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Remote Sensing Platforms
Geography (GEO-1)
University of Delhi
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Remote Sensing
Platforms
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PLATFORMS
Platform is a stage where sensor or camera is mounted to acquire information about a target under investigation.
According to Lillesand and Kiefer (2000), a platform is a vehicle, from which a sensor can be operated. For remote sensing applications, sensors should be mounted on suitable stable platforms. These platforms can be ground based, air borne or space borne based.
As the platform height increases the observational area increases. Thus, higher the sensor is mounted; larger synoptic view is obtained.
The types or characteristics of platform depend on the type of sensor to be attached and its application. Depending on task, platform can vary from ladder to satellite.
Three types of platforms are used to mount the remote sensors –
Ground based Platform
Air - borne Platform, and
Space-borne Platform
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- Permanent ground platforms like towers and cranes are used for monitoring atmospheric phenomenon and long-term monitoring of terrestrial features. Towers can be built on site and can be tall enough to project through a forest canopy so that a range of measurements can be taken from the forest floor, through the canopy and from above the canopy
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Air Based Platforms
- Airborne remote sensing is carried out using specially designed aircrafts or hot air balloons depending on the operational requirements and the availability of budget.
- Aircraft remote sensing system may also be referred to as sub-orbital or airborne, or aerial remote sensing system. At present, airplanes are the most common airborne platform.
- Airborne platforms are employed owing to their mobilization flexibility and capability of recording data covering large spatial areas as compared to the ground based sensors. The speed, altitude as well as orientation of the aircraft must be carefully chosen so as to have minimum influence on the scale, resolution and geometric characteristics of the recorded images.
- Other airborne observation platforms include balloons, drones (short sky spy) and high altitude sounding rockets. Helicopters are occasionally used. 5
Drones
- Drone is a miniature remotely piloted aircraft. It is designed to fulfill requirements for a low cost platform, with long endurance, moderate payload capacity and capability to operate without a runway or small runway.
- Drone includes equipment of photography, infrared detection, radar observation and TV surveillance. It uses satellite communication link. An onboard computer controls the payload and stores data from different sensors and instruments.
- Drone was developed in Britain during World War-II, is the short sky spy which was originally conceived as a military reconnaissance. Now it plays important role in remote sensing. The unique advantage is that it could be accurately located above the area for which data was required and capable to provide both night and day data
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Aircraft Platforms
- Aerial platforms are primarily stable wing aircraft. Helicopters are also occasionally used for this purpose. Generally, aircraft are used to collect very detailed images.
- Special aircraft with cameras and sensors on vibration less platforms are traditionally used to acquire aerial photographs and images of land surface features.
- While low altitude aerial photography results in large scale images providing detailed information on the terrain, the high altitude smaller scale images offer advantage to cover a larger study area with low spatial resolution.
- Aircraft platforms offer an economical method of remote sensing data collection for small to large study areas with cameras, electronic imagers, across- track and along-track scanners, and radar and microwave scanners. 8
Rockets as Platforms
- High altitude sounding rocket platforms are useful in assessing the reliability of the remote sensing techniques as regards their dependence on the distance from the target is concerned.
- Balloons have a maximum altitude of approximately 37 km, while satellites cannot orbit below 120 km. High altitude sounding rockets can be used to a moderate altitude above terrain. Imageries with moderate synoptic view can be obtained from such rockets for areas of some 500,000 square kilometers per frame.
- Prior to use of airplanes, aerial photographs were obtained by rocketing a camera into the sky and then retrieving the camera and film.
- The high altitude sounding rocket is fired from a mobile launcher. During the flight its scanning work is done from a stable altitude, the payload and the spent motor are returned to the ground gently by parachute enabling the recovery of the data. One most important limitations of this system is to ensure that the descending rocket not going to cause damage 10
Space Borne Platforms
Space borne remote sensing is carried out from the outer space or at an altitude higher than the earth’s atmosphere and utilizes space shuttle or more commonly satellites as platforms.
Space-borne or satellite platform are onetime cost effected but relatively lower cost per unit area of coverage, can acquire imagery of entire earth without taking permission. Space-borne imaging ranges from altitude 250 km to 36000 km.
Satellites are man made objects that revolve around the earth and sensors installed onboard captures data of the earth’s surface covering areas of more than hundreds of square kilometers. Because of their orbits, satellites permit repetitive coverage of the earth's surface on a continuing basis.
Ever since the launch of the first earth resources satellite (i., Landsat in 1972), satellite-based remote sensing has continuously served towards the betterment of science and technology
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Content Courtesy:
- Department of Geography, University of Patna, Bihar, India
- Panda. B. C., 2005, Remote sensing principles and Applications,Viva Books Pvt. Ltd., pp. 73-78.
- Bhatta, B, Remote Sensing and GIS, Oxford University Press, New Delhi
- E-PGPathshala
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Remote Sensing Platforms
Course: Geography (GEO-1)
University: University of Delhi
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