I ONCE ENVIED THE LOCAL hawks and buzzards for the spectacular view they have of the countryside around my rural home and laboratory. Now I get a glimpse of what those birds see by towing a camera aloft by balloons or a small blimp. This technique has long been used by archaeologists to take aerial photographs of excavations. I recently spoke with a professor of agronomy who plans to photograph experimental crops with a balloon-lofted camera. Such systems also aid surveyors, farmers and meteorologists.

Balloon-suspended camera systems are inexpensive and can be stored in a comparatively small space. They can quietly float at low altitudes over places totally inaccessible to conventional aircraft; they can also fly over historic monuments, neighborhoods and other areas forbidden to aircraft for reasons of safety and noise. I have rigged balloon-borne cameras to photograph my family's home, the field where we pasture sheep and the creek that borders our property. The resulting images were better than those that I obtained while flying in an airplane because no windows, wings or struts obstructed the view.

The ideal cameras for aerial photography are the point-and-shoot 35millimeter kind with automatic focus and film advance. Some can automatically trigger their shutters at preset intervals. Because these cameras do not require a remote-control system, you can simply attach one of them to a balloon and launch it. The camera automatically takes a series of aerial photographs.

Because this method produces rather haphazard results, I much prefer a radio-controlled aerial camera, which is more flexible and reliable. Most cameras can be triggered by a radio-actuated servomechanism like those made for radio-controlled cars, but the mechanism is heavy and consumes much power. A better design incorporates a point-and-shoot camera that can be directly actuated by an electronic signal. Although the details that follow apply to my camera, a Ricoh FF-7, they should be applicable to many electronically actuated cameras manufactured by other companies.

Many kinds of radio-control systems will remotely trigger a camera. Controllers salvaged from toy cars work, although they have limited range and are highly susceptible to false triggering from citizens-band radios and other sources of radio waves. More costly systems designed for large model cars and boats have considerably more range and are much less prone to false signals.

Be sure never to select a radio-control system designed for model airplanes. In the U.S., the Federal Communications Commission assigns specific frequencies to radio-control systems for model airplanes because interfering radio signals can cause a model airplane to crash. You would not want to accidentally redirect your neighbor's model airplane through a window or into a wall.

For two years I have remotely triggered cameras with a single-channel radio-control system made by Ace Radio Control, Inc. (Box 511, Higginsville, MO 64037). Ace recently introduced a system called the Shutter Bug, which has greater immunity to interfering signals than do earlier models. The system, consisting of a transmitter, a receiver and an output module, costs about $85 (catalogue number 40E83).

The diagram above shows how to connect the receiver of the Shutter Bug to my camera. The receiver, which is housed in a small plastic enclosure, has several wires emerging from it. The single wire is the antenna. The twisted red and black wires with a small toggle switch are the power-supply connections. Three twisted wires connect the receiver to its output module. Other parts can be obtained from an electronics supplier, such as Radio Shack.

The wires from the output module should be soldered to the coil terminals of a miniature five-volt relay with a coil resistance of 250 ohms or more (The relay is an electromechanical switch that can actuate an electronically controlled camera.) You should next connect one end of a pair of wires to the relay's moving and normally open terminals. Solder the other end to a 1/8-inch phone jack. Make a cable to connect this output jack to the camera's remote-control jack. Solder a 1/8-inch phone plug to each end of the cable.

The receiver requires a six-volt power supply, which can be made from four 1.5-volt cells connected in series. Obtain a four-cell AAA battery holder. Solder the receiver's red lead to the positive terminal of the battery and the black lead to the negative terminal. Double-check the connections before reinstalling the receiver's batteries.

Then turn on the power switches of the transmitter and receiver. Be sure the camera is turned on. When you press the transmitter's fire button, the relay's contacts will close, the camera shutter will trip and the film will be advanced. If the camera does not respond, keep the transmitter button pressed down for a second or so. If nothing happens, check the wiring and make sure the batteries are delivering five to six volts.

Install the receiver system and battery pack in a plastic enclosure [see illustration above]. Secure the receiver with double-sided tape or hook-and-loop fastening tape, and stuff foam plastic between the components. Shake the assembled system to make sure it still works.

You can attach the receiver system to the back of the camera with rubber bands. Even better, mount the camera and receiver on a platform made from a thin sheet of aluminum or model-airplane plywood [see below]. A pattern of holes drilled in the platform saves weight and provides attachment points for the receiver, camera and rigging.

The receiver can be secured with a machine bolt, and the camera can be mounted directly on the platform with a screw (from a camera store) that fits its tripod receptacle. You can reorient the camera by rigging the platform in various ways or by affixing the camera to a ball-and-socket mount (found in most camera stores). As a safety measure, tie the camera to the platform with a short line.

To guarantee that the platform hangs vertically, I sometimes attach the receiver to a strip of aluminum extending from the platform. The strip offsets the weight of the camera. To prevent the camera from rotating and swinging, I tie the nylon tether that prevents the camera system from floating away directly to the platform instead of to the balloons.

You will next need to obtain the balloons themselves, the helium and a reel to wind the tether around. Surplus weather balloons can be used, but they are fragile. Whenever I do use them, I tie the camera system to a parachute whose canopy is tied to the balloon, or I deploy two or more balloons. These precautions twice saved my camera when a balloon suddenly burst high in the sky.

A more robust and very inexpensive alternative to weather balloons and costly rubber balloons is what I call the BPTB lifting device, better known as the black plastic trash bag. Trash bags are available in various colors, so you will need to change the designation accordingly (a yellow bag is a YPTB, red is RPTB and so forth). Black is best because it absorbs the heat from the sun, thereby expanding the volume of the bag and enhancing the bag's lifting capacity. Find the largest-capacity bags possible.

Helium can be purchased from welding shops and party stores. Helium and cylinder rental prices vary widely. In my area, enough helium to fill a cylinder with a capacity of 6.5 cubic meters (230 cubic feet) sells for around $40 at a welding supply center. There is an additional charge for renting the cylinder ($3.75 a month) and a balloon-filler nozzle fitted with a pressure gauge ($7.50 a month). If you plan to launch many balloons or trash bags, you can save money by buying a nozzle and leasing a cylinder.

Gas cylinders are heavy; when transporting them, be sure they are well secured so they cannot fall. Although helium is an odorless, nontoxic and inert gas, it becomes an asphyxiant when it displaces the oxygen required to sustain life. You should therefore fill balloons outdoors or in a well-ventilated room.

At sea level, helium can lift approximately 1.1 kilograms per cubic meter, or 1.1 ounces per cubic foot. The simplest way to determine the lifting capacity of a single BPTB where you live is to fill one with helium, attach a small container and add water to the container until its weight exceeds the lifting capacity of the BPTB. Then weigh the container. This method reveals that a 50-gallon BPTB Will lift around 70 grams (2.5 ounces).

Unless you have a large balloon or a small blimp, you will need a cluster of balloons to lift your camera. The total weight of my camera and a Shutter Bug receiver installed in a plastic enclosure is 460 grams. The platform and tether add another 100 to 200 grams. A cluster of nine 50-gallon BPTBS will lift the system with an excess margin of 10 to 15 percent. Avoid the temptation to fly your camera from a cluster that provides just enough lift to float. Instead, add one or two extra BPTBS in order to keep the camera airborne should one of the BPTBS develop a leak. Doing so will also help keep the system from blowing down in a light breeze.

For your first flight, gather all the required equipment in a suitable spot. Load the camera with film and test the radio-control system. Then launch a small helium balloon tied to a 10-meter tether. If the balloon is blown to the ground, it is too windy to fly the camera platform.

Before you inflate a trash bag with helium, squeeze all the air out. Next gather the bag's open end over the helium-tank nozzle and hold it in place while the gas flows inside. When the bag is full, twist the gathered opening,. bend it over against itself and secure it in place with tape. Tie a two-meter length of nylon tether above the taped region. Make a loop out of the other end and temporarily connect the loop to a snap swivel, such as those used in fishing tackle [see illustration at left]. The snap swivel should be attached to a block of wood, which you can later use as a ground anchor.

When all the BPTBS are inflated, attach the loops at the ends of their lines to another snap swivel tied to the camera platform. Be certain that the tether attached to the camera platform is temporarily but securely anchored to the ground.

Trash bags and spherical balloons have the aerodynamic properties of tumbleweeds. Even a light breeze will blow down a tethered balloon if its lifting power is only slightly greater than its payload. You can compensate for this imbalance by launching upwind from the point you wish to photograph. Attach the tether reel to a ground anchor downwind from the target. Hold on to the balloon and walk upwind, unwinding the tether as you go. Then release the balloon and race back to the tether reel. (Please watch the ground during this phase of flight.)

Watch the camera carefully as it approaches the target. When it is reasonably still, press the transmitter fire button. If the camera is swinging, press the button when the camera is at the apex of each swing.

The balloon may be blown down when it reaches the end of its tether, so be sure there are no roads, power lines or other hazards below its flight path. Avoid pulling on the tether when the balloon is over trees or other obstacles, because you may pull the balloon down onto the obstacle you are trying to avoid. In addition, always fly when the air is calm and never when an electrical storm is nearby. Use only helium to inflate balloons. Hydrogen and other lighter-than-air gases are highly flammable and can explode. Never use a wire tether. And never attempt to trigger a camera with a pair of wires leading to the ground. Should the wire or wires touch a power line, you or anyone coming in contact with them may receive a fatal shock. Avoid flying tethered balloons near airports, tall buildings, power lines and busy roads.

If you wish to upgrade from trash bags, the blimps used for lifting advertisements and meteorological instruments are well suited for lifting cameras. Because they are aerodynamically stable, they can be flown in a breeze, and their large capacity permits them to lift several kilograms to 200 meters or more. Blimps are expensive-small ones cost from around $400 to $1,000.

I fly my cameras and various instruments from a blimp supplied by Atmospheric Instrumentation Research, Inc. This blimp, now manufactured by Aerial Innovations (8111 Raleigh St., Westminster, CO 80030), has a length of 4.2 meters and a maximum diameter of .9 meter. It will lift two cameras and a radio receiver system.

Much can be learned from aerial photographs. For example, you can measure the dimensions of objects in a vertical photograph. Dividing the height (h) of the camera by its focal length (f) gives a scale factor known as the photo scale reciprocal (PSR). If the image dimension of an object is d and the actual dimension is D, then PSR = D/d. If d and the PSR are both known, then D = d x PSR.

Assume that a camera with a focal length of 35 millimeters provides a photograph of a fence from an altitude of 100 meters. This gives a PSR of 100/.035, or 2,857. If the length of the fence as measured on the photograph's negative (d) is 20 millimeters, the length of the fence (D) is then .02 x 2,857, or 57.1 meters.

You may want to know the altitude of the balloon. It can be calculated if you know the actual dimension of an object in a photograph. The formula is h = (f x D)/d. Assume, for example, that a driveway you know to be 20 meters long has a length of 10 millimeters on a negative produced by a camera with a focal length of 35 millimeters. The altitude is (.035 x 20)/.01, or 70 meters.

These formulas will help you determine how high to fly a camera to photograph a given area. A 35-millimeter slide or negative measures about 23 millimeters wide and 35 long. A 35-millimeter camera with a lens whose focal length is the same size will therefore cover a space that measures 197 by 300 meters when the camera is flown at an altitude of 300 meters.

Those readers who fly balloon-borne cameras will soon accumulate a collection of adventure stories, all nicely illustrated by portfolios of aerial photographs. May your breezes be light and your landings soft.

Bibliography

AIRBORNE CAMERA: THE WORLD FROM AIR AND OUTER SPACE. Beaumont Newhall. Hastings House, 1969.

The Society for Amateur Scientists (SAS) is a nonprofit research and educational organization dedicated to helping people enrich their lives by following their passion to take part in scientific adventures of all kinds.