332
Chapter 11 Images from Space
Landsats 4 and 5 were also equipped with a new remote sensing device
called the TM (Thematic Mapper). The TM was also a multispectral sensor
that allowed for sensing in seven bands in the electromagnetic spectrum
simultaneously as follows:
a Band 1: Blue (0.45 to 0.52 micrometers)
a Band 2: Green (0.52 to 0.60 micrometers)
a Band 3: Red (0.63 to 0.69 micrometers)
a Band 4: Near infrared (0.76 to 0.90 micrometers)
a Band 5: Middle infrared (1.55 to 1.75 micrometers)
a Band 6: Thermal infrared (10.4 to 12.5 micrometers)
a Band 7: Middle infrared (2.08 to 2.35 micrometers)
These bands were chosen for TM because they were key to a variety of
studies (such as bands 3 and 4 being used for vegetation monitoring and NDVI
as discussed in Chapter 10), while band 5 is useful when examining the water
content of plants and band 7 is useful in separating various rock and mineral
types. The thermal band 6 enabled the monitoring of heat energy in a variety
of settings. The TM bands had improved radiometric resolution over MSS of
8 bits while the spatial resolution of bands 1-5 and 7 was improved to 30 meters (band 6 had a spatial resolution of 120 meters) and had a swath width
of 185 kilometers. TM also had an improved temporal resolution of 16 days.
Landsat 4 was launched in 1982 and ended its mission in 1993. Landsat 5
was launched in 1984 and still continues sensing and transmitting viable data
to Earth today. Landsat 5 is more than twenty-five years old, so it should raise
some curiosity that it’s still relied upon so heavily, given the importance of
Landsat in remote sensing. Landsat 5 was not likely intended to be the cornerstone of the program—however, Landsat 6 (launched in 1993) did not achieve
orbit and was lost, continuing the mission of Landsat 5.
Landsat 7 (Figure 11.8) was launched in 1999, not carrying either the
MSS or the TM, but a new sensor called the ETM+ (Enhanced Thematic Mapper Plus). This new device senses the same 7 bands as TM at the same swath
width and radiometric and spatial resolutions (although the thermal band 6’s
spatial resolution was improved to 60 meters), but also added a new eighth band,
a panchromatic one with a spatial resolution of 15 meters. With this improved
spatial resolution, the panchromatic band could be used to pan-sharpen the
quality of the other imagery. Landsat 7’s temporal resolution was still 16 days
but could acquire about 250 images per day (see Figure 11.9 for an example of
Landsat 7 imagery and Hands-on Application 11.2: Streaming Landsat Imagery
on page 334 for some examples of recent imagery collected by Landsat).
Each Landsat scene measures an area about 170 kilometers long by
183 kilometers wide (for the TM and ETM+ sensors) and is considered a
separate image. At this size, it would take several images just to cover one
state. Thus, if you want access to imagery of a particular area, you need to
know which scene that ground location is in. Landsat uses a Worldwide Reference System that divides the entire globe into a series of Paths (columns)
TM the Thematic
Mapper sensor onboard
Landsat 4 and 5.
Landsat 5 the fifth
Landsat mission,
launched in 1984,
which carries both the
TM and MSS sensors.
Landsat 7 the seventh
Landsat mission,
launched in 1999,
which carries the ETM+
sensor.
ETM+ the Enhanced
Thematic Mapper sensor
onboard Landsat 7.
Landsat scene a
single image obtained
by a Landsat satellite
sensor.
Worldwide Reference
System the global
system of Paths and
Rows that is used to
identify what area
on Earth’s surface
is present in which
Landsat scene.
Chapter 11 Images from Space
Landsats 4 and 5 were also equipped with a new remote sensing device
called the TM (Thematic Mapper). The TM was also a multispectral sensor
that allowed for sensing in seven bands in the electromagnetic spectrum
simultaneously as follows:
a Band 1: Blue (0.45 to 0.52 micrometers)
a Band 2: Green (0.52 to 0.60 micrometers)
a Band 3: Red (0.63 to 0.69 micrometers)
a Band 4: Near infrared (0.76 to 0.90 micrometers)
a Band 5: Middle infrared (1.55 to 1.75 micrometers)
a Band 6: Thermal infrared (10.4 to 12.5 micrometers)
a Band 7: Middle infrared (2.08 to 2.35 micrometers)
These bands were chosen for TM because they were key to a variety of
studies (such as bands 3 and 4 being used for vegetation monitoring and NDVI
as discussed in Chapter 10), while band 5 is useful when examining the water
content of plants and band 7 is useful in separating various rock and mineral
types. The thermal band 6 enabled the monitoring of heat energy in a variety
of settings. The TM bands had improved radiometric resolution over MSS of
8 bits while the spatial resolution of bands 1-5 and 7 was improved to 30 meters (band 6 had a spatial resolution of 120 meters) and had a swath width
of 185 kilometers. TM also had an improved temporal resolution of 16 days.
Landsat 4 was launched in 1982 and ended its mission in 1993. Landsat 5
was launched in 1984 and still continues sensing and transmitting viable data
to Earth today. Landsat 5 is more than twenty-five years old, so it should raise
some curiosity that it’s still relied upon so heavily, given the importance of
Landsat in remote sensing. Landsat 5 was not likely intended to be the cornerstone of the program—however, Landsat 6 (launched in 1993) did not achieve
orbit and was lost, continuing the mission of Landsat 5.
Landsat 7 (Figure 11.8) was launched in 1999, not carrying either the
MSS or the TM, but a new sensor called the ETM+ (Enhanced Thematic Mapper Plus). This new device senses the same 7 bands as TM at the same swath
width and radiometric and spatial resolutions (although the thermal band 6’s
spatial resolution was improved to 60 meters), but also added a new eighth band,
a panchromatic one with a spatial resolution of 15 meters. With this improved
spatial resolution, the panchromatic band could be used to pan-sharpen the
quality of the other imagery. Landsat 7’s temporal resolution was still 16 days
but could acquire about 250 images per day (see Figure 11.9 for an example of
Landsat 7 imagery and Hands-on Application 11.2: Streaming Landsat Imagery
on page 334 for some examples of recent imagery collected by Landsat).
Each Landsat scene measures an area about 170 kilometers long by
183 kilometers wide (for the TM and ETM+ sensors) and is considered a
separate image. At this size, it would take several images just to cover one
state. Thus, if you want access to imagery of a particular area, you need to
know which scene that ground location is in. Landsat uses a Worldwide Reference System that divides the entire globe into a series of Paths (columns)
TM the Thematic
Mapper sensor onboard
Landsat 4 and 5.
Landsat 5 the fifth
Landsat mission,
launched in 1984,
which carries both the
TM and MSS sensors.
Landsat 7 the seventh
Landsat mission,
launched in 1999,
which carries the ETM+
sensor.
ETM+ the Enhanced
Thematic Mapper sensor
onboard Landsat 7.
Landsat scene a
single image obtained
by a Landsat satellite
sensor.
Worldwide Reference
System the global
system of Paths and
Rows that is used to
identify what area
on Earth’s surface
is present in which
Landsat scene.