Orthorectified Landsat data were obtained from the University of Maryland Global Land Cover Facility. These data are from the Landsat 7 satellite and table 1 lists the spectral bands that were measured. Coverage of the study area required data from four Landsat scenes. Because of radiometric differences among the scenes, corrections were applied to them to achieve spectral consistency in the study area. Data from the overlap between scenes were used to calculate transformation equations designed to make histograms of the data approximately the same.
Figure 11 shows a composite image of Landsat visible bands (3, 2, 1) as shades of red, green, and blue. Figure 12 shows a composite image of Landsat red bands (5, 4, 3) as shades of red, green, and blue. Figure 13 shows a composite image of Landsat infrared bands (5, 4, 7) as shades of red, green, and blue. For those interested in more information about Landsat images, NASA offers an on-line tutorial on remote sensing.
According to Knepper and Simpson (1992), the ratio of band 5 to band 7 detects mineral groups that include clays (kaolinite, montmorillonite, illite), micas (muscovite, biotite, lepidolite), carbonates (calcite, dolomite, borax), sulfates (alunite, gypsum, jarosite), and various alteration minerals. Band ratio 5/7 also detects vegetation. From data in table C-2 of Vincent (1997), most of these minerals and vegetation should appear as light gray to white on a 5/7 image. Illite and biotite, however, would be dark gray to black. A band ratio 3/1 image detects iron oxides (hematite, goethite, jarosite) (Knepper and Simpson, 1992) and the iron oxides should appear as light gray to white in a 3/1 image (table C-2, Vincent, 1997). A band ratio 3/4 image is not very diagnostic for minerals but is very dark for vegetation and can be used to identify areas where vegetation dominates the spectral response (Knepper and Simpson, 1992). Figure 14 shows a color-ratio composite (CRC) of band ratios 3/4, 3/1, and 5/7 as shades of red, green, and blue.
Table 1. Landsat spectral bands.
|
Band Number |
Spectral Range (Microns) |
EM Region |
General Applications |
|
1 |
0.45 - 0.52 |
Visible Blue |
Coastal water mapping, differentiation of vegetation from soils |
|
2 |
0.52 - 0.60 |
Visible Green |
Assessment of vegetation vigor |
|
3 |
0.63 - 0.69 |
Visible Red |
Chlorophyll absorbtion for vegetation differentiation |
|
4 |
0.76 - 0.90 |
Near Infrared |
Biomass surveys and delineation of water bodies |
|
5 |
1.55 - 1.75 |
Middle Infrared |
Vegetation and soil moisture measurements; differentiation between snow and cloud |
|
6 |
10.40- 12.50 |
Thermal Infrared |
Thermal mapping, soil moisture studies and plant heat stress measurement |
|
7 |
2.08 - 2.35 |
Middle Infrared |
Hydrothermal mapping |
Intro | Geology | Gamma-ray Data | Landsat Data | Maps | Discussion | Conclusions | Listing of Data Files | References | Tutorial
U.S. Department of the Interior |
U.S. Geological Survey
URL: http://pubsdata.usgs.gov/pubs/of/2005/1371/html/landsat.htm
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