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While going through your Mapping and 3D modelling training (3DR Tower App Demo), noted something about "geotag is a little bit hit and miss..." at minutes 3:47 of the video. I don't quite understand what this means as I believe if the GPS HDOP is of good quality, then position will be good and geotagging should never be a problem, i.e. not a hit-and-miss. Photogrammetry - as I understand it relies on good positioning for mosaicing purposes. If we could not rely on geotagged coordinates, how could we overcome problems with image-stitching or mosaicing at processing stage? Indeed drone opens-up good opportunity for a wider use of aerial 3D photogrammetry, but we can only really save a lot of time and sweat by having the practicality of geotag features onboard. Will certainly appreciate your specific experience on dealings with geotagging issues, be it accuracy, latency, etc.

Thanks, in advance - Zane


Edited by Zane

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Sorry about the delayed response. I thought this forum was getting folded into the other.

The coordinate data has two important pieces here:

1) Quality of the data/position. This is what you are referring to w/ the HDOP etc. If those values are good, they will be more precise (but not as good as survey level data).

2) Embedding that data to the JPEG file (or whatever format) so it can be easily read by the processing software. 

You could/can overcome geotagging issues with the photogrammetry process, but as you have larger data sets, it introduce either a lot more processing power, or the chance for more error. 

The hit or miss comment probably came from us geotagging early on with a custom built UAV and adding geotags after the flight. If you end up with one picture too few/many, or don't pull the right flight log, etc. In our minds it just adds another step and another spot to potentially screw up. 

The accuracy will never be constant until the sensors get much better.

Without knowing which video, my guess is our advice is aimed at encouraging people who value their time to make sure they don't have to do this unless there is a good reason to do so.

I don't feel like I've completely answered your question, just wanted to clarify our position. 

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