Dr. Xin MiaoDr. Xin MiaoDepartment of Geography, Department of Geography,

Geology and PlanningGeology and PlanningMissouri State University Missouri State University

Dr. Xin MiaoDr. Xin MiaoDepartment of Geography, Department of Geography,

Geology and PlanningGeology and PlanningMissouri State University Missouri State University

Introduction to Remote SensingIntroduction to Remote SensingIntroduction to Remote SensingIntroduction to Remote Sensing

A remote sensing instrument collects information about an object or phenomenon within the instantaneous-field-of-view (IFOV) of the sensor system without being in direct physical contact with it. The sensor is located on a suborbitalor satellite platform.

A remote sensing instrument collects information about an object or phenomenon within the instantaneous-field-of-view (IFOV) of the sensor system without being in direct physical contact with it. The sensor is located on a suborbitalor satellite platform.

ASPRS adopted a combined formal definition of ASPRS adopted a combined formal definition of photogrammetryphotogrammetry andand remote sensingremote sensing as (Colwell, as (Colwell, 1997):1997):

““the art, science, and technology of obtaining the art, science, and technology of obtaining reliable information about physical objects and reliable information about physical objects and the environment, through the process of the environment, through the process of recording, measuring and interpreting imagery recording, measuring and interpreting imagery and digital representations of energy patterns and digital representations of energy patterns derived from derived from noncontactnoncontact sensor systems”. sensor systems”.

ASPRS adopted a combined formal definition of ASPRS adopted a combined formal definition of photogrammetryphotogrammetry andand remote sensingremote sensing as (Colwell, as (Colwell, 1997):1997):

““the art, science, and technology of obtaining the art, science, and technology of obtaining reliable information about physical objects and reliable information about physical objects and the environment, through the process of the environment, through the process of recording, measuring and interpreting imagery recording, measuring and interpreting imagery and digital representations of energy patterns and digital representations of energy patterns derived from derived from noncontactnoncontact sensor systems”. sensor systems”.

Remote Sensing Data CollectionRemote Sensing Data CollectionRemote Sensing Data CollectionRemote Sensing Data Collection

Jensen Jensen 20052005

Jensen Jensen 20052005

How is Energy Transferred?How is Energy Transferred?How is Energy Transferred?How is Energy Transferred?

Energy may be transferred three ways: conduction, convection, and radiation. a) Energy may be conducted directly from one object to another as when a pan is in direct physical contact with a hot burner. b) The Sun bathes the Earth’s surface with radiant energy causing the air near the ground to increase in temperature. The less dense air rises, creating convectional currents in the atmosphere. c) Electromagnetic energy in the form of electromagnetic waves may be transmitted through the vacuum of space from the Sun to the Earth.

Energy may be transferred three ways: conduction, convection, and radiation. a) Energy may be conducted directly from one object to another as when a pan is in direct physical contact with a hot burner. b) The Sun bathes the Earth’s surface with radiant energy causing the air near the ground to increase in temperature. The less dense air rises, creating convectional currents in the atmosphere. c) Electromagnetic energy in the form of electromagnetic waves may be transmitted through the vacuum of space from the Sun to the Earth.

Wave Model of Electromagnetic Radiation (1)Wave Model of Electromagnetic Radiation (1)Wave Model of Electromagnetic Radiation (1)Wave Model of Electromagnetic Radiation (1)

In the 1860s, In the 1860s, James Clerk MaxwellJames Clerk Maxwell (1831–1879) conceptualized (1831–1879) conceptualized electromagnetic radiation (EMR) as an electromagnetic wave that travels electromagnetic radiation (EMR) as an electromagnetic wave that travels through space at the speed of light,through space at the speed of light, cc, which is 3 x 10, which is 3 x 1088 meters per second meters per second (hereafter referred to as m s(hereafter referred to as m s-1-1) or 186,282.03 miles s) or 186,282.03 miles s-1-1. A useful relation for . A useful relation for quick calculations is that light travels about 1 ft per nanosecond (10quick calculations is that light travels about 1 ft per nanosecond (10 -9 -9 s). Thes). The electromagnetic waveelectromagnetic wave consists of two fluctuating fields—one consists of two fluctuating fields—one electricelectric and the and the other other magneticmagnetic. The two vectors are at right angles (orthogonal) to one . The two vectors are at right angles (orthogonal) to one another, and both are perpendicular to the direction of travel.another, and both are perpendicular to the direction of travel.

In the 1860s, In the 1860s, James Clerk MaxwellJames Clerk Maxwell (1831–1879) conceptualized (1831–1879) conceptualized electromagnetic radiation (EMR) as an electromagnetic wave that travels electromagnetic radiation (EMR) as an electromagnetic wave that travels through space at the speed of light,through space at the speed of light, cc, which is 3 x 10, which is 3 x 1088 meters per second meters per second (hereafter referred to as m s(hereafter referred to as m s-1-1) or 186,282.03 miles s) or 186,282.03 miles s-1-1. A useful relation for . A useful relation for quick calculations is that light travels about 1 ft per nanosecond (10quick calculations is that light travels about 1 ft per nanosecond (10 -9 -9 s). Thes). The electromagnetic waveelectromagnetic wave consists of two fluctuating fields—one consists of two fluctuating fields—one electricelectric and the and the other other magneticmagnetic. The two vectors are at right angles (orthogonal) to one . The two vectors are at right angles (orthogonal) to one another, and both are perpendicular to the direction of travel.another, and both are perpendicular to the direction of travel.

The relationship between the wavelength, , and frequency, , of electromagnetic radiation is based on the following formula, where c is the speed of light:

The relationship between the wavelength, , and frequency, , of electromagnetic radiation is based on the following formula, where c is the speed of light:

Wave Model of Electromagnetic Energy (3)Wave Model of Electromagnetic Energy (3)

cvcvvc vc

c

v c

v

Note that frequency, is inversely proportional to wavelength, The longer the wavelength, the lower the frequency, and vice-versa.

Note that frequency, is inversely proportional to wavelength, The longer the wavelength, the lower the frequency, and vice-versa.

Wave Model of Electromagnetic Energy (4)Wave Model of Electromagnetic Energy (4)Wave Model of Electromagnetic Energy (4)Wave Model of Electromagnetic Energy (4)

This cross-section of an This cross-section of an electromagnetic wave illustrates electromagnetic wave illustrates the inverse relationship between the inverse relationship between wavelengthwavelength ( () and ) and frequencyfrequency ( (). ). The longer the wavelength the The longer the wavelength the lower the frequency; the shorter lower the frequency; the shorter the wavelength, the higher the the wavelength, the higher the frequency. The frequency. The amplitudeamplitude of an of an electromagnetic wave is the height electromagnetic wave is the height of the wave crest above the of the wave crest above the undisturbed position. Successive undisturbed position. Successive wave crests are numbered 1, 2, 3, wave crests are numbered 1, 2, 3, and 4. An observer at the position and 4. An observer at the position of the clock records the number of of the clock records the number of crests that pass by in a second. crests that pass by in a second. This frequency is measured in This frequency is measured in cycles per second, or hertzcycles per second, or hertz

This cross-section of an This cross-section of an electromagnetic wave illustrates electromagnetic wave illustrates the inverse relationship between the inverse relationship between wavelengthwavelength ( () and ) and frequencyfrequency ( (). ). The longer the wavelength the The longer the wavelength the lower the frequency; the shorter lower the frequency; the shorter the wavelength, the higher the the wavelength, the higher the frequency. The frequency. The amplitudeamplitude of an of an electromagnetic wave is the height electromagnetic wave is the height of the wave crest above the of the wave crest above the undisturbed position. Successive undisturbed position. Successive wave crests are numbered 1, 2, 3, wave crests are numbered 1, 2, 3, and 4. An observer at the position and 4. An observer at the position of the clock records the number of of the clock records the number of crests that pass by in a second. crests that pass by in a second. This frequency is measured in This frequency is measured in cycles per second, or hertzcycles per second, or hertz

Electromagnetic Electromagnetic SpectrumSpectrum

Electromagnetic Electromagnetic SpectrumSpectrum

The Sun produces a The Sun produces a continuous spectrumcontinuous spectrum of of energy from gamma rays to energy from gamma rays to radio waves that continually radio waves that continually bathe the Earth in energy. bathe the Earth in energy. The visible portion of the The visible portion of the spectrum may be measured spectrum may be measured using wavelength (measured using wavelength (measured in micrometers or in micrometers or nanometers, i.e., nanometers, i.e., m or nm) m or nm) or electron volts (eV). All or electron volts (eV). All units are interchangeable.units are interchangeable.

The Sun produces a The Sun produces a continuous spectrumcontinuous spectrum of of energy from gamma rays to energy from gamma rays to radio waves that continually radio waves that continually bathe the Earth in energy. bathe the Earth in energy. The visible portion of the The visible portion of the spectrum may be measured spectrum may be measured using wavelength (measured using wavelength (measured in micrometers or in micrometers or nanometers, i.e., nanometers, i.e., m or nm) m or nm) or electron volts (eV). All or electron volts (eV). All units are interchangeable.units are interchangeable.

Spectral Bandwidths of Landsat and SPOT Sensor SystemsSpectral Bandwidths of Landsat and SPOT Sensor SystemsSpectral Bandwidths of Landsat and SPOT Sensor SystemsSpectral Bandwidths of Landsat and SPOT Sensor Systems

Spectral Spectral ResolutionResolution

(1)(1)

Spectral Spectral ResolutionResolution

(1)(1)Marina in the Ace Basin, South CarolinaMarina in the Ace Basin, South CarolinaMarina in the Ace Basin, South CarolinaMarina in the Ace Basin, South Carolina

Airborne Visible Airborne Visible Infrared Imaging Infrared Imaging

Spectrometer Spectrometer (AVIRIS) Datacube (AVIRIS) Datacube of Sullivan’s Island of Sullivan’s Island

Obtained on Obtained on October 26, 1998October 26, 1998

Airborne Visible Airborne Visible Infrared Imaging Infrared Imaging

Spectrometer Spectrometer (AVIRIS) Datacube (AVIRIS) Datacube of Sullivan’s Island of Sullivan’s Island

Obtained on Obtained on October 26, 1998October 26, 1998

Color-infrared color composite on top of the datacube was created using three of the 224 bands

at 10 nm nominal bandwidth.

Spectral Spectral ResolutionResolution

(2)(2)

Spectral Spectral ResolutionResolution

(2)(2)

Spatial Spatial ResolutionResolution

(1)(1)

Spatial Spatial ResolutionResolution

(1)(1)

Electromagnetic Energy InteractionsElectromagnetic Energy InteractionsElectromagnetic Energy InteractionsElectromagnetic Energy Interactions

EnergyEnergy recorded by remote sensing systems undergoes recorded by remote sensing systems undergoes fundamental interactions that should be understood to properly fundamental interactions that should be understood to properly interpret the remotely sensed data. For example, if the energy interpret the remotely sensed data. For example, if the energy being remotely sensed comes from the Sun, the energy:being remotely sensed comes from the Sun, the energy:

•• is radiated by atomic particles at the source (the Sun), is radiated by atomic particles at the source (the Sun),

•• propagates through the vacuum of space at the speed of light,propagates through the vacuum of space at the speed of light,

•• interacts with the interacts with the Earth's atmosphereEarth's atmosphere, ,

•• interacts with the interacts with the Earth's surfaceEarth's surface,,

•• interacts with the interacts with the Earth's atmosphere once againEarth's atmosphere once again, and , and

•• finally reaches the remote sensor where it interacts with finally reaches the remote sensor where it interacts with various optical systems, filters, emulsions, or detectors.various optical systems, filters, emulsions, or detectors.

EnergyEnergy recorded by remote sensing systems undergoes recorded by remote sensing systems undergoes fundamental interactions that should be understood to properly fundamental interactions that should be understood to properly interpret the remotely sensed data. For example, if the energy interpret the remotely sensed data. For example, if the energy being remotely sensed comes from the Sun, the energy:being remotely sensed comes from the Sun, the energy:

•• is radiated by atomic particles at the source (the Sun), is radiated by atomic particles at the source (the Sun),

•• propagates through the vacuum of space at the speed of light,propagates through the vacuum of space at the speed of light,

•• interacts with the interacts with the Earth's atmosphereEarth's atmosphere, ,

•• interacts with the interacts with the Earth's surfaceEarth's surface,,

•• interacts with the interacts with the Earth's atmosphere once againEarth's atmosphere once again, and , and

•• finally reaches the remote sensor where it interacts with finally reaches the remote sensor where it interacts with various optical systems, filters, emulsions, or detectors.various optical systems, filters, emulsions, or detectors.

Energy-matter Energy-matter interactions in interactions in

the the atmosphereatmosphere, , at the at the study areastudy area, ,

and at the and at the remote sensor remote sensor

detectordetector

Energy-matter Energy-matter interactions in interactions in

the the atmosphereatmosphere, , at the at the study areastudy area, ,

and at the and at the remote sensor remote sensor

detectordetector

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

• • RayleighRayleigh,,

• • MieMie,, and and

• • Non-selectiveNon-selective. .

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

• • RayleighRayleigh,,

• • MieMie,, and and

• • Non-selectiveNon-selective. .

ScatteringScatteringScatteringScattering

Atmospheric Atmospheric ScatteringScattering

Atmospheric Atmospheric ScatteringScattering

Type of scattering is a function of:

1) the wavelength of the incident radiant energy, and

2) the size of the gas molecule, dust particle, and/or water vapor droplet encountered.

Type of scattering is a function of:

1) the wavelength of the incident radiant energy, and

2) the size of the gas molecule, dust particle, and/or water vapor droplet encountered.

Rayleigh ScatteringRayleigh ScatteringRayleigh ScatteringRayleigh Scattering

• • Rayleigh scatteringRayleigh scattering is responsible for the is responsible for the blueblue skysky. The short violet . The short violet and blue wavelengths are more efficiently scattered than the longer and blue wavelengths are more efficiently scattered than the longer orange and red wavelengths. orange and red wavelengths.

• • Rayleigh scattering is responsible forRayleigh scattering is responsible for redred sunsetssunsets. . Since the Since the atmosphere is a thin shell of gravitationally bound gas surrounding atmosphere is a thin shell of gravitationally bound gas surrounding the solid Earth, sunlight must pass through a longer slant path of air the solid Earth, sunlight must pass through a longer slant path of air at sunset (or sunrise) than at noon. Since the violet and blue at sunset (or sunrise) than at noon. Since the violet and blue wavelengths are scattered even more during their now-longer path wavelengths are scattered even more during their now-longer path through the air than when the Sun is overhead, what we see when we through the air than when the Sun is overhead, what we see when we look toward the Sun is the residue - the wavelengths of sunlight that look toward the Sun is the residue - the wavelengths of sunlight that are hardly scattered away at all, especially the oranges and reds.are hardly scattered away at all, especially the oranges and reds.

• • Rayleigh scatteringRayleigh scattering is responsible for the is responsible for the blueblue skysky. The short violet . The short violet and blue wavelengths are more efficiently scattered than the longer and blue wavelengths are more efficiently scattered than the longer orange and red wavelengths. orange and red wavelengths.

• • Rayleigh scattering is responsible forRayleigh scattering is responsible for redred sunsetssunsets. . Since the Since the atmosphere is a thin shell of gravitationally bound gas surrounding atmosphere is a thin shell of gravitationally bound gas surrounding the solid Earth, sunlight must pass through a longer slant path of air the solid Earth, sunlight must pass through a longer slant path of air at sunset (or sunrise) than at noon. Since the violet and blue at sunset (or sunrise) than at noon. Since the violet and blue wavelengths are scattered even more during their now-longer path wavelengths are scattered even more during their now-longer path through the air than when the Sun is overhead, what we see when we through the air than when the Sun is overhead, what we see when we look toward the Sun is the residue - the wavelengths of sunlight that look toward the Sun is the residue - the wavelengths of sunlight that are hardly scattered away at all, especially the oranges and reds.are hardly scattered away at all, especially the oranges and reds.

Mie ScatteringMie ScatteringMie ScatteringMie Scattering

Non-selective ScatteringNon-selective ScatteringNon-selective ScatteringNon-selective Scattering

• • AbsorptionAbsorption is the process by which radiant energy is is the process by which radiant energy is absorbed and converted into other forms of energy. An absorbed and converted into other forms of energy. An absorption bandabsorption band is a range of wavelengths (or frequencies) is a range of wavelengths (or frequencies) in the electromagnetic spectrum within which radiant in the electromagnetic spectrum within which radiant energy is absorbed by substances such as energy is absorbed by substances such as waterwater (H (H22O), O),

carbon dioxidecarbon dioxide (CO (CO22), ), oxygenoxygen (O (O22), ), ozoneozone (O (O33), and ), and nitrous nitrous

oxideoxide (N (N22O). O).

•• The cumulative effect of the absorption by the various The cumulative effect of the absorption by the various constituents can cause the atmosphere toconstituents can cause the atmosphere to close downclose down in in certain regions of the spectrum. This is bad for remote certain regions of the spectrum. This is bad for remote sensing because no energy is available to be sensed. sensing because no energy is available to be sensed.

• • AbsorptionAbsorption is the process by which radiant energy is is the process by which radiant energy is absorbed and converted into other forms of energy. An absorbed and converted into other forms of energy. An absorption bandabsorption band is a range of wavelengths (or frequencies) is a range of wavelengths (or frequencies) in the electromagnetic spectrum within which radiant in the electromagnetic spectrum within which radiant energy is absorbed by substances such as energy is absorbed by substances such as waterwater (H (H22O), O),

carbon dioxidecarbon dioxide (CO (CO22), ), oxygenoxygen (O (O22), ), ozoneozone (O (O33), and ), and nitrous nitrous

oxideoxide (N (N22O). O).

•• The cumulative effect of the absorption by the various The cumulative effect of the absorption by the various constituents can cause the atmosphere toconstituents can cause the atmosphere to close downclose down in in certain regions of the spectrum. This is bad for remote certain regions of the spectrum. This is bad for remote sensing because no energy is available to be sensed. sensing because no energy is available to be sensed.

AbsorptionAbsorptionAbsorptionAbsorption

Absorption of the Sun's Incident Electromagnetic Energy in Absorption of the Sun's Incident Electromagnetic Energy in the the

Region from 0.1 to 30 Region from 0.1 to 30 m by Various Atmospheric Gasesm by Various Atmospheric Gases

Absorption of the Sun's Incident Electromagnetic Energy in Absorption of the Sun's Incident Electromagnetic Energy in the the

Region from 0.1 to 30 Region from 0.1 to 30 m by Various Atmospheric Gasesm by Various Atmospheric Gases

window

Typical spectral Typical spectral reflectance curves reflectance curves

for urban–suburban for urban–suburban phenomena in the phenomena in the

region 0.4 – 0.9 region 0.4 – 0.9 m.m.

Typical spectral Typical spectral reflectance curves reflectance curves

for urban–suburban for urban–suburban phenomena in the phenomena in the

region 0.4 – 0.9 region 0.4 – 0.9 m.m.

Spectra of Three Minerals Spectra of Three Minerals Derived from NASA’s Derived from NASA’s

Airborne Visible Infrared Airborne Visible Infrared Imaging Spectrometer Imaging Spectrometer

(AVIRIS) and as Measured (AVIRIS) and as Measured Using A Laboratory Using A Laboratory Spectroradiometer Spectroradiometer

(after Van der Meer, 1994)(after Van der Meer, 1994)

Spectra of Three Minerals Spectra of Three Minerals Derived from NASA’s Derived from NASA’s

Airborne Visible Infrared Airborne Visible Infrared Imaging Spectrometer Imaging Spectrometer

(AVIRIS) and as Measured (AVIRIS) and as Measured Using A Laboratory Using A Laboratory Spectroradiometer Spectroradiometer

(after Van der Meer, 1994)(after Van der Meer, 1994)

Mineral Maps of Mineral Maps of Cuprite, NV, Derived Cuprite, NV, Derived

from Low Altitude (3.9 from Low Altitude (3.9 km AGL) and High km AGL) and High

Altitude (20 km AGL) Altitude (20 km AGL) AVIRIS Data obtained AVIRIS Data obtained on October 11 and June on October 11 and June

18, 199818, 1998

Mineral Maps of Mineral Maps of Cuprite, NV, Derived Cuprite, NV, Derived

from Low Altitude (3.9 from Low Altitude (3.9 km AGL) and High km AGL) and High

Altitude (20 km AGL) Altitude (20 km AGL) AVIRIS Data obtained AVIRIS Data obtained on October 11 and June on October 11 and June

18, 199818, 1998

Hyperspectral data were Hyperspectral data were analyzed using the USGS analyzed using the USGS

Tetracorder program.Tetracorder program.

Hyperspectral data were Hyperspectral data were analyzed using the USGS analyzed using the USGS

Tetracorder program.Tetracorder program.

ReviewReview

What is Remote Sensing (definition)?What is Remote Sensing (definition)? Electromagnetic Spectrum;Electromagnetic Spectrum; Remote Sensor Resolution (Spectral, Spatial);Remote Sensor Resolution (Spectral, Spatial); Remote Sensing Process;Remote Sensing Process; Scattering, atmospheric window;Scattering, atmospheric window; Spectral signature;Spectral signature; Geological applications.Geological applications.