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  Landsat TM Images (1982 to present)Back to Title Page

General Comments

The temporal resolution of both Landsat Thematic Mapper (referred to as Landsat TM or TM), which have been collected since 1983, and Landsat MSS data, is about two weeks. The TM data have a spatial resolution of 30 meters, compared to 75 meters for the MSS, and six rather than four spectral bands; three visible bands (blue, green, and red) versus two for the MSS data, plus a near-infrared and two mid-infrared bands versus two near-infrared for the MSS. Therefore, more detailed regional and local eolian erosion vulnerability image maps can be generated using the TM data. However, like the MSS data, its temporal resolution of about two weeks makes the data not very useful for monitoring and detecting active dust storms. Also, because of the relatively high spatial resolution of the TM data, compared to GOES, SeaWiFS, and WiFS, detailed analysis of vegetation dynamics at dust source sites can be made. In the deserts, with the two week revisit time and commonly cloud free conditions it is usually not diffcult to find multitemporal TM data for change analysis between different years and/or seasons to evaluate vegetation changes caused by climate variations at both regional and relatively local scales. This type of multitemporal vegetation change analysis is an important part of this project.

Landsat TM Characteristics

 Spatial Resolution30 m
 Spectral Resolution3 visible
1 NIR
2 mid-IR
 Temporal Resolution2 weeks

Image group 5: Online date, 21 February 2001


Southwestern U.S.
1997 Landsat TM Mosiac
2-4-5 False Color Composite
(525 x 400, 210 kilobytes)
[metadata]
[Click to view Figure 1: Precipitation Graphs]
Figure 1
1992 and 1997 Precipitation
(600 x 800, 40 kilobytes)
A digital image map mosaic was generated using twelve Landsat TM images collected during the summer of 1997 (eight images were collected in June, three on July 15th, and one on May 21st). The 1997 digital image mosaic (shown on the left) represents land surface conditions during a dry season in a dry year. The data are being used to compare with a digital image mosaic generated using 1992 Landsat TM images which represents land surface conditions during a wet season in a wet/El Niño year. The wet year image mosaic was generated using Landsat TM images collected during April 1992. Figure 1 (lower left) shows the regional rainfall for for a portion of the Southwest from 1992 and 1997, (600 x 800, 40 kilobytes).

Besides using the Landsat TM image mosaics to generate digital change images, which help with several issues including those dealing with vegetation change and the transport of fine sediments, we are also using the image maps to extract information about soil types, vegetation cover, and surface armouring/protection. The spatial resolution of the mosaics is 30 meters. Landsat TM bands 2, 4, and 5 were used to generated the color composite shown on the left. In order to better show the land surface information in both bright and dark regions on a single product, a large spatial filter was applied to the data.

Click the 1997 Landsat TM image mosaic thumbnail image (upper left) to view the mosaic at higher resolutions.

Image group 4: Online date, 22 February 1999

[Landsat TM 234 Color Composite]
Landsat TM
2-3-4 False Color Composite
Kelso Dunes Area
(600 x 691, 740 kilobytes)		[Landsat TM 234 Color Composite]
Landsat TM
2-3-4 False Color Composite
Laughlin, Nevada Area
(600 x 691, 780 kilobytes)		Click one of the thumbnails to view a pair of images collected on two different dates: 19 April 1992 and 20 June 1997. The images are animated, alternating (blinking) between the pair, to better visualize where vegetation and other surface changes have occured. Viewing images in this manner allows one to easily see changes between the two dates.

The blink animations require a JavaScript capable/enabled browser, such as Netscape or MS Internet Explorer versions 3.0 and higher. Contact webman@TerraWeb.wr.usgs.gov for help or comments.


Image group 2: Online date, 12 August 1998

[Landsat TM 245 Color Composite]
Landsat TM
2-4-5 False Color Composite
20 June 1997
(732 x 688, 336 kilobytes)		[Landsat TM Eolian Vulnerability Map]
Landsat TM
Eolian Erosion Vulnerability Image Map
20 June 1997
(732 x 688, 283 kilobytes)		Click one of the thumbnails to view an 10x compressed overview image and access full resolution images of subareas of particular interest.

Click on the Blink button to view a 10x compressed image pair: the false color composite and the eolian erosion vulnerability image map of the region. The images will be animated, alternating (blinking) back and forth between the pair. Viewing images in this manner allows one to easily compare vulnerable areas (yellow tones in the map) with the false color composite.

The blink animations require a JavaScript capable/enabled browser, such as Netscape or MS Internet Explorer versions 3.0 and higher. Contact webman@TerraWeb.wr.usgs.gov for help or comments.

[Blink] 		 

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Online Since: 12 August 1998
Last Modified: 22 February 1998
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