Definition History of Remote Sensing Basic components of Remote sensing Electromagnetic Remote...

Definition History of Remote Sensing Basic components of Remote sensing Electromagnetic Remote Sensing Process Electromagnetic spectrum Passive and active remote sensing

Different types of Resolution◦ Spatial Resolution◦ Spectral Resolution◦ Radiometric Resolution◦ Temporal Resolution

Characteristics of various sensors Satellites: IRS Fundamentals of Image Processing

Component of Remote Sensing

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)

•Two characteristics of electromagnetic Radiation

•wavelength • frequency.

8

:

3 10 /

c

where

wavelengthof light

c speed of light m s

frequency of light

Ex. Assume the speed of light to be 3x108 m/s. If the frequency of an electromagnetic wave is 500,000 GHz (GHz =gigahertz = 109 m/s), what is the wavelength of that radiation? Express your answer in micrometres (μm).

Problems• Ex . A given SLAR system transmits pulses over a duration of

Find the range resolution of the system at a depression angle 450

• Ans: 21m

• Ex. A given SLAR system has a 1.8 mrad antenna beamwidth. Determine the azimuthal resolution of the system at ranges of 6 km and 12 km

• Ans: 10.8 m & 21.6 m

• Ex. A given SLAR system has a 2 mrad antenna beamwidth and wavelength of the transmitted pulse is 5 cm. Determine the length of the antenna

• Ans: 25 m

0.1 sec.

The deficiencies of brute force operation are overcome in synthetic aperture radar (SAR) systems.

Having short physical antenna through modified data recording and processing techniques, but synthesize the effect of a very long antenna.

The result of this mode of operation is a narrow effective antenna beamwidth, even at far ranges, without requiring physically long antenna or a short operating wavelength.

At the detailed level, the operation of SAR systems is quite complex

SLAR

Fig. Concept of an array of real antenna positions forming a synthetic aperture

Operate on the principle of using the sensor motion along track to transform a single physically short antenna into an array of such antennas that can be linked together mathematically as part the data recording and processing procedures

The "real" antenna is shown in several successive positions along the flight line.

These successive positions are treated mathematically as if they are simply successive elements of a single long synthetic antenna

Fig. Variation of spatial resolution of a) SLAR b) SAR