Photosynth Thesis

A couple of weeks ago I took some photos and video from the KAP rig lofted on the Flow Form 16 kite above a clearing behind the house. I did not get far stitching the images into a panorama, and had to move on to other business. Since then I have used Photosynth, which will not only display stitched panoramas, but the multiple unstitched overlapping images. The photos do not need to be taken from the same place, so KAP images should be well suited. Photosynth will create and display a 3D model of the surfaces in the photographs. The model consists of the points that Photosynth has determined are shared in two or more photos, and the 3D plot of those points based on photogrammetric analysis of the images. You can toggle a display of the point cloud in the Photosynth viewer below.

The SD1100 ready to take video
The SD1100 ready to take video

I had hoped this exercise would help me choose photos that would stitch into a panorama, and it does show how the photos overlap. But the photos are not named, and there appears to be no way to know the file names of the photos displayed. I gave Photosynth 88 photos and it included 72% of them (63 photos?) in the model and display. I just don’t know which 63. [Update: A log file in AppData/Local/Temp/Photosynther lists the file names in a reasonably interpretable manner.]

By mistake, when I flew the KAP rig to take all those photos the CHDK setting for saving RAW was enabled. So the 4 GB SD card filled up after 268 photos were taken instead of after 1100. The extra time to save the RAW data as well as a jpg for each photo probably prevented the rig from taking two shots at each pan/tilt position. So there were not enough images to choose from to find good overlapping coverage of the scene. Making a “synth” instead of a stitched panorama is less demanding of overlap and consistency so is a good fallback when images won’t stitch properly. And a synth is somewhat useful for viewing this type of image, I guess.

The video above was taken with a Canon SD1100 on the KAP rig just to see how it would work. Below is the Photosynth viewer with a 360° view of the scene. There is a large gap (east of the nadir) in the coverage of overlapping photos, so they would not stitch well into a panorama.

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