>On Friday 25 October 2024 at 16:45:57 GMT+1, ael via Talk-GB ><[email protected]> wrote:
>Just a comment. I capture gps traces (usually on a garmin handheld) and also images (normally jpeg) from various cameras including a dashcam and a Gopro type body worn camera, but also from everyday cameras. I then use gps-correlate to add the gps exif data to the photographs, so I end up with a geotagged jpeg images. Whenever I had looked into contributing such images to the various OSM image repositories, there was no simple way just to upload them. This seems like a glaring omission. My Nextbase dashcam produces geotagged mp4 video, and there is no simple way to upload those. I do realise that the gps information in the mp4 videos is not standardised, so there may be an excuse for the video. Not to mention the sheer size of the files. >ael A user described how they uploaded a georeferenced video here https://www.openstreetmap.org/user/Branko%20Kokanovic/diary/403952 I have a Nextbase dashcam and the positions it gives are not very accurate. They are generally less accurate than you would get from a smartphone. I have even seen position offsets of up to 30m in a location which is not particularly difficult. The speed seems to be pretty accurate however. I looked closely at a section of footage and found other issues too. The in-vision speed and position data are slightly delayed relative to the video. I had a Garmin hand-held SatNav (GPS receiver) mounted on the windscreen. I used it to record a tracklog at the same time. It gives considerably more accurate positions than you would get from a smartphone. It helped me find these issues. The video file recorded by the dashcam contains a data stream. You can extract the data stream using the -ee option of Phil Harvey's ExifTool. The stream includes the actual data from the dashcam's SatNav chip. This data is in the usual NMEA format. The data is not easy to work with because (a) the checksums have been clobbered and (b) the NMEA data is mixed up with other data. I found the in-vision timestamp was two seconds out (relative to the in-vision speed and position). I don't know whether that is an oddity of this particular piece of footage, or whether it's always like that. Most of the time, it wouldn't matter, but you run a dashcam in case there is an incident and then the exact time could be important.
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