images on flight path randomly assigned the 'home' co-ordinate

[Ignatius_Krogh]

Some images just randomly plot directly at the Home point of my DJI. as if the drone suddenly went back ‘home’ took a picture, then magically continued for a few pictures on the flight path, then back to home again etc…
 I cannot use the GPS metadata of the images. any ideas please?

ignatius

 

[Julie_Pichon]

Hi Ignatius,

It looks indeed like you cannot use the geotags of the images since they would mislead the software.
Did you Pix4Dcapture to acquire the images? Are you processing from the images saved on the drone’s SD card or the .p4d file that is generated at the end of the mission with our app? We would recommend to create a process from scratch when to import the images saved on the drone.

If the issue remains, we would suggest the following:

1. On the menu bar click Project > Image Properties Editor…
2. In the Image Properties Editor, under section Geolocation and Orientation, click Clear. This will remove the image geolocation written by DJI and that is not precise enough to be processed with Pix4Dmapper.
3. Click OK.
4. Start processing step 1 without geolocation information.

Then there are 3 options:

• Use measured ground control points (GCPs) for high accuracy: https://support.pix4d.com/hc/en-us/articles/202558699
• Use Scale and Orientation constraints. It will not geolocalize the model but it will help the reconstruction and provide relative accuracy (enough for measurements):
  https://support.pix4d.com/hc/en-us/articles/205360375
  https://support.pix4d.com/hc/en-us/articles/205360385
• Use coordinates of points taken from a Web Map Server. They will substitute GCPs but the accuracy will not be as good and it will still be less accurate than with image geotags.

For the third option you could get for instance 5 points from a Web Map Service server over your area (e.g. Daft Logic):
https://support.pix4d.com/hc/en-us/articles/202560149

1. Make sure to define the appropriate GCP coordinate system. The Daft Logic website takes the coordinates from Google Maps which refers to the mean sea level (MSL) egm96 to estimate the vertical coordinate.
2. On the menu bar, click Project > GCP/MTP Manager… > GCP Coordinate System > Edit… > choose WGS 84.
3. Then click Advanced Coordinate System > select MSL egm96.
4. Then insert/import the points according: https://support.pix4d.com/hc/en-us/articles/202560349
5. In the field Type make sure to set Ground Control Point, and manually enter the coordinates you took from the website.
6. Then on the menu bar, click Process > Reoptimize.

Hope this will help.

Regards,