How to get angle?

[Ken-Kuroki]

Hi, I've been using EasyIDP to extract plots from drone images, and I wonder how to get the angles in which a given plot is captured in the images. I'm currently using the relative position of the plot within the image, and it works OK to pick the near-nadir images. But when you, for example, want to compare the accuracy of downstream analyses, the position in the image isn't the most intuitive metric to use, and I prefer to use angle instead. Do you have any suggestion to implement it using EasyIDP in a straightforward way? Thanks!

[HowcanoeWang]

Got a little confused about this description, do you mean the image rotation angle?
https://support.pix4d.com/hc/en-us/articles/202558969-Yaw-Pitch-Roll-and-Omega-Phi-Kappa-angles

If in this case, current EasyIDP doesn't read image rotation properties for pix4d and metashape. This may take some time to implement such function (the camera rotation in real-world != camera rotation in the reconstructed model, this need some convention)

---

Or you need something like this? (The green part angles?)

[Ken-Kuroki]

My bad for unclear explanation. I think it's the latter. I want to get angles for 1, 2, and 3 in this drawing.

[Ken-Kuroki]

Can I continue this topic with ver2.0 on Metashape projects?
To get camera coordinates, it seems I can use ms._local2world(ms.photos[i].transform[0:3, 3]) to obtain world coordinates and then calculate distance from ROIs after converting their coordinates to world coordinate as well using ms._crs2world(roi). However, it gives very large angles that seem incorrect. I think this is because the world coordinate system is, although I don't quite understand, the coordinate in the space not on the ground surface.

So I instead tried to convert photo coordinates to CRS with ms._world2crs(ms._local2world(ms.photos[i].transform[0:3, 3])), which gave me the following error. It would be great if you can tell me how to avoid this error. If there are other packages to do the same conversion then that's just fine too.

Traceback (most recent call last):
  File "<string>", line 1, in <module>
  File "/root/.cache/pypoetry/virtualenvs/easyidptrial-xS3fZVNL-py3.7/lib/python3.7/site-packages/easyidp/metashape.py", line 99, in _world2crs
    return convert_proj3d(points_np, self.world_crs, self.crs)
  File "/root/.cache/pypoetry/virtualenvs/easyidptrial-xS3fZVNL-py3.7/lib/python3.7/site-packages/easyidp/metashape.py", line 1047, in convert_proj3d
    return out[0, :]
UnboundLocalError: local variable 'out' referenced before assignment

[HowcanoeWang]

I could replicate the error you mentioned here

>>> import easyidp as idp
>>> lotus = idp.data.Lotus()
>>> ms = idp.Metashape(lotus.metashape.project, chunk_id=0) 
>>> ms._world2crs(ms._local2world(ms.photos[0].transform[0:3, 3])) 
array([139.54053245,  35.73458169, 130.09433649])

But if you changed the ms.crs to geotiff and then do the same thing:

>>> import pyproj                                   
>>> ms.crs = pyproj.CRS.from_epsg(32654)              
>>> ms._world2crs(ms._local2world(ms.photos[0].transform[0:3, 3]))
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "D:\OneDrive\Program\GitHub\EasyIDP\easyidp\metashape.py", line 99, in _world2crs
    return convert_proj3d(points_np, self.world_crs, self.crs)
  File "D:\OneDrive\Program\GitHub\EasyIDP\easyidp\metashape.py", line 1047, in convert_proj3d
    return out[0, :]
UnboundLocalError: local variable 'out' referenced before assignment

Fix this error info in 5913fdf (at local, not pushed yet)

Temporary solution:

Set ms.crs = pyproj.CRS.from_epsg(4326) first and then get photo location, and transform to GIS crs by

pos = {p.label: ms._world2crs(ms._local2world(p.transform[0:3, 3]))   for p in ms.photos}
transformer = pyproj.Transformer.from_crs("epsg:4326", "epsg:32654")

out = {}
for k,v in pos.items():
    # here the lon and lat need to be reversed for pyproj package
    transformed = transformer.transform(v[1], v[0], v[2])
    out[k] = np.asarray(transformed).T

Detailed explanation:
Ths crs in the Metashape is created from photos' meta_info, often epsg4326 with lon and lat, and the software will "display" in this coords.

local -> world -> crs(photo_meta)

When you export outputs from Metashape, you can specify another CRS for geotiff (in this case is epsg:32654)

local -> world -> crs(photo_meta) -> geotiff

Probably in the next release, the ms.crs -> ms.photo_meta_crs, and then ms.crs -> geotiff.crs

and you can get photo position at current geotiff crs by

>>> ms.get_photo_position(photos[0], crs=geotiff.crs)
array([[ 368030.75661044, 3955476.94877388, 129.8508284]])

[Ken-Kuroki]

Thank you so much! I'll try that out!

[Ken-Kuroki]

It worked perfect! Appreciate your quick response.

[HowcanoeWang]

It worked perfect! Appreciate your quick response.

In v2.0.0.dev3, you should be able to do:

# get all photos and return a dict, and use ms.crs as output geo-coord
>>> ms.get_photo_position()   

# use given crs as output geo-coord
>>> ms.get_photo_position(to_crs=pyproj.CRS.from_epsg(4326))

# same as the pix4d
>>> p4d.get_photo_position(to_crs=pyproj.CRS.from_epsg(4326))