Remote Sensing Systems
The different acquisition techniques of remote sensing can, for instance, be distinguished according to the type of the electromagnetic radiation used. There are remote sensing systems working with sunlight reflected by the surface of the Earth. These acquisition systems are called passive remote sensing systems (left). Active remote sensing systems proceed in another way. These systems actively emit microwaves onto the surface of the Earth and then collect the amount of radiation reflected by the surface of the Earth (right).
Passive and active remote sensing systems for data acquisition.
Another distinctive feature of acquisition systems in remote sensing is the transportation technique. In airborne remote sensing, the sensor is being attached to the aircraft. Such sensors are very precise as they are characterised by a very high spatial resolution due to their short distance to the surface of the earth. However, they are only able to fly across a small part of the surface of the earth, so they are mainly used for rather specific investigations.
The animation shows airborne remote sensing for landscape imaging.
The second transportation technique is characterised by sensors being attached to satellites. Spaceborne acquisition systems are very expensive and have a lower spatial resolution than airborne acquisition systems. However, scientists benefit from the fact that these sensors can continually fly across the whole surface of the earth collecting data over a period of several years. In the animation below the different component parts of a satellite are shown, i.e. the drive module, the solar panel for energy input or the sensors.
Schematic setup of a satellite. Mouse over the single component parts in order to find out more about their functioning.
The most important characteristic to distinguish remote sensing systems is the specific technology. Generally, it is differentiated between three main categories: Photographic systems, spectral systems, and microwave systems. These techniques will be addressed in the following chapters.
|Photographic Systems are normally attached to aircraft and work with the visible range of the electromagnetic spectrum of sunlight.|
|Spectral Systems can be attached to satellites or, less often, to airplanes. They can record the electromagnetic spectrum in the range from visible light to thermal radiation.|
|Radar systems can be attached either to airplanes or to satellites. They use long wavelength, the so-called microwaves. The resulting images are more difficult to analyse than those of the other two systems.|