iPhone 5S - Hero2 - XGPS160 - out of sync

Help on issues you run into with LapTimer; in case you have a question on how to use LapTimer, use the forum "Using LapTimer" instead
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PJH1987
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iPhone 5S - Hero2 - XGPS160 - out of sync

Post by PJH1987 »

Dear All,

I have searched the forum and tried some different settings, but can't seem to sync everything up as it should be.

My process:
- Record video with a Gopro Hero 2
- Time the lap with harry's laptimer
- Record data with the SkyPro XGPS160 connect to the app
- At home, upload video to an iPhone 5S
- Manually sync the video's end point

I noticed that when I use the slider in the app to set the endpoint to where the endpoint should be according to the video, that if I render the video the timing starts early and ends early. The time difference is about 3 seconds, the g-force and speed are about 1 second ahead of the video (so G-force shows that I'm cornering when I haven't turned in yet).

You can see the finishline behind the left outside mirror:
Image

The timing starts 3 seconds early, although I set the syncpoint right:
Image

At the actual startpoint the laptimer shows in the windscreen shows 1 second, that's about right I think. The overlay shows more than 3 seconds:
Image

If I adjust the video's endpoint so that start and end render about right, the G-force and speed data are now slow:

Video shown in the screenshots with the sync point set so that start and end match up:
[youtube]https://www.youtube.com/watch?v=ToUyb0xrbeM[/youtube]

Video without XGPS160 shows the same result in lag, speed is less accurate:
[youtube]https://www.youtube.com/watch?v=ToUyb0xrbeM[/youtube]

Can someone please help me with my settings or give me pointers on what I can do? Can i fix these laps so that they sync correctly or do I have to go out on track again and just hope for the best?

Kind regards,
Pieter-Jan

PS: just hear that M42 sing :D
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Harry
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Re: iPhone 5S - Hero2 - XGPS160 - out of sync

Post by Harry »

Please search for "sensor delay" here on the forum. All but GPS sensors do not come with a valid timestamp for when data has actually been measured. This means any hardware configuration will have different timing behavior and probably needs some fine adjustments. The relation of GPS / acceleration / OBD data is fixed during recording. Any change in sensor delays will have no effect on existing recordings, but for new recordings only. The relation between data and video can be adjusted after the fact - before overlaying it. This video delay setting is not relevant for you because you do not use automatic video recording but adjust it manually. When using manual syncing, I suggest to select a rough lap end position in Overlay Sync first. Return to Lap Details and press "Play" to see the overlaid video in real time. Watch acceleration and video relation and identify how much adjustment is necessary. Return to Overlay Sync (Lap Details ‣ Video Preview ‣ sync time row in the bottom) and use the arrow keys to adjust the sync point. Ignore the frame shown in this phase. Repeat until it is fine for you. Syncing GPS speeds is nothing I recommend. GPS speed data is often over smoothed and hard to get in line to the last tenth second.

- Harry
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