introduction to remote sensing instructor dr. abdul-wahab mashat

Introduction to Remote SensingIntroduction to Remote Sensing

InstructorInstructorDr. Abdul-Wahab MashatDr. Abdul-Wahab Mashat

د./ عبدالوهاب سليمان مشاطد./ عبدالوهاب سليمان مشاطمحاضر المادة: محاضر المادة:

05055200960505520096الجوال: الجوال:

البريد االلكتروني:البريد االلكتروني:[email protected]

Feel free to send me an e-mail with any questions Feel free to send me an e-mail with any questions about the course or if you want to arrange an about the course or if you want to arrange an appointment.appointment.

الصفحة الشخصية على اإلنترنت: الصفحة الشخصية على اإلنترنت:

http://amashat.kau.edu.sahttp://amashat.kau.edu.sa//

Text:Text: Class NotesClass Notes Jensen, J. R,Jensen, J. R, 2006: Remote Sensing of Environment. Prentice 2006: Remote Sensing of Environment. Prentice

Hall; 2 edition.Hall; 2 edition.

References:References: Campbell, J. B, 2006Campbell, J. B, 2006: Introduction to Remote Sensing. The : Introduction to Remote Sensing. The

Guilford Press, Fourth EditionGuilford Press, Fourth Edition.. Chuvieco, E, 2007Chuvieco, E, 2007: Fundamentals of Satellite Remote Sensing, : Fundamentals of Satellite Remote Sensing,

CRC-Press.CRC-Press. Cracknel, A. P, 2006: Introduction to Remote Sensing. Taylor & Cracknel, A. P, 2006: Introduction to Remote Sensing. Taylor &

Francis, 2Francis, 2ndnd Edition. Edition. Elachi, C. and van Zyl, J. J,Elachi, C. and van Zyl, J. J, 2006: Introduction to The Physics 2006: Introduction to The Physics

and Techniques of Remote Sensing. Wiley-Interscience.and Techniques of Remote Sensing. Wiley-Interscience. Grainger, R. G,Grainger, R. G, 2007: Atmospheric Remote Sounding, CRC- 2007: Atmospheric Remote Sounding, CRC-

Press.Press. Jensen, JJensen, J, 2006: Introduction to Remote Sensing. Prentice Hall, , 2006: Introduction to Remote Sensing. Prentice Hall,

2nd Edition.2nd Edition. Rees, W. G,Rees, W. G, 2001: Physical Principles of Remote Sensing. 2001: Physical Principles of Remote Sensing.

Cambridge University Press; 2nd edition.Cambridge University Press; 2nd edition. Verbyla, D,Verbyla, D, 1995: Satellite Remote Sensing of Natural 1995: Satellite Remote Sensing of Natural

Resources. CRC-Press.Resources. CRC-Press.

Grading PoliciesGrading Policies:: QuizQuiz 20%20% Term PaperTerm Paper 20%20% HomeworkHomework 20%20% LabLab 20%20% Final ExamFinal Exam 20%20%AttendanceAttendance will be taken. Grades will be awarded on the basis of a “curve”. Homework, and term will be taken. Grades will be awarded on the basis of a “curve”. Homework, and term

paper must be done independently and submitted on time. Late submission will be penalized. paper must be done independently and submitted on time. Late submission will be penalized. Submission must be neat and clean on A4 paper. All examinations will be of the closed-book, Submission must be neat and clean on A4 paper. All examinations will be of the closed-book, closed-notes type. If needed, pocket calculators may be used. closed-notes type. If needed, pocket calculators may be used. Cheating will not be allowedCheating will not be allowed!!!!

: المادة :مواضيع المادة مواضيعتعريف االستشعار عن بعدتعريف االستشعار عن بعد

مناقشة التعاريف المختلفة لالستشعار عن بعد، أمثلة لالستشعار عن بعد مناقشة التعاريف المختلفة لالستشعار عن بعد، أمثلة لالستشعار عن بعد مثل آلة التصوير، ...مثل آلة التصوير، ...

تاريخ االستشعار عن بعدتاريخ االستشعار عن بعد

بداية تاريخ االستشعار عن بعد، التطور الهائل الذي حصل خالل الحرب بداية تاريخ االستشعار عن بعد، التطور الهائل الذي حصل خالل الحرب العالمية األولى والثانية، والحرب الباردة في مجال االستشعار عن بعد.العالمية األولى والثانية، والحرب الباردة في مجال االستشعار عن بعد.

عناصر عملية االستشعار عن بعدعناصر عملية االستشعار عن بعد

مصدر الطاقة أو الضوء، الوسط )الغالف الجوي(، الهدف، جهاز مصدر الطاقة أو الضوء، الوسط )الغالف الجوي(، الهدف، جهاز االستقبال، عملية معالجة البيانات، تفسير وتحليل البيانات، التطبيق.االستقبال، عملية معالجة البيانات، تفسير وتحليل البيانات، التطبيق.

أنظمة االستشعار عن بعد السالبة والفعالةأنظمة االستشعار عن بعد السالبة والفعالة

األجهزة السالبة، األجهزة الفعالة.األجهزة السالبة، األجهزة الفعالة.

: المادة مواضيع :تكملة المادة مواضيع تكملةأساسيات تعريف األجسامأساسيات تعريف األجسام

الشكل، المقاس أو الحجم، اللون، النمط، الظل، القوام.الشكل، المقاس أو الحجم، اللون، النمط، الظل، القوام.

الخرائط وفن رسم الخرائطالخرائط وفن رسم الخرائط

المقياس، اإلسقاط، الرموز.المقياس، اإلسقاط، الرموز.

مبادئ الموجات الكهرومغناطيسيةمبادئ الموجات الكهرومغناطيسية

طول الموجه، التردد، سرعة الضوء، االشعاع، االشعة التحت حمراء، طول الموجه، التردد، سرعة الضوء، االشعاع، االشعة التحت حمراء، االشعة المرئية، ...االشعة المرئية، ...

األساسيات الفيزيائية لالستشعار عن بعداألساسيات الفيزيائية لالستشعار عن بعد

الطيف الكهرومغناطيسي، قوانين األشعة الكهرومغناطيسية.الطيف الكهرومغناطيسي، قوانين األشعة الكهرومغناطيسية.

: المادة مواضيع :تكملة المادة مواضيع تكملة

تطبيقات االستشعار عن بعدتطبيقات االستشعار عن بعد

أمثلة عن تطبيقات االستشعار عن بعد في علوم األرصاد الجوية.أمثلة عن تطبيقات االستشعار عن بعد في علوم األرصاد الجوية.

الدراسات البحثية الحديثة الجارية، والبرامج المستقبليةالدراسات البحثية الحديثة الجارية، والبرامج المستقبلية

االطالع على األبحاث الجارية والمستقبلية وذلك باستخدام االنترنت.االطالع على األبحاث الجارية والمستقبلية وذلك باستخدام االنترنت.

Introduction to Remote SensingIntroduction to Remote Sensing المشكلة: دراسة األحوال المشكلة: دراسة األحوال

الجوية، حماية البيئة، الجوية، حماية البيئة، تلوث الهواء، الكوارث تلوث الهواء، الكوارث

الطبيعية، ...الطبيعية، ... لحل أي مشكلة نحتاج لحل أي مشكلة نحتاج

إلى جمع معلومات، إلى جمع معلومات، وجمع المعلومات يحتاج وجمع المعلومات يحتاج

إلى جهد وزمن وتكاليف إلى جهد وزمن وتكاليف باهظة.باهظة.

What is remote sensingWhat is remote sensing? ?

Remote – away Remote – away from or at a from or at a distancedistance

Sensing – detecting Sensing – detecting a property or a property or characteristic characteristic

Remote SensingRemote SensingThe term "remote The term "remote

sensing," first used in the sensing," first used in the United States in the United States in the 1950s by Ms. Evelyn 1950s by Ms. Evelyn Pruitt of the U.S. Office Pruitt of the U.S. Office of Naval Researchof Naval Research

DefinitionsDefinitions

""Remote sensing is teaching us Remote sensing is teaching us a new way of seeinga new way of seeing".".

Remote sensingRemote sensing has been defined has been defined in many waysin many ways..

Definition (1)Definition (1)

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


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


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


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


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


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


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

بعد عن بعد اإلستشعار عن اإلستشعار

علم يختص بجمع المعلومات عن علم يختص بجمع المعلومات عنهدف ما من مسافة بعيدة دون أن هدف ما من مسافة بعيدة دون أن

يكون هناك اتصال مباشر بين الهدف يكون هناك اتصال مباشر بين الهدف وجهاز االلتقاط وذلك باستخدام وجهاز االلتقاط وذلك باستخدام

خواص الموجات الكهرومغناطيسية خواص الموجات الكهرومغناطيسية المنبعثة أو المرتدة أو المنعكسة.المنبعثة أو المرتدة أو المنعكسة.

Brief History of Remote Brief History of Remote SensingSensing

1839, the first 1839, the first photographs.photographs.

1849, used photography 1849, used photography in topographic mapping.in topographic mapping.

1858, balloons were 1858, balloons were being used to acquire being used to acquire photography of large photography of large areas.areas.

1925-19451925-1945

Mid 1930s, color photography.Mid 1930s, color photography. Aerial photography became Aerial photography became

widespread during World War II, widespread during World War II, with improved lenses and with improved lenses and platform stability, enemy platform stability, enemy positions and military installations positions and military installations could be identified from aircraft.could be identified from aircraft.

RadarRadar

1945-19601945-1960 Cameras were launched on rockets Cameras were launched on rockets

as this science expanded in the as this science expanded in the post-World War II era.post-World War II era.

In 1957, the Russians launched the In 1957, the Russians launched the first successful Earth satellite, first successful Earth satellite, Sputnik 1 Sputnik 1

In 1958, the US launched its first In 1958, the US launched its first satellite, Explorer 1.satellite, Explorer 1.

In 1959, the first satellite with a In 1959, the first satellite with a meteorological instrument meteorological instrument )Vanguard 2( was launched.)Vanguard 2( was launched.

In 1960, the first satellite images In 1960, the first satellite images ever made of the earth comes from ever made of the earth comes from the TIROS 1the TIROS 1

1960-19721960-1972 This was the age of instrument development.This was the age of instrument development. In 1964, the Nimbus satellite series of In 1964, the Nimbus satellite series of

experimental meteorological remote sensing experimental meteorological remote sensing was initiated.was initiated.

By 1966, meteorological satellites moved from By 1966, meteorological satellites moved from being experimental to being operational with being experimental to being operational with the introduction of the ESSA series of satellites the introduction of the ESSA series of satellites which included Automatic Picture.which included Automatic Picture.

The Defense Meteorological Satellite Program The Defense Meteorological Satellite Program )DMSP( was started by the U.S. Air Force in )DMSP( was started by the U.S. Air Force in 1966.1966.

1972, Landsat 1 )also referred to as Earth 1972, Landsat 1 )also referred to as Earth Resources Technology Satellite.Resources Technology Satellite.

19721972--presentpresent 1975:1975: The Synchronous Meteorological Satellites. The Synchronous Meteorological Satellites. 1976:1976: Laser Geodynamic Satellite I. Laser Geodynamic Satellite I. 1978:1978: The Heat Capacity Mapping Mission. The Heat Capacity Mapping Mission. 1978:1978: Seasat demonstrated techniques for global monitoring Seasat demonstrated techniques for global monitoring

of the Earth's oceans. of the Earth's oceans. 1978:1978: Nimbus 7, the final satellite in that series, was Nimbus 7, the final satellite in that series, was

launched. launched. 1984:1984: The Earth Radiation Budget (ERBE) satellite began its The Earth Radiation Budget (ERBE) satellite began its

study of how the Earth absorbs and reflects the Sun's energy.study of how the Earth absorbs and reflects the Sun's energy. 1991:1991: The Upper Atmosphere Research Satellite (UARS) The Upper Atmosphere Research Satellite (UARS)

began its study of the chemistry and physics of the Earth's began its study of the chemistry and physics of the Earth's atmosphere.atmosphere.

Today, the Today, the GOES (Geostationary Operational Environmental (Geostationary Operational Environmental Satellite) system of satellites provides most of the remotely Satellite) system of satellites provides most of the remotely sensed weather information for North America.sensed weather information for North America.

The element of the remote The element of the remote sensing processsensing process

1)1) Energy Source or Energy Source or IlluminationIllumination

2)2) Radiation and the Radiation and the AtmosphereAtmosphere

3)3) Interaction with the Interaction with the TargetTarget

4)4) Recording of Energy by Recording of Energy by the Sensorthe Sensor

5)5) Transmission, Reception, Transmission, Reception, and Processingand Processing

6)6) Interpretation and Interpretation and AnalysisAnalysis

7)7) ApplicationApplication

Recording of Energy by Recording of Energy by the Sensorthe Sensor

Active and Passive Remote Active and Passive Remote Sensing systemsSensing systems

Passive: The Passive: The sensor records sensor records energy that is energy that is reflected or reflected or emitted from the emitted from the source, such as source, such as light from the sun. light from the sun. This is also the This is also the most common most common type of system.type of system.

Passive remote sensorsPassive remote sensors

RadiometerRadiometer Imaging RadiometerImaging Radiometer SpectrometerSpectrometer SpectroradiometerSpectroradiometer

Active and Passive Remote Active and Passive Remote Sensing systemsSensing systems

Active: where the Active: where the object is object is illuminated by illuminated by radiation radiation produced by the produced by the sensors, such as sensors, such as radar or radar or microwaves.microwaves.

Active remote sensorsActive remote sensors

Radar (Radio Detection and Radar (Radio Detection and Ranging)Ranging)

ScatterometerScatterometer Lidar (Light Detection and Ranging)Lidar (Light Detection and Ranging)

Uses of Remote Uses of Remote SensingSensing Weather:Weather: It is possible It is possible

now to get immediate now to get immediate information on climate information on climate and weather and weather conditions from remote conditions from remote sensing satellites. sensing satellites. Images over time allow Images over time allow us to predict weather us to predict weather behavior.behavior.

Uses of Remote Uses of Remote SensingSensing

Agriculture:Agriculture: Crop mapping Crop mapping and yield and yield prediction; crop prediction; crop damage due to damage due to storm, drought storm, drought or disease and or disease and insect insect outbreaks.outbreaks.


Environmental Environmental ImpactsImpacts: : Remote Sensing Remote Sensing to determine oil to determine oil spill size, spill size, location, location, direction and direction and magnitude of magnitude of movement.movement.

Coastal oil spill, Wales, EnglandCoastal oil spill, Wales, England


Forestry Forestry InventoryInventory: Remote : Remote Sensing used for Sensing used for forest inventory, forest inventory, mapping cut-mapping cut-overs, forest fire overs, forest fire mapping, species mapping, species identification.identification.

Burned and burning forest near Norman Wells, NWT , CanadaBurned and burning forest near Norman Wells, NWT , Canada


Geological Geological MappingMapping: Mapping : Mapping faults, folds, faults, folds, lineaments and lineaments and rock types.rock types.

Syncline/Anticline structures in the Applachians of Pennsylvania.Syncline/Anticline structures in the Applachians of Pennsylvania.

Principles of Object Principles of Object Identification)1(Identification)1(

ShapeShape: this : this characteristic alone characteristic alone may serve to identify may serve to identify many objects. many objects. Examples include the Examples include the long linear lines of long linear lines of highways, the highways, the intersecting runways of intersecting runways of an airfield, the an airfield, the perfectly rectangular perfectly rectangular shape of buildings, or shape of buildings, or the recognizable shape the recognizable shape of an outdoor baseball of an outdoor baseball diamond.diamond.


SizeSize: noting the relative and absolute : noting the relative and absolute sizes of objects is important in their sizes of objects is important in their identification. The scale of the image identification. The scale of the image determines the absolute size of an determines the absolute size of an object. As a result, it is very important object. As a result, it is very important to recognize the scale of the image to to recognize the scale of the image to be analyzed. be analyzed.


Image Tone or ColorImage Tone or Color: all objects reflect : all objects reflect or emit specific signatures of or emit specific signatures of electromagnetic radiation. In most cases, electromagnetic radiation. In most cases, related types of objects emit or reflect related types of objects emit or reflect similar wavelengths of radiation. Also, similar wavelengths of radiation. Also, the types of recording device and the types of recording device and recording media produce images that are recording media produce images that are reflective of their sensitivity to particular reflective of their sensitivity to particular range of radiation.range of radiation.


Pattern: Pattern: many many objects arrange objects arrange themselves in themselves in typical patterns. typical patterns. This is especially This is especially true of human-true of human-made made phenomena.phenomena.


ShadowShadow: shadows can sometimes be : shadows can sometimes be used to get a different view of an object. used to get a different view of an object. For example, an overhead photograph of a For example, an overhead photograph of a towering smokestack or a radio towering smokestack or a radio transmission tower normally presents an transmission tower normally presents an identification problem. This difficulty can identification problem. This difficulty can be over come by photographing these be over come by photographing these objects at sun angles that cast shadows. objects at sun angles that cast shadows. These shadows then display the shape of These shadows then display the shape of the object on the ground. Shadows can the object on the ground. Shadows can also be a problem also be a problem


TextureTexture: imaged objects display some : imaged objects display some degree of coarseness or smoothness. This degree of coarseness or smoothness. This characteristic can sometimes be useful in characteristic can sometimes be useful in object interpretation. For example, we object interpretation. For example, we would normally expect to see textural would normally expect to see textural differences when comparing an area of differences when comparing an area of grass with a field corn. Texture, just like grass with a field corn. Texture, just like object size, is directly related to the scale of object size, is directly related to the scale of the image.the image.

Maps & Cartography

Maps have three main attributes: •Scale •Projection•Symbolization

Scale Representation: There are three ways to represent map scales ;

•as a Ratio or Representative Fraction (RF): for example: 1:12,000 or 1/12,000(NOTE that the Numerator and Denominator must be in the same units, making the RF a unitless representation.)

•as a sentence demonstrating equivalence (verbal scale):for example: 1 inch equals 12,000 inches

•as a Graphic or Bar Scale:for example:

Scale

Map projections

Cylindrical Projection

Conic Projection

Planar Projection

Map Symbolization

How is Energy TransferredHow is Energy Transferred??

Electromagnetic Electromagnetic radiationradiation

The wavelength is the The wavelength is the length of one wave cyclelength of one wave cycle,,

FrequencyFrequency

Frequency refers to the number of Frequency refers to the number of cycles of a wave passing a fixed cycles of a wave passing a fixed point per unit of time. Frequency is point per unit of time. Frequency is normally measured in normally measured in hertzhertz (Hz), (Hz),

Wavelength and frequency are Wavelength and frequency are related by the following formularelated by the following formula::

Frequency, Frequency, is is inversely inversely proportional to proportional to wavelength, wavelength,

The longer the The longer the wavelength, the wavelength, the lower the lower the frequency, and frequency, and vice-versa. vice-versa.

ScatteringScattering

Once electromagnetic radiation is Once electromagnetic radiation is generated, it is propagated through the generated, it is propagated through the earth's atmosphere almost at the speed earth's atmosphere almost at the speed of light in a vacuum. of light in a vacuum.

Unlike a vacuum in which nothing Unlike a vacuum in which nothing happens, however, the atmosphere may happens, however, the atmosphere may affect not only the speed of radiation affect not only the speed of radiation but also its wavelength, intensity, but also its wavelength, intensity, spectral distribution, and/or direction.spectral distribution, and/or direction.

ScatteringScattering

ScatterScatter differs from differs from reflectionreflection in that the in that the direction associated with scattering is direction associated with scattering is ununpredictable, whereas the direction of predictable, whereas the direction of reflection is predictable. There are reflection is predictable. There are essentially three types of scattering: essentially three types of scattering:

• • Rayleigh, Rayleigh,

• • Mie, and Mie, and

• • Non-selective. Non-selective.

Atmospheric ScatteringAtmospheric Scattering

Type of scattering is a function Type of scattering is a function of:of:

• the the wavelengthwavelength of the of the incident radiant energy, and incident radiant energy, and

• the the sizesize of the gas molecule, of the gas molecule, dust particle, and/or water dust particle, and/or water vapor droplet encountered.vapor droplet encountered.

Rayleigh scatteringRayleigh scattering

Rayleigh scatteringRayleigh scattering occurs when the occurs when the diameter of the matter (usually air diameter of the matter (usually air molecules) are molecules) are many times smaller than many times smaller than the wavelength of the incident the wavelength of the incident electromagnetic radiationelectromagnetic radiation. .

The amount of scattering is inversely The amount of scattering is inversely related to the fourth power of the related to the fourth power of the radiation's wavelengthradiation's wavelength. For example, blue . For example, blue light (0.4 light (0.4 m) is scattered 16 times more m) is scattered 16 times more than near-infrared light (0.8 than near-infrared light (0.8 m).m).

Rayleigh scatteringRayleigh scattering

Rayleigh scatteringRayleigh scattering is responsible is responsible for the for the blueblue skysky..

Rayleigh scattering is responsible Rayleigh scattering is responsible forfor redred sunsetssunsets..

Rayleigh ScatteringRayleigh Scattering

The intensity of The intensity of Rayleigh Rayleigh scattering varies scattering varies inversely with inversely with the fourth power the fourth power of the of the wavelength (wavelength (-4-4).).

Mie scatteringMie scattering

Mie scatteringMie scattering takes place when there takes place when there are essentially are essentially sphericalspherical particles present particles present in the atmosphere in the atmosphere with diameters with diameters approximately equal to the wavelength approximately equal to the wavelength of radiation being consideredof radiation being considered. .

The amount of scatter is greater than The amount of scatter is greater than Rayleigh scatter and the wavelengths Rayleigh scatter and the wavelengths scattered are longer. scattered are longer.

Non-selective scatteringNon-selective scattering

Non-selective scatteringNon-selective scattering is produced is produced when there are particles in the when there are particles in the atmosphere atmosphere several times the diameter of several times the diameter of the radiation being transmittedthe radiation being transmitted..

Scattering can severely reduce the Scattering can severely reduce the information content of remotely sensed information content of remotely sensed data to the point that the imagery looses data to the point that the imagery looses contrast and it is difficult to differentiate contrast and it is difficult to differentiate one object from another. one object from another.

AbsorptionAbsorption

AbsorptionAbsorption is the process by which is the process by which radiant energy is absorbed and radiant energy is absorbed and converted into other forms of energy.converted into other forms of energy.

the atmosphere does not absorb all of the atmosphere does not absorb all of the incident energy but transmits it the incident energy but transmits it effectively. Parts of the spectrum that effectively. Parts of the spectrum that transmit energy effectively are called transmit energy effectively are called “atmospheric windows”.“atmospheric windows”.

Absorption of the Sun’s Incident Absorption of the Sun’s Incident Electromagnetic Energy in the Region from Electromagnetic Energy in the Region from 0.1 to 30 0.1 to 30 m by Various Atmospheric Gasem by Various Atmospheric Gasess

window

ReflectanceReflectance

ReflectanceReflectance is the is the process whereby process whereby radiation “bounces radiation “bounces off” an object like a off” an object like a cloud or the terrain.cloud or the terrain.

The angle of The angle of incidence and the incidence and the angle of reflection are angle of reflection are equal.equal.

Index of RefractionIndex of Refraction

The The index of refraction (nindex of refraction (n) is a measure of the optical density of a ) is a measure of the optical density of a substance. This index is the ratio of the speed of light in a vacuum, substance. This index is the ratio of the speed of light in a vacuum, cc, , to the speed of light in a substance such as the atmosphere or water, to the speed of light in a substance such as the atmosphere or water, ccnn

(Mulligan, 1980):(Mulligan, 1980):

The speed of light in a substance can never reach the speed of light in The speed of light in a substance can never reach the speed of light in a vacuum. Therefore, its index of refraction must always be greater a vacuum. Therefore, its index of refraction must always be greater than 1. For example, the index of refraction for the atmosphere is than 1. For example, the index of refraction for the atmosphere is 1.0002926 and 1.33 for water. Light travels more slowly through 1.0002926 and 1.33 for water. Light travels more slowly through water because of water’s higher density.water because of water’s higher density.

nc

cn

nc

cn

Snell’s LawSnell’s Law

Refraction can be described by Snell’s law, which states that for a Refraction can be described by Snell’s law, which states that for a given frequency of light (we must use frequency since, unlike given frequency of light (we must use frequency since, unlike wavelength, it does not change when the speed of light changes), the wavelength, it does not change when the speed of light changes), the product of the index of refraction and the sine of the angle between the product of the index of refraction and the sine of the angle between the ray and a line normal to the interface is constant:ray and a line normal to the interface is constant:

From the accompanying figure, we can see that a nonturbulent From the accompanying figure, we can see that a nonturbulent atmosphere can be thought of as a series of layers of gases, each with a atmosphere can be thought of as a series of layers of gases, each with a slightly different density. Anytime energy is propagated through the slightly different density. Anytime energy is propagated through the atmosphere for any appreciable distance at any angle other than atmosphere for any appreciable distance at any angle other than vertical, refraction occurs.vertical, refraction occurs.

2211 sinsin nn 2211 sinsin nn

Atmospheric RefractionAtmospheric Refraction

Refraction in three nonturbulent Refraction in three nonturbulent atmospheric layers. The incident atmospheric layers. The incident energy is bent from its normal energy is bent from its normal trajectory as it travels from one trajectory as it travels from one atmospheric layer to another. atmospheric layer to another. Snell’s law can be used to predict Snell’s law can be used to predict how much bending will take how much bending will take place, based on a knowledge of place, based on a knowledge of the angle of incidence (the angle of incidence () and the ) and the index of refraction of each index of refraction of each atmospheric level, atmospheric level, nn11, , nn22, , nn33..

The element of the remote The element of the remote sensing processsensing process

1)1) Energy Source or Energy Source or IlluminationIllumination

2)2) Radiation and the Radiation and the AtmosphereAtmosphere

3)3) Interaction with the Interaction with the TargetTarget

4)4) Recording of Energy by Recording of Energy by the Sensorthe Sensor

5)5) Transmission, Reception, Transmission, Reception, and Processingand Processing

6)6) Interpretation and Interpretation and AnalysisAnalysis

7)7) ApplicationApplication

Recording of Energy by Recording of Energy by the Sensorthe Sensor

Planck’s Radiation Function )Planck’s Law(

1)/exp(

2)(

2

3

kThfc

hfTB f

Planck’s Radiation Function )Planck’s Law(

1)/exp(

2)(

5

2

Tkhc

hcTB

1-16 deg erg101.3806constant sBoltzmann' k

sec erg106.6262constant sPlanck' -27h

Blackbody Radiation Blackbody Radiation CurvesCurves

Rayleigh – Jeans Approximation

2

22)(

c

kTfTB f

For microwave hf << kT

Stephen Boltzmann LawStephen Boltzmann LawThe The total emitted radiationtotal emitted radiation from a blackbody is from a blackbody is proportional to the fourth power of its absolute proportional to the fourth power of its absolute temperature. This is known as the temperature. This is known as the Stefan-Stefan-Boltzmann lawBoltzmann law and is expressed asand is expressed as::

WhereWhere

0

4)()( bTdTBTB

-4-1-25 deg sec cm erg1067.5constant Boltzmann -Stefan he tb

Wein’s Displacement LawWein’s Displacement Law

0)(

TB

T

amax

wherewhere

deg 2897constant a

TT is the absolute temperature in kelvin is the absolute temperature in kelvin..

Kirchoff’s Law

aFor a blackbody

1 a 1 a

For a blackbody For a gray body

RadianceRadiance ( (LLTT)) from paths 1, from paths 1,

3, and 5 contains intrinsic 3, and 5 contains intrinsic valuable spectral information valuable spectral information about the target of interest. about the target of interest. Conversely, the Conversely, the path path radianceradiance ( (LLpp)) from paths 2 from paths 2

and 4 includes diffuse sky and 4 includes diffuse sky irradiance or radiance from irradiance or radiance from neighboring areas on the neighboring areas on the ground. This path radiance ground. This path radiance generally introduces generally introduces unwanted radiometric noise unwanted radiometric noise in the remotely sensed data in the remotely sensed data and complicates the image and complicates the image interpretation process.interpretation process.

RadianceRadiance ( (LLTT)) from paths 1, from paths 1,

3, and 5 contains intrinsic 3, and 5 contains intrinsic valuable spectral information valuable spectral information about the target of interest. about the target of interest. Conversely, the Conversely, the path path radianceradiance ( (LLpp)) from paths 2 from paths 2

and 4 includes diffuse sky and 4 includes diffuse sky irradiance or radiance from irradiance or radiance from neighboring areas on the neighboring areas on the ground. This path radiance ground. This path radiance generally introduces generally introduces unwanted radiometric noise unwanted radiometric noise in the remotely sensed data in the remotely sensed data and complicates the image and complicates the image interpretation process.interpretation process.

Jensen Jensen 20072007


RadiometriRadiometric Variablesc Variables

RadiometriRadiometric Variablesc Variables



Path 1Path 1 contains spectral solar contains spectral solar irradiance ( ) that was irradiance ( ) that was attenuated very little before attenuated very little before illuminating the terrain illuminating the terrain within the IFOV. Notice in within the IFOV. Notice in this case that we are this case that we are interested in the solar interested in the solar irradiance from a specific irradiance from a specific solar zenith angle ( ) and solar zenith angle ( ) and that the amount of irradiance that the amount of irradiance reaching the terrain is a reaching the terrain is a function of the atmospheric function of the atmospheric transmittance at this angle ( transmittance at this angle ( ). If all of the irradiance ). If all of the irradiance makes it to the ground, then makes it to the ground, then the atmospheric the atmospheric transmittance ( ) equals transmittance ( ) equals one. If none of the irradiance one. If none of the irradiance makes it to the ground, then makes it to the ground, then the atmospheric the atmospheric transmittance is zerotransmittance is zero

Path 1Path 1 contains spectral solar contains spectral solar irradiance ( ) that was irradiance ( ) that was attenuated very little before attenuated very little before illuminating the terrain illuminating the terrain within the IFOV. Notice in within the IFOV. Notice in this case that we are this case that we are interested in the solar interested in the solar irradiance from a specific irradiance from a specific solar zenith angle ( ) and solar zenith angle ( ) and that the amount of irradiance that the amount of irradiance reaching the terrain is a reaching the terrain is a function of the atmospheric function of the atmospheric transmittance at this angle ( transmittance at this angle ( ). If all of the irradiance ). If all of the irradiance makes it to the ground, then makes it to the ground, then the atmospheric the atmospheric transmittance ( ) equals transmittance ( ) equals one. If none of the irradiance one. If none of the irradiance makes it to the ground, then makes it to the ground, then the atmospheric the atmospheric transmittance is zerotransmittance is zeroJensen Jensen

20072007


oEoE

oo

oTo

T

oTo

T

Path 2Path 2 contains spectral diffuse contains spectral diffuse sky irradiance ( ) that never sky irradiance ( ) that never even reaches the Earth’s surface even reaches the Earth’s surface (the target study area) because (the target study area) because of scattering in the atmosphere. of scattering in the atmosphere. Unfortunately, such energy is Unfortunately, such energy is often scattered directly into the often scattered directly into the IFOV of the sensor system. As IFOV of the sensor system. As previously discussed, Rayleigh previously discussed, Rayleigh scattering of blue light scattering of blue light contributes much to this diffuse contributes much to this diffuse sky irradiance. That is why the sky irradiance. That is why the blue band image produced by a blue band image produced by a remote sensor system is often remote sensor system is often much brighter than any of the much brighter than any of the other bands. It contains much other bands. It contains much unwanted diffuse sky irradiance unwanted diffuse sky irradiance that was inadvertently scattered that was inadvertently scattered into the IFOV of the sensor into the IFOV of the sensor system. Therefore, if possible, system. Therefore, if possible, we want to minimize its effects. we want to minimize its effects. Green (2003) refers to the Green (2003) refers to the quantity as the upward quantity as the upward reflectance of the atmosphere ( reflectance of the atmosphere ( ). ).

Path 2Path 2 contains spectral diffuse contains spectral diffuse sky irradiance ( ) that never sky irradiance ( ) that never even reaches the Earth’s surface even reaches the Earth’s surface (the target study area) because (the target study area) because of scattering in the atmosphere. of scattering in the atmosphere. Unfortunately, such energy is Unfortunately, such energy is often scattered directly into the often scattered directly into the IFOV of the sensor system. As IFOV of the sensor system. As previously discussed, Rayleigh previously discussed, Rayleigh scattering of blue light scattering of blue light contributes much to this diffuse contributes much to this diffuse sky irradiance. That is why the sky irradiance. That is why the blue band image produced by a blue band image produced by a remote sensor system is often remote sensor system is often much brighter than any of the much brighter than any of the other bands. It contains much other bands. It contains much unwanted diffuse sky irradiance unwanted diffuse sky irradiance that was inadvertently scattered that was inadvertently scattered into the IFOV of the sensor into the IFOV of the sensor system. Therefore, if possible, system. Therefore, if possible, we want to minimize its effects. we want to minimize its effects. Green (2003) refers to the Green (2003) refers to the quantity as the upward quantity as the upward reflectance of the atmosphere ( reflectance of the atmosphere ( ). ).

dEdE

duE duE

Path 3Path 3 contains energy from contains energy from the Sun that has undergone the Sun that has undergone some Rayleigh, Mie, and/or some Rayleigh, Mie, and/or nonselective scattering and nonselective scattering and perhaps some absorption and perhaps some absorption and reemission before reemission before illuminating the study area. illuminating the study area. Thus, its spectral Thus, its spectral composition and polarization composition and polarization may be somewhat different may be somewhat different from the energy that reaches from the energy that reaches the ground from path 1. the ground from path 1. Green (2003) refers to this Green (2003) refers to this quantity as the downward quantity as the downward reflectance of the atmosphere reflectance of the atmosphere ( ).( ).

Path 3Path 3 contains energy from contains energy from the Sun that has undergone the Sun that has undergone some Rayleigh, Mie, and/or some Rayleigh, Mie, and/or nonselective scattering and nonselective scattering and perhaps some absorption and perhaps some absorption and reemission before reemission before illuminating the study area. illuminating the study area. Thus, its spectral Thus, its spectral composition and polarization composition and polarization may be somewhat different may be somewhat different from the energy that reaches from the energy that reaches the ground from path 1. the ground from path 1. Green (2003) refers to this Green (2003) refers to this quantity as the downward quantity as the downward reflectance of the atmosphere reflectance of the atmosphere ( ).( ).

ddE ddE



Path 4Path 4 contains radiation that contains radiation that was reflected or scattered by was reflected or scattered by nearby terrain ( ) covered nearby terrain ( ) covered by snow, concrete, soil, by snow, concrete, soil, water, and/or vegetation into water, and/or vegetation into the IFOV of the sensor the IFOV of the sensor system. The energy does not system. The energy does not actually illuminate the study actually illuminate the study area of interest. Therefore, if area of interest. Therefore, if possible, we would like to possible, we would like to minimize its effects. minimize its effects.

Path 2 and Path 4 combine to Path 2 and Path 4 combine to produce what is commonly produce what is commonly referred to as referred to as Path Radiance, Path Radiance, LLpp..

Path 4Path 4 contains radiation that contains radiation that was reflected or scattered by was reflected or scattered by nearby terrain ( ) covered nearby terrain ( ) covered by snow, concrete, soil, by snow, concrete, soil, water, and/or vegetation into water, and/or vegetation into the IFOV of the sensor the IFOV of the sensor system. The energy does not system. The energy does not actually illuminate the study actually illuminate the study area of interest. Therefore, if area of interest. Therefore, if possible, we would like to possible, we would like to minimize its effects. minimize its effects.

Path 2 and Path 4 combine to Path 2 and Path 4 combine to produce what is commonly produce what is commonly referred to as referred to as Path Radiance, Path Radiance, LLpp..

nn



Path 5Path 5 is energy that was is energy that was also reflected from nearby also reflected from nearby terrain into the atmosphere, terrain into the atmosphere, but then scattered or reflected but then scattered or reflected onto the study area.onto the study area.

Path 5Path 5 is energy that was is energy that was also reflected from nearby also reflected from nearby terrain into the atmosphere, terrain into the atmosphere, but then scattered or reflected but then scattered or reflected onto the study area.onto the study area.

Jensen 2007

Jensen 2007

The total radiance reaching the sensor The total radiance reaching the sensor from the target is:from the target is:

The total radiance reaching the sensor The total radiance reaching the sensor from the target is:from the target is:

pTS LLL pTS LLL

The total radiance The total radiance recorded by the sensor recorded by the sensor

becomes:becomes:

The total radiance The total radiance recorded by the sensor recorded by the sensor

becomes:becomes:

dETETL dooovT cos

1 2

1

dETETL dooovT cos

1 2

1

Jensen 2007

Jensen 2007

The total radiance reaching The total radiance reaching the sensor from the targetthe sensor from the target

dETETL dooovT cos

1 2

1

dETETL dooovT cos

1 2

1 The total radiance recorded The total radiance recorded by the sensor becomes:by the sensor becomes:

The total radiance recorded The total radiance recorded by the sensor becomes:by the sensor becomes:

pTS LLL pTS LLL

140ÞE 180ÞE 20ÞE

Useful GOES coverage

Communication range

GOES West

GOES East

140ÞW 100ÞW 60ÞW 20ÞW

GOES West

GOES East

140ÞE 180ÞE 20ÞE

Useful GOES coverage

Communication range

GOES West

GOES East

140ÞW 100ÞW 60ÞW 20ÞW

GOES West

GOES East

introduction to remote sensing instructor dr. abdul-wahab mashat

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