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What is remote sensing?Definition 1 – Remote sensing is the
acquiring of information about an object or scene without touching it through using electromagnetic energy
a. RS deals with systems whose data can be used to recreate images
b. RS deals with detection of the atmosphere, oceans, or land surface
M = T4
The amount of EM radiation (M) emitted from a body in Watts m-2 can be calculated as
Stefan-Boltzmann Law*
Wien Displacement Law* The wavelength
with the highest level of emitted radiation (max) for an object of temperature T can be calculated as
max = k / T
Types of thermal energy transfer Models of EM radiation/energy
Particle Model Photon absorption, excitation, de-excitation
Wave Model Characteristics of EM waves
Polarization, speed of light, wavelength, frequency Laws governing EM radiation
Stephan-Boltzman Law Planck’s Formula Wien Displacement Law
Remote sensing in the visible and reflected infrared region of the EM spectrum Maximum Solar Output Wavelengths λ Examples of Visible & RIR λ Images Basic Interactions of EM energy & the earths surface
Descriptors of EM radiation Radiant flux Radiant flux density – irradiance and exitance
Radiation budget equation Reflection Absorption Transmission
Remote Detection of Exitance Radiance
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Lecture Topics
8
Wavelength region for VI/ reflected IR remote sensing is between 0.4
and 2.6 m
Visible λ
Reflected near and SW infrared
Figure 1
Reflected IR λ
Types of thermal energy transfer Models of EM radiation/energy
Particle Model Photon absorption, excitation, de-excitation
Wave Model Characteristics of EM waves
Polarization, speed of light, wavelength, frequency Laws governing EM radiation
Stephan-Boltzman Law Planck’s Formula Wien Displacement Law
Remote sensing in the visible and reflected infrared region of the EM spectrum Maximum Solar Output Wavelengths λ Examples of Visible & RIR λ Images Basic Interactions of EM energy & the earths surface
Descriptors of EM radiation Radiant flux Radiant flux density – irradiance and exitance
Radiation budget equation Reflection Absorption Transmission
Remote Detection of Exitance Radiance
12
Lecture Topics
0.7 to 1.3 m – Near infrared1.3 to 2.8 m – Reflected Middle or Shortwave
(SW) IR region
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Reflected IR Region of EM Spectrum
Types of thermal energy transfer Models of EM radiation/energy
Particle Model Photon absorption, excitation, de-excitation
Wave Model Characteristics of EM waves
Polarization, speed of light, wavelength, frequency Laws governing EM radiation
Stephan-Boltzman Law Planck’s Formula Wien Displacement Law
Remote sensing in the visible and reflected infrared region of the EM spectrum Maximum Solar Output Wavelengths λ Examples of Visible & RIR λ Images Basic Interactions of EM energy & the earths surface
Descriptors of EM radiation Radiant flux Radiant flux density – irradiance and exitance
Radiation budget equation Reflection Absorption Transmission
Remote Detection of Exitance Radiance
23
Lecture Topics
24
Key components of VIS/RIR remote sensing 1. Sun is EM
Energy Source
2. Energy emitted from sun based on Stephan/Boltzmann Law, Planck’s
formula, and Wein Displacement Law
3. EM Energy interacts with the
atmosphere
4. EM energy interacts with the Earth’s Surface
VIS/NIR Satellite
EM energy
6. EM energy detected by a
remote sensing system
5. EM Energy interacts with the
atmosphere
Types of thermal energy transfer Models of EM radiation/energy
Particle Model Photon absorption, excitation, de-excitation
Wave Model Characteristics of EM waves
Polarization, speed of light, wavelength, frequency Laws governing EM radiation
Stephan-Boltzman Law Planck’s Formula Wien Displacement Law
Remote sensing in the visible and reflected infrared region of the EM spectrum Maximum Solar Output Wavelengths λ Examples of Visible & RIR λ Images Basic Interactions of EM energy & the earths surface
Descriptors of EM radiation Radiant flux Radiant flux density – irradiance and exitance
Radiation budget equation Reflection Absorption Transmission
Remote Detection of Exitance Radiance
25
Lecture Topics
The fundamental unit to measure electromagnetic radiation is radiant flux -
is defined as the amount of energy that passes into, through, or off of a surface per unit time
Radiant flux () is measured in Watts (W)
26
Radiant Flux -
Newton - force required to cause the mass of one kilogram to accelerate at a rate of one meter per second squared
Joule - the amount of energy exerted when a force of one newton is applied over a displacement of one meter
Watt – one joule / second
27
Definition of a Watt (FYI – I won’t ask about these definitions on exams)
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Radiant Flux Density
Radiant flux density is simply the amount of radiant flux per unit area
Radiant flux density represents the amount of EM energy coming from the area represented by a pixel
Radiant flux density = /area
29
Irradiance and Exitance
Irradiance is the radiant flux energy
that strikes a surface
Exitance is the radiant flux density coming from
a surface
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Irradiance - I Irradiance is the amount of incident
radiant flux per unit area to strike a plane surface in Watts/square meter (W m –2 )
Fig 2-20 in Jensen
I
31
Exitance - M Exitance is the amount of radiant flux per
unit area leaving a plane surface in Watts per square meter (W m –2 )
Fig 2-20 in Jensen
Types of thermal energy transfer Models of EM radiation/energy
Particle Model Photon absorption, excitation, de-excitation
Wave Model Characteristics of EM waves
Polarization, speed of light, wavelength, frequency Laws governing EM radiation
Stephan-Boltzman Law Planck’s Formula Wien Displacement Law
Remote sensing in the visible and reflected infrared region of the EM spectrum Maximum Solar Output Wavelengths λ Examples of Visible & RIR λ Images Basic Interactions of EM energy & the earths surface
Descriptors of EM radiation Radiant flux Radiant flux density – irradiance and exitance
Radiation budget equation Reflection Absorption Transmission
Remote Detection of Exitance Radiance
32
Lecture Topics
Three things can happen to incident EM energy [i] when it interacts with a feature
1. Reflected2. Absorbed3. Transmitted
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Radiation Budget Equation
i
The degree to which EM energy is reflected, transmitted, and absorbed is dependent on the wavelength of the EM
energy & the characteristics of the material the EM energy is interacting with
Reflectance (r) is the ratio of incident EM radiation that is directly reflected from a surface of an object: r = r / i
Absorption () is the ratio of incident EM that is absorbed by the object: = a / i
Transmittance () is the ratio of incident EM radiation that is transmitted through an object: = t / i
34
Reflectance, Absorption, & Transmittance
i (λ)= r (λ)+ t (λ) + a (λ)
i (λ)= Incident Energy
r (λ)= Reflected Energy
a (λ)= Absorbed Energy t (λ)= Transmitted Energy
i = r + t + a
r is the amount of energy reflected from the surface
a is the amount of energy absorbed by the surface
t is the amount of energy transmitted through the surface
41
Radiation Budget Equation*
Types of thermal energy transfer Models of EM radiation/energy
Particle Model Photon absorption, excitation, de-excitation
Wave Model Characteristics of EM waves
Polarization, speed of light, wavelength, frequency Laws governing EM radiation
Stephan-Boltzman Law Planck’s Formula Wien Displacement Law
Remote sensing in the visible and reflected infrared region of the EM spectrum Maximum Solar Output Wavelengths λ Examples of Visible & RIR λ Images Basic Interactions of EM energy & the earths surface
Descriptors of EM radiation Radiant flux Radiant flux density – irradiance and exitance
Radiation budget equation Reflection Absorption Transmission
Remote Detection of Exitance Radiance
42
Lecture Topics
43
VIS/RIR Remote Sensor
For a VIS/RIR remote sensing system, the surface
characteristic being detected is the result of reflectance from the earth’s surface
The sensors only detect reflected EM radiation from a certain direction and in certain wavelength regions
44
In remote sensing, we are not interested in all exitance, but only that exitance in the direction of the satellite system
Because of diffuse scattering, there is exitance in all directions from a surface
45
Detection of Exitance by a remote sensing system
θ – Sensor viewing angle
Area as seen by the sensor (projected area) = A cos θ
Satellite Radiometer
A = area on ground being sensed
Radiance Solid angle of the sensor
Flux from a surface is actually being emitted or reflected in all directions equally, i.e., it is being distributed into a hemisphere
The radiometer intercepts a fraction of the exitance from a surface, this fraction is defined by the solid angle, Ω, of the sensing system, which can defined by the area of the detector surface (a) and the distance to the target area (d)Ω = a/d
d
a
48
SyllabusLecture/Hourly Exam Schedule and Assigned Readings (Subject to Change)
Week Date Lecture Topic Reading Part I Remote Sensing Basics
1 26-Jan 1 Introduction to Remote Sensing Ch 1 28-Jan University Closed
2 02-Feb 2 Principles of EM radiometry and basic EM Theory Ch 204-Feb Principles of EM radiometry and basic EM Theory II
3 09-Feb 3 Atmospheric Influences on EM Radiation 11-Feb 4 Photographic Systems/Image Interpretation Ch 3,5
4 16-Feb 5 The Digital Image I Ch 4,1018-Feb The Digital Image II
5 23-Feb 6 Applications with areal and space photography 25-Feb Exam 126-FebLab 1 Introduction to ENVI – manipulation of digital imagery