This is my third time typing this because I keep inadvertently closing the window I'm typing in. So I'm making a long story very very short for the sake of my nerves. But this is a fun KAP story, so I figured I'd share:
I asked Santa for an RC airplane for Christmas. I guess I was a good boy last year, because I found one under the tree with my name on it. Over the last month I've learned how much fun it is to fly an RC plane. I've also found out just how much more stressful it is than flying a kite! But I've also learned that the two play very nicely together.
Last Friday evening the light was good and the wind was almost not there, so I grabbed my plane and went flying in town. Things were going so well, when I swapped to my second battery, I decided to try inverted flying. After launching and getting up to a safe altitude, I put the plane into a roll and gave it some down nose to keep it in the air. Less than a second later I saw the canopy pop off, and the battery come tumbling out of the plane. I lost all control of the plane at that point, of course, and had to watch in horror as it slowly tumbled to earth.
The plane was largely unharmed, and I was able to recover it and the canopy with no problem. But the battery was nowhere to be found. I quartered the field until sunset without finding it, and even another two hours of searching the next day didn't turn anything up. I was about ready to give up on it. But then I decided to give KAP a try.
A couple of years ago I was asked to overfly the interface between two lava flows. The idea was to identify the iron rich rock from the older flow, and separate it from the newer flow. To do that I ran the photos through a filter that generated a grayscale image in which each pixel value was calculated from the (R-B)/(R+B) values of the original photo. This preferentially found red objects in the frame.
I figured something similar would work. My batteries are blue, so I ran the KAP photos through a filter that used the (B-R)/(B+R) values of the source image. Should work, right?
After a fashion, it did. It found every piece of surveyor's tape, PVC pipe, glass bottles, plastic bottles, plastic bags, and all other trash in the field where I was flying. It also highlighted every shadow cast by anything taller than a blade of grass. But it also found a curious rectangular shape on the far side of the fence that borders the edge of the field.
(These are full 4000x3000 photos, uploaded full-size to Flickr. If you want to play with the photos I was using, feel free.)
It's hard to see at this zoom level, but there's a little rectangle on the far side of the fence line. The more I zoomed in, the more rectangular it looked.
I finally zoomed in to 200% and looked at it really closely. It looked like a blue rectangle with a square of black in the middle of it, and maybe something sticking out of its upper left corner. That was enough for me! "Found it!" I yelled to my wife.
"Then you'd better go get it!" she yelled back. I grabbed my keys and headed out. It took me only a few minutes to walk out to the fence and look over. Sure enough, there it was:
And sure enough, the wires were poking out from the upper left corner, and the Velcro I'd stuck on it to keep it in the plane was facing up. Just as I'd guessed from the KAP photo!
In case you're wondering about the sticker on the side of the battery that says, "Porthos 2", I name my batteries so I can keep track of which one was used last, how many times I've charged it, etc. The first battery in this set is Athos. The third is Aramis. You get the idea.
KAP to the (search and) rescue!
P.S. In my defense, I never searched over the fenceline. I figured the battery couldn't have fallen that far from the plane. KAP proved me wrong. Excellent!