[Contextcapture] Reality model from German Flown Aerial Photography, 1939 - 1945

RE: [Contextcapture] Reality model from German Flown Aerial Photography, 1939 - 1945

Oto — Fri, 31 Mar 2023 13:20:35 GMT

We recently georeferenced batch of 200 historic aerial photos from interwar period(barn find in national archive) with total set of 15k as a proof of concept . Contextcapture is ok but artificial limitations makes it not so suitable as Pix4D. So most likely if no improvements are made then Contextcapture license will not be considered for this project.

Contextcapture disadvantages regarding old aerial photos:

Does not support true greyscale images but no issues if it is saved as color image.
Does not allow to lower minimum number of tie points to 2 so orthophotos are with holes even where there is overlap.
Unreliable DSM because of bumpy roads feature.
No option to update original input photos with georeference(world files).

Result:

I have also found such excellent paper:

Reconstructing the Past in 3D Using Historical Aerial Imagery (Michael Broadbent)

Main conclusions:

Photos need to be standartized/normalized for use in SfM softwares. It means correction for rotation and same image size(script attached) so they are imported as one photogroup.
Photos need to be from same flight as changes in vegetation cause issues with AT. To be safe each flight need to be as separate photogroup. Needs improvements in feature detection(spline detection) to be more useful for such cases.
Camera metadata helps. If AT is wrong(upside down/curved) it means sensor size is not correct. Need to provide only size of capture not full physical frame size.
AT works even without geolocation. So GCPs can be added after AT.
In latest Contexcapture versions need to use "Legacy engine" preset.

communities.bentley.com/.../Aerial_2D00_standartize_2D00_python.zip

RE: [Contextcapture] Reality model from German Flown Aerial Photography, 1939 - 1945

Robert McGrath — Fri, 31 Mar 2023 09:38:36 GMT

It's amazing. I was also interested in historical satellite images from German aerial photography, 1939-1945. Thank you for sharing such useful and interesting information. For my part, I would like to share a useful article on historical satellite images https://eos.com/blog/historical-satellite-images/. There is no information about reality models from German aerial photography, but there is also some interesting information for those who are interested in this topic.

RE: [Contextcapture] Reality model from German Flown Aerial Photography, 1939 - 1945

Enrico Pieri — Wed, 14 Feb 2018 16:55:00 GMT

here is the secon file attached....communities.bentley.com/.../mesh.zip

RE: [Contextcapture] Reality model from German Flown Aerial Photography, 1939 - 1945

Enrico Pieri — Wed, 14 Feb 2018 16:53:24 GMT

Hi Oto,

good idea and really interesting.

I did your exercise in a different way (even if i used your kml to identify the area):

1) in google earh i choose 4 point visible in the photo to use as GCP and so i created a gcp txt file

2) Import the txt file of GCP in CC

3) I launch the AT with rigid registration due to inaccurate GCP,

4) I changed the AT default setting ( keypoint density high, pair selection exhaustive, component construction mode multi pass), in this way one more photo was recognized in main component.

and it works good...

Here attached a file folder with GCP txt file some snapshot and 2 productions (3mx mesh file and kml mesh file).

communities.bentley.com/.../example.zip