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What Is Remote Sensing Actually Sensing?
able to see ultraviolet (UV) light (like bees can) and if you could see slightly
longer wavelengths of energy, you’d be able to see infrared light. However,
the human eye is only sensitive to electromagnetic energy in this very small
range of wavelengths.
The visible spectrum can be broken down further to the colors that it
represents. Shorter visible light wavelengths (between 0.4 and 0.5 micrometers) represent the blue portion of the spectrum. Medium visible light
wavelengths (between 0.5 and 0.6 micrometers) represent the green portion of the spectrum. Longer visible light wavelengths (between 0.6 and
0.7 micrometers) represent the red portion of the spectrum. For instance,
when you see a shirt with a bright red color, your eyes are actually sensing the reflection of light with a wavelength measurement somewhere between 0.6 and 0.7 micrometers.
Each of these narrow portions of wavelengths of the electromagnetic
spectrum that represents a different form of light is referred to as a band
of energy in remote sensing. For example, the shorter wavelengths of 0.4
to 0.5 micrometers are referred to as the blue band of the electromagnetic
spectrum since the properties of those wavelengths of light correspond to the
characteristics of blue energy. Similarly, the section of wavelengths between
0.5 and 0.6 micrometers make up the green band of the electromagnetic
spectrum, and the range of wavelengths of 0.6 to 0.7 micrometers make up
the red band.
Keep in mind that while the human eye is restricted to seeing only
these narrow bands of the electromagnetic spectrum, remote sensing devices have the capability to sense energy from other portions of the spectrum. For instance, the infrared (IR) light portion of the electromagnetic
spectrum extends to wavelengths between 0.7 and 100 micrometers in
length. A sensor could be tuned to only measure the reflection of a narrow infrared band of energy between 0.7 and 0.9 micrometers, and even
though this energy is not visible to the human eye, a remote sensing device can easily measure this reflection of energy. As we’ll see, there’s an
enormous amount of information that can be gained from examining the
reflection of these other forms of energy off objects. When doing remote
sensing of infrared light, there are a few wavelength ranges that are commonly utilized:
a 0.7 to 1.3 micrometers—Bands of this portion are referred to as “near
infrared” (NIR), which is commonly used by satellite remote sensing (see
Chapter 11) and also in infrared photography (see Chapter 9).
a 1.3 to 3.0 micrometers—Bands of this portion are referred to as “middle
infrared” (MIR), which is also utilized by different satellite sensors. For
instance, measurements of bands of MIR energy are used in studies related to water content of plants.
a 3.0 to 14.0 micrometers—Bands of this portion are referred to as “thermal
infrared” (TIR), which is used for measuring heat sources or radiant heat
energy.
UV (ultraviolet)
the portion of the
electromagnetic
spectrum with
wavelengths
between 0.01 and
0.4 micrometers.
band a narrow range
of wavelengths being
measured by a remote
sensing device.
blue band the range
of wavelengths
between 0.4 and
0.5 micrometers.
green band the
range of wavelengths
between 0.5 and 0.6
micrometers.
red band the range
of wavelengths
between 0.6 and
0.7 micrometers.
IR (infrared) the portion
of the electromagnetic
spectrum with
wavelengths
between 0.7 and
100 micrometers.
NIR (near infrared)
the portion of the
electromagnetic
spectrum with
wavelengths
between 0.7 and
1.3 micrometers.
MIR (middle infrared)
the portion of the
electromagnetic
spectrum with
wavelengths
between 1.3 and
3.0 micrometers.
TIR (thermal infrared)
the portion of the
electromagnetic
spectrum with
wavelengths
between 3.0 and
14.0 micrometers.
What Is Remote Sensing Actually Sensing?
able to see ultraviolet (UV) light (like bees can) and if you could see slightly
longer wavelengths of energy, you’d be able to see infrared light. However,
the human eye is only sensitive to electromagnetic energy in this very small
range of wavelengths.
The visible spectrum can be broken down further to the colors that it
represents. Shorter visible light wavelengths (between 0.4 and 0.5 micrometers) represent the blue portion of the spectrum. Medium visible light
wavelengths (between 0.5 and 0.6 micrometers) represent the green portion of the spectrum. Longer visible light wavelengths (between 0.6 and
0.7 micrometers) represent the red portion of the spectrum. For instance,
when you see a shirt with a bright red color, your eyes are actually sensing the reflection of light with a wavelength measurement somewhere between 0.6 and 0.7 micrometers.
Each of these narrow portions of wavelengths of the electromagnetic
spectrum that represents a different form of light is referred to as a band
of energy in remote sensing. For example, the shorter wavelengths of 0.4
to 0.5 micrometers are referred to as the blue band of the electromagnetic
spectrum since the properties of those wavelengths of light correspond to the
characteristics of blue energy. Similarly, the section of wavelengths between
0.5 and 0.6 micrometers make up the green band of the electromagnetic
spectrum, and the range of wavelengths of 0.6 to 0.7 micrometers make up
the red band.
Keep in mind that while the human eye is restricted to seeing only
these narrow bands of the electromagnetic spectrum, remote sensing devices have the capability to sense energy from other portions of the spectrum. For instance, the infrared (IR) light portion of the electromagnetic
spectrum extends to wavelengths between 0.7 and 100 micrometers in
length. A sensor could be tuned to only measure the reflection of a narrow infrared band of energy between 0.7 and 0.9 micrometers, and even
though this energy is not visible to the human eye, a remote sensing device can easily measure this reflection of energy. As we’ll see, there’s an
enormous amount of information that can be gained from examining the
reflection of these other forms of energy off objects. When doing remote
sensing of infrared light, there are a few wavelength ranges that are commonly utilized:
a 0.7 to 1.3 micrometers—Bands of this portion are referred to as “near
infrared” (NIR), which is commonly used by satellite remote sensing (see
Chapter 11) and also in infrared photography (see Chapter 9).
a 1.3 to 3.0 micrometers—Bands of this portion are referred to as “middle
infrared” (MIR), which is also utilized by different satellite sensors. For
instance, measurements of bands of MIR energy are used in studies related to water content of plants.
a 3.0 to 14.0 micrometers—Bands of this portion are referred to as “thermal
infrared” (TIR), which is used for measuring heat sources or radiant heat
energy.
UV (ultraviolet)
the portion of the
electromagnetic
spectrum with
wavelengths
between 0.01 and
0.4 micrometers.
band a narrow range
of wavelengths being
measured by a remote
sensing device.
blue band the range
of wavelengths
between 0.4 and
0.5 micrometers.
green band the
range of wavelengths
between 0.5 and 0.6
micrometers.
red band the range
of wavelengths
between 0.6 and
0.7 micrometers.
IR (infrared) the portion
of the electromagnetic
spectrum with
wavelengths
between 0.7 and
100 micrometers.
NIR (near infrared)
the portion of the
electromagnetic
spectrum with
wavelengths
between 0.7 and
1.3 micrometers.
MIR (middle infrared)
the portion of the
electromagnetic
spectrum with
wavelengths
between 1.3 and
3.0 micrometers.
TIR (thermal infrared)
the portion of the
electromagnetic
spectrum with
wavelengths
between 3.0 and
14.0 micrometers.