These Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER)
images cover an area of 8 x 4 km in Railroad Valley,
NV, and were acquired August 17, 2001. The top image shows center-pivot
irrigated fields, with healthy vegetation in red. The middle image
displays the Normalized Difference Vegetation Index (NDVI), a calculated
quantity that portrays the amount of vegetation. (To learn more about NDVI, read: Measuring Vegetation)
The color code shows
highest vegetation content in dark green, low vegetation cover in light green and pale yellow,
and barren areas in light brown. The bottom image is a
thermal infrared channel, with warmer temperatures in white, and colder
in black. In the thermal image, the northern-most and western-most
fields are markedly colder on their northwest areas, even though no
differences are seen in the visible image or the NDVI image. This can be
attributed to the presence of excess water, which can lead to crop
damage. The combination of information from different bands is a
powerful tool to monitor crop health and maintenance procedures.
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This image originally appeared on the Earth Observatory. Click here to view the full, original record.