What is Remote Sensing?
“Remote sensing is the science (and to some extent, art) of acquiring information about the Earth’s surface without actually being in contact with it.”
This is done by sensing and recording reflected or emitted energy and processing, analyzing, and applying that information.
Principle of Remote Sensing
The electromagnetic radiation that an object emits or reflects is the source of the remotely sensed data, which is used to identify and categorise the object.
Main Stages of Remote Sensing
A. Energy Source or Illumination: Illuminates or provides electromagnetic energy to the target of interest.
B. Radiation and the atmosphere: Energy travels from its source to the target and comes in contact with & interacts with the atmosphere it passes through.
C. Interaction with the Target: Once the energy has passed through the atmosphere and reached the target, it interacts with the target based on the characteristics of both the radiation and the target.
D. Recording of Energy by the Sensor: We need a remote sensor-one that is not in direct touch with the target-to gather and record the electromagnetic radiation after the energy has been scattered by or emitted from the target.
E. Transmission, Reception, and Processing: The energy that the sensor has captured must be sent, frequently in electronic form, to a station that receives the data and processes it into an image (hardcopy or digital).
F. Interpretation and Analysis: A visual, digital, or electronic interpretation of the processed image is used to extrapolate details about the illuminated target.
G. Application: The application of the data we were able to extract from the target’s image to better comprehend it, expose new information, or help with a specific problem is the last step in the remote sensing process.
Types of Remote Sensing
There are two types of remote sensing technology, active and passive remote sensing.
Active sensors use their energy to scan objects and spaces; after doing so, a sensor picks up and measures any radiation that the target has reflected or backscattered. In active remote sensing techniques like RADAR and LiDAR, the location, velocity, and direction of an object are determined by measuring the time interval between emission and return.
Radiation that an object or its surroundings emit or reflect is collected by passive sensors. The most typical radiation source identified by passive sensors is reflected sunlight. Film photography, infrared, charge-coupled devices, and radiometers are a few examples of passive remote sensors.
Advantages of Remote Sensing
- Provides data on large areas.
- Provides data on inaccessible areas.
- Able to obtain imagery of any area over a continuous period
- Relatively less expensive compared to employing a team of surveyors.
- Easy and rapid data collection.
- Rapid production of maps and interpretation
Disadvantages of Remote Sensing
- Interpretation of imagery requires a certain skill level.
- Needs cross-verification with ground(field) survey data.
- Data from multiple sources may create confusion.
- Objects can be misclassified.