Improve Accuracy by using DEM Height instead of EXIF

[GünterDörffel]

Hi everybody,

I had recently processed a series of drone flights over densly closed forest. Hardly any ground visibility at all. Results were "sub-optimal".
The first thing I wanted to improve upon were very bad height-values stored in the EXIF of the images. I luckily have a DEM and was able to improve the results (especially the location/scaling) considerably.

The drone data was from a DJI 330 on a Phantom4 consumer drone. I learned that it actually only has a height value stored for the starting point and then the flight height as such. So the "individual" height values on each image were pretty off because the start-height was off. To improve, I followed this workflow:

• Exported EXIF of all imges in a folder to csv using EXIF-Tools  (If I improve that, I'll use a python exif extractor)
• Modify elevation/height in csv with height from Starting point PLUS Flight height
• (Optionally also convert WGS84 X/Y into projected coordinate system including transformation
• After loading images to Drone2Map replace the elevation by reading in the csv file 
• Process ...

I have all this in python and would actually be willing to share as a toolbox - but would like to have some community-input first:

• Is this the way to go?
• Any suggestions what to include in addition?
• Has anyone got an idea how "valuable" YAW/PITCH/ROLL values stored by a Phantom4 are?
  (and how to make use of them in Drone2Map?   Photoscan/AGIsoft seems to be able to read/use them)

So fire away ... 🙂  Thanks

[ChrisToynbee1]

Hi Günter,

I know this was a long time ago but I am new to this field and have only just come across your post. From what I have been reading it sounds like your suggestion is a good one and for me (as i say I am still new to this) sounds like the way to go. I don't know if Drone2Map has now made it possible to incorporate yaw pitch and roll, but I think that level of detail would only improve the photogrammetry process, so worth keeping that data if possible. 

I am surprised nobody else has messaged on here but I would be keen to take a look at the toolbox you made if you are happy to share?

Thanks for posting.

Chris

[JasonMartin3]

Sounds like a useful toolbox! Have you come to any conclusions? I'm am still learning and messing around with settings, but have had very little luck with forested landscapes.

Thanks,

Jason

[MervynLotter]

Hi Gunter

I too would find such a toolbox useful. I have a DJI Phantom 4 Pro. I have suggested that a similar function to be added to Drone2Map whereby the user needs to provide (1) a fixed altitude of Drone takeoff site, and (2) the height of the flight, and then the image properties would accordingly be corrected. Do see https://community.esri.com/ideas/15040 . However I don't know if this will ever be implemented as it is not yet in product plan. So your proposal sounds like very useful functionality to  have.