In this article, you will learn about what is a platform and its importance, what are different types of platforms used in remote sensing etc.
Platform is one of the important component in remote sensing. Platform is the arrangement or device which holds the sensor used for remote sensing process. Depending on how and where a platform is located, it is classified into several types. Following classification describes different types of platforms used in remote sensing.
Different Types of Platforms used in Remote Sensing:
Depending on altitude i.e., at what height a platform is located, platforms are classified into 3 types.
- Ground Borne platforms
- Air Borne Platforms
- Space Borne Platforms
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Ground Borne Platforms:
These platforms are primary located on the ground. Some of these platforms are placed at certain height, however still they take the support from the ground. Hence, ground platforms can be grouped into platforms which are present on ground or very less height from ground i.e., in the order of few meters.
If remote sensing is performed using ground borne platforms, it is called as ground borne remote sensing.
Examples of these platforms include handheld cameras, cameras mounted on vehicles, towers, cranes etc. Sensors from all these platforms capture data from very less height.
As the height of photography is very less, the captured data is normally of very high resolution. Very less area is covered in a single capture. Hence, to study a large area many photographs are required. This photographs are conventionally taken as reference data or ground truth and as sample data most of the times. This data is very simple to understand as it directly represents the objects on the ground.
More time is required for capturing a large city. However, complete control of photography is possible as it is performed from the ground it self. Most often photography or remote sensing is performed in visible portion of electromagnetic energy in this case. Data will not be captured similar to birds eye view in this case (more explanation about this point will be updated soon).
Air Borne Platforms:
These are platforms which are present a relatively higher altitude from the ground surface. As the name says, they are practically present in the air at the time of photography i.e., data capture. The height of platforms used for photography or remote sensing ranges from few meters (in case of drones) to few kilometers (in case of aeroplanes).
If remote sensing is performed using air borne platforms, it is called as air borne remote sensing.
Examples for airborne platforms include aerial cameras and sensors mounted on aeroplanes, helicopters, drones, hot air balloons etc.
As platform altitude is increased compared with ground borne platforms, here more area coverage is possible in a single instance. In less time and with less no of photographs, it is possible to cover the entire city. The photographs captured can be understood by common public also, however in some instances there will be some difficulties depending on resolution of image (size of objects appearing in photos). Multi spectral sensors can also be used to perform remote sensing in this case.
The applications of this type of air borne platform based remote sensing include reconnaissance surveys, disaster management, aerial surveys etc.
However, it is not possible to totally control the remote sensing process, as the sensors are present in air. It is practically not possible to maintain complete uniform velocity and smooth propagation of an aeroplane (platform) during the photography. Due to wind and platform perturbations some amount distortions are observed in the aerial photographs. The distortions include crab, drift etc.
Thus aerial platforms play a crucial role in remote sensing process.
Space Borne Sensors:
These platforms are present at a great height from the earth surface. The altitude of platforms range from few hundred kilometers to several thousand kilometers.
Example for these platforms include satellites, space shuttles and rockets etc.
Polar orbiting satellites (i.e., platforms) revolve around the earth in a orbit ranging from few hundred kilometers to few thousand kilometers, where as geo synchronous satellites used in remote sensing orbit at a height of 36,000 kilometers approximately.
These satellites while moving in the orbits around the earth capture data continuously and transmits the same to ground stations.
A wide variety of sensors i.e., multi spectral, panchromatic and hyper spectral sensors used in the remote sensing process. Also, depending on the sensor used and resolution characteristics of the sensor, the data captured is used in wide range of applications. The applications include weather, climate, forest and agriculture mapping, glacier studies, urban studies etc.
A large area (some times entire city or country) can be captured in a single scene (or photo) depending on altitude and resolution of sensor. For example, Geosynchronous satellites capture approximately 50% of the earth surface in a single scene.
However, the process cannot be controlled completely from the ground. Because, the platform velocity, atmospheric variations, sensor problems etc, lot of noise is included in the data collected. To remove noise, different types of image processing operations are performed at the ground level.
It is very difficult for a novice person and common public to understand the details present in the image captured using space borne remote sensing sensors. The data captured using space remote sensing normally has less resolution compared with ground and airborne sensors or devices.
Usage of Captured Data in Different Cases:
The data captured in each case is used for solving a specific type of problems or for specific type of applications. For example, in studying climate related process to get a quick overview space borne data can be used rather than other two. In the same fashion, for reconnaissance survey aerial survey can be performed than ground based photography.