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Looking at the JSON file, it does seem to be a direct dump of the GPMF data embedded in the MP4. Here's a collapsed view of what's in the file which shows the headers but not the data itself: Looking at the "GPS5" key, it seems to include only 5 values: latitude longitude altitude 2D speed 3D speed In addition, nested in the GPS5 data, it occasionally includes two more pieces of information: "fix" - This seems to be the GNSS fix type (3 for 3D, 2 for 2D, etc.). "precision" - If I had to guess, I'd say this is position accuracy in cm. That's not too bad. There are a couple of things missing compared to FlySight's data: Components of 3D velocity. In principle you can recover the vertical component from 3D speed and 2D speed, but there's no way to get north and east speed directly from this data. You would have to go through latitude and longitude, which will likely result in some additional error. Components of accuracy. FlySight includes horizontal and vertical position accuracy as well as speed accuracy. Number of satellites used in the fix. This can be a useful diagnostic, but there is arguably some overlap with the position accuracy figure reported in the GPMF data. I suspect at 18 Hz this is GPS only, for the reasons given above, but it may be that if you drop down to 10 Hz the unit will automatically switch over to GPS + GLONASS. Here's the relevant table from the u-blox M8 datasheet: Assuming their velocity is coming from the same place FlySight's is, I feel like the GoPro data would be just fine for most uses.

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Well, you can always put me on your 'ignore' list. That is one handy little doo-dad. Makes all the hassle of learning the new site functions worth it. Somebody has to be reasonable and sensible. Bill has been that 'voice' in the past, but lately he's just been bickering with the resident trolls. He's fallen into the 'I know you are but what am I?" trap. Many of the other 'reasonable' folks have left. I don't blame them. It's gotten pretty damned stupid in here of late.

It's been a while since I checked the forums, but I came across this post and thought I'd add a little more information. The latest FlySight hardware uses the NEO-M8Q module, which supports 10 Hz update while tracking both GPS and GLONASS satellites, or 18 Hz while tracking a single GNSS constellation. There's nothing magical about 18 Hz, so I think the GoPro is probably also using a u-blox M8 chip. The main limitation with the latest FlySight hardware is processor speed. I haven't checked to see if we can run at 18 Hz, but it might be possible, especially if we disable audio output. However, I would say that we've seen some really good results with GPS + GLONASS tracking. Roughly speaking, this doubles the number of satellites in view, which makes the fix a little more accurate and a lot more robust. If I had to choose, I would probably go with 10 Hz and two constellations as opposed to 18 Hz and GPS only. My guess is that the GoPro is using GPS only at 18 Hz. This could be confirmed by looking at the number of satellites used in the fix (assuming this is reported). If you see a number around 8-12, it's likely GPS only. If you see a number more like 12-18, it's probably tracking GPS and GLONASS. There is one other thing I would pay close attention to. One of the things I like most about the u-blox module inside the FlySight is that it reports 3D velocity, so there is no need to calculate velocity from differences in position (which is notoriously error prone). This may very well be the same interface that the GoPro uses, but it's very common for consumer GPS units to use the NMEA interface instead. This is an old interface which doesn't have native support for 3D velocity, which means vertical speed needs to be calculated from differences in elevation. You can probably tell which method GoPro is using by looking specifically at vertical speed. How clean are the measurements? If you hold the GoPro in your hand and wave it over your head, up and down, etc., do you see clean velocity measurements on all three axes (even though position may not reflect that motion)?