In the images, the white areas represent the ocean and large lakes.
The bright colors (red, light blue, etc) represent a high Normalized Digitized Vegetation
Index (NDVI) values, while the
dark colors represent low NDVI values. Seasonal variations of the NDVI values are
noticeable in the animations.
Northeast US
Japan and Korea
The NDVI is defined by
Where b2 and b1 refer to the reflected radiation at channel 2 (IR radiation)
and channel 1 (visible red light). High values of NDVI, representing high
reflectance in the IR band (and low reflectance in the red), means the foliage
is healthy and abundant with green vegetation, where as low values could reflect
on the lack of green leaves, higher pigmentation, or unhealthy foliage. Most plants,
trees, vegetation, and agricultural land have characteristic reflection spectrums.
NDVI values can be used for analyzing seasonal variations in the foliage, monitoring
agricultural activities, or studying the effects of deforestation and urban development.
Differences in NDVI values can be attributed to locations like mountainous areas,
desert areas, and rain forests.
The data was part of the NOAA/NASA Pathfinder Advance Very High-Resolution Radiometer
(AVHRR) Land program. The AVHRR is a broad band sensor operating with 5 bands: 1 in the red,
1 in the near IR, and three bands in the far IR as listed in the table. The period covered is
from 1981 to 1994 using the meteorological satellites NOAA-7, 9, and 11. The satellites are sun
synchronous, near polar orbits (inclinations of 98.8 degrees) with an altitude of 833 km and
orbital periods of 102 minutes. The sensor provides global area coverage with resolutions of
4 km resolution at nadir with a swath of 2399 km wide. Data was recorded during the afternoon
hours of LMT.
