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In this page you can watch 3D video from the nadir HD camera onboard the ISS. How does it work?
The brain perceives 3D views when the images coming from both the eyes, which describe the scene from slight different perspectives,
are merged together. On board the ISS we don't have two cameras pointing to the same target, however the ISS itself is
moving, thus, two images captured by the same camera at different times actually represent two different perspectives of the
Earth. In the case of the nadir camera, the apparent ISS movement is from right to left, therefore, it's quite easy to obtain
two perspectives as if they were seen from the right and left eye.
In this page two images captured from the nadir camera are displayed one next to the other, so that
it is possible to present one image to the left eye and the other to the right eye: the simplest way to obtain this is by crossing the eyes until
the left one sees the right image and the right one sees the left image. When the two perceived images overlap, the 3D scene appears. More details about this technique (cross eye viewing) can be
found here.
In the case of the ISS view we don't have to expect very impressive 3D effects. To understand this, just consider that the
ISS altitude is of about 400 km, whilst the altitude difference between ground and clouds can be of only 5 - 7 km. If we had
a globe on the table and we watched at it from a distance of 1 m, the clouds distance from the globe would be
of just 17 mm, thus difficult to be perceived but not impossible. The good point in our case is that we can magnify the 3D effect by increasing
the equivalent eye-distance just by increasing the time distance between left and right image.
To obtain a correct 3D pair, the right video has to be delayed with respect to the left one, thus, the trick would be to start
the left video a few seconds before the right one. Unfortunately, UStream, in many cases, re-synchronises the video and this trick fails
(the best solution would require to have directly from Ustream the second channels with a fixed delay of a few seconds...).
We suggest starting with the following method:
- start both the video simultaneously; (you can click here)
- cross the eyes until the images overlap (the scene will appear flat since the right and left images are identical);
- pause the right video. As the time passes the 3D effect will appear and increase.
We have also prepared a script that tries the trick of starting both the videos with a small delay on the right.
Try it by clicking here.
Some screenshots have been included at the end of this page.
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