Your browser does not appear to support JavaScript, or you have turned JavaScript off. You may use unl.edu without enabling JavaScript, but certain functions may not be available.

TM Band

Wavelength

Spectral Region

Target Reflectance

1

0.45-0.52

Blue-green

Separation of Soil &Vegetation

2

0.52-0.60

Green

Reflection from Vegetation

3

0.63-0.69

Red

Chlorophyll Absorption

4

0.76-0.90

Near-IR

Delineation of Water Bodies

5

1.55-1.75

Mid-IR

Vegetative Moisture

7

2.08-2.35

Mid-IR

Plant Heat Stress

6

10.4-12.5

Thermal

Hydrothermal Mapping

Landsat data can be used to interpret numerous phenomena. The
interpretations are based on the spectral reflectance of the
target. Spectral reflectance is the portion of the
incident energy that is reflected. These spectral reflectance
curves chart the reflectance of soil, vegetation, and water as a
function of wavelength.

The fraction of energy reflected at a particular wavelength
varies with different earth features, and the reflectance of each
earth feature varies at different wavelengths. Thus, two features
that are indistinguishable in one spectral range may be very
different in another wavelength band.

Soil: Soil texture, surface roughness, and the presence
of moisture, iron oxide, and organic matter can reduce soil
reflectance in the visible region. Decreases in soil reflectance
because of moisture are most notable in TM bands 5 and 7, which
provide useful information for building construction and soil
trafficability.

Vegetation: The spectral reflectance curve for healthy,
green vegetation normally shows peaks and valleys. The
reflectance in bands 1, 2, and 3 is indicated by pigments in
plant leaves. Chlorophyll strongly absorbs energy in wavelengths
of 0.45 and 0.67m. Healthy vegetation appears green because of
the relatively high reflection of green energy by plant leaves
and the high absorption of blue and red.

Reflectance in near-infrared Band 4 is determined by plant
cell structure. In the mid-infrared bands 5 and 7, reflectance is
due to plant water content.

A plant's spectral reflectance varies during its cycle of
growth. The reflectance of a plant canopy depends upon the depth,
density, age and diversity of the canopy.

Water: In the visible wavelengths, the energy reaching
the sensor from a water body may be reflected from the surface of
the water, from particulates in the water, or from the bottom if
the water is clear and shallow. Water containing large quantities
of suspended sediment normally has much higher reflectance than
clear water in the same geographic area.

The three most common materials suspended in water are
chlorophyll, tannin, and non-organic sediments. Because an
increase in chlorophyll tends to decrease water reflectance in
blue wavelengths and increase in green wavelengths, analysts can
use Landsat TM data to monitor algae. Reflectance data can also
be used to determine the presence of tannin dyes in bogs.

The visible bands provide information on water turgidity,
bathymetry, currents and sediment plumes. Because water absorbs
energy at infrared wavelengths, the infrared bands are used to
easily locate and delineate water bodies.

Energy sensed with Band 6 is emitted, not reflected, from the
earth's surface. Because it is not dependent on reflected
sunlight, Band 6 imagery can be collected at night.

Since water is the only object whose emissivity is constant
under different conditions, its temperature can be reliably
estimated from it's radiance. Analysts often spot potential
safety or environmental problems with Band 6 data by monitoring
the water temperature of the cooling ponds and rivers near
nuclear power plants.