Landsat TM NDVI

The Landsat Thematic Mapper, a satellite sensor that shows much more detailed surface information than the NOAA AVHRR also captured the drought of 1999. The following NDVI images show just a portion of the Chesapeake Bay watershed, mostly within Maryland and centered on Washington DC, for July of 1997 and 1999. The Chesapeake Bay and other water bodies appear black and one can, for example, trace the Potomac river from the Bay up to Washington DC. These two images are actually from different Landsat satellites - 1997 was from Landsat-5 and 1999 was from the Landsat-7. In fact, this was one of the first Landsat-7 scenes available to the public since it was launched on April 15th.

A comparison of July 14, 1997 and July. 28 1999 shows a number of interesting features. The most obvious is the large cloud bank in the upper left (northwest) corner of the 1999 image, which appears green. It's clear from the 1997 image that the cloud obscured a dense forest area (which appears bright red). Portions of the 1997 image have higher NDVI (more reds) than in 1999, whereas the opposite is true in other areas (e.g., the lower left portion of the images). These differences are easier to identify in the following "change" image, that is, the change in NDVI between years.

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