Fundamental of Remote Sensing Chapter_3.ppt material for Geographers.

This is Fundamental of Remote Sensing Chapter_3.ppt material for Geographers.

1. Fundamentals of Remote Sensing
GeES3032
GGK
1 May, 2024
By: Andualem F (MA

2. 2 May, 2024

3. A satellite is any natural or artificial body moving around a heavenly body
such as planets and stars.

In our context, reference is made only to artificial satellites orbiting the
planet Earth.

These satellites are put into the desired orbit and have a payload depending
upon the intended application.
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3.1 Satellites

4. Satellites…
4
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5. 1. Polar Orbiting Satellites (Sun Synchronous)
Are running between N and S Poles with inclination angle
between 80 to 100 degrees.
Pass over all places on earth having the same altitude
twice in each orbit at the same local sun time.
They are considered Low Earth Orbiters (LEO), which orbit the Earth at an
altitude of approximately 300 km.
Offer a higher resolution.
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3.1.1 Types of RS Satellites, Based on Orbit

6. Polar Orbiting Satellites, Continued…
Examples:

Landsat
SPOT
NOAA
IRS etc.
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7. Orbits the Earth in an equatorial orbit.
Placed above the equator at a distance of some 36,000km.
Its period is equal to that of the Earth's rotation (24 hours).
Offer a continuous view.
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2. Geostationary Satellites

8. Continued…
Examples:
GOES
METEOSAT
INTELSAT
INSAT etc.
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9. Continued…
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10. Types of Satellites Based on Purpose
1. Communication Satellites
Provides communication over long distances by reflecting or
relaying signals radio-frequency

.
Examples:
Score,1958 by USA (the
1
st
active communication satellite)
Echo 1, 1960 by USA
Telstar 1, 1962 by USA
Echo 2, 1964 by USA
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11. 2. Metrological Satellites (Weather Satellites)
Are used to monitor weather conditions and weather forecasting around the
globe
Examples:
TIROS-1, 1960 by USA
ATS-1, 1966, by USA, NASA
GOES 1, 1975 by USA
NOAA AVHRR, 1983 by USA
GOES 7, 1992 by USA
GOES 8, 1994 by USA
Continued…
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12. Continued…
3. Resource Satellites
Are optimized for detailed mapping of
the land surface
Landsat -1, by NASA, USA in
1972 (the 1
st
satellite to monitor
the Earth’s surface)
SPOT-1, by France in 1986
IRS-1C, by India in 1995
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Examples:

13. Continued…
4. Marine Observation Satellites
Are used for monitoring the
oceans of the planet.
Examples:
MOS-1,by Japan in 1987 (the 1
st

marine observation satellite)
MOS-1b, by Japan in 1990
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14. Continued…
5. Strategic (Military) Satellites
Are used for surveillance of a wide
variety of targets of interest to
military intelligence units.
Examples:
IKONOS, by USA in 1999 (the first
commercial high resolution satellite)
QuickBird, by USA in 2001
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15. Satellites have several unique characteristics which make them
particularly useful for remote sensing of the earth’s surface.
1. Orbit:
refers to the path followed by a satellite.
Orbit selection can vary in terms of:
Their orientation and rotation relative to the earth
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3.1.2 Characteristics of Satellites

16. 2. Altitude:
Refers to the distance (in Km) from the satellite to the mean
surface level of the earth.
The distance influences to a large extent which area is viewed and
at which detail.
Polar orbit, 600 – 800 km
Geostationary orbit, 36,000 km
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Continued…

17. 3. Inclination Angle:
Refers to the angle made by the plane of the orbit with respect
to the plane of the equator.
It determines:
The felid of view of sensor
The latitude to be observed
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Continued…

18. 4. Period:
Refers to the time (in minutes) required to complete one full orbit.
The speed of the platform has implications for the type of images that
can be acquired (time for ‘exposure’).
5. Repeat Cycle :
Refers to the time between two subsequent images of the same area or the time
(in days) between two successive identical orbits.

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Continued…

19. Continued…
6. Swath:
As a satellite revolves around the Earth,
the sensor "sees" a certain portion of
the Earth's surface.
The area imaged on the surface, is
referred to as the swath.
The swath for satellite image is very large
between tens and hundreds of kilometers
wide.
Swath
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20. Continued…
7. Nadir:
If we start with any randomly selected pass
in a satellite's orbit, an orbit cycle will be
completed when the satellite retraces its
path, passing over the same point on the
Earth's surface directly below the satellite
(called the nadir point) for a second time.
Is the point of shortest distance from the
satellite, immediately below it.
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21. Continued…
8. Descending and Ascending Passes:
The path traversed by satellite when it
moves from north to south is called
descending and its journey from south
to north is ascending.
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22. Continued…
9. IFOV (Instantaneous Field of View):
Refers to the solid angle through which a
detector is sensitive to radiation.
Is the angular cone of visibility of the sensor
(A) and determines the area on the Earth's
surface which is "seen" from a given altitude
at one particular moment in time (B).
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23. Cont…
The size of the area viewed is determined by multiplying the
IFOV by the distance from the ground to the sensor (C).
This area on the ground is called the resolution cell and
determines a sensor's maximum spatial resolution.

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24. A platform is a stage to mount to
the camera or sensor bout a target
under acquire the information a
investigation.
Based on their altitude a platforms
may be classified in to above earth
surface, different types.

3.2 Platforms
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25. Are platforms that position the sensor at the Earth's surface.
Ground Based Platforms are fixed to the Earth.
Ground-based sensors can be placed on tall structures such as towers,
scaffolding, or buildings to elevate the platform.
Ground-based sensors are generally less expensive to operate and maintain
than aircraft or satellite sensors.
They do not provide the aerial extent of the airborne platforms.
Are often used to record detailed information about the surface.
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3.2.1. Ground Based Platforms

26. Continued…
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27. Are most often sensors mounted on fixed-wing aircraft, though other
airborne platforms, such as balloons, rockets, and helicopters can be used.
Aerial systems elevate the sensor above the Earth's surface in order to
increase its aerial coverage.
More recently, cameras mounted on aircraft have been used to monitor land
use practices, locate forest fires, and produce detailed and accurate maps of
remote or inaccessible locations on our planet.
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3.2.2 Airborne Platforms

28. Continued…
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29. Airborne Remote Sensing
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30. Here platforms are freely moving in their orbits around the
earth carrying different types of sensors.
Are very expensive.
Demand higher stage of technological advancement.
Covers large area even the entire world at fractions of periods.
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3.2.3 Space Borne Platforms

31. Continu ed…
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32. A sensor is a device that measures and records electromagnetic
energy.
Sensors are classified in to two based on their energy
illumination.
3.3 Sensors
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33. November 29, 2017 33
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34. Are those which are designed to detect naturally occurring energy.
Depend on an external source of energy, usually the sun (although rally
occurring energy is sometimes the earth itself)
Can only work when the natu available.
Cover the EM spectrum in the range from gamma
rays to micro & radio waves.
3.3.1 Passive Sensors
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35. Passive Detection
Camera or sensor
scattering
transmittance
absorption
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36. Examples:
The gamma ray spectrometer
Video camera
Photo camera without flash
Multispectral scanner
Imaging Spectrometer
Thermal scanner
Radiometer
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Continued…

37. Provide their own energy source for illumination of the target.
Illuminate radiation at the target and use sensors to measure how the target
interacts with the energy.
They can be used for examining energy types that are not
sufficiently provided by the sun, such as microwaves or
to mandated better control the way a target is illuminate
Active Sensor stems require the generation of a fairly
large amount of energy to adequately
They are used to obtain mea illuminate targets
regardless of the time of day or season
3.3.2 Active Sensors
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38. Active Detection
received signal
transmitted signal
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39. Examples:
Laser scanner
Radar altimeter
Doppler radar
Atmospheric sounder
Imaging radar
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Continued…

40. 40 May, 2024
Electromagnetic energy may be detected either photographically or
electronically.
It is important to distinguish between the terms images
and photographs in remote sensing.
An image refers to any pictorial representation, regardless of what wavelengths or
remote sensing device has been used to detect and record the electromagnetic
energy.
A photograph refers to images that have been detected as well as recorded on
photographic film over the wavelength range from 0.3 µm to 0.9 µm in the visible
and reflected infrared.
All photographs are images, but not all images are photographs.
3.4 Sensor and Image Data Characteristics

41. Picture element have both spatial and spectral properties.
oThe spatial property defines the "on ground" height and width.
oThe spectral property defines the intensity of spectral response
for a cell in particular band.
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Continued…

42. Continued…
The ‘quality’ of image data is primarily determined by characteristics of the
sensor-platform system.
Data collected by remote sensing systems can be in either analog format (e.g.
hardcopy aerial photography) or digital format (e.g. a matrix of “brightness
values” or video data) corresponding to the average used within an image
pixel.

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43. The success of data collection from remotely sensed imagery requires an
understanding of four basic resolution characteristics of sensors.
Resolution:
Is defined as the ability of the system to extract the information at the
smallest discretely separable quantity in terms of distance (spatial),
wavelength band of EMR ( spectral), time (temporal) and radiation
quantity ( radiometric).
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3.4.1 Sensor Characteristics

44. Refers to the smallest unit area measured, it indicates the minimum size
of objects that can be detected.
It is a measurement of the minimum distance between two objects that
will allow them to be differentiated from one another.
Spatial resolution determines the level of spatial details that can be
observed on the earth’s surface.
The higher the spatial resolution means the higher the detail it will show.
High spatial resolution: 0.5 - 4 m
Medium spatial resolution: 4 - 30 m
Low spatial resolution: 30 - >1000 m
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1. Spatial Resolution

45. Continued…
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46. Spatial Resolution, Continued…
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47. Refers to the ability of the sensor to define fine wavelength intervals or
the number of spectral band within which images acquired.
Refers to the Number and position of bands in the electromagnetic
spectrum that the sensor measures.
High spectral resolution is achieved by narrow bandwidths and more
number of bands.
High spectral resolution: - 220 bands
Medium spectral resolution: 3 - 15 bands
Low spectral resolution: - 3 bands
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2. Spectral Resolution

48. Continued…
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49. Refers to the sensitivity of the sensor to the magnitude of the electromagnetic
energy.
The radiometric resolution of an imaging system describes its ability to
discriminate very slight differences in energy.
The finer the radiometric resolution of a sensor, the more sensitive it is to
detecting small differences in reflected or emitted energy.
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3. Radiometric Resolution

50. Refers to the revisiting frequency of a satellite sensor for a specific
location.
The time between two successive image acquisitions over the same
location on the earth.
High temporal resolution: < 24 hours - 3 days
Medium temporal resolution: 4 - 16 days
Low temporal resolution: > 16 days
Example: Landsat = 16 days
4. Temporal Resolution
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51. A. Image size:
The number of rows and columns in a scene.
B. Number of bands:
The number of wavelengths band stored.
C. Quantization:
The data format used to store the
measurements (Value of Digital Numbers)
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energy
D. Ground pixel size:
The area coverage of a pixel on the ground.
3.4.2 Image Data Characteristics

52. E. Gray Scale:
Gray scale is a color scale that ranges from black to white, with varying
intermediate shades of gray.
A value of 0 represents a pure black color, the value of 255 represents pure
white, and each value in between represents a progressively darker shade of
grey.
Continued…
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53. 1.Spatio-temporal characteristics:
How much is the pixel resolution?
Does it have Altitudinal information?
Does the acquisition Time proper?
2.Availability of image data:
Is the data available?
Where can we get?
3.Cost of Image data:
Is the data affordable?
How much does it cost?
3.5 Data Selection Criteria
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54. Data collected from a remote sensing system must be
retrieved and delivered to the end users.
The transmission, re
distribution of data from
carefully designed to me
ception, processing, and
a satellite sensor must be et
the users' needs.
3.6 Communication and Data Collection
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55. Ground-based remote sensing platforms can transmit data using ground-
based communication systems, such as radio and microwave transmissions
or computer networks.
Data collected in an aircraft can be stored on board and retrieved once the
aircraft lands.
Satellite data, however, is very difficult to obtain since the satellite remains
in space during its entire operational lifetime.
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Continued…

56. This data must be transmitted back to the Earth to a ground receiving
station, which can receive the data and process it for distribution to the end
user.
A satellite can transmit data directly to a ground receiving station that is
within its line of sight.
When the satellite is not in sight of a ground station, it can store its data on
board and "dump" the data later, when it is back in sight of a ground station.
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Continued…

57. 58
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