KAP - Kite Aerial Photography
What? KAP? Kite Aerial Photography? What the heck is this?
Well, actually, it's very simple: Take a camera, put on some means of triggering it, fix it on the line of a kite and let it be lifted into the air by said kite. That's the basic principle. Actually, it's a bit more complicated and it can get really high-tech complex.
A god example of a very simple device has been built by Olivier Humez from France. He took a disposable camera which he mounted between two wooden bars. The upper bar is fixed on one side only. The other is held down by a rubber band. A small bulge positioned where the trigger of the camera is pushes that trigger to take a picture. As you don't want to take the picture before the camera is high in the air, he installed a balloon between the bars. Blown up and with a hole to let the air out slowly, tha balloon keeps the upper bar away from the camera for long enough to lift it into the air. It's a very simple design and you have to get the camera down between each picture, but it's definetely the cheapest way to do aerial photography.
Of course, there's the other extreme too. But before we get to that, lets do it step by step. The main disadvantage of the basic design is that you have to get the camera down between shots. So we can upgrade our rig by using a motorized camera to have automatic film transport. But how do we trigger it? If you're lucky, it has an electronic interval automatic which you can program to take a picture each minute for example. Some KAPers build mechanical triggers with rotating discs that push the trigger in regular intervals. If you can trigger the camera electronicaly (if it has a cable connector for the trigger), you can build your own electronic timer and use that. You could also add a simple radio control to trigger it, but you can do without.
So now, we have more freedom. We can walk our kite around and let the camera take its pictures until the film or memory card is full. How can we do better? We haven't spoken about camera orientation yet. We just fixed it on the kites' line ... in a fixed orientation, probably looking straight down. If we want it to look somewhere else, we have to get it down and change the way it's fixed. But then, we would be back to where we have to get the camera down between shots if we wanted to look in another direction. So here, we can't avoid a radio control (RC) anymore. Logically we would start with 3 channels: one for horizontal rotation (pan), one for vertical rotation (tilt) and one for the trigger. That would be a basic RC rig. Now you may ask: How do I know which way it's looking when I'm on the ground and the camera is 50m/150ft up? There's a very simple solution for this: Put a brightly colored (yellow) stick on the rig and let it point straight back from the camera (so it's on the same line, but won't interfere with the picture). That's for the pan. For the tilt, you can usually use a proportional control, so you know the cameras' orientation from the position of the stick/trimmer on your transmitter.
OK, you say, but it's still difficult to realize what the camera is seeing up there. Well, that's part of the fun and suspense of it! But ... this is where we get to the high-tech. The final stage of rig development is the video rig. You put a miniature video camera (spy cam) parallel to your camera (or you use the video out connector if you have a digital camera) and send it's picture down to a receiver which shows you more (digital camera) or less (parallel spy cam) exactly what your picture will be like before you make it.