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#     University of Maryland Global Land Cover Classifications               #
#                 at 0.25, 0.5 and 1 degree (1992-1993)                      #
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The files in this directory were provided by Drs. Ruth DeFries and Matt Hansen 
from the Department of Geography at the University of Maryland, College Park. 
These are global, coarse resolution (1/4, 1/2 and 1 degree spatial resolutions) 
land cover classifications (dominant type and fractional cover) generated using 
data from the Advanced Very High Resolution Radiometer (AVHRR) (see Hansen et 
al. 2000).

The objective of this study was to create a land cover map derived from 1 
kilometer AVHRR data using all available bands and derived Normalized Difference 
Vegetation Index (NDVI) and a full year of data (April 1992-March 1993). This 
thematic map was resampled to 0.25, 0.5 and 1.0 degree grids for the 
International Satellite Land Surface Climatology Project (ISLSCP) data 
initiative II. During this re-processing, the original UMD land cover type and 
fraction maps were adjusted to match the water/land fraction of the ISLSCP II 
land/water mask. These maps were generated for use by modelers of global 
biogeochemical cycles and others in need of an internally consistent, 
global depiction of land cover. This 1km map was also one of the MODIS (Moderate 
Resolution Imaging Spectroradiometer) at-launch land cover maps.  

The data set describes the geographic distributions of 13 classes of vegetation 
cover (plus water and unclassified classes) based on a modified International 
Geosphere-Biosphere Programme (IGBP) legend (Rasool 1992). The data set also 
provides the fraction of each of the 15 classes within the coarser resolution 
cells. The data set is provided at three spatial resolutions of 0.25, 0.5 and 1 
degrees in latitude and longitude. We refer the reader to the reference below 
for more information on data processing of the original 1km data set.

Please acknowledge Drs. DeFries and Hansen and the ISLSCP2 data collection when 
these data are used. Please cite the following publications when these data are 
used:

Hansen, M. C., DeFries, R.S., Townshend, J.R.G., and Sohlberg, R., 2000, Global 
land cover classification at 1km spatial resolution using a classification tree 
approach, International Journal of Remote Sensing, 21, 1331-1364.

Any problems encountered with the data set should be reported to Eric Brown de 
Colstoun at ericbdc@ltpmail.gsfc.nasa.gov

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File Name Convention
--------------------
The data sets in this directory are provided at three spatial resolutions of 
0.25, 0.5 and 1 degrees lat./long. For each spatial resolution there is a land 
cover type classification layer (with numbers from 0 to 14) and 15 associated 
layers that provide the fraction, from 0 to 100, of each land cover type per 
cell. The land cover type files are named umd_landcover_class_XX.asc, where XX 
is qd, hd, or 1d, denoting a spatial resolution of 1/4, 1/2 or 1 degrees, 
respectively. The fractional files are called umd_landcover_XX_cZZ.asc, where XX 
is the same as above, and ZZ is a number from 00 to 14 which represents the land 
cover type code as described below. As an example, the file named 
umd_landcover_qd_c02.asc is the fraction of Evergreen Broadleaf Forest at a 
quarter degree spatial resolution. This file is associated with the 
umd_landcover_class_qd.asc land cover type file.

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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 
values in the land cover class type files are written as integers from 0 to 14. 
All values in the land cover fraction files are written as real numbers.

The files at different spatial resolutions each contain the following numbers of 
columns and rows:
   One degree: 360 columns by 180 rows 
   1/2 degree: 720 columns by 360 rows 
   1/4 degree: 1440 columns by 720 rows 

All files are gridded to a common equal-angle lat/long grid, where the 
coordinates of the upper left corner of the files are located at 180oW, 90oN and 
the lower right corner coordinates are located at 180oE, 90oS. Data in the files 
are ordered from North to South and from West to East beginning at 180 degrees 
West and 90 degrees North. 

The data files are PKZip compressed. On UNIX, they can be decompressed using the 
"unzip -a" command. On Windows, they can be decompressed using WinZip or other 
PKZip software. On the Macintosh, they can be decompressed using Stuffit 
Expander.

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Land Cover Type Codes and Definitions
-------------------------------------
The following 15 classes are used. Note that here are no cells with a value of 
13 (Urban and Builtup) in the 1degree land cover type file.

0 = Water bodies: oceans, seas, lakes, reservoirs, and rivers.  Can be either 
    fresh or salt water. This class is derived from a land/water mask.

1 = Evergreen Needleleaf Forests: lands dominated by trees with a percent canopy 
    cover >60% and height exceeding 5m. Almost all trees remain green all year. 
    Canopy is never without green foliage.

2 = Evergreen Broadleaf Forests: lands dominated by trees with a percent canopy 
    cover > 60% and height exceeding 5m. Almost all trees remain green all year.  
    Canopy is never without green foliage.

3 = Deciduous Needleleaf Forest: lands dominated by trees with a percent canopy 
    cover >60% and height exceeding 5m. Trees shed their leaves simultaneously in 
    response to cold seasons.

4 = Deciduous Broadleaf Forests: lands dominated by trees with a percent canopy 
    cover >60% and height exceeding 5m. Trees shed their leaves simultaneously in 
    response to dry or cold seasons.

5 = Mixed Forests: lands dominated by trees with a percent canopy cover >60% and 
    height exceeding 5m. Consists of tree communities with interspersed mixtures or 
    mosaics of needleleaf and deciduous forest types. Neither type has <25% or >75% 
    landscape coverage.

6 = Woodlands: lands with herbaceous or woody understories and tree canopy cover 
    of >40% and <60%. Trees exceed 5m in height and can be either evergreen or 
    deciduous.

7 = Wooded Grasslands/Shrublands: lands with herbaceous or woody understories and 
    tree canopy cover of >10% and <40%. Trees exceed 5m in height and can be either 
    evergreen or deciduous.

8 = Closed Bushlands or Shrublands: lands dominated by bushes or shrubs.  Bush and 
    shrub percent canopy cover is >40%. Bushes do not exceed 5m in height. Shrubs 
    or bushes can be either evergreen or deciduous. Tree canopy cover is <10%. The 
    remaining cover is either barren or herbaceous.

9 = Open Shrubland: lands dominated by shrubs.  Shrub canopy cover is >10% and 
    <40%. Shrubs do not exceed 2m in height and can be either evergreen or 
    deciduous. The remaining cover is either barren or of annual herbaceous type.

10 = Grasslands: lands with continuous herbaceous cover and <10% tree or shrub 
     canopy cover.

11 = Croplands: lands with >80% of the landscape covered in crop-producing fields.  
     Note that perennial woody crops will be classified as the appropriate forest or 
     shrubs land cover type.

12 = Barren: lands of exposed soil, sand, rocks, snow or ice which never have more 
     than 10% vegetated cover during any time of year.

13 = Urban and Builtup: land covered by buildings and other man-made structures.  
     Note that this class is not mapped from the AVHRR imagery but is developed from 
     the populated places layer that is part of the Digital Chart of the World (Danko 
     1992).

14 = Unclassified: Points where the ISLSCP2 land/sea mask was labeled as land and 
     the UMD original data had sea and which could not be filled in from a 3 by 3 
     average of surrounding cells.

