff brands only pull data at 3Hz, whereas the real kiwi units get 6Hz. With the kiwi unit you can display/log rpm and throttle position, plus HLT can calculate gear position for you.

I ended up returning my HLT gear though. There are a few issues with HLT
1) wireless. update rates are slower and not as reliable
2) HLT will only export one lap of data at a time. If you want to overlay onto gopro video using something like trackvision or race render, you're stuck with one lap.
3) HLT interpolates data to make it look smoother than things really are. The best you are getting is 5hz with emprum, but Harry's interpolates the data to 30hz. Therefore there are 6 points of fake data for every one point of real data. The feature is nice to smooth out video, but he only interpolates if you use his data overlays on the iphone. The exported data is not interpolated.
4) HLT video overlay skips every other lap (next version is supposed to fix this issue)
5) HLT video overlay gauges not so great looking (green/red?)
6) data analysis software is very basic

HLT is great for the money, but I wanted something better. I think you can get accurate lap times with HLT, but the video and datalogging was lacking for me. I ponied up for an AiM Solo DL. I've got 20Hz through the CAN lines, 10Hz GPS, and everything is wired. Solo features a predictive laptimer. The data analysis software is much more useful than HLT. I've been reading this e-book, and it's very interesting stuff:
http://lapfaster.com/Portals/0/ebook/www.LapFaster.com_free_ebook.pdf

March 17th will be my trial run of the Solo DL. There are 6 of us running the AiM solo DL that day. Another nice benefit is being able to share data and even run virtual races.

Let's pray it doesn't rain next weekend.... I'm going nuts watching the weather forecast.
 

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Discussion Starter #18
Matt, I've been doing the datalogger 'dance' for the past few months. I ditched my racechrono setup because I have having problems with dropping data, and the data analysis software was horrible. Then I switched to Harry's. You need the emprum GPS unit to get decent accuracy. Internal 1Hz updates at one reading per second. Not ideal. At 5Hz you get 5 points per second (every .2 seconds). If you get the Kiwi unit, don't cheap out like I did because the knockoff brands only pull data at 3Hz, whereas the real kiwi units get 6Hz. With the kiwi unit you can display/log rpm and throttle position, plus HLT can calculate gear position for you.

I ended up returning my HLT gear though. There are a few issues with HLT
1) wireless. update rates are slower and not as reliable
2) HLT will only export one lap of data at a time. If you want to overlay onto gopro video using something like trackvision or race render, you're stuck with one lap.
3) HLT interpolates data to make it look smoother than things really are. The best you are getting is 5hz with emprum, but Harry's interpolates the data to 30hz. Therefore there are 6 points of fake data for every one point of real data. The feature is nice to smooth out video, but he only interpolates if you use his data overlays on the iphone. The exported data is not interpolated.
4) HLT video overlay skips every other lap (next version is supposed to fix this issue)
5) HLT video overlay gauges not so great looking (green/red?)
6) data analysis software is very basic

HLT is great for the money, but I wanted something better. I think you can get accurate lap times with HLT, but the video and datalogging was lacking for me. I ponied up for an AiM Solo DL. I've got 20Hz through the CAN lines, 10Hz GPS, and everything is wired. Solo features a predictive laptimer. The data analysis software is much more useful than HLT. I've been reading this e-book, and it's very interesting stuff:
http://lapfaster.com/Portals/0/ebook/www.LapFaster.com_free_ebook.pdf

March 17th will be my trial run of the Solo DL. There are 6 of us running the AiM solo DL that day. Another nice benefit is being able to share data and even run virtual races.

Let's pray it doesn't rain next weekend.... I'm going nuts watching the weather forecast.

That's funny - I've been reading the exact same e-book. Some really good info in there.

The only thing I disagree with is your point #2. You can export either individual laps, or an entire day's worth of laps (currently just the last day acquired, but the next version will allow selection of the day).

I'll post up some video I took at VIR last weekend using HLT, GoPro, and Dashware software to combine the two - you can see the kind of information it can give you. Hopefully have it done by tonight.

Good luck with the weather - funny how when you have a track day coming up you suddenly become obsessed with the Weather Channel!
 

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The only thing I disagree with is your point #2. You can export either individual laps, or an entire day's worth of laps (currently just the last day acquired, but the next version will allow selection of the day).
Are you sure about that? Everytime I try to export an entire track day, you only get the lap times for the day, and not all of the actual data in .csv format. Am I doing something wrong?
 
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