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Weird Issue with Harry’s Lap Timer

 
Old 05-17-2019, 01:17 AM
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GrantG
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Default Weird Issue with Harry’s Lap Timer

My lap videos have the gps speed and g-forces very out of synch with the video (shows the speed like 3 seconds off from where it should be - i.e. shows top speed happening while the car is braking for a hairpin). Anyone experience this or have ideas for a fix?

Thanks!
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Old 05-17-2019, 01:40 AM
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John Mclane
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Originally Posted by GrantG
My lap videos have the gps speed and g-forces very out of synch with the video (shows the speed like 3 seconds off from where it should be - i.e. shows top speed happening while the car is braking for a hairpin). Anyone experience this or have ideas for a fix?

Thanks!
Are you using the phone gps? It has low rate at 1hz, which give unreliable reads of position and speed. It's fine for navigation but at higher speeds and particularly on the bends, it can't keep up.
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Old 05-17-2019, 09:15 AM
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Get a vbox sport (20hz gps, and good accelerometers), pair it to your mobile, done.

i have seen videos of track laps with mobile internal gps or the porsche track app using the internal dashboard digital speed, in both cases: Fake speeds, fake lap times.

My vbox has been no more than 0.3 secs off from my aim transponder for lap times. For speeds in straight line, gps works fine, but once you throw curves, they are not that precise.

For lap times, any transponder with a sensor on the racetrack is closer to precise that all the gps based lap timers.
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Old 05-17-2019, 09:45 AM
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Originally Posted by John Mclane View Post
Are you using the phone gps? It has low rate at 1hz, which give unreliable reads of position and speed. It's fine for navigation but at higher speeds and particularly on the bends, it can't keep up.
Yes, using phone gps. I’ve used app for years and I realize it’s not super accurate, but now it is Way off (several seconds)
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Old 05-17-2019, 09:58 AM
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Dual makes an external GPS device that I use that has a 10Hz sampling rate. Bluetooth to the phone once it acquires multiple satellites and you're off. My first one died after two or three years and the replacement wouldn't connect to any satellites right out of the box. Third one worked last year just fine but I haven't it used it yet in 2019 so we'll see.
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Old 05-17-2019, 10:06 AM
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John Mclane
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I bought a dual XGPS 160 as well, refreshes at 10hz. Racelogic is the "gold standard " according to some, but I found to be quite expensive for my amateur habiliteis.

If you use android there are more options. Non-jailbroken iPhone is stuck with MFI devices.
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Old 05-17-2019, 11:14 AM
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First check if you need to upgrade the software to the most recent version (I think it’s v23), then look to upgrade you GPS receiver (I use Dual XGPS160). It may help, it’s not perfect but among the lower cost and generally reliable solution for us casual track guys/girls.
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Old 05-17-2019, 11:54 AM
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Dual XGPS160 here as well. Works fine so long as my mount for on the windshield doesn't come unstuck and fly around the cabin at 100mph like earlier this week but, that's the mounts problem not the GPS 😀
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Old 05-17-2019, 12:11 PM
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Originally Posted by iphilips View Post
Dual XGPS160 here as well. Works fine so long as my mount for on the windshield doesn't come unstuck and fly around the cabin at 100mph like earlier this week but, that's the mounts problem not the GPS 😀
I keep the Dual XGPS160 in the armrest and it seems to lock on to the satellites fine. Over 8 sessions at a time trials the greatest difference was .03 sec from the transponder. Harry's would occasionally not start timing, so I switched to RaceChronoPro and much prefer their app.
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Old 05-17-2019, 01:00 PM
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I had conversation with Harry - don't think it has anything to do with external GPS (I'm not quibbling about inaccuracy of a fraction of a second). I had to edit the raw video to define the finish line. That fixed the synchronization, but am having all kinds of other problems now (the session of many laps now one single lap and the lap video doesn't reflect the proper start/stop time). Really frustrating. I would love to keep Harry's (even if accuracy is a bit off), but they are making it difficult. And new iPhone with video stabilization makes for lousy bouncy vid...
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Old 05-17-2019, 02:32 PM
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Yes, a few options: one is to go under Administration -> Settings -> Expert Settings -> Overlay Syncroninzation -> correct to appropriate delay. (the delay can be different during different sessions)
Another option is to sync your phone to an OBD2 device, and that may also get rid of the delay.
Last option is to get a GPS locator device connected to your phone, with a 10 Hz locator, as opposed to the 1 Hz on the phone (although you may still have to do option 1 with this)
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Old 05-17-2019, 03:09 PM
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Thanks guys!

This worked from Harry (in case anyone has same issue):

Hello,


Please start with increasing LapTimer ‣ Administration ‣ Settings ‣ Expert Settings ‣ Timing / Same Session Pitstop from 2 to 10 seconds. This will allow LapTimer to recognize the four laps you have in scope are considered a common session. Back in Lap List, select Session grouping in the top. You should see the track day like this:





Tap the session with four laps now. From here, revert all laps so they reference the original video again. You should see something like this now:





Select your fastest lap and select the row Video / Preview; scroll to the bottom. You will see the list of lap sync points now. Due to the individual changes you applied before, they do not form a proper sequence currently:





Now, select any lap's row you can identify in the video and adjust the frame shown to match the point in time you finished that lap. Press Set and LapTimer will bring up the Full Session / Lap dialog.


Back in the video's details view, all lap sync points are ordered now:







Now, return to your favorite lap in Lap List and press Play in the Video section to check the sync.


Greetings Harald
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Old 05-18-2019, 10:24 AM
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Glyndellis
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Originally Posted by GrantG
Thanks guys!

This worked from Harry (in case anyone has same issue):

Hello,


Please start with increasing LapTimer ‣ Administration ‣ Settings ‣ Expert Settings ‣ Timing / Same Session Pitstop from 2 to 10 seconds. This will allow LapTimer to recognize the four laps you have in scope are considered a common session. Back in Lap List, select Session grouping in the top. You should see the track day like this:





Tap the session with four laps now. From here, revert all laps so they reference the original video again. You should see something like this now:





Select your fastest lap and select the row Video / Preview; scroll to the bottom. You will see the list of lap sync points now. Due to the individual changes you applied before, they do not form a proper sequence currently:





Now, select any lap's row you can identify in the video and adjust the frame shown to match the point in time you finished that lap. Press Set and LapTimer will bring up the Full Session / Lap dialog.


Back in the video's details view, all lap sync points are ordered now:







Now, return to your favorite lap in Lap List and press Play in the Video section to check the sync.


Greetings Harald
The graphics don't show up for me. Would it be possible to post the screenshots?
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Old 05-18-2019, 12:01 PM
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Originally Posted by GrantG View Post
I had conversation with Harry - don't think it has anything to do with external GPS (I'm not quibbling about inaccuracy of a fraction of a second). I had to edit the raw video to define the finish line. That fixed the synchronization, but am having all kinds of other problems now (the session of many laps now one single lap and the lap video doesn't reflect the proper start/stop time). Really frustrating. I would love to keep Harry's (even if accuracy is a bit off), but they are making it difficult. And new iPhone with video stabilization makes for lousy bouncy vid...
Im with you on this...I discovered the inaccuracies months ago at my last track day when i was following another car doing hot laps. The other guy and i talked after..we were having a great time...He said he was doing 2:19's ...my Harry's app said 22-23's and a 17..all over the place especially corner speeds. This is not typical of my driving and i didn't experience this when i used RaceKeeper few years back. His Aim Solo is more accurate. I've given up on gps on the phone. I'll be get something better this summer.
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Old 05-18-2019, 12:31 PM
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Originally Posted by Glyndellis View Post
The graphics don't show up for me. Would it be possible to post the screenshots?
If you PM me your email address, I'll forward Harry's email...
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