Aerial Photography

Introduction

I’ve always been fascinated with such things as the sky, heights, flying, outter space, and photography. The reason that I wear glasses is because of my visit to an optometrist when I was 16 to see if my vision was good enough to fly a plane. “You need glasses.”, he said. And even long before that I had tried to lift a camera with a small box kite. Although that experiment was unsuccessful, the desire stayed with me, and now many years later I’m back at it, trying to go where we cannot go by ourselves… up!

I’ve always been fascinated with such things as the sky, heights, flying, outter space, and photography. The reason that I wear glasses is because of my visit to an optometrist when I was 16 to see if my vision was good enough to fly a plane. “You need glasses.”, he said. And even long before that I had tried to lift a camera with a small box kite. Although that experiment was unsuccessful, the desire stayed with me, and now many years later I’m back at it, trying to go where we cannot go by ourselves… up!

Initial Ideas

The idea started with the desire to launch a helium-filled weather balloon, complete with a camera module and radio position tracking system. The balloon would be let free, and using a computer and a radio receiver, the balloon’s position would be tracked with the hopes of recovering the equipment. During the flight the camera inside would take pictures and save them to local storage. I read about a very cool project which somewhat resembles what I want to do. But there are many factors which make this a one-shot deal, and one that is expensive. In the meantime I want to accomplish the goal of aerial photography for little money, using a method that is flexible and fun. Once I read about KAP (Kite Aerial Photography) I realised that it was the perfect way for me to learn about aerial photography. These pages document my experiences.

Cameras and Hardware

Pod Rig

The beginning of my experiments into aerial photography involved the desire to launch a helium-filled weather balloon with a camera/tracking system payload attached. I started building my first pod with this in mind, before deciding that KAP (Kite Aerial Photography) would be a better way to begin learning about the challenges of getting a camera into the sky. Once I have all the details worked out I would like to send an unteathered balloon into the skies. My pod rig was built for this purpose. I was hoping to use the rig with a kite as well, but so far it has been too heavy to get it up very high. My pod remains ready and waiting for a strong kite and eventually a balloon.

The goal of the KAP Pod Rig is to provide a camera, time lapse circuit, GPS position tracking system with a modem and radio transmitter to send the position data back to the ground, plus batteries to run everything. My original pod was made from two 12″ plastic salad bowls. They proved to be too large and heavy, so redesigned my container. My second attempt uses a 3l Rubbermaid container, which proves to be much better. With the camera system and position tracking system and batteries, the entire pod weighs about 1060g. The pod is as follows:

  • 2.9l Rubbermaid Container - Very easy to work with, the plastic container was modified to have a window of plexiglas in the front for the camera to look out of. The see-through container makes the camera able to meter the shot easily with only a small window for the lens to look through.
  • Kodak DC215 Digital Camera - Capable of taking 1152×864 pixel images, this old digital camera seemed the perfect tradeoff between quality and low cost, since it is not longer my main camera. It does have very high power consumption, which facilitates the need for large batteries. The camera is fitted with a 128MB CF card, allowing over 450 pictures to be taken at full resolution.
  • Time Lapse Circuit - A small PIC microcontroller-based time lapse circuit monitors the camera power status, maintaining the camera in an “on” state, and taking pictures at a configurable interval.
  • Garmin Geko 201 GPS Receiver - To track the position of the pod, the GPS receiver is used. It sends serial data of its current position once per second.
  • RTTY Modulator - Receiving signals from the GPS, the RTTY modulator stores a position message from the GPS and generates a 45bps RTTY (Radio TeleTYpe) audio signal which can be broadcast over radio to the ground station.
  • Sylvania FRS Radio - The FRS radio transmits the audio tones from the RTTY modulator to the ground station. The VOX mode is used to allow the modulator to key up the radio automatically by simply generating the tones. The modulator waits between messages to allow the radio a chance to go off the air, thus saving battery power.
  • Batteries - The GPS receiver and FRS radio use their own AAA batteries, and the rest of the circuitry and the camera are all powered from 6 AA NiMh batteries.

With all the hardware in the pod, it is possible for the camera to take pictures continuously during the flight, and the position tracking system to send position updates about twice per minute to the ground station. For kite lifting, I have so far been unsuccessful lifting the kite more than 10 metres or so.

Recovery Considerations

With an unteathered flight, knowing how to recover the balloon is important. Certainly if the balloon is lost or detroyed, the images will be lost as well, not to mention the equipment on board. Weather balloons are designed to burst at a specific altitude. This is based on less dense air high up causing the balloon to expand to a breaking pressure. This can be in the order of 70,000 feet or more. Certainly if the pod were to fall from such a height, it would be destroyed, and possibly destroy whatever it landed on! The only suitable way to recover the balloon is with some sort of parachute. Other balloon photographers have used mechanical severance mechanisms to release or destroy the balloon and deploy a parachute when the balloon reaches a predetermined height. I have still not built the recovery mechanism, as I would like to test the pod with a kite capable of lifting it first, to check the operation of the equipment and the quality of the images, before doing an unteathered flight. The Pod is definitely a work in progress, but I hope to be able to use it soon.

KAP Stylecam Rig

Introduction

After several unsuccessful flights with my 1kg camera pod and the Parafoil 7.5, I found myself with several options. I either needed a bigger kite, more wind, or a smaller camera. Although the kite could pull quite hard, even in light winds, the weight of the camera pulled down on the kite line, changing the attitude of the kite. This would make the kite fly poorly, losing most of the power and leaving the pod sitting on the ground most of the time.

The choice was clear. I like the Parafoil 7.5, and I don’t really have much control over the wind, so getting a smaller camera seemed the best option. I remebered seeing a very tiny keychain digital camera at a College St. computer store, so Chris and I ventured west to see if they still had them. There was a sale on, and they had the SiPix Digital Stylecam Blink II for $29. The guy at the store was pretty honest that it was “webcam” quality. I bought it, expecting the worst. Much to my surprise, it was actually quite decent considering the size and price. And at 30g plus a single AAA battery, I was sure it couldn’t get much smaller and lighter than this. It’s actually fun to use just as a camera.

Stylecam Hacking

Although the Stylecam is fun to use, it won’t work as a KAP camera because there is no self-timer or way to remote control it. Keeping with my desire for a super lightweight camera, I wasn’t about to add radio control and all of the other fancy items that other KAP photographers use. This camera should add unoticable weight to my kite. If the kite will fly by itself, then it should be able to fly with the Stylecam attached.

Time Lapse Circuit

Many other KAP rigs I’ve seen allow the operator to control the shutter release from the ground. While this is necessary with film cameras, digital photography is cheap. I have always considered the use of a time lapse circuit to be the most ideal way to trigger the camera. As long as there is enough memory, lots of pictures can be taken, and only the best used. My goal was a super small time lapse circuit that would power off the camera. I set out to hack the camera and make it so.

Above you can see the inside of the stylecam. The circuit board has a large corner cutout to make room for the viewfinder. I decided that apart from the viewfinder (which I don’t like to use anyway) I would like to keep the camera mostly intact. By making a small cut to the side of the case, I was able to install a 3 pin female molex plug, bringing power, ground and the shutter release button to the outside. With my scope I probed around and found that the camera generates 3.3v internally from the 1.5v AAA cell. I found a place where this voltage switches on and off with the camera power. I tacked wires here, on a ground connection and on the shutter release button, and ran them to the connector on the side of the camera. So now, coming out of the side of my camera is:

  • Pin 1 - 3.3v
  • Pin 2 - shutter releae
  • Pin 3 - ground

The shutter release is normally high. Shorting it to ground makes the camera take a picture. Now I needed a timer circuit, so I decided that I should dust off an old 555 timer chip and see if it could run on 3.3v. The NE555 has better specs than the original LM555, and it works perfectly at 3.3v. I made a very small circuit using the 555, 2 resistors and a capacitor to make a timer. It’s high for about 5 seconds and low for about 0.5s repeating. You can download the schematic. I soldered it SMT style, by bending the leads of the 555 to look like an SO DIP, and then tacked all the parts around the chip. This left the back of the board non-metalic and smooth. I put velcro on the back so that it could be attached to the back of the camera.

Hanging Mount

To attach the camera to the kite I wanted little added weight, so I came up with another use of velcro. With a piece of velcro centred on the back of the camera, I made a small bracket out of 14 gague solid copper wire, and a piece of circuit board. I soldered the wire to the copper on the board and bent it so that it attaches to the clip on the kite, and the kite line also threads through a second part to keep the camera aligned with the kite string. This will make it take pictures of the people on the ground, although bending the wire will allow the camera to be placed in any orientation.

Overall the entire contraption weighs less than 50g, and causes no noticable change in the performance of the kite. This is definitely my trusty standby for times when the kite will not lift anything else, or I just want an easy time of it. The camera will take about 70 640×480 images, making for about 5 minutes of shooting with my timer. Unfortunately the memory is not removable, so having a laptop nearby to download the pictures is the only way to do more than one set of images on an outting. Although at $29, perhaps I can have a second camera at the ready, should I not want to bring my laptop with me. :)

Some Resultant Images

Probably the biggest problem is that the camera is not very good. It tends to make wavy pictures like the ones below when there is a lot of motion. (the camera is, of course, swinging wildly around on the top of the string) Better lightweight cameras are probably available which would solve this problem.