Lect 4 energy interactions-rs

October 15, 2020
Fundamentals of RS
1
Lecture-4

Lecture # 3 & 4 Dated:14&15/10/2020
Course(502) Introduction
to GIS and RS
Fundamentals of Remote Sensing
Topic
Presented by
Rehana Jamal (Geometiciation, GIS Specialist & Geographer)
Visiting lecturer
studentsdatafiles@gmail.com
Faculty of Agricultural Engineering, Arid Agriculture University,
Rawalpindi
2
 What is Remote sensing
 Characteristics of Electromagnetic radiation
 Energy Sources or Illumination
 How Remote Sensing works?
Lect-3
Lect-4  Energy interaction with the Atmosphere
 Energy Interactions wit the Earth
Sub-topics

“Remote Sensing (RS) is the
science and art of acquiring
information about material
objects, area, or phenomenon,
without coming into physical
contact with the objects, area, or
phenomenon under investigation”
What is Remote sensing?
October 14, 2020
3
Fundamentals of RS
Source: https://www.google.com/

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RS happens due to the radiation of Electromagnetic waves from coming the sun
C (Velocity of light)
Source of Electromagnetic waves

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7
Source: https://phys.org/news/2018-04-vr-focus-nanostructure-meta-lenses.html
Visible Band of Electromagnetic waves
Fundamentals of RS

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Fundamentals of RS
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Characteristics of Electromagnetic radiation
Electromagnetic Energy can be modelled in two ways
i. By waves ii. By Photons (Energy bearing particles)
Electromagnetic waves consist of a combination of oscillating electrical
and magnetic fields, perpendicular to each other.
C (Velocity of light)

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Electromagnetic Spectrum

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Electromagnetic Spectrum

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i. It can travel through empty space.
ii. The speed of light is constant in space.
iii. Wavelength: Distance between crests or troughs through visible light
iv. Velocity: 186,000 miles per second or 300,000 kilometers per second or
299,790,000m/s or 3*108 m/s
v. Amplitude: The amplitude of electromagnetic waves relates to its intensity or
brightness(as in the case of visible light) or the maximum extent of a vibration or
oscillation, measured from the position of equilibrium (mid point of wavelength)
vi. Frequency:
 The number of crests of the waves that pass by a point per second.
 Measured in units of hertz(Hz)
 1 hertz = 1 wave crest/second
Characteristics of Electromagnetic radiation / Crest

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/ Crest
Velocity of light, c

October 14, 2020
Fundamentals of RS
13 Note the trends: bluer light has shorter wavelength, higher frequency,
and more energy. Redder light has longer wavelength, lower frequency,
and less energy.
Wavelength is inversely proportional to the Frequency

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Fundamentals of RS
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f or V = c/
Relation between the speed of light (c),
wavelength ( ), and frequency (f or V ):
Thus, there is an inverse relationship between
wavelength and frequency

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Thus (frequency [f or V] * wavelength[lambda]) is equal to a constant (c)
Relation between the speed of light (c), wavelength ( ),
and frequency (f or V ):

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Measurement of Electromagnetic Energy(E/Q)
The amount of energy held by a photon of a
specific wavelength is given by
E or Q = h v
Since c = v
v/ƒ = frequency
v/ƒ = c/
h = 6.6262 x 10 -34 j/s Plank’s constant
E or Q = h x c/
c = 3 x 10 8 m/s Speed of light is constant
E or Q =
6.6262 x 10 -34
(3 x10 8)
x
(500nm x 10 – 9 m)
E or Q = (3.98 x 10 -19 j)
(500 x 10 – 9 m)
= 500nm

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Fundamentals of RS
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Types of Energy Resources/Types of RS on the basis of Energy
(1.Passive & 2.Active)

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1. Passive Remote Sensing: Makes use of sensors that detect the
reflected or emitted electro-magnetic radiation from natural sources.

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2. Active remote Sensing: Makes use of sensors that detect reflected
responses from objects that are irradiated from artificially-generated
energy sources, such as radar.

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Source:
https://en.wikipedi
a.org/wiki/Remote
_sensing#/media/F
ile:Remote_Sensin
g_Illustration.jpg

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Fundamentals of RS
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How Remote Sensing works?/How the Energy
is recorded by the Sensor (D)?
Elements of RS

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Source:http://giswin.geo.tsukuba.ac.jp/sis/tutorial/koko/remotesensing/Fundamental
RemoteSensing.pdf
Fundamentals of RS

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Fundamentals of RS
23
Recording of Energy by the Sensor in the form of Digital Number(DN values)

Lecture # 4 Dated:15/10/2020
Course(502) Introduction
to GIS and RS
Fundamentals of Remote Sensing
Topic
Presented by
Rehana Jamal (Geometiciation, GIS Specialist & Geographer)
Visiting lecturer
studentsdatafiles@gmail.com
Faculty of Agricultural Engineering, Arid Agriculture University,
Rawalpindi
24
1. Energy interaction with the Atmosphere
 Absorption
 Transmission
 Scattering(Types of scattering)
 Reflection
2. Energy Interactions with the Earth
 Vegetation
 Soil
 Water
Sub-topics

25
Energy interactions in the atmosphere
Source
of
energy Sun
October 15, 2020
Fundamentals of RS
All matter with a temperature
above zero(0º K) radiates EM
energy due to molecular agitation.
The matter that is capable of
absorbing and re-emitting all EM
energy is known as black body

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 Absorption
 Transmission
 Scattering
 Reflection
Fundamental interactions in the atmosphere
Incident ray
of sunlight
S

27 Efficient absorbers of solar radiation
in the atmosphere
 Ozone(O3)
 Water vapour (H2O)
 Carbon dioxide(CO2)
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Fundamentals of RS

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Atmospheric Scattering
Amount of scattering depends on following factors:
 wavelength of the radiation
 the amount of particles & gases
 radiation distance
October 15, 2020
Fundamentals of RS
Source:https://www.google.com/

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Atmospheric Scattering
Types of scattering
Rayleigh scattering (Particle size < wavelength) Particle < 50nm
Mie scattering ( Particle size = wavelength) Particle ≥ 50-500nm
Non-selective scattering (Particle size > wavelength) Particle > 1µm
October 15, 2020
Fundamentals of RS

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Fundamentals of RS
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Source:https://www.slideserve.com/alden/electromagnetic-
radiation-interaction-with-matter-and-atmosphere
Types of scattering

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1. Rayleigh scattering (Particle size < wavelength)
Particle < 50nm
Source:https://www.google.com/

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Source: http://www.mkrgeo-blog.com//
Particle < 50nm

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Particle < 50nm

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2. Mie scattering ( Particle size = wavelength)
Particle ≥ 50-500nm
Causes:
Aerosols i.e.
 A mixture of gases
 Water vapours
 Dust
Mie scattering influences
Spectral region/band
0.02 um 1000 um

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Fundamentals of RS
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3. Non-selective scattering (Particle size > wavelength)
Particle > 1µm
Causes:
 Water droplets
 Large dust particles

36
Incoming solar
radiation 100%
Earth’s surface
Scattered/Reflected
Absorbed
14 % By
atmospheric
components
3% By clouds
47%
31%
22%
25%By clouds
5% By dust
Total atmospheric absorption 17 % Total scattering/reflection 30% (albedo)
Diffuse
radiation
Direct
radiation
Fig. Energy interactions in the atmosphere
Clouds
Clouds Clouds
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Fundamentals of RS

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Energy interactions with the Earth’s surface
In remote sensing applications, Land & Water have different surface characteristics
Energy interactions: When electro-magnetic energy is incident on any given
earth surface feature, three fundamental energy interactions with the features
are possible:-
1.Reflection , 2.Absorption , 3.Transmission
October 15, 2020
Fundamentals of RS

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Two types of Reflection
Specular reflection (mirror like reflection from smooth surface)
Diffuse reflection (reflection from rough surface)
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Fundamentals of RS

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Fig.9
Fig.10
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Fundamentals of RS

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Vegetation: 50%
but in water containing plants reflection is
high in green band
Soil : 30-40%
Water: 10%
Percentage of Spectral reflectance of
vegetation, soil & water is :
October 15, 2020
Fundamentals of RS
But turbid water has high reflectance

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Fundamentals of RS
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Summary
1. Energy interaction with the Atmosphere
 Absorption
 Transmission
 Scattering(Types of scattering)
 Reflection
2. Energy Interactions with the Earth
 Vegetation
 Soil
 Water
Rayleigh scattering:
(Particle size < wavelength)
Mie scattering:
(Particle size = wavelength)
Non-selective scattering:
(Particle size > wavelength)

References:
• www.google.com
• www.wikipedia.com
•https://www.nrcan.gc.ca/maps-tools-publications/satellite-imagery-air-photos/remote-
sensing-tutorials/fundamentals-remote-sensing-introduction/9363
• https://staff.aub.edu.lb/~webeco/rs%20lectures.htm
• Principles of Remote sensing
• edited by Lucas L.F. Janssen
•https://www.nrcan.gc.ca/sites/www.nrcan.gc.ca/files/earthsciences/pdf/resource/tutor/fu
ndam/pdf/fundamentals_e.pdf
•http://giswin.geo.tsukuba.ac.jp/sis/tutorial/koko/remotesensing/FundamentalRemoteSe
nsing.pdf
October 15,
2020
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Fundamentals of RS

Lect 4 energy interactions-rs

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