Remote Sensing

1. 3 Month Diploma Course
“Hydraulic Engineering in River basins”
Module HERB 2.2:
Introduction to GIS & RS Applications in River Basin Management
Module coordinator: Dr. Al Sayed Ibrahim Diwedar
Lecturer: Dr. Al Sayed Ibrahim Diwedar
RS Concepts, Theory and Techniques
2016 Lecturer: Dr. Al Sayed I. Diwedar 1

2. Objective
After the lecture the participants will
Understand the basics of RS techniques
Decide if RS is applicable in work field and the specific
arena to apply RS.
2016 Lecturer: Dr. Al Sayed I. Diwedar 2

3. Contents
Principles of Remote Sensing
Remote Sensing Process
Platforms and Sensors
Images and Bands
Resolution
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4. Principles of Remote Sensing
Detection objects or surface features means detecting
and recording of radiant energy reflected or emitted by
objects or surface material.
Different objects return different amount and kind of
energy in different bands of the electromagnetic
spectrum, incident upon it.
 This unique property depends on the property of
material.
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5. Types of Remote Sensing
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1- Passive remote sensing system.
2- Active remote sensing system.
Passive Active

6. Types of Remote Sensing
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7. Types of remote sensing
 Passive remote sensing system
It detects natural radiation that is
emitted or reflected by the object
or surrounding area being
observed.
Reflected sunlight is the most
common source of radiation
measured by passive sensors.
Ex: Landsat
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8. Types of Remote Sensing
 Active remote sensing system
An active Remote Sensing system
supplies its own source of energy,
which is directed at the object in order
to measure the returned energy.
Ex: radar
Advantage:
The ability to obtain measurements
anytime.
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9. Remote Sensing Process
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10. Remote Sensing Process
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)
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11. Remote Sensing Process
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12. Remote Sensing Process
1. Energy Source or Illumination (A)
The first requirement for remote sensing is
to have an energy source
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13. Remote Sensing Process
2. Radiation and the Atmosphere (B)
I. Electromagnetic Radiation
II. Interactions with the Atmosphere
III. Electromagnetic Spectrum
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14. Remote Sensing Process
I. Electromagnetic Radiation
The first requirement for remote sensing is to have
an energy source to illuminate the target. This
energy is in the form of electromagnetic radiation.
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15. Remote Sensing Process
II. Interactions with the Atmosphere
Electromagnetic radiation may be affected by
particles and gases that are found on the
atmosphere. This effect may be represented as
scattering and absorption
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16. Remote Sensing Process
 Scattering:
Is the unpredictable diffusion of radiation by
particles in the atmosphere.
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17. Remote Sensing Process
 Absorption:
Electromagnetic energy traveling through the
atmosphere is partly absorbed by molecules.
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18. Remote Sensing Process
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19. Remote Sensing Process
III. Electromagnetic Spectrum
Electromagnetic Spectrum is a range of
electromagnetic radiation extending from
shorter wavelengths (Gamma and X- rays) to
the longer wavelengths (Radio Waves).
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20. Remote Sensing Process
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21. Remote Sensing Process
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22. Remote Sensing Process
 Gamma Rays
This range is completely absorbed by the
upper atmosphere and not available for
remote sensing.
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23. Remote Sensing Process
 X-Rays
This range is completely
absorbed by the
atmosphere and not
employed in remote
sensing.
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24. Remote Sensing Process
 Ultraviolet
o It has the shortest wave lengths which are
practical for remote sensing.
o It has the ability to illustrate some earth
surface materials, rocks and minerals.
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25. Remote Sensing Process
 Ultraviolet
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26. Remote Sensing Process
 Visible Light
o The visible wavelengths
cover a range from
approximately 0.4 to 0.7
μm.
o The longest visible
wavelength is red and
the shortest is violet
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27. Remote Sensing Process
Visible Light
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28. Remote Sensing Process
Infrared
o This region is sensitive
to plant water content,
which is a useful
measure in studies of
vegetation health.
o It is also used for
distinguishing clouds,
snow, and ice.
o
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29. Remote Sensing Process
Infrared
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30. Remote Sensing Process
 Microwaves (Radar)
Images can be acquired
in the active or passive
mode.
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31. Remote Sensing Process
Microwaves (Radar)
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32. Remote Sensing Process
 Radio and TV Waves
The longest-wavelength portion of
the electromagnetic spectrum.
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33. Remote Sensing Process
4. Interaction with the Target (C)
 The energy emitted by the sun is following the
normal wave theory as it travels in sinusoidal type
with the velocity of the light
 EI (λ) = ER(λ) + EA (λ) + ET (λ)
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34. Remote Sensing Process
4. Interaction with the Target (C)
Reflection
 For the remote sensing application the surface
reflection of the electromagnetic energy is the most
important and useful process,
 R (λ) = (ER (λ) / EI (λ))*100
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35. Remote Sensing Process
4. Interaction with the Target (C)
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36. Remote Sensing Process
4. Interaction with the Target (C)
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37. Remote Sensing Process
4. Interaction with the Target (C)
Absorption and Transmission
 It happen when the energy is absorbed by the target
soil, water or any other feature
 When a radiation passes through a material without
significant reduction, this is defined as transmission
 (Ʈ) = Transmitted Radiation / Incident Radiation
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38. Remote Sensing Process
5. Recording of Energy by the Sensor (D)
 The reflected radiation or electromagnetic energy by
the features is received and recorded by the sensors
 Sensor must be located on a stable platform not in
contact with the target.
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39. Remote Sensing Process
5. Recording of Energy by the Sensor (D)
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40. Remote Sensing Process
6. Transmission, Reception, and Processing (E)
 The energy recorded by the sensor has to be
transmitted,
 Receiver and processing station receive the data
 Data are processed into an image (hardcopy and/or
digital).
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41. Remote Sensing Process
7. Interpretation and Analysis (F)
 The processed image is interpreted, visually and/or
digitally or electronically, (Digital Image Processing)
 Information about the target is extracted
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42. Remote Sensing Process
8. Application (G)
 Apply the information we have been able to extract
from the imagery
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43. Platform and Sensors
 Sensor is the instrument that measure the
electromagnetic energy emitted from the
objects on the earth
 Platform is the carrier of the sensor
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44. Platform and Sensors
 A sensor is a device used to acquire a
photograph or an image, it measure the amount
of radiated energy reflected from an object
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45. Sensor Types
 Aerial Camera: is a passive sensor that collects a direct,
continuous tone pictorial image in the visible light (0.4–
0.7µm) range.
 Video Camera: installed on aircraft. This passive sensor
records a continuous band of raster data covering a
moving scene of the terrain, and the videotape can be
played on a graphic screen much like a video movie.
 Scanner: is passive sensors that capture the reflected or
emitted energy intensity from observed objects into
digital picture elements called pixels.
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46. Platform Types
 Airborne: downward or sideward looking sensors are
mounted on an aircraft to obtain images of the earth's
surface
 Satellite: is a celestial body orbiting around a planet.
The moon is a natural satellite moving around the Earth.
The first artificial satellite was launched by the Soviet
Union and since then many artificial satellites have been
launched mostly for communication but also for
observing the Earth and taking images
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47. Images Types and Bands
 An image is defined by Liew, 2001 as a two-
dimensional representation of objects in a real
scene.
 Remote sensing images are representations of parts
of the earth surface as seen from space.
 The images may be analog or digital.
 Aerial photographs are examples of analog images
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48. Images Types and Bands
 A digital image is a two-dimensional
array of pixels.
 Each pixel has an intensity value
(represented by a digital number) and a
location address (referenced by its row
and column numbers).
 Each of these pixels contains
information about the study area which
the image covers describing the
monitored feature as a physical
quantity represented by the energy in
specific wavelength.
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49. Images Types and Bands
 Multilayer images can be formed by combining
images obtained from different sensors, and
other subsidiary data
 Multispectral image consists of several bands of
data
 Hyperspectral image consists of about a
hundred or more contiguous spectral bands
forming a three-dimensional (two spatial
dimensions and one spectral dimension)
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50. Images Types and Bands
 Band is defined as the wavelength interval in
the electromagnetic spectrum
 Different satellites have different amount of
bands and each band measure a specific feature
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51. Images Types and Bands
• All colors created from additive primary colors:
– Red
– Green
– Blue
• Complementary colors:
– Magenta
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52. Images Types and Bands
 When these three colours are combined in
various proportions, they produce different
colours in the visible spectrum.
 Combining different bands may cause a false
colour, known as false colour composite.
 true colour composite, means that the resulting
image has the same visible color photograph
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53. 53
Vegetation
Urban
3,2,1 (RGB) 4,3,2 (RGB)
4,5,3 (RGB)
Images Types and Bands
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54. Resolution
 Spatial: Related to size in 2 dimensional space.
 Spectral: Related to a range of EM Radiation.
 Temporal: Related to frequency and time.
 Radiometric: Related to electronic sensitivity
and digital byte size.
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55. Resolution
 Spatial:
 The size of the smallest object that can be
resolved on the ground
 This is related to the pixel size
 "High Resolution" image refers to one with a
small resolution size.
 "Low Resolution" image is one with a large
resolution size
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56. Resolution
 Spatial:
10 m Resolution, 10 m Pixel 30 m Resolution, 10 m Pixel
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57. Resolution
 Spectral
 It describes the specific wavelengths that the
sensor can record within the electromagnetic
spectrum.
 For example, the “photographic infrared” band
covers from about 0.7 – 1.0 micrometers.
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58. Resolution
 Spectral
1-Band 3-Band
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59. Resolution
Temporal
 It is a description of how often a sensor can
obtain imagery of a particular area of interest.
 For example, the Landsat satellite revisits an
area every 16 days as it orbits the Earth, while
the SPOT satellite can image an area every 1 to 4
days.
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60. Resolution
Radiometric
 Radiometric Resolution refers to the smallest
change in intensity level that can be detected by
the sensing system.
 In a digital image, the radiometric resolution is
limited by the number of discrete quantization
levels used to digitize the continuous intensity
value.
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61. Resolution
Radiometric
The number of discernable signal levels is determined
by the number of digital bit levels used to record the
data. Bit levels act exponentially.
1 Bit = 21 possible signal levels (DNs).
3 Bit = 23 = 8 possible signal levels (DNs).
8 Bit = 28 = 256 possible signal levels (DNs).
24 Bit = 224 = 16,777,216 possible signal levels (DNs).
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62. The ability of a sensor to perceive differences in
brightness value levels
22 or 4 intensity levels
28 or 256 intensity levels
3
2
1
1
2
0
0
3 2
3
2
1
1
2
0
0
3 2
Sensor “A”
Sensor “B”
225
190
72
124
137
63
0
255 141
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Resolution
Radiometric

63. Resolution
Radiometric
8-bit quantization (256 levels) 6-bit quantization (64 levels)
4-bit quantization (16 levels) 3-bit quantization (8 levels)
2-bit quantization (4 levels) 1-bit quantization (2 levels)
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