This page describes some of the history and the current state of research directed toward development of a low cost system for aerial imaging. All the images are inline and will load as you read. Be patient, I am working to further compress the photos to speed up this page.
Initial experiments using wireless video were carried out in radio controlled aircraft ranging from J-3 Cubs to helicopters. Of all the aircraft tested, the Sig Kadet Senior proved to be the best suited to the task. It is a very easy to handle, slow flying aircraft with a large payload capacity. The original Kadet video plane shown below is still in operation today serving as a test platform and HAM video demo aircraft. Both operators are licensed amateur radio operators, and a HAM band video transmitter is used for testing and demonstration flying. A low-power, license-free system is used for all commercial applications.
In 1994, after realizing the potential of the system for aerial photography. I enlisted the help of friend and fellow modeler Bill Dickerson to assist in the development of an aircraft capable of producing both video and still images. Design objectives were to make the system low cost, durable, and easy to launch, operate, and recover. Another objective was to use off the shelf hardware and components as much as possible to limit the amount of custom design and fabrication. New Perspective Aerial Photography was incorporated and a small group of investors helped fund development.
The image below shows the first aircraft dedicated to carrying a still camera. The camera was mounted pointing out the left side, or out the bottom of the aircraft. Initial shot alignment when shooting oblique was made by pointing the wing at the subject, shooting a lot of film, and hoping at least a couple of shots would be framed correctly. Eventually, the aircraft was modified, and a second "alignment" video camera was mounted looking directly through the still camera viewfinder. Although this system worked, positioning the aircraft to frame the shot while looking out the side proved to be difficult.
The Sig Kadet Senior design was scaled up by 15% to decrease wing loading and airspeed. The wing is conventional Sig Kadet construction, with the exception of bolt-on mounting, Kevlar reinforced laminated spars, and increased dihedral bracing. The fuselage has been modified considerably. Most model airplanes are over-built to withstand the stresses of aerobatic flying and rough landings. This airframe was built to be light weight and functional. Hatches were built into the top and sides of the aircraft wherever possible to provide easy access to components. The nose was extended to provide room to house all the flying controls and a larger fuel tank. The payload section was increased in both height and width to allow a forward looking still camera to be mounted under the belly of the aircraft. A forward looking camera allows easier and more precise framing of shots and has proven to be superior to shooting out the side of the aircraft. The following image shows the operational aircraft with all hatches removed.
Because the design has proven to be easy to operate and maintain, a nearly identical backup aircraft was built. A close-up of this aircraft is shown below prior to covering.
Power is an O.S. 48FS. (a 0.48 cubic inch 0.6 horsepower four
stroke model aircraft engine) burning glow fuel and swinging a 12-6 prop.
Although the aircraft is underpowered in comparison to most model aircraft,
the engine is sufficient for the task. A small engine minimizes fuel consumption,
vibration, weight, and cost. Effects of engine vibration are further reduced by
vibration isolators mounted between the two firewalls. The 48 engine is no longer in
production, and has been replaced by the O.S. 52FS. The 52 provides 12% more power
and weighs less than the 48.
The still camera is a Canon EOS. This camera was chosen for it's
light weight, interchangeable lenses, electronic triggering, and low cost.
The image below shows the EOS with the alignment video camera mounted.
Foam between the two provides shock mounting and a light
blocking seal.
The camera mount in the aircraft is capable of greater than 90 degrees of rotation in-flight, allowing the camera to be positioned with the lens anywhere from retracted into the fuselage to pointing straight down. The camera mount incorporates latex rubber vibration isolators to allow slow shutter speeds to be used. The image below was taken from the front end of the aircraft looking up at the belly and shows the camera in it's mount facing forward for oblique photography. A second video camera is mounted just in front of and to the left of the still camera and is used for flying the aircraft. A simple LED array placed in the field of view of this camera provides a simple status display.
The flight control system is a JR XF-622. The receiver, servos, and power supply are mounted in the nose of the aircraft. This configuration leaves the center section of the aircraft available for payload, and physically isolates the receiver from the video transmitter mounted behind the wing.
The flight control section includes a micro controller that decodes still and
video camera control signals, monitors signal integrity, and provides battery
voltage monitoring and provides a "fail safe" function in the event of an invalid control signal.
Camera control, battery status, and signal integrity information is
transmitted to the camera control equipment in the payload section over fiber optic
cable. This provides electrical isolation and effectively reduces RF noise
at the receiver. The image below shows the nose section of the operational aircraft.
The camera control system and power supply is mounted in the payload section of the aircraft. This unit provides camera tilt control, camera triggering, video camera switching, camera positioning during failsafe, status display, and battery voltage monitoring. The image below show the payload section of the aircraft viewed from above.
The ground control system is housed in the trailer pictured below. The trailer is self contained and includes a complete AC power system.
Operator controls are mounted in a retractable panel
below the video monitor. An LCD display provides
current camera states, and exposure
count. A VCR allows taping of flights. The picture below shows
the bench, video system, and control panel extended.
The aircraft is a stable slow flying design in which size and weight have been minimized. On the ground, dual control transmitters are used, with a safety pilot maintaining visual contact with the aircraft at all times. In the event of failure of the ground control system, control can be immediately transferred to the visual pilot. A "hot standby" video reception system provides backup in the event of failure of the primary system.
As noted above, the airborne flight control system monitors battery voltages and control signal integrity, providing feedback via the status display. Signal range and areas of interference can easily be identified and avoided. The unit also provides failsafe control settings in the event of control signal interference, with an automatic return of control when a valid signal is re-established.
Future enhancements to this aircraft will include autonomous GPS navigation and digital control and telemetry. A much smaller rear engine aircraft is currently being constructed for the purpose of color video capture and long range flight.
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