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Nov 11 2011

GoPro HERO 2 in hand, now I just need time!

OK, so now I have a new GoPro HERO2 camera shooting 11MP stills at 2fps, I just need the time to go out and test it at our study sites.

First things first, this camera is shooting stills with relatively wide field of view (FOV) and we don't know what that is going to do to structure from motion computation.  The camera shoots in full 170º FOV in 11MP and full or medium 127º FOV at 8MP and 5MP.  Narrow, 90º FOV, options most similar (although still wider) than the other cameras used in our research, are only available in video mode.

Some initial tests with ground subjects on campus have produced somewhat positive results, I think it is too early to tell for sure.

More to follow, when I can get to it.

Oct 29 2010

Testing the Scanning Camera

  Flashback to a couple of weeks ago- this shot was taken with the scanning camera when the Hexakopter believed that it had flown its intended route and was waiting for someone to tell it to land. While the flight itself was a disaster we did gain some valuable information from the photos it took.

  As you can see from the picture we did get some good quality photos, even though it’s mostly parking lots… However what was most concerning was that the pictures taken were not consistent in terms. You can clearly see the difference between the two pictures taken less than three minutes apart.


  What I wanted to know was why the second shot blurred, at the time of this shot the Hexakopter was hovering in the same spot for about 5 minutes with little movement. At first I thought that the vibration caused by the motors or the gyro reaction to the swinging mass had affected the shots.

  So in the lab, with Jonathan’s help, we came up with a way to test my theories. We suspended a Hexakopter from a pipe and mounted the scanning camera on the Hexakopter, in the  same fashion as the previous flight. We started by turning on the scanning camera without the Hexakopter on, in other words this was our control test. We quickly found out that the swinging motion did not cause the Hexakopter to move at all, putting some doubt on one of my theories.  After close examination of the setup in action, I noticed a small vibration occurred on the camera mount whenever the camera moved to the front or back. Noting this, we continued the test except with the Hexakopter powered and the motors on. With the motors on, the Hexakopter reacted no differently than with the motors off. We did observe a cool damping effect whenever you pushed the Hexakopter.

  After the testing was completed, I decided to take a look at the pictures that were taken by the scanning camera throughout the entire test. I found that the small vibrations from the camera moving forward did in fact cause the photos to come out blurred. In addition, I found that making the mounting the scanning camera on a more stable base reduced the vibrations, resulting in sharper images.

Much later I found out that the two above images were taken at different shutter speeds. The above left photo was taken at a shutter speed of 1/320 sec, while the one right was taken at a shutter speed of 1/100 sec. Upon checking the rest of the photos taken by the camera that day, I saw that alot of the images had varying shutter speeds. I tried to compare these photos with the ones taken in the lab and found out that the two sets were incomparable due to different lighting conditions and consequently much different shutter speeds (the lab photos were taken arround 1/60 sec).

  In the end, Jonathan found out that the scanning camera setup would still sweep back and forth without the camera attached. Using the fact that the scanning camera had inconsistent shutter speeds, he attached the Cannon SD4000 to the setup.