Kite Aerial Photography
Kite Aerial Photography , or KAP for short, is a type of photography in which the pulling force of a tethered kite is used to move a camera into an elevated position. The height of the summit is limited by the maximum flight altitude of 100 meters prescribed in Germany and thus enables very close to earth and detailed aerial images with unusual perspectives.
The altitude (up to 100 m) is well below the altitude of aircraft (from 300 m). In this way, recordings of the surroundings are created in the usual way of seeing and not in the abstract, map-like perspective of airplane or satellite photos.
Due to falling prices and decreasing weight, especially of cameras and technology, and the simultaneous growth in technical possibilities, the community of KAP practitioners has grown rapidly in recent years.
Flat land or water with few obstacles for the wind, especially upwind, and only little thermal effect from the sun offer the best setting for kite flying.
To start the kite camera system, first let the kite rise a little to fly over the turbulence close to the ground. If the wind is strong and constant there, the camera system is hung on the flying line and the line is unrolled in a controlled manner until the desired recording height is reached.
When the wind is stable in direction, the pick-up point can be moved by walking around with the end of the line close to the ground in an area roughly parallel to the ground . By means of a suitable suspension at two points on the line that are close together, the suspension base of the camera is oriented horizontally via gravity and in the horizontal direction after the line.
The orientation of the camera (in horizontal and vertical angles) in relation to its suspension base can be set before take-off and recognized from a direction indicator from a distance or, today, it can often be varied "in flight" by radio remote control. The camera, which works digitally today, is also triggered typically by radio. To transmit a viewfinder image by radio to the monitor on the ground requires a much more complex ongoing radio transmission of the image data.
For years, kite aerial photography has been competing with multicopters with integrated cameras, mostly video cameras, which are becoming increasingly smaller, foldable, cheaper and more capable, but have no wind as the ideal flight condition - like a camera that ascends by balloon or is just thrown. Around 2019, for the first time - radio-transmitted - video recordings were made from a small camera with a GPS tracker that was strapped to the back of an eagle.
history
From ancient Chinese traditions it is known today that the first remote sensing by means of a fettered dragon took place in late medieval China. This is not surprising in that China is considered the country of origin for kites. During armed conflicts, people were brought to the heights by means of a kite in order to monitor the approach of an approaching army.
In 1858 (or in 1859 at the Battle of Solferino ) the French Gaspard Felix Tournachon (Nadar) took the first aerial photo, but from a tethered balloon . He patented the idea of using aerial photos to produce maps.
In the spring of 1888, the French Arthur Batut read "La photographie en ballon" (1886, with an aerial photo of a balloon from a height of 600 m) by Gaston Tissandier and came up with the idea of using a bondage kite to lift the camera. In 1888 he created the world's first kite aerial photography. In 1988 - 100 years later - a museum was dedicated to him in his hometown of Labruguière . After three failures, he took a picture with a kite showing his hometown Labruguière on May 29, 1889 from a height of 90 m. The paper-covered kite used was 2.50 m long, had wood with a 5 × 30 mm cross-section built into the edges, had a 12 m long tail made of cord and weighed 1.800 kg. The camera, part of the suspension and a can barometer weighed 1.172 kg. The 3.5 mm diameter hemp rope was 244 m long and weighed 1.878 kg. The recordings were triggered by a glow cord with a burning speed of 5 cm per minute that melted a thin wire - easily, cheaply and reliably. An electrical release that would require two insulated copper wires to the ground was discarded. The lens is required to be free of distortion and a 40 ° or 90 ° recording angle. The picture from 1889 published in 1890 was made with a Steinheil aplanat with a focal length of 166 mm. After every exposed picture, the kite had to be landed again in order to insert a new, glass photo plate into the camera.
William Abner Eddy (1850–1909, accountant, journalist and kite experimenter, the inventor of the Eddy kite) took the first kite aerial photographs in the USA on May 30, 1895 in Bayonne, New Jersey.
On April 29, 1902, Silas J. Conyne (USA) registered a kite with the patent number 698.634, the shape of which is now slightly modified and built in every kite workshop. His model flew reliably even in low winds and was also very good-natured in flight behavior.
With a staggered arrangement of several of these dragons according to Conyne, George R. Lawrence (USA) succeeded in creating the icon of all early KAP recordings: San Francisco, 6 weeks after the devastating earthquake of 1906. A masterpiece if you internalize the state of the art at that time. Lawrence exposed a 45 cm × 120 cm negative at a height of 2000 feet (about 610 m), which despite the mediocre optics allowed a high level of detail. It was triggered with a fuse, which made the success of the picture a matter of luck. The slightly sloping horizon on the most famous picture of the photo series is evidence of this. Lawrence previously used hot air balloons as a camera base, crashed, and luckily survived. A copy template on the picture says: "From Lawrence Captive Airship".
From 1916 to 1918, the German archaeologist Theodor Wiegand (head of the German-Turkish monument protection command ) used aerial photographs in Palestine for the first time to document antiquities, which were obtained with the kite, since motorized aircraft could only be used to a limited extent for non-military purposes during the First World War.
With the advent of aviation, interest in KAP photography declined noticeably. Due to the independence from wind, the quick change of location and the safe control, the aircraft made itself indispensable for generating aerial photographs.
technology
suspension
The kite line is generally sloping upwards and with a slack. A single pulling force and the weight of a homogeneous line would allow it to form a chain line . Wind action on the cord Line itself deform its line somewhat. If a kite does not stop at one point, but drives, additional forces of the inertia of the line and the air resistance act on the line. As a result of the formation of Karmann vortices in the lee of the line against which the flow is flowing, a line - with a large diameter and fast flow - can also begin to vibrate.
A soft line can only transmit force along its linear course. If a line (which is not vertical) is loaded with a weight load, it will bend at the point of loading. If this load is applied at two points, there are 2 kinks lying in one plane. A curved or flexible support bracket can impose a curve along its effective length on the line.
Dragon ferry
In principle, a load can be mounted at a fixed point on the kite line or by traveling up the line from a kite ferry (also known as a kite cable car, kite lift).
A dragon ferry can have different drives:
- Up with a pull cord, by deflecting the cord through a pulley (or eyelet) at a high, fixed point on the kite line. / Downwards due to the force of gravity of the load releasing this cord.
- Up through the ferry's own kite area. / Automatically downwards by folding down the kite surface by a device clamped to a fixed point on the kite line. / If, however, a cord is taken along during the wind-driven upward journey, this can limit the height of ascent, delay reaching the fold-over point, or pull it down again against the pull of the kite area of the ferry.
- Up and down by a cord that runs endlessly around a pulley near the kite. This construction requires the handling of lines and 2 lines, but guarantees that you can go downhill even in weak winds when the line is almost horizontal at the bottom.
In order to run smoothly, a kite ferry requires two pulleys to be suspended from a suspension cable, similar to a cable car.
Basics of alignment
If the alignment of the camera (or an adjustable camera suspension = rig) around the vertical axis is to be connected to the kite line so that it cannot rotate, the coupling on the line requires two points on this tensioned line that are a bit distant in order to be able to transmit a restoring torque. The further alignment of the camera (or rig) can be done by the gravity of the load. In the simplest case, the camera is always aligned horizontally to a point on the horizon.
Rig, trigger
An angle-adjustable camera suspension is called a rig . For this purpose, the camera can be swiveled around its horizontal transverse axis in a frame, i.e. aligned upwards or downwards. This frame can in turn be rotated on its upper side about a vertical axis so that the camera - provided the kite line points in the horizontal direction of a wind flow - can be aligned in any direction. This frame can be interrupted here so that a camera can also look vertically downwards without getting a frame of the rig into the picture. A permanently adjustable rig must be adjusted before the start with a kite or kite ferry. A radio-controlled rig allows the camera to be aligned in the position close to the kite.
A dark rod protruding from the camera in the opposite direction to the optical axis can make its alignment roughly visible. 4 bars that point from the camera side in the direction of the 4 corners of the image make the recording angle easier to observe.
The center of gravity of the camera and remote control should be at the intersection of the rig's axes of rotation, and the center of gravity of the rig and camera should again be centered under the pendulum suspension from the kite line.
Remote control
Historically, the exposure of the photo plate was triggered by burning a certain length of fuse or glow cord. The release can be preset by a self-timer with clockwork. Wireless camera releases typically only have a short range. A single-channel radio remote control with a suitable servo and cam is sufficient for triggering. To align the camera on a motorized 2-axis adjustable rig, 2 additional remote control channels are required.
If the film is not lifted by a motor from the camera, the camera must be pulled in after each recording and opened by hand.
A digital camera may need to be turned on before shutter release.
In order to transmit a viewfinder image (mostly of reduced resolution) from a digital still camera to a monitor on the floor, sufficient radio bandwidth and transmission power are required, and many more are required to transmit a moving image.
Rod pendulum
A simple suspension consists of a stiff rod pendulum up to 1.5 m long , which hangs vertically from a rod with eyelets or a channel with rollers or a pipe, which is connected to a piece of the line. The camera is attached to the lower end of the pendulum using a rig. The pendulum ensures that the camera is aligned right-left-horizontally, i.e. the horizon shown runs parallel to the lower and upper edge of the image.
Picavet
The suspension by means of a multiple rope pendulum, which Pierre L. Picavet published about it from 1912 on, is only called Picavet for short .
Different types of picavets couple two points of the kite line, about 1–2 m apart, with a rod, triangle or cross hanging horizontally below.
Depending on the construction, one or two loops of thread run through pulleys or eyelets that hang from both the 2 points of the kite line and the ends of the rods.
The sliding of the thread in the many eyes or rollers dampens the swaying when the light Picavet thread pendulum is aligned downwards.
The camera is mounted on the rod or rods of the Picavet using a rig.
The geometric body spanned by the threads of the Picavet is roughly the same height, width and length.
While the kite line can change its incline, the Picavet's cross remains largely horizontal. The thread, taut by the weight of the camera, runs through 8 rollers or eyelets in such a way that its 8 taut stretches adapt.
Picavets with a triangle have 2 threads and 6 thread stretches. Picavets with just a stick of 1 thread and 4 stretches.
Camera frame (KAP rig)
The rig is a gondola attached to the suspension (picavet or similar), which carries the camera technology.
There are very simple designs without sophisticated suspensions and without the possibility of specific remote control. These are particularly interesting for beginners, as the financial investment is low. A prerequisite for this variant is a camera that has an adjustable interval trigger (triggering can be carried out continuously with a fixed time interval). The disadvantage of these entry-level rigs is the high reject rate within the triggered image series and the total wind dependence in relation to the direction of view.
The slightly more expensive but much more comfortable variant is the remote-controllable rig. Depending on the version, you can use this rig to rotate and tilt the camera in the air, and trigger it at any time. Some KAPers also provide their rig with the option of turning the camera in the air so that it can be swiveled between portrait and landscape format. The movements are mostly carried out by so-called servos (special electric motors for the control) from model building technology. These servos are connected to a remote control receiver and thus carry out the movements that the KAPer controls from the ground with a standard remote control.
Components for a remote controllable rig (technical pod for the camera)
- a lightweight, rotatable and swiveling frame in which the camera can be mounted.
- Servos that perform the turning and swiveling movement
- a servo, or if the camera is to be triggered electrically, a relay, for actuating the trigger
- a remote control receiver with three or four channels that receives the control signals from the transmitter and forwards them to the servos
- an accumulator or a battery for the power supply of the remote control
- a receiving antenna
- a hanging device for the kite line
- possibly a direction indicator to better control the alignment from the ground.
Dragons
- Rod kites
- DoPeRo (double Pearson scooter) - a single line that has been further developed for KAP purposes
- Eddy
- delta
- Rokkaku (very high load capacity, very quiet and stable flight)
- Rodless
- FlowForm / a kite that gets its flight stability through the individual cells. Each cell has a large entry hole for the wind and a smaller exit. This shape creates a load-bearing wing with enormous lift. Another advantage of the FlowForm is the small pack size. A kite measuring 4 meters × 3 meters can be transported on the luggage rack of a bicycle without any major problems. The flight behavior of a neatly crafted FlowForm is very good-natured. With it, camera heights of up to 95 m (85 ° angle of inclination of the kite line) can be realized.
- Power Sled
- Fled (mix of flow and sled)
safety
There are rules that a good KAPer should follow - for their own safety and that of others.
- Safety takes precedence over good photos.
- Lift kites for KAP photography are not toys. You develop e.g. T. enormous tensile forces that have to be mastered.
- In Germany, the line length may not exceed 100 meters. Exceptions (for example at kite festivals) must be registered with the authorities.
- Minimum distances from airfields (1.5 km) and heliports must be strictly observed.
- Avoid the proximity of high voltage lines, tall buildings, dense settlements (traffic, etc.) and industrial plants.
- No flight during a thunderstorm
- No night flight
- The material must be checked thoroughly before each flight. This is especially true for lines, knots and the kite itself.
- Exact knowledge of the wind strength and the wind range for your own kite should be available.
Bubble panoramas
A variant of kite aerial photography is the creation of so-called bubble panoramas. These are all-round views in which one appears to be standing in the middle of a sphere or bubble and can look around in all directions as well as up and down. Such all-round views can also be made from the ground. Aerial shots from a camera hanging on a kite can be much more interesting.
How the images were created
Panorama shots on the ground can be put together from any number of shots. The camera stands on a tripod and the subject is taken with individual photos that slightly overlap. These are then put together in the computer to form a panorama picture. In this way, fantastic recordings can be made with a huge resolution. You can use a normal wide angle lens with a focal length of 35 or 28 millimeters. The smaller the focal length, the fewer images are required, but the lower the resolution.
However, if the camera is in the air, hanging on a flying kite, you cannot take picture by picture and then put these individual pictures together on the computer. Because the kite and thus the camera are constantly moving, the camera position changes constantly. This makes it almost impossible to combine several images into a panorama. A single picture must suffice here.
Create a bubble panorama from the air
- Step 1
The lower part of the later bubble panorama:
Since only one picture can be made, everything must be included in this one picture. This is achieved with a fisheye lens . The camera hangs on the kite and looks straight down. The photo then contains the entire lower part of the later panorama.
- step 2
The upper part of the later bubble panorama:
A panoramic view does not only include the floor or the lower part of the bubble panorama, but also the upper part, i.e. the sky. However, the sky does not need to be made from the kite, but can be photographed vertically upwards from the ground.
- step 3
The two halves of the image are then put together in the computer to form a finished bubble panorama and converted into a display format. However, a corresponding viewer must be installed on the computer for viewing.
See also
Events
- KAPiCA / 02 - Kite Aerial Photography in California, Pacific Grove , November 1, 2002, April 15-19 . October 2003
- FLiBB - fettered kite aerial photo days in Bad Bevensen , D, 1996 and 2000.
- JKPA Contest 2001 - Japan Kite Aerial Photography Association
literature
- Niels A. Fries: Kite Aerial Photography. Aerial photography for beginners and climbers! Eigen-Verlag, Neuss 2010. (2013?) 54 pp.
- Batut, Arthur: La photographie aérienne par cerf-volant , Paris 1890. - (74 pp., PDF; 1.8 MB) - on: fr.wikisource.org
Web links
- nielsfries.de - literature, remote control technology and kites
- Charles C. Benton (USA)
- Kite Aerial Photography pinterest.de, Michael, picture collection
- David Hunt: KAPER - Kite Aerial Photography E-Resources (engl.)
- Ken Conrad: brooxes.com Kite Aerial Photography kits, kites, parts, & accessories - also instructions and pictures of many camera rigs
Individual evidence
- ↑ Note. A possible purpose of a barometer is to document the maximum height reached, or to trigger the camera from a certain minimum height. With the stated weight of 0.325 kg, a clockwork-driven writing mechanism could possibly also have been included.
- ↑ Ralf Beutnagel: Dragon cableways dopero.de, 1996-2012 accessed 28 May 2020th
- ↑ Minox ML Rigg dopero.de, 1996–2012, accessed May 28, 2020.
- ↑ Picavet suspension: The cable guide of elliptical cable pendulum suspensions dopero.de, 1996–2012, accessed May 28, 2020.
- ↑ Dopero dopero.de, 1996-2012 accessed 28 May 2020.
- ↑ David Hunt: KAPiCA / 02 - Friday's Program davidhunt.me, December 27, 2002, accessed May 28, 2020.