42. What is REMOTE SENSING ?
REMOTE SENSING includes all
methods and techniques used to
gain qualitative and quantitative
information about distant objects
without coming into direct contact
with these objects.
Look-Look, NO Touch
43. What is REMOTE SENSING ?
Remote Sensing (RS) methods try to
answer four basic questions:
HOW MUCH of WHAT is WHERE?
What is the SHAPE and EXTENT
of ... ? (Area, Boundaries, Lineaments, ...)
Has it CHANGED?
What is the MIX of Objects
44. What is REMOTE SENSING ?
HOW MUCH of WHAT is WHERE?
WHAT: Type, Characteristic and
Properties of Object. Eg. Water,
Vegetation, Land; Temperature,
Concentration, State of Development;
Subtype, Species, Use of ... ;
Includes determination of generic
object type, character and property
as well as it’s abstract meaning.
=> DATA INTERPRETATION
45. What is REMOTE SENSING ?
HOW MUCH of WHAT is WHERE?
HOW MUCH: determine by simple
COUNTING, measuring AREA covered or
percentage of total area coverage.
WHERE: Relate locations and area covered
to either a standard map or to the actual
location on the ‘ground’ where the object
occurs.
NOTE: WHERE also refers to a moment in time
46. What is REMOTE SENSING ?
What is the SHAPE and EXTENT
of ... ? (Area, Boundaries, Lineaments, ...)
This extends the ‘WHERE’ to be a completely
GEOMETRIC problem. MAP PRODUCTION
methods are to be applied to the analysis of
RS information. These include:
Photogrammetric Methods:
Identification and Delineation of Boundaries
and Lineaments (Roads, Rivers, Fault Lines)
47. What is REMOTE SENSING ?
Has it CHANGED?
CHANGE may occur with progress of TIME.
Change may be detected through comparison of
observed states at different moments in time.
=> CHANGE DETECTION
48. What is REMOTE SENSING ?
What is the MIX of Objects?
The surface of the Earth is covered by
objects like Soil, Water, Grass, Trees,
Houses, Roads and so on. These are
‘GENERIC OBJECTS’. We know these
well, but we also know objects like Open
Forest, Residential and Industrial
Estates, etc. Each of these ABSTRACT
OBJECTS are made up of a typical
collection of Generic Objects.
49. What is REMOTE SENSING ?
What is the MIX of Objects?
One important task for Remote Sensing is to
identify
GENERIC OBJECTS as well as
ABSTRACT OBJECTS within areas of
interest
The following lessons will be devoted to
techniques and methods as well as to the
logistic for finding answers to the four
basic questions.
50. What is REMOTE SENSING ?
Remote Sensing (Look-
Look, No Touch) is a
much wider field than we
will discuss in this lecture
series. We will
Vision Medical Imaging
concentrate on that part
of RS dealing with
EARTH LAND
RESOURCES
Sound and Radio Wave Detection
51. What is REMOTE SENSING ?
What makes it tick ???
(1) RS requires a CARRIER of information,
which can bridge distances.
(2) RS requires a SENSOR which can detect
changes in the carried Signal.
(3) RS requires RECORDING, ANALYSIS,
INTERPRETATION and
REPRESENTATION of the sensed
information in a purposeful way.
52. What is REMOTE SENSING ?
(1) RS requires a CARRIER of information,
which can bridge distances.
These Carriers of Information are FIELDS of
FORCES:
* Pressure Wave Fields of Sound,
* Gravity Force Fields,
* Magnetic Force Fields and
* Electro-magnetic Force Fields.
The latter are of our main interest, since they
include visible and invisible LIGHT.
53. What is REMOTE SENSING ?
(2) RS requires a SENSOR which can detect
changes in the carried Signal.
Apart from our own eyes and ears, technology has
provided us with a multitude of sensors operating
in the detection of force fields:
microphones, geophones,
photographic film, video cameras and photo
detectors,
radio wave receivers, gravimeters and
magnetometers.
54. What is REMOTE SENSING ?
(3) RS requires RECORDING, ANALYSIS,
INTERPRETATION and
REPRESENTATION of the sensed
information in a purposeful way.
This is a technique based topic. It is essential
for the success or failure of RS in respect of
it’s anticipated purpose.
This topic will be dealt with in it’s main
aspects (but not completely) in the
following lessons.
55. What is REMOTE SENSING ?
Sensor System eg. Camera
Source of Force
Field
Resulting RS Data Set
DATA eg. Image
ACQUISITION
Reflection
Object (generic)
56. What is REMOTE SENSING ?
DATA
PROCESSING
Interpretation
(secondary) Measurements
Data Processing & Mapping (geometric)
Presentation of Processing Results
Explaining deduced OBJECT INFORMATION
RS Data Set
eg. Image
Object(s)
57. ER, the Physical Basis of RS
Fraunhofer, Joseph (1877-1826), German optician and
physicist, Spectroscopy
Wien, Wilhelm (1864-1928), German physicist, 1911
Nobel Prize in Physics, Wien’s Displacement Law
Planck, Max Karl Ernst Ludwig (1858-1947), German
physicist, 1918 Nobel Prize in Physics, laid basis to
Quantum Physics, developed Planck’s Law
Einstein, Albert (18779-1955), German(?) physicist,
1921 Nobel Prize in Physics, General Theory of
Relativity, and E = m c^2
Serious, Jahoo (still alive), son of Tasmanian apple
grower,, How to put bubbles into beer: E = m c^2
58. ER, the Physical Basis of RS
Fraunhofer discovered ‘black
lines’ in the spectrum of light
emitted by various superheated
chemical elements. These lines
Fraunhofer Lineswere as typical for each of the
elements as fingerprints for
humans.
Chemical Composition of
objects effects emitted ER
in a unique way for each
element.
(found empirically by observation)
59. ER, the Physical Basis of RS
In Einstein's formula
E = mc^2
Fraunhofer Lines E = Energy
m = mass (of matter/object)
c = propagation velocity of
light
What does that tell us ?
There is a well defined
relationship between
MATTER, ENERGY and
2 ELECTROMAGNETIC
E = mc RADIATION (eg. light)
60. ER, the Physical Basis of RS
The basic building blocks of all
matter are ATOMS
The basic building blocks of
Atoms are the NUCLEUS
(Neutrons and Protons) and
several ELECTRONS.
Electrons are thought to be
spinning around the
Nucleus at orbits of
different, but well pre-
defined discrete sequential
radii.
61. ER, the Physical Basis of RS
Neutrons are thought to carry NO
Energy charge.
Protons are thought to carry a
charge of energy defined as
being positive.
Electrons are thought to carry a
charge of energy defined as
being negative.
Because of the dual polarity
(positive <=> negative) an
energy potential exists
between Nucleus and
Electrons
62. ER, the Physical Basis of RS
An equal number of Electrons
and Protons exist in all atoms
(isotopes excluded).
A balance exists quasi
mechanical between the
attraction forces of opposite
charges and centrifugal forces
of the spinning Electrons.
This balance is an intricate
compromise of these forces
and the actual energy level
inherent to each atom.
63. ER, the Physical Basis of RS
The energy level contained in
an atom can be changed
(eg. by heating or cooling).
The balance of forces inside
the atom will automatically
adept to energy level
changes by moving
electrons to higher or
lower orbits.
64. ER, the Physical Basis of RS
To have an electron move
from it’s current orbit to the
next outer orbit, an energy
amount equal to one
Planck’s Quantum has to
be added to the atom (eg.
by heating).
To have an electron drop back
from an outer orbit to the
next inner one, the same
amount of energy has to be
extracted from the atom.
65. ER, the Physical Basis of RS
It is this EXTRACTION of
energy from an atom when
electrons drop back to
lower orbits which is of
interest to us.
One widely accepted theory
says, that atoms lose
energy in form of
Electromagnetic
Radiation
Energy differential = 1 Planck’s Quantum
66. ER, the Physical Basis of RS
Electromagnetic
Radiation
One theory explains ER as a
WAVE field,
another as a field of a stream
of PHOTONS, particles so
small that they have no
mass.
Both are said to propagate at
Wave light speed.
Photon
Energy differential = 1 Planck’s Quantum E = mc^2
67. ER, the Physical Basis of RS
c = const ~ 300000 km/sec
Electromagnetic Radiation
Some atoms may have been
charged to a higher energy
level; pushing electrons
further than one orbital level.
In turn they can drop back
over more than one orbit
level: more energy than one
Quantum
Wave
Photon
Energy differential = 1 Planck’s Quantum E = mc^2
68. ER, the Physical Basis of RS
c = const ~ 300000 km/sec
2 Quantum charge Electromagnetic Radiation
Gerd’s interpretation:
Since c is constant, all photons
travel about 300,000 km/sec
Those with a higher energy
charge will use a ‘more
wiggly’ (thus, longer) wave
path than those with lesser
charge.
Wave
Photon
Energy differential = 1 Planck’s Quantum E = mc^2
69. ER, the Physical Basis of RS
Electromagnetic Radiation
Wave characteristics:
λ λ = Wave length = distance
between consecutive wave
peaks (measured in µm)
f = frequency = number of wave
peaks (wiggles) in the wave
train propagating for 1 sec
(measured in Hz)
λ=c/f
c = const ~ 300000 km/sec
70. ER, the Physical Basis of RS
Electromagnetic Radiation
Summing up:
λ High Energy Radiation
proceeds at higher
frequencies (shorter
wavelength compared to low
energy radiation.
Radiation wave length mix
depends on amount of (heat)
energy contain in an atom
PLANCK’s LAW
c = const ~ 300000 km/sec
71. ER, the Physical Basis of RS
PLANCK’s LAW
λ
Total Radiation
Energy emitted
Radiation Energy Curve for
an object (BLACK BODY)
at constant temperature.
peak
short long
c = const ~ 300000 km/sec Wave Length λ
72. ER, the Physical Basis of RS
WIEN’s DISPLACEMENT LAW
Total Radiation
λ Energy emitted
Radiation Energy Curves for
an object (BLACK BODY)
at various constant
temperatures.
6000K
3000k
1000K
300K
0K = -273 degree Celsius short long
300K = 27 degree Celsius Wave Length λ
73. ER, the Physical Basis of RS
Using Fraunhofer’s Observations
A Black Body is a theoretical, not a
real object.
λ
Real Objects will produce somewhat
different radiation output pattern.
Radiation Energy Curve for
an object at constant temperature.
Gerd’s real
object
short long
c = const ~ 300000 km/sec Wave Length λ
74. ER, the Physical Basis of RS
Using Fraunhofer’s Observations
The variation in Radiation output from a REAL OBJECT
depends on it’s chemical composition. Water has a different
SPECTRAL SIGNATURE than soil or chlorophyll containing
leaf matter, etc.
QUESTIONS:
Radiation Energy Curve for
• Can we use these facts to
an object at constant temperature.
measure object temperatures?
• Can we use these facts to Gerd’s real
identify the chemical object
composition of objects and
• can we use the latter to
short long
identify the object itself?
Wave Length λ
75. ER, the Physical Basis of RS
The Average Temperature ofWIEN’s DISPLACEMENT
Earth’s Surface rarely LAW
exceeds 300 K, an object Total Radiation
temperature to low to Energy emitted
Radiation Energy Curves for
provide for EMITTED
an object (BLACK BODY)
RADIATION of sufficient at constant temperatures.
strength to register on most 6000K
of the available sensors 3000k
(except in thermal IR). 1000K
300K
(Even warm nights can be pitch
black) short long
Wave Length λ
76. ER, the Physical Basis of RS
The surface of the Sun’s outer WIEN’s DISPLACEMENT
atmosphere (photosphere) LAW
has a temperature of about Total Radiation
5800K, hot enough to Energy emitted
Radiation Energy Curves for
provide adequate radiation
an object (BLACK BODY)
energy. (Peak output in at constant temperatures.
GREEN of visible light). 6000K
3000k
Most RS systems utilise
1000K
reflected sun light.
300K
short long
Wave Length λ
77. ER, the Physical Basis of RS
WIEN’s DISPLACEMENT
QUESTION: Does incident
LAW
sun light interact in a Total Radiation
similar way with matter as Energy emitted
described is the case for Radiation Energy Curves for
emitted radiation? an object (BLACK BODY)
at constant temperatures.
ANSWER: YES! 6000K
ER (including light) is a form 3000k
of energy (as is heat). Matter 1000K
(atoms) can absorb as well as 300K
emit energy.
short long
Wave Length λ
78. ER, the Physical Basis of RS
Objects under illumination by
sun light will partially WIEN’s DISPLACEMENT
absorb radiation.
Total Radiation
Absorption level varies with Energy emitted
wave length depending on Radiation Energy Curves for
chemical composition of an object (BLACK BODY)
the object at constant temperatures.
6000K
Radiation not absorbed is 3000k
mostly reflected and 1000K
available for RS. 300K
Spectral Signatures short long
Wave Length λ
79. ER, the Physical Basis of RS
Examples of Spectral Signatures
(not to exact scale; see Textbook)
%
Reflectance Vegetation (green)
(of Sun Light)
50
Bare Soil (Grey/Brown)
Water (clear)
0
µm
(<= UV) 0.4 (blue) 0.5 (green) 0.6 (red) 0.7 (IR=>) 0.8 1.0
80. ER, the Physical Basis of RS
The Electromagnetic Spectrum
(not to exact scale; see Textbook)
Wave Length
10^-6 10^-3 0.1 1 100 10^5 10^8 µ m
(.... Sound
not part of ER)
Micro-
γ -Rays X-Ray UV Wave
TV/Radio
Note: outside
Thermal Infrared the visible Range,
Visible Near & Mid Infrared no colours or
shades will be
Blue Green Red perceived.
0.4 0.5 0.6 0.7 µ m
81. ER, the Physical Basis of RS
The General Remote Sensing
Radiation Model
Source
S
I = Incident ER Sensor
R = Reflected Simplified
A = Absorbed Radiation-
T = Transmitted I Balance
S = Scattering
I=R+A+T
R
R=I-A-T
T
A A
82. ER, the Physical Basis of RS
A bright Idea for RS
% G R IR
Vegetation (green)
Reflectance
(of Sun Light)
Bare Soil (Grey/Brown)
50 Truth Table
Veg. Soil
G med med
R low high
IR high+ high
0
µm
(<= UV) 0.4 (blue) 0.5 (green) 0.6 (red) 0.7 (IR=>) 0.8 1.0
83. ER, the Physical Basis of RS
Truth Table
A bright Idea for RS Veg. Soil
G med med
R low high
IR high+ high
G R IR