Thermal Infrared Remote SensingThermal Infrared Remote SensingThermal Infrared Remote SensingThermal Infrared Remote Sensing

Radiant versus Kinetic temperature

Blackbody radiation

Atmospheric effect

Principle of energy conservation

Radiation from Real Materials

Kirchhoff radiation law

Selected Applications of Thermal Infrared

Remote Sensing

Selected Applications of Thermal Infrared

Remote Sensing

Thermal Infrared Remote SensingThermal Infrared Remote SensingThermal Infrared Remote SensingThermal Infrared Remote Sensing

Thermal infrared EM radiation is emitted from all objects that have a is emitted from all objects that have a temperature greater than absolute zero (K). temperature greater than absolute zero (K).

Our eyes cannot detect differences in thermal infrared energy Our eyes cannot detect differences in thermal infrared energy because they are primarily sensitive to short wavelength visible light because they are primarily sensitive to short wavelength visible light from from 0.4 0.4 m to 0.7 m to 0.7 mm. .

Thermal infrared sensorsThermal infrared sensors are sensitive to thermal infrared are sensitive to thermal infrared

radiation radiation ((3.0 - 14 µm3.0 - 14 µm))..

Thermal infrared EM radiation is emitted from all objects that have a is emitted from all objects that have a temperature greater than absolute zero (K). temperature greater than absolute zero (K).

Our eyes cannot detect differences in thermal infrared energy Our eyes cannot detect differences in thermal infrared energy because they are primarily sensitive to short wavelength visible light because they are primarily sensitive to short wavelength visible light from from 0.4 0.4 m to 0.7 m to 0.7 mm. .

Thermal infrared sensorsThermal infrared sensors are sensitive to thermal infrared are sensitive to thermal infrared

radiation radiation ((3.0 - 14 µm3.0 - 14 µm))..

Kinetic versus Radiant TemperatureKinetic versus Radiant TemperatureKinetic versus Radiant TemperatureKinetic versus Radiant Temperature

•• The The energy of particles of matter in random motion energy of particles of matter in random motion is called is called kinetic heatkinetic heat (also referred to as internal or true heat). All objects having a temperature (also referred to as internal or true heat). All objects having a temperature above absolute zero (0 ˚K; or -273.16 ˚C) exhibit this random motion. above absolute zero (0 ˚K; or -273.16 ˚C) exhibit this random motion.

•• The The amount of kinetic heat amount of kinetic heat can be measured in can be measured in kinetic temperaturekinetic temperature ((TTkinkin) using a ) using a thermometer through direct contact with the objectthermometer through direct contact with the object. .

•• The The energy of particles of matter in random motion energy of particles of matter in random motion is called is called kinetic heatkinetic heat (also referred to as internal or true heat). All objects having a temperature (also referred to as internal or true heat). All objects having a temperature above absolute zero (0 ˚K; or -273.16 ˚C) exhibit this random motion. above absolute zero (0 ˚K; or -273.16 ˚C) exhibit this random motion.

•• The The amount of kinetic heat amount of kinetic heat can be measured in can be measured in kinetic temperaturekinetic temperature ((TTkinkin) using a ) using a thermometer through direct contact with the objectthermometer through direct contact with the object. .

Kinetic versus Radiant TemperatureKinetic versus Radiant TemperatureKinetic versus Radiant TemperatureKinetic versus Radiant Temperature

•• The electromagnetic radiation exiting an object is called The electromagnetic radiation exiting an object is called radiant exitanceradiant exitance ((). ).

• The concentration of the amount of radiant exitance The concentration of the amount of radiant exitance emittedemitted from an from an object is its object is its radiant temperatureradiant temperature ((TTradrad). ).

•• There is a There is a high positive correlation high positive correlation between the between the kinetic temperaturekinetic temperature of an of an object (object (TTkinkin) and radiant temperature () and radiant temperature (TTradrad). ).

•Therefore, we can utilize radiometers placed some distance from the object Therefore, we can utilize radiometers placed some distance from the object to measure its to measure its radiant temperatureradiant temperature which hopefully correlates well with the which hopefully correlates well with the object’s true kinetic temperature. object’s true kinetic temperature. ThisThis is the basis of thermal infrared is the basis of thermal infrared remote sensingremote sensing. .

•• The electromagnetic radiation exiting an object is called The electromagnetic radiation exiting an object is called radiant exitanceradiant exitance ((). ).

• The concentration of the amount of radiant exitance The concentration of the amount of radiant exitance emittedemitted from an from an object is its object is its radiant temperatureradiant temperature ((TTradrad). ).

•• There is a There is a high positive correlation high positive correlation between the between the kinetic temperaturekinetic temperature of an of an object (object (TTkinkin) and radiant temperature () and radiant temperature (TTradrad). ).

•Therefore, we can utilize radiometers placed some distance from the object Therefore, we can utilize radiometers placed some distance from the object to measure its to measure its radiant temperatureradiant temperature which hopefully correlates well with the which hopefully correlates well with the object’s true kinetic temperature. object’s true kinetic temperature. ThisThis is the basis of thermal infrared is the basis of thermal infrared remote sensingremote sensing. .

Thermal Infrared Atmospheric WindowsThermal Infrared Atmospheric WindowsThermal Infrared Atmospheric WindowsThermal Infrared Atmospheric Windows

•• The atmosphere allows a portion of the infrared energy to be transmitted The atmosphere allows a portion of the infrared energy to be transmitted from the terrain to the detectors. Regions that pass energy are called from the terrain to the detectors. Regions that pass energy are called atmospheric windowsatmospheric windows. .

EM spectrum regions that absorb most of the infrared energy are called EM spectrum regions that absorb most of the infrared energy are called absorption bandsabsorption bands. Water vapor (H. Water vapor (H22O), carbon dioxide (COO), carbon dioxide (CO22), and ozone ), and ozone

(O(O33) are responsible for most of the absorption. ) are responsible for most of the absorption.

For example, atmospheric water vapor (HFor example, atmospheric water vapor (H22O) absorbs most of the energy O) absorbs most of the energy

exiting the terrain in the region from exiting the terrain in the region from 5 to 7 5 to 7 mm making it almost useless making it almost useless for remote sensing.for remote sensing.

•• The atmosphere allows a portion of the infrared energy to be transmitted The atmosphere allows a portion of the infrared energy to be transmitted from the terrain to the detectors. Regions that pass energy are called from the terrain to the detectors. Regions that pass energy are called atmospheric windowsatmospheric windows. .

EM spectrum regions that absorb most of the infrared energy are called EM spectrum regions that absorb most of the infrared energy are called absorption bandsabsorption bands. Water vapor (H. Water vapor (H22O), carbon dioxide (COO), carbon dioxide (CO22), and ozone ), and ozone

(O(O33) are responsible for most of the absorption. ) are responsible for most of the absorption.

For example, atmospheric water vapor (HFor example, atmospheric water vapor (H22O) absorbs most of the energy O) absorbs most of the energy

exiting the terrain in the region from exiting the terrain in the region from 5 to 7 5 to 7 mm making it almost useless making it almost useless for remote sensing.for remote sensing.

Atmospheric Windows in the Electromagnetic SpectrumAtmospheric Windows in the Electromagnetic SpectrumAtmospheric Windows in the Electromagnetic SpectrumAtmospheric Windows in the Electromagnetic Spectrum

Thermal Infrared DetectorsThermal Infrared DetectorsThermal Infrared DetectorsThermal Infrared Detectors

•• TIR detectors are TIR detectors are made sensitive to made sensitive to thermal infrared radiant energythermal infrared radiant energy exiting the terrain in the two primary thermal infrared windows: exiting the terrain in the two primary thermal infrared windows: 3 - 5 m and and 8 - 14 8 - 14 mm. .

•• The Earth’s ozone (OThe Earth’s ozone (O33) layer absorbs much of the thermal energy ) layer absorbs much of the thermal energy

exiting the terrain in an absorption band from approximately 9 - 10 exiting the terrain in an absorption band from approximately 9 - 10 m. m. Therefore, Therefore, satellite thermal infrared remote sensing systems satellite thermal infrared remote sensing systems usually usually only record data in the region from only record data in the region from 10.5 - 12.5 10.5 - 12.5 m m to avoid the to avoid the absorption band.absorption band.

•• TIR detectors are TIR detectors are made sensitive to made sensitive to thermal infrared radiant energythermal infrared radiant energy exiting the terrain in the two primary thermal infrared windows: exiting the terrain in the two primary thermal infrared windows: 3 - 5 m and and 8 - 14 8 - 14 mm. .

•• The Earth’s ozone (OThe Earth’s ozone (O33) layer absorbs much of the thermal energy ) layer absorbs much of the thermal energy

exiting the terrain in an absorption band from approximately 9 - 10 exiting the terrain in an absorption band from approximately 9 - 10 m. m. Therefore, Therefore, satellite thermal infrared remote sensing systems satellite thermal infrared remote sensing systems usually usually only record data in the region from only record data in the region from 10.5 - 12.5 10.5 - 12.5 m m to avoid the to avoid the absorption band.absorption band.

Thermal Radiation LawsThermal Radiation LawsThermal Radiation LawsThermal Radiation Laws

•• A A blackbodyblackbody is a hypothetical, ideal radiator that totally absorbs and is a hypothetical, ideal radiator that totally absorbs and reemits all energy incident upon it. reemits all energy incident upon it.

• • No objects in nature are true blackbodiesNo objects in nature are true blackbodies, however, we may think of , however, we may think of the the SunSun as approximating a 6,000 ˚K blackbody and the as approximating a 6,000 ˚K blackbody and the EarthEarth as a 300 as a 300 ˚K blackbody.˚K blackbody.

•• A A blackbodyblackbody is a hypothetical, ideal radiator that totally absorbs and is a hypothetical, ideal radiator that totally absorbs and reemits all energy incident upon it. reemits all energy incident upon it.

• • No objects in nature are true blackbodiesNo objects in nature are true blackbodies, however, we may think of , however, we may think of the the SunSun as approximating a 6,000 ˚K blackbody and the as approximating a 6,000 ˚K blackbody and the EarthEarth as a 300 as a 300 ˚K blackbody.˚K blackbody.

Blackbody Radiation Curves for Several

Objects including the Sun and Earth

Blackbody Radiation Curves for Several

Objects including the Sun and Earth

The relationship between the kinetic temperature of a blackbody (The relationship between the kinetic temperature of a blackbody (TT) and ) and its its dominant wavelength dominant wavelength ((mm) where peak exitance occurs is described by ) where peak exitance occurs is described by

Wein’s displacement lawWein’s displacement law: :

The relationship between the kinetic temperature of a blackbody (The relationship between the kinetic temperature of a blackbody (TT) and ) and its its dominant wavelength dominant wavelength ((mm) where peak exitance occurs is described by ) where peak exitance occurs is described by

Wein’s displacement lawWein’s displacement law: :

Wein’s Displacement LawWein’s Displacement LawWein’s Displacement LawWein’s Displacement Law

m

A

T

For example, the average temperature of the For example, the average temperature of the EarthEarth is 300 ˚K is 300 ˚K (80 ˚F). (80 ˚F).

We compute the We compute the Earth’s dominant wavelength Earth’s dominant wavelength as:as:

maxmax = = 2898 2898 m ˚Km ˚K

TT

maxmax = = 2898 2898 m ˚Km ˚K = = 9.67 9.67 m m

300 ˚K300 ˚K

For example, the average temperature of the For example, the average temperature of the EarthEarth is 300 ˚K is 300 ˚K (80 ˚F). (80 ˚F).

We compute the We compute the Earth’s dominant wavelength Earth’s dominant wavelength as:as:

maxmax = = 2898 2898 m ˚Km ˚K

TT

maxmax = = 2898 2898 m ˚Km ˚K = = 9.67 9.67 m m

300 ˚K300 ˚K

Wein’s Displacement LawWein’s Displacement LawWein’s Displacement LawWein’s Displacement Law

• • The The dominant wavelength dominant wavelength provides valuable information about which provides valuable information about which part of the thermal spectrum we might want to sense in. For example, if part of the thermal spectrum we might want to sense in. For example, if we are looking for we are looking for 800 ˚K forest fires 800 ˚K forest fires that have a dominant wavelength of that have a dominant wavelength of approximatelyapproximately 3.62 3.62 m m then the most appropriate remote sensing system then the most appropriate remote sensing system might be a might be a 3-5 m thermal infrared detector. thermal infrared detector.

• • If we are interested inIf we are interested in soil, water, and rock with ambient soil, water, and rock with ambient temperatures on the earth’s surface of 300 ˚K temperatures on the earth’s surface of 300 ˚K and a dominant and a dominant wavelength of wavelength of 9.66 9.66 mm, then a thermal infrared detector operating in the , then a thermal infrared detector operating in the 8 8 - 14 - 14 m m region might be most appropriate.region might be most appropriate.

• • The The dominant wavelength dominant wavelength provides valuable information about which provides valuable information about which part of the thermal spectrum we might want to sense in. For example, if part of the thermal spectrum we might want to sense in. For example, if we are looking for we are looking for 800 ˚K forest fires 800 ˚K forest fires that have a dominant wavelength of that have a dominant wavelength of approximatelyapproximately 3.62 3.62 m m then the most appropriate remote sensing system then the most appropriate remote sensing system might be a might be a 3-5 m thermal infrared detector. thermal infrared detector.

• • If we are interested inIf we are interested in soil, water, and rock with ambient soil, water, and rock with ambient temperatures on the earth’s surface of 300 ˚K temperatures on the earth’s surface of 300 ˚K and a dominant and a dominant wavelength of wavelength of 9.66 9.66 mm, then a thermal infrared detector operating in the , then a thermal infrared detector operating in the 8 8 - 14 - 14 m m region might be most appropriate.region might be most appropriate.

Wein’s Displacement LawWein’s Displacement LawWein’s Displacement LawWein’s Displacement Law

Developments from Planck’s Law:Stefan-Boltzmann Law

The area under the Planck curve represents the total energy (M) emitted by an object at a given temperature (T)

The Stefan-Boltzmann lawcalculate this energy for a blackbody at a given temperature (T).

Total radiant exitanceTotal radiant exitance (M) leaving the surface of a (M) leaving the surface of a blackbodyblackbody is is proportional to the fourth power of its temperature (proportional to the fourth power of its temperature (TT). This is the ). This is the Stefan-Stefan-Boltzmann law. Boltzmann law.

where σ is the Stefan-Boltzmann constant, 5.6697 x 10-8 W m-2 K-4.

Thus the remote measurement of radiant exitance M from a surface can be Thus the remote measurement of radiant exitance M from a surface can be used to infer the temperature T of the surface. It is this indirect approach to used to infer the temperature T of the surface. It is this indirect approach to temperature measurement that is used in thermal sensing.temperature measurement that is used in thermal sensing.

Total radiant exitanceTotal radiant exitance (M) leaving the surface of a (M) leaving the surface of a blackbodyblackbody is is proportional to the fourth power of its temperature (proportional to the fourth power of its temperature (TT). This is the ). This is the Stefan-Stefan-Boltzmann law. Boltzmann law.

where σ is the Stefan-Boltzmann constant, 5.6697 x 10-8 W m-2 K-4.

Thus the remote measurement of radiant exitance M from a surface can be Thus the remote measurement of radiant exitance M from a surface can be used to infer the temperature T of the surface. It is this indirect approach to used to infer the temperature T of the surface. It is this indirect approach to temperature measurement that is used in thermal sensing.temperature measurement that is used in thermal sensing.

Stephen Boltzmann LawStephen Boltzmann LawStephen Boltzmann LawStephen Boltzmann Law

4M T

• • Real objects (such as rocks, soil, and water) emit only a fraction of the Real objects (such as rocks, soil, and water) emit only a fraction of the energy emitted from a blackbody at the same temperature.energy emitted from a blackbody at the same temperature.

EmissivityEmissivity, , , is the ratio between the radiant exitance emitting from a , is the ratio between the radiant exitance emitting from a real-world object real-world object and that from a and that from a blackbody at the same temperature:blackbody at the same temperature:

• • Real objects (such as rocks, soil, and water) emit only a fraction of the Real objects (such as rocks, soil, and water) emit only a fraction of the energy emitted from a blackbody at the same temperature.energy emitted from a blackbody at the same temperature.

EmissivityEmissivity, , , is the ratio between the radiant exitance emitting from a , is the ratio between the radiant exitance emitting from a real-world object real-world object and that from a and that from a blackbody at the same temperature:blackbody at the same temperature:

Radiation from real Materials & Radiation from real Materials & EmissivityEmissivity

Radiation from real Materials & Radiation from real Materials & EmissivityEmissivity

• All real world materials have emissivities ranging from 0 to <1 that fluctuate depending upon the wavelengths of energy being considered.

• A graybody outputs a constant emissivity that is less than one at all wavelengths.

• Some materials like water have emissivities close to one (0.99) over the wavelength interval from 8 - 14 m.

• Others such as polished aluminum (0.08) and stainless steel (0.16) have very low emissivities.

• All real world materials have emissivities ranging from 0 to <1 that fluctuate depending upon the wavelengths of energy being considered.

• A graybody outputs a constant emissivity that is less than one at all wavelengths.

• Some materials like water have emissivities close to one (0.99) over the wavelength interval from 8 - 14 m.

• Others such as polished aluminum (0.08) and stainless steel (0.16) have very low emissivities.

EmissivityEmissivityEmissivityEmissivity

Spectral emissivity of a Spectral emissivity of a blackbody, a graybody, and a blackbody, a graybody, and a

hypothetical selective hypothetical selective radiatorradiator

Spectral emissivity of a Spectral emissivity of a blackbody, a graybody, and a blackbody, a graybody, and a

hypothetical selective hypothetical selective radiatorradiator

2x reduction2x reduction

1

0.5

0.1

0.1 1 10 100

0.1 100

100101

102

104

106

108

Wavelength, m

Wavelength, m

Spe

ctra

l E

mis

sivi

ty,

Spe

ctra

l R

adia

nt E

xita

nce

W m

-2

m-1

selective radiator

blackbody

6,000 ÞK blackbody = 1.0

graybody

6,000 ÞK graybody = 0.1

6,000 ÞK selective radiator

a.

b.

1

0.5

0.1

0.1 1 10 100

0.1 100

100101

102

104

106

108

Wavelength, m

Wavelength, m

Spe

ctra

l E

mis

sivi

ty,

Spe

ctra

l R

adia

nt E

xita

nce

W m

-2

m-1

selective radiator

blackbody

6,000 ÞK blackbody = 1.0

graybody

6,000 ÞK graybody = 0.1

6,000 ÞK selective radiator

a.

b.

Spectral radiant exitance Spectral radiant exitance distribution of the blackbody, distribution of the blackbody, graybody, and hypothetical graybody, and hypothetical

selective radiatorselective radiator

Spectral radiant exitance Spectral radiant exitance distribution of the blackbody, distribution of the blackbody, graybody, and hypothetical graybody, and hypothetical

selective radiatorselective radiator

Spec

tral

Em

issi

vity

, S

pec

tral

Rad

ian

t E

xita

nce

W m

-2 u

m-1

Two objects lying next to one another on the ground could have the same kinetic temperature but have different radiant temperatures when sensed by a thermal radiometer simply because their emissivities are different.

The emissivity of an object may be influenced by a number factors, e.g.

- color -- darker colored objects are usually better absorbers and emitters (i.e. they have a higher emissivity than lighter colored objects which tend to reflect more of the incident energy.

- moisture content -- the more moisture an object contains, the greater its ability to absorb energy and become a good emitter. Wet soil particles have a high emissivity similar to water.

Two objects lying next to one another on the ground could have the same kinetic temperature but have different radiant temperatures when sensed by a thermal radiometer simply because their emissivities are different.

The emissivity of an object may be influenced by a number factors, e.g.

- color -- darker colored objects are usually better absorbers and emitters (i.e. they have a higher emissivity than lighter colored objects which tend to reflect more of the incident energy.

- moisture content -- the more moisture an object contains, the greater its ability to absorb energy and become a good emitter. Wet soil particles have a high emissivity similar to water.

EmissivityEmissivityEmissivityEmissivity

• Incident (incoming) energy (i) is equal to the sum of the amount of energy reflected from the surface (r), the amount of energy absorbed by the surface (a), and the amount of energy transmitted through the surface (t).

i = r + +

• Incident (incoming) energy (i) is equal to the sum of the amount of energy reflected from the surface (r), the amount of energy absorbed by the surface (a), and the amount of energy transmitted through the surface (t).

i = r + +

Principle of Energy ConservationPrinciple of Energy Conservation

• Dividing each of the variables by the original incident energy:

i / i = (r / i) +( / i) +( / i)

allows us to rewrite the initial equation as:

= r + +

where r is spectral reflectance by the terrain, is spectral absorptance, and is spectral transmittance.

• Dividing each of the variables by the original incident energy:

i / i = (r / i) +( / i) +( / i)

allows us to rewrite the initial equation as:

= r + +

where r is spectral reflectance by the terrain, is spectral absorptance, and is spectral transmittance.

• • The The Russian physicist Kirchhoff Russian physicist Kirchhoff found that found that in the infrared portion of in the infrared portion of the spectrum the spectral emissivity of an object generally equals its the spectrum the spectral emissivity of an object generally equals its spectral absorptance, i.e. spectral absorptance, i.e. ~~ . This is often phrased as:. This is often phrased as:

““good absorbers are good emitters”good absorbers are good emitters”..

• In most remote sensing applicationsIn most remote sensing applications, objects are usually opaque to , objects are usually opaque to thermal radiation. Therefore, we may assume transmittance, thermal radiation. Therefore, we may assume transmittance, = 0 = 0. .

Substituting emissivity for absorptance and removing transmittance from Substituting emissivity for absorptance and removing transmittance from the equation yields:the equation yields:

= r= r + +

• • The The Russian physicist Kirchhoff Russian physicist Kirchhoff found that found that in the infrared portion of in the infrared portion of the spectrum the spectral emissivity of an object generally equals its the spectrum the spectral emissivity of an object generally equals its spectral absorptance, i.e. spectral absorptance, i.e. ~~ . This is often phrased as:. This is often phrased as:

““good absorbers are good emitters”good absorbers are good emitters”..

• In most remote sensing applicationsIn most remote sensing applications, objects are usually opaque to , objects are usually opaque to thermal radiation. Therefore, we may assume transmittance, thermal radiation. Therefore, we may assume transmittance, = 0 = 0. .

Substituting emissivity for absorptance and removing transmittance from Substituting emissivity for absorptance and removing transmittance from the equation yields:the equation yields:

= r= r + +

Kirchoff’s Radiation LawKirchoff’s Radiation LawKirchoff’s Radiation LawKirchoff’s Radiation Law

• • If reflectivity increases then emissivity must decrease. If emissivity If reflectivity increases then emissivity must decrease. If emissivity increases then reflectivity must decrease.increases then reflectivity must decrease.

• For example, For example, waterwater absorbs almost all incident energy and reflects absorbs almost all incident energy and reflects very little. Therefore, water is a very good emitter and has a high very little. Therefore, water is a very good emitter and has a high emissivity close to 1. Conversely, a emissivity close to 1. Conversely, a sheet metal roofsheet metal roof reflects most of reflects most of the incident energy, absorbs very little, yielding an emissivity much the incident energy, absorbs very little, yielding an emissivity much less than 1. less than 1.

• Therefore, metal objects such as cars, aircraft, and metal roofs almost Therefore, metal objects such as cars, aircraft, and metal roofs almost always look very cold (dark) on thermal infrared imagery.always look very cold (dark) on thermal infrared imagery.

• • If reflectivity increases then emissivity must decrease. If emissivity If reflectivity increases then emissivity must decrease. If emissivity increases then reflectivity must decrease.increases then reflectivity must decrease.

• For example, For example, waterwater absorbs almost all incident energy and reflects absorbs almost all incident energy and reflects very little. Therefore, water is a very good emitter and has a high very little. Therefore, water is a very good emitter and has a high emissivity close to 1. Conversely, a emissivity close to 1. Conversely, a sheet metal roofsheet metal roof reflects most of reflects most of the incident energy, absorbs very little, yielding an emissivity much the incident energy, absorbs very little, yielding an emissivity much less than 1. less than 1.

• Therefore, metal objects such as cars, aircraft, and metal roofs almost Therefore, metal objects such as cars, aircraft, and metal roofs almost always look very cold (dark) on thermal infrared imagery.always look very cold (dark) on thermal infrared imagery.

Implications of Kirchoff’s Radiation Law

Implications of Kirchoff’s Radiation Law

• • TThe radiant temperature of an object recorded by a remote sensor is he radiant temperature of an object recorded by a remote sensor is related to its kinetic temperature and emissivity by the following related to its kinetic temperature and emissivity by the following relationship: relationship:

TTradrad = = 1/41/4TTkinkin

• • TThe radiant temperature of an object recorded by a remote sensor is he radiant temperature of an object recorded by a remote sensor is related to its kinetic temperature and emissivity by the following related to its kinetic temperature and emissivity by the following relationship: relationship:

TTradrad = = 1/41/4TTkinkin

Relationship b/w TRelationship b/w Tradrad and T and TkinkinRelationship b/w TRelationship b/w Tradrad and T and Tkinkin

• • The The diameterdiameter of the circular ground area viewed by the of the circular ground area viewed by the sensor, sensor, DD, is a function of the , is a function of the instantaneous-field-of-viewinstantaneous-field-of-view, , , , of the scanner measured in milliradians (mrad) and the of the scanner measured in milliradians (mrad) and the altitude altitude of the scanner above ground levelof the scanner above ground level, , HH, where:, where:

D = H x D = H x

For example, if the IFOV of the scanner is 2.5 mrad, the For example, if the IFOV of the scanner is 2.5 mrad, the ground size of the pixel in meters is a product of the IFOV ground size of the pixel in meters is a product of the IFOV (0.0025) and the altitude above ground level (AGL) in meters. (0.0025) and the altitude above ground level (AGL) in meters. IFOVs range from 0.5 to 5 milliradiansIFOVs range from 0.5 to 5 milliradians

• • The The diameterdiameter of the circular ground area viewed by the of the circular ground area viewed by the sensor, sensor, DD, is a function of the , is a function of the instantaneous-field-of-viewinstantaneous-field-of-view, , , , of the scanner measured in milliradians (mrad) and the of the scanner measured in milliradians (mrad) and the altitude altitude of the scanner above ground levelof the scanner above ground level, , HH, where:, where:

D = H x D = H x

For example, if the IFOV of the scanner is 2.5 mrad, the For example, if the IFOV of the scanner is 2.5 mrad, the ground size of the pixel in meters is a product of the IFOV ground size of the pixel in meters is a product of the IFOV (0.0025) and the altitude above ground level (AGL) in meters. (0.0025) and the altitude above ground level (AGL) in meters. IFOVs range from 0.5 to 5 milliradiansIFOVs range from 0.5 to 5 milliradians

Thermal Infrared Multispectral ScannersThermal Infrared Multispectral ScannersThermal Infrared Multispectral ScannersThermal Infrared Multispectral Scanners

Daytime Optical Daytime Optical and Nighttime and Nighttime

Thermal Infrared Thermal Infrared Imagery of New Imagery of New

York CityYork City

Daytime Optical Daytime Optical and Nighttime and Nighttime

Thermal Infrared Thermal Infrared Imagery of New Imagery of New

York CityYork City

Thermal InfraredThermal InfraredThermal InfraredThermal InfraredAerial PhotographAerial PhotographAerial PhotographAerial Photograph

Daytime Optical and Daytime Optical and Nighttime Thermal Infrared Nighttime Thermal Infrared

ImageryImagery

Daytime Optical and Daytime Optical and Nighttime Thermal Infrared Nighttime Thermal Infrared

ImageryImagery

AprilApril 26, 19814:56 am 1 x 1 m

AprilApril 26, 19814:56 am 1 x 1 m

2x reduction

steam lines

steam plant

manhole cover

library

parking

soccer field

dorms

one-dimensional relief

displacement

Vertical Aerial Photograph

Pre-dawn Thermal Infrared Image

line-of-flight

science buildings

a.

b.

steam lines

steam plant

manhole cover

library

parking

soccer field

dorms

one-dimensional relief

displacement

Vertical Aerial Photograph

Pre-dawn Thermal Infrared Image

line-of-flight

science buildings

a.

b.

Pre-dawn Thermal Infrared Image of Effluent Entering the Savannah River Swamp SystemPre-dawn Thermal Infrared Image of Effluent Entering the Savannah River Swamp System

March 31, 19814:28 am; 3 x 3 m

March 31, 19814:28 am; 3 x 3 m

Savannah River

Pre-dawn Thermal Infrared Image of a Pre-dawn Thermal Infrared Image of a Residential Subdivision in Forth Worth, TexasResidential Subdivision in Forth Worth, Texas

Pre-dawn Thermal Infrared Image of a Pre-dawn Thermal Infrared Image of a Residential Subdivision in Forth Worth, TexasResidential Subdivision in Forth Worth, Texas

a b

c

d

e

f

h

g

a b

c

d

e

f

h

g

250 m AGL1 mrad IFOV

6:45 amJan 10, 19800.25 x 0.25 m

250 m AGL1 mrad IFOV

6:45 amJan 10, 19800.25 x 0.25 m

Nighttime Thermal Infrared Imagery of an AirportNighttime Thermal Infrared Imagery of an AirportNighttime Thermal Infrared Imagery of an AirportNighttime Thermal Infrared Imagery of an Airport