Remote Sensing Overview
Remote sensing is gathering information about something without being in direct contact with it. It is the exact opposite of in-situ sensing, This is done by sensing and recording reflected or emitted energy and processing, analyzing, and applying that information. Your eyes are remote sensing devices, since they obtain information about your surroundings without actually touching them. Cameras are also remote sensing devices, and we will discuss them in more later.
Sensors collect and store data about the spectral reflectance of natural features and objects, both of which reflect radiation. This radiation can be quantified on an electromagnetic spectrum.
The electromagnetic spectrum is a continuum of electromagnetic energy arranged according to its frequency and wavelength. As the electromagnetic waves are radiated through space, their energy interacts with matter and one of three reactions occurs. The radiation will either be:
Aircraft and satellites are the common platforms for remote sensing observations.
The term remote sensing is commonly restricted to methods that employ electromagnetic energy such as heat, light and radio-waves, as the means of detecting and measuring target characteristics.
This definition of remote sensing excludes electrical, gravity and magnetic surveys that measure force fields rather than electromagnetic radiation.
Aerial photography is the original form of remote sensing and has played a major role in the discovery of many oil and mineral deposits around the world.
The success of aerial photography, using the visible spectrum of the electromagnetic radiation, suggested that it might be possible to obtain comparable results by using the other wavelength regions.
In the 1960s, technological development enabled the acquisition of images at other wavelengths, including thermal infrared (IR) and microwave.
The development and deployment of manned and unmanned satellites provided an orbital vantage point for acquiring images of the earth.
Elements of Remote Sensing
In much of remote sensing, the process involves an interaction between incident radiation and the targets of interest. This is exemplified by the use of imaging systems where the following seven elements are involved.
Note, however that remote sensing also involves the sensing of emitted energy and the use of non-imaging sensors.
1. Energy Source or Illumination (A)
2. Radiation and the Atmosphere (B)
3. Interaction with the Target (C)
4. Recording of Energy by the Sensor (D)
5. Transmission, Reception, and Processing (E)
6. Interpretation and Analysis (F)
7. Application (G)
Remote Sensing Devices
In this class we will look at four main types of remote sensing systems:
This website is hosted by
Department of Geology
Aligarh Muslim University, Aligarh - 202 002 (India)