02 The Basic Concept of Remote Sensing

Remote Sensing is derived from two words,

REMOTE + SENSING

Remote means distance

Sensing means observation

Remote sensing means ‘sensing an object or phenomenon, from a distance with the help of a suitable device/platform.

“Colwell (1984)”

Remote sensing is the acquiring of data about an object without touching it.

“American Society of Photogrammetry, 1952; 1966”

The art or science of obtaining reliable measurements using photography.

“In 1988, ASPRS adopted a combined definition of photogrammetry and remote sensing”

Photogrammetry and remote sensing are the art, science, and technology of obtaining reliable information about physical objects and the environment through recording, measuring, and interpreting imagery and digital representations of energy patterns derived from non-contact sensor systems.

A remote sensing instrument collects information about an object or phenomenon within the instantaneous- field-of-view (IFOV) of the sensor system without being in direct physical contact with it. The remote sensing instrument may be located just a few meters above the ground and onboard an aircraft or satellite platform.

Advantages of remote sensing data

1. Provide useful information in various wavebands.

2. Large area coverage.

3. Repetitive coverage provides to monitor dynamic themes like agriculture.

4. Easy data acquisition.

5. Reducing the amount of fieldwork.

6. Stereo satellite data may be used for three-dimensional studies.

Disadvantages of remote sensing data

1. Expensive for small areas.

2. Requires specialized training for analysis of images.

3. Aerial photos are costly if repetitive photos are required.

Overall view of working remote sensing system

1. The origin of electromagnetic energy (sun transmitter carried by the sensor).

2. Transmission of energy from the atmosphere of the earth.

3. Interaction of energy with the earth’s surface (reflectance/absorption/transmission) or self-emission.

4. Transmission of the reflectance/emitted energy to the remote sensor.

5. Detection of energy by the sensor, converting it into a photograph may be digital or analog.

6. Transmission/recording of the sensor output.

7. Pre-processing of the data and generation of the data product.

8. A collection of ground truth and other collateral information.

9. Data analysis and interpretation 10- various themes, or other applications.