File Name Convention
--------------------
There are four total files in this data set. Two files contain the land cover 
types representing potential natural vegetation before human alteration and are 
named "potential_veg_XX.asc", where XX can be either hd or 1d, meaning a spatial 
resolution of 0.5 and 1 degree in both latitude and longitude, respectively. The 
two other files are named "potential_veg_diffs_XX.asc" and contain those points 
in the original data set submitted by the Principal Investigator that have been 
modified in order to match the land/water mask of the ISLSCP Initiative II. 
These latter two files can be used with the "potential_veg_XX.asc" files to 
reconstruct the original data set.

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ASCII File Format
------------------
All of the files in the ISLSCP Initiative II data collection are in the ASCII, 
or text format. The file format consists of numerical fields of varying length, 
which are delimited by a single space and arranged in columns and rows. The 
files in this data set contains 720 columns by 360 rows for the 0.5 degree data 
sets, and 360 columns and 180 rows for the 1 degree data sets. Values are 
written as integers varying from 0 to 16 for the "potential_veg_XX.asc" files 
and 0 to 15 for the "potential_veg_diffs_XX.asc" files. 

The files are gridded to a common equal-angle lat/long grid with spatial 
resolutions of 0.5 x 0.5 and 1 x 1 degree in latitude and longitude, where the 
coordinates of the upper left corner of the files are located at 180 degrees W, 
90 degrees N and the lower right corner coordinates are located at 180 degrees E, 
90 degrees S. Data in the files are ordered from North to South and from West to 
East beginning at 180 degrees West and 90 degrees North. 

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Potential Land Cover Type Codes
-------------------------------
The following 17 classes are used. Note that the original land cover categories 
ranged from 0 to 15, with 0 representing both water bodies and missing data. The 
ISLSCP II staff has created two separate categories for this original category 
for water bodies (Value=0) and no data over land (Value=16). The 
"potential_veg_XX.asc" files have values from 0 to 16 and the 
"potential_veg_diffs_XX.asc" files from 0 to 15. 

Each number in the files represents a Vegetation Class for that cell. These
Class Numbers are listed below.

Class #     Biome Type
-------     ----------
   0        Water Bodies (Water bodies OR missing data for
            "potential_veg_diffs_XX.asc" files)
   1        Tropical Evergreen Forest/Woodland
   2        Tropical Deciduous Forest/Woodland
   3        Temperate Broadleaf Evergreen Forest/Woodland
   4        Temperate Needleleaf Evergreen Forest/Woodland
   5        Temperate Deciduous Forest/Woodland
   6        Boreal Evergreen Forest/Woodland
   7        Boreal Deciduous Forest/Woodland
   8        Mixed Forest
   9        Savanna
  10        Grassland/Steppe
  11        Dense Shrubland
  12        Open Shrubland
  13        Tundra
  14        Desert
  15        Polar desert/Rock/Ice
  16        No Data over Land (not included in "potential_veg_diffs_XX.asc" 
            files)