Camera control idea

So here is my idea for the camera on the balloon: Camera on a mount which is tilted via a servo. Arduino controls servo and basically moves it to 3 different positions: down, up and sideways. This part should be pretty easy as servo control via the arduino is simple. The tricky part is telling the camera when to fire, If I just want to snap a picture thats pretty easy - but it would be really cool to tell it to take either a picture or a short video. I've seen that with the CHDK software running on the camera you can measure the state of the usb input and it will count how many milliseconds there is 5v applied. So with a uBasic script you count the number of milliseconds and either take a pic or take a video based on that value. I've seen a example program and it looks doable. I'm eager to try it out when I get the arduino.

Also I'll need to make some tests of how long the battery(s) will last doing this. Most likely the little battery for the camera will be insufficient and I will have to wire in an external lipo - should not be too hard. Same deal with the arduino since it will be powering itself and the servo. Also need to calculate the needed SD storage space based on how many pics / videos I will end up taking over x amount of time.

I have not even touched the communication / gps part yet besides some basic stuff. Can't really do much until I have my ham radio license - I'm taking the test May 9th. I do have a Garmin 18x lvc gps (looks like a hockey puck with bare wires). With a firmware update it is capable of working above 60k feet (which most gps devices are not)