12.3 Global Vegetation Map

NOAA AVHRR data (see 5.1) are very useful for producing a global vegetation maps which cover the whole world, because NOAA has edited global cloud free mosaics in the form of a GVI(global vegetation index) on a weekly basis since April of 1982.

The GVI data include information about NDVI (normalized difference vegetation index) as computed as follows

Ch.1 : visible band
Ch.2 : near infrared band

NDVI is sometimes simply called. NVI (normalized vegetation index).

NDVI or NVI are indicators of the intensity of biomass.

The larger the NVI is, the denser the vegetation.

Though the original resolution of NOAA AVHRR is 1.1 km per pixel of the Equator, the GVI has a low resolution of 16 km x 16 km per pixel at the Equator. In spite of the low resolution, the GVI is useful for producing a global vegetation map.

As much noise is involved in weekly data, noise free GVI compiled on a monthly base should be used. Figure 12.3.1 shows six categories out of a total of 13 categories obtained from cluster analysis (see 11.2).

Figure 12.3.2 shows the result of a cluster analysis applied to GVI data from 1987.

Though the clustered map in Figure 12.3.2 has not yet been verified, it shows the possibility of using remote sensing data for global map production.


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