Remote Sensing_2020-21 (1).pdf

REMOTE SENSING
LECTURE NOTES
2020-2021
PROF. DR. FÜSUN BALIK ŞANLI

Outline
1. Definition
2. History of remote sensing
3. Principles of radiation
4. Radiation-target interaction
5. Spectral signatures
6. Resolution
7. Satellite orbits
8. Applications

What is remote sensing ?
• Remote – away from or at a
distance
• Sensing – detecting a
property or characteristic

Remote sensing
The term "remote sensing," first used in
the united states in the 1950s by Ms.
Evelyn Pruitt of the U.S. Office of naval
research

"REMOTE SENSING IS TEACHING US A NEW WAY OF SEEING".
REMOTE SENSING HAS BEEN DEFINED IN MANY WAYS.
Remote Sensing Definitions

Definition 1
Remote sensing is "the acquisition of
information about an object,
without being in physical contact
with that object"

Definition 2
Remote sensing is "the ability to measure the properties of an
object without touching it".

Definition 3
Remote sensing can be defined as "the collection of data about an
object from a distance. Humans and many other types of animals
accomplish this task with aid of eyes or by the sense of smell or
hearing".

Remote sensing is "the examination, measurement, and analysis of
an object without being in contact with it".
Definition 4

Remote sensing is "the science and art of obtaining information
about an object, area, or phenomenon through the analysis of
data acquired by a device not in contact with the object, area, or
phenomenon in question".
Definition 5

Remote sensing is "the science (and to some extent, art)
of acquiring information about the earth's surface
without actually being in contact with it. This is done by
sensing and recording reflected or emitted energy and
processing, analyzing, and applying that information".
Definition 6

Remote sensing is by definition "the science of gathering information about
phenomena using devices that are not in contact with the object.
Currently remote sensing technologies include a number of differing air
and space borne instruments that gather data about the earth and its
features".
Definition 7

Remote sensing is a method for getting information about of different
objects on the planet, without any physical contacts with it.
Image Source: cimss.ssec.wisc.edu
Definition 8

Science and art of obtaining information about an object, area or
phenomenon through an analysis of data acquired by a device
that is not in direct contact with the area, object or phenomenon
under investigation.
Lillesand, Thomas M. and Ralph W. Kiefer, “Remote Sensing and Image Interpretation”
John Wiley and Sons, Inc, 1979, p. 1
What are some common examples of remote sensors?
Definition 9

Remote sensing is a technology for sampling electromagnetic radiation to acquire and read
non-immediate geospatial data from which to pull info more or less features and objects on
the earths land surface, seas, and air.
- Dr. Nicholas Short
Definition 10
What we see & why
Eyes: Sunlight is reflected onto our nerve cells in the retina.
What we see: Visible spectrum (blue, green, red
wavelengths)
Remote sensing equipment allows us to sense electromagnetic
radiation beyond the visible spectrum

The Importance of RS
• Large amounts of data needed, and Remote Sensing can provide it
• Reduces manual field work dramatically
• Allows retreval of data for regions difficult or impossible to reach:
• Open ocean
• Hazardous terrainn (high mountains, extreme weather areas, etc.)
• Ocean depths
• Atmosphere
• Allows for the collection of much more data in a shorter amount of time
• Leads to increased land coverage and
• Increase ground resolution of a GIS
• Digital imagery greatly enhances a gis
• DIRECTLY: imagery can serve as a visual and
• INDIRECTLY: can serves as a source to derive information such as…
• Land use/land cover
• Atmospheric emisions
• Vegetation
• Water bodies
• Cloud cover
• Change detection (ıncludıng sea ıce, coastlines, sea levels, etc.)

• Provides a view for the large region
• Offers Geo-referenced information and digital information
• Most of the remote sensors operate in every season, every day,
every time and even in real tough weather
A summary RS

History of Remote Sensing
1609 - Invention of the telescope
Galileo

• 1839, the first photographs.
• 1849, used photography in
topographic mapping.
• 1858, balloons were being used to
acquire photography of large
areas.

1859 - First aerial photographer
Gaspard Felix Tournachon, also known as Nadar
1862 - US Army balloon corp

1909 - Dresden International
Photographic Exhibition
1903 - The Bavarian Pigeon Corps

1914-1918 - World War I
1908 - First photos from an airplane
First flight, Wright Bros., Dec. 1903

• Mid 1930s, color photography.
• Aerial photography became widespread
during world war II, with improved
lenses and platform stability, enemy
positions and military installations could
be identified from aircraft.
• Radar
1930-1945

• Cameras were launched on rockets as this science
expanded in the post-world war II era.
• In 1957, the Russians launched the first successful earth
satellite, Sputnik 1
• In 1958, the US launched its first satellite, Explorer 1.
• In 1959, the first satellite with a meteorological
instrument (Vanguard 2) was launched.
• In 1960, the first satellite images ever made of the earth
comes from the Tiros 1
1945-1960

• This was the age of instrument development.
• In 1964, the Nimbus satellite series of experimental meteorological
remote sensing was initiated.
• By 1966, meteorological satellites moved from being experimental to
being operational with the introduction of the ESA series of satellites
which included automatic picture.
• The defense meteorological satellite program (DMSP) was started by
the U.S. Air force in 1966.
• 1972, Landsat 1 (also referred to as earth resources technology
satellite.
1960-1972

• 1975: the synchronous meteorological satellites.
• 1976: laser geodynamic satellite.
• 1978: the heat capacity mapping mission.
• 1978: SEASAT demonstrated techniques for global monitoring of the
earth's oceans.
• 1978: NIMBUS 7, the final satellite in that series, was launched.
• 1984: the earth radiation budget (ERBE) satellite began its study of how
the earth absorbs and reflects the sun's energy.
• 1991: the upper atmosphere research satellite (UARS) began its study of
the chemistry and physics of the earth's atmosphere.
• Today, the goes (geostationary operational environmental satellite) system
of satellites provides most of the remotely sensed weather information for
North America.
1972-Present

REMOTE SENSING
• "Remote sensing is the science of acquiring information about
the Earth's surface without actually being in contact with it. This is
done by sensing and recording reflected or emitted energy and
processing, analyzing, and applying that information."
Sensor
Object
to be
sensed
Electro Magnetic Radiation
Three Essential Things for Remote Sensing

Solar Energy
Incident Radiation
Absorption
Scattering
Reflected energy
Thermal emission
Transmission
Platforms
& Sensors
Ground Borne
Air Borne
Space Borne
Antenna
Data Processing
Data Products Soft Copy
Data Products Hard Copy
Visual Interpretation
Digital Interpretation
Outputs Softcopy
Outputs Hard Copy
Decision Making

SIX STAGES IN REMOTE SENSING
Stage-1. Source of energy
Stage-2. Transmission of EMR towards the Object
Stage-3. Interaction of EMR with the Object
Stage-4. Transmission of Interacted EMR towards the Sensor
Stage-5. Recording of the Image by the Detector
Stage-6. Analysis of the Imagery
1
2
3
4
5 (Film)
6
3
3
4

The element of the remote sensing process
1) Energy source or illumination
2) Radiation and the atmosphere
3) Interaction with the target
4) Recording of energy by the
sensor
5) Transmission, reception, and
processing
6) Interpretation and analysis
7) Application

Electromagnetic energy is emitted in waves
Amount of radiation emitted from
an object depends on its temperature
Planck Curve
Principles of radiation
Electromagnetic radiation consists of an
electrical field(E) which varies in magnitude
in a direction perpendicular to the direction in
which the radiation is traveling, and a
magnetic field (M) oriented at right angles to
the electrical field. Both these fields travel at
the speed of light (c).

Electromagnetic radiation energy: Wave-particle duality.
Particle=photon Wavelength

Light speed: c=f 
c = speed of light (186,000 miles/second)
f = light frequency: number of waves passing a reference per unit time
(e.g., second).
The amount of energy carried by a photon:  = hf
h=Planck’s constant (6.62610-34 Js)
Note: The shorter the radiations’ wavelength, the higher its frequency  the
more energy a photon carries
Photons move at the speed of light in wave form

Remote Sensing_2020-21 (1).pdf

INFRARED (IR) REGION
Electromagnetic Spectrum
• Covers the wavelength range from approximately 0.7 µm to 100
µm
• Divided into two categories based on their radiation properties –
the reflected IR(0.7-3.0 µm), NIR(0.7-1.1µm), SWIR(1.55-1.7
µm) and TIR(3-14 µm).

• Radiation in the reflected IR region is used for remote sensing
purposes in ways very similar to radiation in the visible portion.
The reflected IR covers wavelengths from approximately 0.7 µm
to 3.0 µm.
• Photographic IR ranges from 0.7 to 0.9 µm
REFLECTED IR

REFLECTED IR
• Radiation in the reflected IR region is used for remote sensing
purposes in ways very similar to radiation in the visible portion.
The reflected IR covers wavelengths from approximately 0.7 µm
to 3.0 µm.
• Photographic IR ranges from 0.7 to 0.9 µm

THERMAL IR
MICROWAVE REGION
•The microwave region from about 1 mm to 1m
•The thermal IR region is quite different than the visible and reflected IR
portions, as this energy is essentially the radiation that is emitted from the
Earth's surface in the form of heat. The thermal IR covers wavelengths from
approximately 3.0 µm to 100 µm. But the heat energy is sensed in windows
at 3 to 5.5 µm and 8 to 14 µm.

INTERACTION WITH
THE ATMOSPHERE

 Radiation used for remote sensing reaches the Earth's surface
it has to travel through some distance of the Earth's
atmosphere.
 Particles and gases in the atmosphere can affect the incoming
light and radiation.
 These effects are caused by the mechanisms of scattering
and absorption.

Reflection: the direction
predictable
Scattering: direction
unpredictable
Based on wavelength of incident
radiant energy, the size of the
gas molecule, dust particle, or
water vapor droplet essentially
three types of scattering:
• Rayleigh
• Mie
• Non-selective scattering
Water
Droplets
Atmospheric Scattering

SCATTERING
• Scattering occurs when
particles or large gas molecules
present in the atmosphere
interact with and cause the
electromagnetic radiation to be
redirected from its original path.

• Rayleigh scattering occurs particles are
very small compared to the wavelength of
the radiation
 Small specks of dust or nitrogen
and oxygen molecules
 The fact that the sky appears "blue"
during the day is because of this
phenomenon.
 Rayleigh Scattering  1/λ4
RAYLEIGH SCATTERING

MIE SCATTERING
• Mie scattering occurs when the
particles are just about the same size
as the wavelength of the radiation.
e.g., Dust, pollen, smoke and water
vapour
• Mie Scattering  1/ λ to 1/λ2

NONSELECTIVE SCATTERING
• This occurs when the particles are
much larger than the wavelength of the
radiation. Water droplets and large dust
particles can cause this type of
scattering.
• Nonselective scattering gets its name
from the fact that all wavelengths are
scattered in all directions without
following any law.

Two questions:
•Why is the sky blue?
•Why is the sunset orange?
Color of the Sky

•Why is the sky blue?
–A clear cloudless day-time sky is blue because
molecules in the air scatter blue light from the sun more
than they scatter red light
•Why is the sunset orange ?
–When we look towards the sun at sunset, we see red
and orange colors because the blue light has been
scattered out and away from the line of sight
•http://math.ucr.edu/home/baez/physics/General/BlueSky/blue_sky.html
Color of the Sky

The first requirement for remote sensing is to have an energy source
to illuminate the target (unless the sensed energy is being emitted by
the target). This energy is in the form of electromagnetic radiation.
Radiation that is not absorbed or scattered in the atmosphere can
reach and interact with the Earth's surface. There are three (3)
forms of interaction that can take place when energy strikes, or is
incident (I) upon the surface. These are:
• Absorption (A)
• Transmission (T) and
• Reflection (R)
The total incident energy will interact with the surface in one or
more of these three ways. The proportions of each will depend on
the wavelength of the energy and the material and condition of
the feature.
Radiation - Target Interactions

Incident energy (I) from the source
Absorption (A) occurs when
radiation (energy) is absorbed into the
target
Transmission (T) occurs when
radiation passes through a target
Reflection (R) occurs when radiation
"bounces" off the target and is
redirected.
Radiation - Target Interactions

Radiation - target interactions
• Spectral response depends on target
• Leaves reflect green and near IR
• Water reflects at lower end of visible
range

When a surface is smooth we get
specular or mirror-like reflection where
all (or almost all) of the energy is
directed away from the surface in a
single direction.
When the surface is rough and the energy
is reflected almost uniformly in all
directions.
SPECULAR REFLECTION
DIFFUSE REFLECTION

• Specular reflection (a):
smooth (i.e., the average
surface profile is several
times smaller than the
wavelength of radiation)
• Diffuse reflection (b): rough,
the reflected rays go in many
directions
• Lambertian surface (d) the
radiant flux leaving the
surface is constant for any
angle of reflectance to the
surface normal
REFLECTANCE

• Because certain gases absorb electromagnetic energy in
very specific regions of the spectrum, they influence the
wavelengths, which reach the Earth available for remote
sensing.
• Those areas of the spectrum which are not severely
influenced by atmospheric absorption and thus, are useful
to remote sensors, are called atmospheric windows.
ATMOSPHERIC WINDOWS

Atmospheric windows:
Spectral regions in which the atmosphere blocks the energy are
shaded. Remote-sensing data acquisition is limited to the unblocked
spectral regions called atmospheric windows
Each type of molecule has its own set of absorption bands in various
parts of the electromagnetic spectrum. As a result, only the
wavelength regions outside the main absorption bands of the
atmospheric gases can be used for remote sensing.
Atmosferic windows

The transmission and absorption phenomenon varying with the
wavelength
Atmosferic windows

Spectral reflectance curve

SPECTRAL REFLECTANCE OF
VEGETATION,SOIL AND WATER

Strong absorption in blue
and red bands. Reflection
depends on the amount of
chlorophyll in the leaf.
SPECTRAL REFLECTANCE OF VEGETATION

Reflectance peaks in
green, corresponds with
solar maximum

Major reflectance peaks in
NIR, provides energy
balance for vegetation

Water absorption at
1.4 and 1.9 microns
due to leaf moisture

Soil reflectance generally increases gradually from visible to infrared.
SPECTRAL REFLECTANCE OF SOIL

Molecular water absorptions at
1.4 and 1.9 microns
SPECTRAL REFLECTANCE OF SOIL

Spectral Signature Curves
B1 B2 B3 B4 B5 B6 B7
0
15
30
45
60
75
90
105
120
135 CLASS:WATER
Ambazari
Phutala
Gorewada
Gandhi sagar
Lendi talav
DN
VALUES
BANDS
Class: Water
0 2 4 6 8
20
40
60
80
100
120
140
160
CLASS:
THICK VEGETATION
BANDS
DN
VALUES
VNIT NEERI
Koradi Road
20
40
60
80
100
120
140
160
DN
VALUES
Seminary Hills
Class: Thick vegetation

THE BASIC ELEMENTS AND
SAMPLING CHARACTERISTICS
OF SATELLITE ORBITS

IoE 184 - The Basics of Satellite Oceanography. 1. Satellites and Sensors
The basic principles of space technology;
1. The basic elements and sampling characteristics of satellite
orbits;
2. Electromagnetic spectrum and satellite sensors;
3. Active and passive sensors;
4. Data transmission to the Earth;
5. Orbit determination techniques.

All Earth-orbiting satellites have elliptical orbit, or the special case of
a circular orbit.
The basic principles of space technology

orbits - Satellite orbital dynamics
a*e is the displacement of the ellipse center from the center of the Earth;
θ is the angle between the satellite's present radius vector and that at perigee (the orbit's
closest point to the Earth).
a is the semi-major axis of the ellipse;
e is the eccentricity of the ellipse;
For the elliptical orbit the distance r of the
satellite from the center of the Earth is given by
the equation:

From Newtonian dynamics, the period
T for the satellite to travel round the
orbit is
T = 2π (a3 /GM)1/2
where G is the constant of gravitation and M the mass of the Earth, and G * M
= 3.98603 * 1014 m3 s-2 .
The instantaneous rate at which the satellite describes its orbit is
dθ / dt = [G * M * a ( 1 - e2 ) ]1/2 * r-2.

When e is small, a = a * (1-e) and the
orbit is called
“circular orbit”.
In this case the horizontal speed of the
satellite is
V0 = ( G * M / a) 1/2.
Taking into account:
R = 6378 km - Earth's mean equatorial
radius;
g = G * M / R2 - the acceleration due
to gravity.
Hence, V0 = R * [ g / (R+ h)]1/2.

The instantaneous orbital rate of the
satellite V0 and the period it travels
round the orbit T (i. e., the spatial and
temporal resolution of satellite
observations) directly depend on its
orbital axis a (i. e., the height above
the Earth h).
Higher orbit has longer period
and lower orbit has shorter period.

During launch the rocket must be fired to obtain a trajectory such
that at the desired height h of the satellite, its speed is V0 ,
assuming that a circular orbit is required.
• If when the satellite reaches h it is traveling horizontally at speed V, then if V<V0 the
satellite will fall into an elliptical orbit for which a<(h+R).
• Alternatively if V>V0, the satellite moves out into a higher ellipse and a>(h+R) .
• If V>2 * V0 then the elliptical orbit becomes parabolic and the satellite reaches
escape velocity and never returns.

Satellite orbital elements on the celestial shell

So far we have identified six orbital elements
which characterize a satellite's position:
θ - the angular position of the satellite in its
orbit,
a - the semi-major axis of the ellipse,
e - the eccentricity of the ellipse,
i - the inclination of the orbital plane to the Earth equatorial plane,
Ω - the right ascension of the ascending node N, measured eastward from the point of Aries which is a
fixed point in the heavens,
w - the angular distance of perigee around the orbit, measured from the ascending node.
In fact d Ω /dt  -(G*M) 1/2 R2 * a -7/2 (1-e2) -2*cos(i).

For Earth observation, three types of orbit are
most useful:
The satellite orbits in the same direction as the Earth with a period of one day. It is positioned in a circular
orbit above the equator. Therefore, it becomes stationary relative to the Earth and always views the same
area of the Earth's surface.
From equation T = 2π (a3 /GM)1/2 :
T = 1 day = 86400 seconds => a = 42,290 km =>
h = a - R = 35,910 km.
1. Geostationary orbit
Orbit types

• Geosynchronous
- Orbital period of 1 day, i.e., satellite stays over the same spot on the
Earth
- Orbital radius is 42,164 km or 35,786 km above the Earth’s surface
at the Equator where the Earth’s radius is 6.378 * 106
m
- Used for many communication satellites;
> Cover a country like Australia
> Don’t require complex tracking dishes to receive the signals;
Note: satellite stay stationary relative to Earth
SATELLITE OBSERVATONS

most useful:
i (inclination) ~ 90o.
Usually these satellites have height between 500 and 2,000 km and a period of about1 to 2 hours.
As the Earth rotates under this orbit the satellite effectively scans from north to south over one face and south to north
across other face of the Earth, several times each day, achieving much greater surface coverage than if it were in a non-
polar orbit.
2. Polar orbit
Orbit types

most useful:
From equation for d Ω /dt it is possible for a given orbit height by a suitable selection of the
inclination i to achieve d Ω /dt = 0.986 per day, which is equivalent to one rotation of the
orbit plane per year.
In this way the orbit plane is not fixed relative to stars, but fixed relative to the sun. The result is
sun-synchronous orbit, in which the satellite crosses the equator at the same local solar time on
each pass throughout the year.
In practice i is about 100, i. e., the orbit is not polar, but nearly polar.
3. Nearly polar sun-synchronous orbit
Orbit types

• Highly Elliptical Orbits (HEO)
- Typically pass low (1,000 km) over the southern regions,
then loop high over the northern regions
- One pass every 4 to 12 h
- Used in communications to provide coverage of the
higher latitudes and the polar regions
SATELLITE OBSERVATIONS

Orbit characteristics of oceanographic near-polar sun-synchronous satellites
Satellite TIROS-N NOAA-6 NOAA-7 NIMBUS-7
Semi-major
axis a (km)
7244 7202 7250 7335
Semi-minor
axis (km)
7229 7185 7232 7174
Nominal
height h (km)
855 815 860 950
Orbit
inclination i ()
98.9 98.7 98.9 99.3
Period (min) 102.2 101 102.3 104.9
Local equator
crossing time
07.30
south-bound
15.00
north-bound
07.30
south-bound
12.00
north-bound
Orbits per day 14.1 14.2 14.1 13.7

orbits
Spatial and temporal sampling
characteristics of orbits
From the orbital period of sun-synchronous satellite we
can estimate the distance between successive ground
tracks. For example, for Landsat 1 the period is 103.2
min, and the distance is 25.8 degrees, which
corresponds to a spacing at the equator of about
2,865 km. The distance between tracks decreases with
latitude.
Another important characteristic of remotely sensed data is the swath-width of the sensor.
Typical swath-width is 1,500-2,000 km.

Satellite Orbit Determines...
• …what part of the globe can be viewed.
• …the size of the field of view.
• …how often the satellite can revisit the same place.
• …the length of time the satellite is on the sunny side of the
planet.

Data acquisition - satellite orbits
Satellites:
•Sun-synchronous (Landsat, SPOT)
•Geostationary (TIROS)
Satellites:
Sun-synchronous (Landsat, SPOT)
Geostationary (TIROS)

• Lower Earth Orbit (LEO)
- Orbit at 500 - 3,000 km above the Earth (definition varies)
- Used for reconnaissance, localized weather and imaging
of natural resources.
- Space shuttle can launch and retrieve satellites in this orbit
- Now coming into use for personal voice and data
communications
- Weather satellites
> Polar orbit - Note, as the satellite orbits, the Earth is turning
underneath. Current NOAA satellites orbit about 700 - 850 km
above Earth’s surface
> Orbital period about every 98 - 102 min
Satellite Observations
Types of Orbits acording to the height

• Medium Earth Orbit (MEO)
- Orbit at 3,000 - 30,000 km (definition varies)
- Typically in polar or inclined orbit
- Used for navigation, remote sensing,
weather monitoring, and sometimes
communications
> GPS (Global Position System) satellites
‡ 24-27 GPS satellites (21+ active, 3+
spare) are in orbit at 20,000 km
(about 10,600 miles) above the Earth;
placed into six different orbital planes,
with four satellites in each plane
‡ One pass about every 12 h
Types of Orbits acording to the height

• Geosynchronous
- Weather satellites
> GOES (Geosynchronous Operational Environmental Satellites)
Satellite

2. Sensors on satellites
All sensors employed on ocean-observing satellites use electromagnetic radiation to view the
sea. This radiation travels through free space at the speed of light c ~ 3*108m s-1 .
The frequency f and wave length λ are related by f  λ = c.
So, the electromagnetic spectrum used in the sensor can be characterized by wavelength λ
and/or frequency f.

The electromagnetic spectrum, showing some bands definitions and typical remote-sensing
applications.

Emission spectra at different temperatures.

Approximate transmittance of electromagnetic waves through the atmosphere.

The choice of bands for remote-sensing application is governed by both the application and
the atmospheric transmission spectrum. Hence, if features of the land and sea are to be
observed by the reflection of incident solar radiation in the same way as the human eye
observes, then the frequency range 100 nm - 100 m should be used. Alternatively, if the
self-emission of radiation by the sea is to be means of remote sensing, sensors should be used
for the 3 to 40 m wavelength range. However, not all the parts of these ranges are useful,
since the atmosphere will not transmit them, as illustrated by the typical transmission spectrum
of the atmosphere.

Usually the range 400 nm - 1 m is used to measure visible waves and about 10 m for
infrared measurements.
Above 10 mm there is very little absorption. These radar bands are exploited by active
microwave sensors which create their own radiation with which to illuminate the target, and then
observe the nature of the reflected signal, in contrast to passive IR and visible wavelength
sensors which rely on naturally occurring radiation.

Passive sensors Wavelength Information
Visible wavelength
radiometers
400 nm - 1 m Solar radiation reflected
by Earth surface
Infrared (IR) radiometers about 10 m Thermal emission of the
Earth
Microwave radiometers 1.5 - 300 mm Thermal emission of the
Earth in the microwave
Active devices
Altimeters 3 - 30 GHz Earth surface
topography
Scatterometers 3 - 30 GHz Sea surface roughness
Synthetic aperture
radars
3 - 30 GHz Sea surface roughness
and movement

Passive sensors measure incoherent
electromagnetic radiation.
Active sensors illuminate the target (the sea) with
their own pulse of electromagnetic radiation; hence,
they measure not only the amplitude but also the
phase of the reflected signal and the travel time of
the pulse.

Types of RS system
Active RS system Passive RS
system
Artificial Energy
source
Natural Energy
source
e.g. radar systems
SLAR,SAR
e.g.sensors on
satellites
Landsat,SPOT

Remote sensing systems
Human eye
Camera
Radiometer
Radar
Sonar
Laser
• Passive
• Active
{
{

Type  Based on source of the energy recorded by the sensor
1. Passive Remote Sensing: Energy collected by sensors is either
reflected or emitted solar radiation.
• Reflected – must be collected during daylight hours
• Emitted – day or night as long as emissions large enough to record
2. Active Remote Sensing: Energy collected by sensors is actively
generated by a man-made device.
Examples: Radar, LIDAR (Light Detection and Ranging)

AVHRR Thermal Image
http://www.coml.org/edu/tech/count/srs1.htm
QuikSCAT radar image
http://nsidc.org/seaice/study/active_remote_sensing.html
Active and Passive Remote Sensing
A thermal image taken by a geostationary
satellite positioned over the western
Atlantic; warmer water moved along by
the Gulf Stream current is denoted in
reddish-orange.
Infrared imaging: Method of remote
sensing in which optical sensors produce
visible representations of infrared rays or
radiated heat from the observed objects
and the temperature variations are
represented by different colors in the
image.
Scatterometer image of Antarctica, 19 July
2003, from the QuikSCAT (quick
scattterometer) satellite. This composite
image is centered over the South Pole.
Antarctica stands out with a white outline.
Surrounding Antarctica is a large region of
sea ice, shown in medium grey. Sea ice
typically reflects more of the radar energy
emitted by the sensor than the surrounding
ocean, so it appears brighter in a
scatterometer image. The black hole over
the South Pole is a region that the
QuikSCAT satellite does not reach. Image
courtesy of David Long, Brigham Young
University Center for Remote Sensing.

- Ground based
- Aircraft
- Space shuttle
- Satellite
Remote sensing platforms

Satellite Remote Sensing
Resolutions
Spatial: Area visible to the sensor
Spectral: Ability of a sensor to define fine
wavelength intervals
Temporal: Amount of time before site revisited
Radiometric: Ability to discriminate very slight
differences in energy
Scanner types
Along-track
Across-track

• Image depends on the wavelength response of the sensing
instrument (radiometric and spectral resolution) and the emission or
reflection spectra of the target (the signal).
- Radiometric resolution
- Spectral resolution
• Image depends on the size of objects (spatial resolution) that can
be discerned
- Spatial resolution
• Knowledge of the changes in the target depends on how often
(temporal resolution) the target is observed
- Temporal resolution
Four fundamental properties for design

• Number of shades or
brightness levels at a given
wavelength
• Smallest change in intensity
level that can be detected by
the sensing system
Radiometric resolution

80 x 80
Spatial Resolution
320 x 320
40 x 40

Coarser resolution satellite sensors used
LANDSAT Thematic Mapper
Good for regional coverage
30m MS resolution
15 m panchromatic resolution
Most Common Use:
Land Cover/Land Use Mapping
MODIS
36 spectral bands
Most Common Uses:
Cloud/Aerosol Properties
Ocean Color
Atmospheric Water Vapor
Sea/Atmospheric Temperatures

Higher Resolution Satellite Sensors Used
Quickbird
2.5 m multispectral resolution
61 cm (~2 ft.) panchromatic
resolution
IKONOS
4 m visible/infrared resolution
1 m panchromatic resolution
MOST COMMON USES FOR HIGH RESOLUTION:
Accurate Base Maps
Infrastructure Mapping
Disaster Assessment (Smaller Scale)

Spectral response differences
TM Band 3 (Red) TM Band 4 (NIR)

• Example: Black and
white image
- Single sensing device
- Intensity is sum of
intensity of all
visible wavelengths
Can you tell the color of the
platform top?
How about her sash?
0.4 m 0.7 m
Black &
White
Images
Blue + Green + Red
Spectral resolution

• Example: Color image
- Color images need
least three sensing
devices, e.g., red, green,
and blue; RGB
Using increased spectral
resolution (three sensing
wavelengths) adds
information
In this case by “sensing”
RGB can combine to
get full color rendition
0.4 m 0.7 m
Color
Images
Blue Green Red
Spectral resolution

• Example
- What do you believe the
image would look like if you
used a blue only sensitive film?
used a green only sensitive film?
used a red only sensitive film?
Spectral resolution

• Example
- Blue only sensitive film
- Green only sensitive film
- Red only sensitive film
Spectral resolution

• Example
used near and middle
infrared sensitive film?
Spectral resolution

• Example
used a thermal infrared
sensitive film?
Blinded in the darkness, he extended his arms, felt around for obstacles, both to avoid and to
hide behind. The men wearing infrared monocular night-vision units, the lenses strapped
against their eyes by means of a head harness and helmet mount, were doubtless also carrying
handguns. The others had rifles fitted with advanced infrared weapon sights. Both allowed the
user to see in total darkness by detecting the differentials in thermal patterns given off by
animate and inanimate objects.
Ludlum, Robert, 2000: The Prometheus Deception, p. 96.
Spectral resolution

• Example
used a thermal infrared
sensitive film?
Spectral resolution

• Example - Thermal infrared view
Note warmer objects are brighter
Heat - energy transfer

Example of sampling wavelengths
Spectral resolution

Application of Temporal Data: Urban Sprawl
Atlanta, GA
1973 1987

Across-track scanning
Scan the Earth in a series of lines
Lines perpendicular to sensor motion
Each line is scanned from one side of the
sensor to the other, using a rotating mirror
(A).
Internal detectors (B) detect & measure
energy for each spectral band, convert to digital
data
IFOV or Instantaneous Field of View (C) of the
sensor and the altitude of the platform determine the
ground resolution cell viewed (D), and thus the
spatial resolution.
The angular field of view (E) is the sweep of the
mirror, measured in degrees, used to record a scan
line, and determines the width of the imaged swath
(F).
http://ccrs.nrcan.gc.ca/resource/tutor/fundam/chapter2/08_e.php
Scanner types

Scanner types
Along-track scanning
Uses forward motion to record successive scan lines perpendicular
to the flight direction
Linear array of detectors (A) used; located at the focal plane
of the image (B) formed by lens systems (C)
• Separate array for each spectral band
Each individual detector measures the energy for a single
ground resolution cell (D)
• May be several thousand detectors
• Each is a CCD
• Energy detected and converted to digital data
“Pushed" along in the flight track direction (i.e. along track).
“Pushbroom scanners”

Along-track scanners also use the forward motion of the platform to record successive scan lines and build
up a two-dimensional image, perpendicular to the flight direction. However, instead of a scanning mirror, they
use a linear array of detectors (A) located at the focal plane of the image (B) formed by lens systems (C),
which are "pushed" along in the flight track direction (i.e. along track). These systems are also referred to as
pushbroom scanners, as the motion of the detector array is analogous to the bristles of a broom being
pushed along a floor. Each individual detector measures the energy for a single ground resolution cell (D)
and thus the size and IFOV of the detectors determines the spatial resolution of the system. A separate linear
array is required to measure each spectral band or channel. For each scan line, the energy detected by each
detector of each linear array is sampled electronically and digitally recorded.
Along Track mode does not have a mirror looking off at varying angles. Instead there is a line of small
sensitive detectors stacked side by side, each having some tiny dimension on its plate surface; these may
number several thousand. Each detector is a charge-coupled device (CCD), as described in more detail
below on this page. In this mode, the pixels that will eventually make up the image correspond to these
individual detectors in the line array. As the platform advances along the track, at any given moment radiation
from each ground cell area along the ground line is received simultaneously at the sensor and the collection
of photons from every cell impinges in the proper geometric relation to its ground position on every individual
detector in the linear array equivalent to that position. The signal is removed from each detector in
succession from the array in a very short time (milliseconds), the detectors are reset to a null state, and are
then exposed to new radiation from the next line on the ground that has been reached by the sensor's
forward motion. This type of scanning is also referred to as pushbroom scanning (from the mental image of
cleaning a floor with a wide broom through successive forward sweeps). As signal sampling improves, the
possibility of sets of linear arrays, leading to area arrays, all being sampled at once will increase the
equivalent area of ground coverage.

CLASSIFICATİON - SUPERVISED TRANING

Applications of Remote Sensing
• Images serve as base maps
• Observe or measure properties or conditions
of the land, oceans, and atmosphere
• Map spatial distribution of “features”
• Record spatial changes

Generating Topographic
Map Data
DSM-based ortho-image
(false-color).
DEM

Change Detection - Flooding
Landsat imagery of the 1993 Mississippi flood

Change Detection - Flooding

Quantifying Urban Sprawl
San Francisco Bay

Change Detectıon -Urban Sprawl

MONITORING
WEATHER
GOES-8 Water Vapor

DETECTING
AND
MONITORING
WILDLAND
FIRES
Arizona, June 2002
Borneo

MONITORING SEA SURFACE TEMPERATURE

GOES AND MODIS
SPATIAL AND
TEMPORAL
RESOLUTION
• GOES sounder – temporal resolution every hour; spatial resolution
(10 km)
• MODIS instrument on the polar orbiting platforms - up to four
passes a day, two daytime and two nighttime; spatial resolution
(1 km)
AQUA MODIS 24 JAN 2004 GOES LST 2 AM CST

GOES AND MODIS SPECTRAL RESOLUTION
MODIS observes 36 separate frequencies of
radiation, ranging from visible to infrared. GOES
detects only five frequencies.
http://science.nasa.gov/headlines/y2004/09jan_sport.htm

LAND SURFACE TEMPERATURE (LST)
COMPARISON
DRY PERIOD
• JUNE 25-JULY 3, 2004
• JULY 25-AUGUST 3, 2004
WET PERIOD
• JUNE 26-JULY 3, 2005
• JULY 23-31, 2005

LST PRODUCTS
MODIS/TERRA LAND SURFACE TEMPERATURE/EMISSIVITY
DAILY L3 GLOBAL 1 KM SIN GRID (MOD11A1)
DATA SET CHARACTERISTICS
• AREA = ~ 1100 X 1100 KM IMAGE DİMENSİONS = 2 (1200 X 1200
ROW/COLUMN)
• AVERAGE FILE SIZE = 24 MB
• RESOLUTION = 1 KILOMETER (ACTUAL 0.93 KM)
• PROJECTION = SINUSOIDAL
• LAND SURFACE TEMPERATURE (LST) DATA TYPE =16-BİT UNSİGNED INTEGER
• EMISSIVITY DATA TYPE = 8-BİT UNSİGNED INTEGER
• DATA FORMAT = HDF-EOS
• SCİENCE DATA SETS (SDS) = 12
THE MODIS/TERRA LAND SURFACE TEMPERATURE/EMISSIVITY DAILY L3 GLOBAL 1KM
SIN GRID PRODUCT, MOD11A1, IS A GRIDDED VERSİON OF THE LEVEL-2 DAILY LST
PRODUCT. IT IS GENERATED BY PROJECTING MOD11_L2 PİXELS TO EARTH
LOCATIONS ON A SINUSOIDAL MAPPING GRID.

MODIS/TERRA LAND SURFACE TEMPERATURE/
EMISSIVITY DAILY L3 GLOBAL 1 KM SIN GRID
SDS Units Data
Type-bit
Fill
Value
Valid
Range
Multiply
By Scale
Factor
Add
Additional
Offset
Daily daytime
1 km grid Land-
Surface
Temperature
Kelvin 16-bit
unsigned
integer
0 7500-
65535
0.0200 na
Daily nighttime
1 km grid Land-
Surface
Temperature
Kelvin 16-bit
unsigned
integer
0 7500-
65535
0.0200

LAND COVER PRODUCTS
MODIS/TERRA LAND COVER TYPE YEARLY L3 GLOBAL 1 KM
SIN GRID
VERSION VOO4
• THE MOD12 CLASSIFICATION SCHEMES ARE MULTITEMPORAL CLASSES DESCRIBING
LAND COVER PROPERTIES AS OBSERVED DURING THE YEAR (12 MONTHS OF INPUT
DATA).
• THESE CLASSES ARE DISTINGUISHED WITH A SUPERVISED DECISION TREE
CLASSIFICATION METHOD

LEGEND MOD12Q1 LAND COVER TYPE 5
Land Cover Class
Fill Value 255
Water 0
Evergreen needleleaf trees 1
Evergreen broadleaf trees 2
Deciduous needleleaf trees 3
Deciduous broadleaf trees 4
Shrub 5
Grass 6
Cereal crop 7
Broadleaf crop 8
Urban and built up 9
Snow and ice 10
Barren or sparse vegetation 11

How data is extracted:
• Layers such as roads (yellow) and rivers (blue) can be easily seen from
air/satellite photos
• This information is digitized (see next slide), separated into layers, and
integrated into a GIS

Remote Sensing_2020-21 (1).pdf

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