Horrible lag in GPS data

[Leopold]

Sorry for responding to a slightly dated thread but it touches questions and issues I have pretty much dead on.

I noticed the lag in speed readings and decided that I do not want either speed or GPS coordinates stamped on the video file. I could put me in a bad position without any basis in actual truth to the figures. Easily configured in A119, just choose not to display it in the video file.

For sure, everything is still recorded in the file and can easily be extracted by tools like Dashcam viewer etc. It will not be visible on export files which perhaps is what people would like to submit if there are any doubts about who is responsible... but all data is always present in the raw video file and nothing prevents people from asking you to submit those files. Could very well be laggy/faulty data as I said above (and others too), to assess the technical accuracy of the recorded GPS data is not an easy task.

These are not simple considerations. I love the convenience of automatic and accurate GPS time setting but there is more to it, obviously.

 

[roadkill401]

My thought with what to turn on and off was as follows:

The GPS lat/long is how the speed is generally calculated, but from a viewer perspective, it is not likely that someone in their head can calculate that on the fly by looking at numbers. But what having a lat/long does do for you is give a definitive location as to where your car was. So if submitting it in as any form of evidence, it clearly shows where on the planet your car was. So nobody can say, 'but that is just general footage and it's not the place or time you say it was'. it is clearly defined on the video.

Now as for the speed part, I do turn that off. it is totally inaccurate and really doesn't give you and advantage. If anything it will cause more confusion. It is not calibrated and the processor inside the A119 is not fast enough I gather to calculate the speed in real time so it looks like it is doing it as a batch call average. for that reason it it very lagging. The 3rd party viewers take the embedded gps locations and calculate it in realtime to the video frame. So even though the frame rate is not perfect, it does give you a speed much closer to reality.

 

[Leopold]

I'm with you roadkill401, sound logic. I will turn on recording of the lat/long coordinates but since speed readings are so inaccurate (as verified by me and so many), it would only introduce a source of doubt and confusion if I ever need to submit video evidence in relation to an accident.
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I realize that speed can be easily calculated from GPS readings but then it would take some effort taking into account error margins etc. It can never be just a simple figure like the speed you see recorded which is obviously very wrong especially i cases were speed changes rapidly.

 

[jokiin]

the processor inside the A119 is not fast enough I gather to calculate the speed in real time so it looks like it is doing it as a batch call average. for that reason it it very lagging. The 3rd party viewers take the embedded gps locations and calculate it in realtime to the video frame. So even though the frame rate is not perfect, it does give you a speed much closer to reality.

the processor does not calculate speed, the GPS collects the speed data in knots, it is converted to MPH or KMH for display as per your settings, the data in the file is accurate as it can be from the GPS (keep in mind consumer GPS is not a calibrated device for evidence purposes, and has an element of inaccuracy anyway, that is well documented, for the sake of the argument though it it's pretty close to the mark) , the data that is overlaid on the video however is not real time, that has to be extracted from the data which generally happens once per second and an overlay created and is embedded frame by frame so that's happening 30 or 60 times per second and will always have some amount of delay, it's not that the players are doing some kind of conversion or calculation either but when working with the same raw data that is collected you have the processing power of your PC which is enough to show the speed and location info real time, some of the players will do some averaging to smooth things out during playback to account for any anomalies due to GPS signal issues but that's about it

short answer, data overlaid on your video is not so accurate, the data embedded is as accurate as consumer GPS access allows, software players can play this back with much greater accuracy