Sensors in Remote Sensing: Types and Applications
In remote sensing, sensors are devices that detect and measure electromagnetic radiation reflected or emitted from Earth’s surface. These sensors are broadly classified based on their source of energy and the type of data they collect.
What is Sensor?
A Sensor is a device that produces an output signal for the purpose of sensing a physical phenomenon.
Sensors are used in everyday different objects, such as touch-sensitive elevator buttons and lamps. With advances in micro-machinery and easy-to-use micro-controller platforms, the uses of sensors have expanded beyond the traditional fields of temperature, pressure and flow measurement.
Types of Sensors in Remote Sensing
Sensor broadly categorized four types in Remote Sensing:
Based on Energy Source
- Active Sensor
- Passive Sensor
Active Sensor
Active Sensor is a source of light or illumination and its sensor measures reflected energy. The energy is generated and sent from the Remote Sensing platform towards the targets. Radar is an example of Active Sensor.
Active Remote Sensing Instruments:
Passive Sensor
Passive Sensor is a source of energy is that naturally available of the Sun. Most of the Remote Sensing systems work in passive mode, using solar energy as the source of EMR.The Sun, MSS is an example of Passive Sensor.
Passive Remote Sensing Instruments:
- Spectrometer
- Radiometer
- Spectroradiometer
- Hyperspectral radiometer
- Imaging radiometer
- Accelerometer
Based on Wavelength Detected
Optical Sensor
Detect visible, near infrared, and shortwave infrared.
Sensors:
- Sentinel-2 MSI
- Landsat
Thermal Sensor
Detect emitted thermal infrared radiation (heat).
Sensors:
- ASTER TIR
- Landsat TIRS
Microwave Sensor
Use long wavelengths (penetrate clouds, smoke, and vegetation).
Sensors:
- Sentinel-1
- RISAT
- RADARSAT
Based on Platform
Satellite-based Sensor
Satellites orbiting Earth.
Sensors:
- MODIS
- Sentinel
- Landsat
Airborne Sensor
Aircraft or Drones.
Sensors:
- Airborne LiDAR
- Hyperspectral scanners
Based on Data Type
Imaging
Imaging Sensor is the electrons released are used to excite or ionize a substance, like silver in film or to drive an image producing device like a TV or computer monitor or a cathode ray tube or oscilloscope or a battery of electronic detectors.
Sensors:
- Panchromatic
- Multispectral
- Hyperspectral
Non-imaging
Non-imaging Sensor measures the radiation received from all points in the sensed target, integrates this, and reports the result as an electrical signal strength or some other quantitative attribute, such as radiance.
Sensors:
- Radiometers
- Spectrometers
Sensor Resolution
Resolution is commonly used to describe the number of pixels display on a display device, or area on the ground that a pixel represents in an image file.
The resolution of a sensor with a digital output is usually the numerical resolution of the digital output. A sensor’s accuracy may be considerably worse than its resolution. Most sensors are influenced by the temperature of their environment.
4 distinct types of the Resolution must be considered:
- Spectral—specific wavelength intervals that a sensor can record
- Spatial—area on the ground represented by each pixel
- Radiometric—number of possible data file values in each band
- Temporal—how often a sensor obtains imagery of a particular area
