intro rs-i

7/29/2019 Intro RS-I

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FUNDAMANTALS OF REMOTE

SENSING

R.S.DWIVEDI

PART-I


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Remote sensing is the measurement or

acquisition of some property of an object or

phenomenon, by recording device that is not in

physical or intimate contact with the object or

phenomenon under study (Colwell, 1983).

WHAT IS REMOTE SENSING?


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SCOPE


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COMPONENTS OF A SATELLITE REMOTE

SENSING SYSTEM

-Launch Vehicle

-Platform (Satellite)

-Sensor- Data Reception

-Data Processing

-Interpretation/Analysis

-Generation of thematic maps / area statistics/ reports

-Development of Decision Support System (DSS)-Creation of digital database


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DATAArchive

Concept of Remote SensingFrom Space Data to information


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TYPES OF SENSORS


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ACTIVE SENSORS Own energy source for

illumination

Emits radiation which isdirected toward the target tobe investigated

Microwave

Optical

PassiveActiveActive

Passive

LIDAR(ALTM)

Visible, Near &Thermal Infrared ImagersImaging Spectrometer

IMAGINGRADARS

Multi FreqMicrowaveRadiometers.Imagingpossible withscan optionAtmosphericSounders

NON-IMAGINGScatterometerAltimeterRain MappingRadar

PASSIVE SENSORS

Energy from Sun Reflected, Absorbed &

Re Emitted as Thermal IRDuring day for reflected wavelengths

Emitted Energy (such as thermal

infrared) can be detected day or night

SENSORS


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SIDE LOOKING RADARSYSTEMS

IMAGING NONIMAGING

SLR

RAR

SAR

Active

SPACE BORNE SAR

AIR BORNE SAR

GROUND BASED SAR


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REMOTE SENSING : HISTORICAL


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LAUNCH VEHICLE


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Launch Vehicle Family


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WAVE MODELEMR has been thought of as electromagnetic wave that travels through

space at a speed of light (Maxwell 1831).

It consists of two fluctuating fields one electric and the other magnetic.

The two vectors are at right angles (orthogonal) to one another, and both are

perpendicular to direction of travel.

EMR is generated whenever an electrical charge is accelerated.

The wavelength () of the EMR depends upon the length of time that the

charged particle is accelerated. Its frequency (v) depends on the number of

accelerations per second.

Electromagnetic Radiation


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Electromagnetic Spectrum

Violet: 0.4 - 0.446 mm

Blue: 0.446 - 0.500 mm

Green: 0.500 - 0.578 mm

Yellow: 0.578 - 0.592 mm

Orange: 0.592 - 0.620 mm

Red: 0.620 - 0.7 mm


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Optical Infrared (OIR) Region

Visible 0.4-0.7mm

Near infrared (NIR) 0.7-1.5 mm

Shortwave infrared (SWIR) 1.5-3.0 mmMid-wave infrared (MWIR) 3.0-8.0 mm

Thermal infrared (TIR) 8.0-15 mm

Far infrared (FIR) Beyond15 mm

Microwave Region

P Band 0.3 - 1GHz (30 -100 cm)

L Band 1 -2 GHz (15 - 30 cm)

S Band 2 - 4 GHz (7.5 - 15 cm)

C Band 4 - 8 GHz (3.8 - 7.5 cm)

X Band 8 - 12.5 GHz (2.4 - 3.8 cm)

Ku Band 12.5 - 18 GHz (1.7 - 2.4 cm)

K Band 18 - 26.5 GHz (1.1 - 1.7 cm)

Ka Band 26.5 - 40 GHz (0.75 - 1.1 cm)

1 GHz = 109 Hz


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Electromagnetic Radiation

c


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Wavelength and frequency

c = where c = 3 x 108 ms-1

in vacuum


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The particle theory suggests that electromagnetic radiation is

composed of many discrete packets of energy called

Photons or Quanta.

The energy of each quantum is given by

Q = h

where Q is energy of quantum (J), h is Plancks constant (6.626

x 10-34 J-s) and is frequency

Also, Q = hc/ implies the longer the wavelength involved, the lower

its energy content.

Electromagnetic RadiationParticle Theory


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RADIATION LAWS

An ideal thermal emitter is called a

Blackbody. Also known as Planckian

radiator.

That is, its emissivity is equal to 1. In otherwords it radiates the entire energy whatever

it absorbed.

Black Body


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Gray Body

A gray body is one for which emissivity

value is constant but less than unity.

A selective radiator is one for which

emissivity value varies with wavelength..

RADIATION LAWS


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Radiant exitances for a blackbody, gray body anda selective radiator


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PLANCKS LAWPlancks Law: The most general law

Planck's Law allows us to calculate total energy radiated in

all directions from a blackbody (radiator) for a particular

temperature and wavelength.

M( )= C1 -5/[exp(C2/ T) - 1]

where

C1(2 hc2) = 3.74 x 10-16 W m-2,

C2 (hc/k)= 1.44 x 10-2 m K,

wavelength ( m),

T temperature ( K),

M( spectral exitance (W m-2 m-1),

k = 1.38 x 10-23 W s K-1, h = 6.625 x 10-34 J s


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Weins Displacement Law

The dominant wavelength, or wavelength at which a blackbodyradiation curve reaches a maximum, is related to its

temperature

m = (k/T)

where m is wavelength of maximum spectral radiant exitance( m), k = 2898 m K, T is absolute temperature in K

Rayleigh-Jeans law

This law explains blackbody emission at higher wavelengths:

M()=C1-4T/C2

BLACK BODY RADIATION


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RADIATION LAWS

Spectral distribution of

energy radiated by

blackbodies at various

temperatures9.6 m

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