Is there are any way to understand Topodrone’s methodology and try adapt to your system?
I think its will be good for community, since you have good foundation.
This looks great! Sorry for reviving the thread but I was keen to hear how things have gone since you started using this.
In particular I was wondering how things went with combining the RTK positions with the photo time stamps? I was wondering if the error in that sync might be enough to eliminate the benefit of using the additional RTK position data?
Also, I was wondering if there is any reason you couldn’t use PPK to avoid needing a base station?
Thanks!
Hi Xarvia,
I don’t fly this that often, it’s a proof of concept and recreationally I don’t really care about the absolute accuracy. If I fly for work, then we have an OA so fly P4Pro RTK’s anyway. Of the 5-10 test surveys I did with it, the flight characteristics were all very stable.
Re. the timing, yes it’s an issue, see the screenshot below which shows the reconstructed locations are all shifted slightly along-track from the recorded position due to the time delay.
The best solution I had for this was to have a rooted android device running a third party time-sync app on it which either pulled from GPS time or NTP, this gets rid of the offset but not the command latency. Unfortunately this seems to be getting harder and harder on newer android versions which starts to run into conflict with being able to run DroneLink or DJI Fly.
The two other options I tried are:
- Sit stable for a few seconds each side of a photo, this is slow, and not that effective because the drone still drifts ever so slightly.
- Note the time offset by taking a calibration image at the start of the flight (i.e take a photo of an accurate clock on your phone or something) and this will give you the offset at least down to the full second. You then add this offset in to the exif tagging which is straightforward to do and works reasonably well.
As for PPK, you still need a base station, be it your own or from a CORS network, to provide the corrections at some point. The accurate description for this project is that it’s short range RTK and long range PPK as it will drop the WiFi link used for the corrections.
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Thanks a lot for that!
Looking at the exif data I think the timestamps are only to the nearest second, so for mapping (taking pictures whilst moving at 5m/s) I’m not sure it can be done?
My application is mapping with photogrammetry to provide an additional layer for creating orienteering maps. I think some ground control points (with an RTK gps) and the standard onboard gps fix are probably going to be good enough.
Down the track though I’m quite interested in an approach like your LIDAR drone. (The photogrammetry is limited to open areas such as dunes and fields, whilst most of our maps are forested)