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1.4 +
1.5 +##############################################################################
1.6 +# University of Maryland Global Land Cover Classifications #
1.7 +# at 0.25, 0.5 and 1 degree (1992-1993) #
1.8 +##############################################################################
1.9 +
1.10 +The files in this directory were provided by Drs. Ruth DeFries and Matt Hansen
1.11 +from the Department of Geography at the University of Maryland, College Park.
1.12 +These are global, coarse resolution (1/4, 1/2 and 1 degree spatial resolutions)
1.13 +land cover classifications (dominant type and fractional cover) generated using
1.14 +data from the Advanced Very High Resolution Radiometer (AVHRR) (see Hansen et
1.15 +al. 2000).
1.16 +
1.17 +The objective of this study was to create a land cover map derived from 1
1.18 +kilometer AVHRR data using all available bands and derived Normalized Difference
1.19 +Vegetation Index (NDVI) and a full year of data (April 1992-March 1993). This
1.20 +thematic map was resampled to 0.25, 0.5 and 1.0 degree grids for the
1.21 +International Satellite Land Surface Climatology Project (ISLSCP) data
1.22 +initiative II. During this re-processing, the original UMD land cover type and
1.23 +fraction maps were adjusted to match the water/land fraction of the ISLSCP II
1.24 +land/water mask. These maps were generated for use by modelers of global
1.25 +biogeochemical cycles and others in need of an internally consistent,
1.26 +global depiction of land cover. This 1km map was also one of the MODIS (Moderate
1.27 +Resolution Imaging Spectroradiometer) at-launch land cover maps.
1.28 +
1.29 +The data set describes the geographic distributions of 13 classes of vegetation
1.30 +cover (plus water and unclassified classes) based on a modified International
1.31 +Geosphere-Biosphere Programme (IGBP) legend (Rasool 1992). The data set also
1.32 +provides the fraction of each of the 15 classes within the coarser resolution
1.33 +cells. The data set is provided at three spatial resolutions of 0.25, 0.5 and 1
1.34 +degrees in latitude and longitude. We refer the reader to the reference below
1.35 +for more information on data processing of the original 1km data set.
1.36 +
1.37 +Please acknowledge Drs. DeFries and Hansen and the ISLSCP2 data collection when
1.38 +these data are used. Please cite the following publications when these data are
1.39 +used:
1.40 +
1.41 +Hansen, M. C., DeFries, R.S., Townshend, J.R.G., and Sohlberg, R., 2000, Global
1.42 +land cover classification at 1km spatial resolution using a classification tree
1.43 +approach, International Journal of Remote Sensing, 21, 1331-1364.
1.44 +
1.45 +Any problems encountered with the data set should be reported to Eric Brown de
1.46 +Colstoun at ericbdc@ltpmail.gsfc.nasa.gov
1.47 +
1.48 +##############################################################################
1.49 +
1.50 +File Name Convention
1.51 +--------------------
1.52 +The data sets in this directory are provided at three spatial resolutions of
1.53 +0.25, 0.5 and 1 degrees lat./long. For each spatial resolution there is a land
1.54 +cover type classification layer (with numbers from 0 to 14) and 15 associated
1.55 +layers that provide the fraction, from 0 to 100, of each land cover type per
1.56 +cell. The land cover type files are named umd_landcover_class_XX.asc, where XX
1.57 +is qd, hd, or 1d, denoting a spatial resolution of 1/4, 1/2 or 1 degrees,
1.58 +respectively. The fractional files are called umd_landcover_XX_cZZ.asc, where XX
1.59 +is the same as above, and ZZ is a number from 00 to 14 which represents the land
1.60 +cover type code as described below. As an example, the file named
1.61 +umd_landcover_qd_c02.asc is the fraction of Evergreen Broadleaf Forest at a
1.62 +quarter degree spatial resolution. This file is associated with the
1.63 +umd_landcover_class_qd.asc land cover type file.
1.64 +
1.65 +##############################################################################
1.66 +
1.67 +ASCII File Format
1.68 +------------------
1.69 +All of the files in the ISLSCP Initiative II data collection are in the ASCII,
1.70 +or text format. The file format consists of numerical fields of varying length,
1.71 +which are delimited by a single space and arranged in columns and rows. The
1.72 +values in the land cover class type files are written as integers from 0 to 14.
1.73 +All values in the land cover fraction files are written as real numbers.
1.74 +
1.75 +The files at different spatial resolutions each contain the following numbers of
1.76 +columns and rows:
1.77 + One degree: 360 columns by 180 rows
1.78 + 1/2 degree: 720 columns by 360 rows
1.79 + 1/4 degree: 1440 columns by 720 rows
1.80 +
1.81 +All files are gridded to a common equal-angle lat/long grid, where the
1.82 +coordinates of the upper left corner of the files are located at 180oW, 90oN and
1.83 +the lower right corner coordinates are located at 180oE, 90oS. Data in the files
1.84 +are ordered from North to South and from West to East beginning at 180 degrees
1.85 +West and 90 degrees North.
1.86 +
1.87 +The data files are PKZip compressed. On UNIX, they can be decompressed using the
1.88 +"unzip -a" command. On Windows, they can be decompressed using WinZip or other
1.89 +PKZip software. On the Macintosh, they can be decompressed using Stuffit
1.90 +Expander.
1.91 +
1.92 +################################################################################
1.93 +
1.94 +Land Cover Type Codes and Definitions
1.95 +-------------------------------------
1.96 +The following 15 classes are used. Note that here are no cells with a value of
1.97 +13 (Urban and Builtup) in the 1degree land cover type file.
1.98 +
1.99 +0 = Water bodies: oceans, seas, lakes, reservoirs, and rivers. Can be either
1.100 + fresh or salt water. This class is derived from a land/water mask.
1.101 +
1.102 +1 = Evergreen Needleleaf Forests: lands dominated by trees with a percent canopy
1.103 + cover >60% and height exceeding 5m. Almost all trees remain green all year.
1.104 + Canopy is never without green foliage.
1.105 +
1.106 +2 = Evergreen Broadleaf Forests: lands dominated by trees with a percent canopy
1.107 + cover > 60% and height exceeding 5m. Almost all trees remain green all year.
1.108 + Canopy is never without green foliage.
1.109 +
1.110 +3 = Deciduous Needleleaf Forest: lands dominated by trees with a percent canopy
1.111 + cover >60% and height exceeding 5m. Trees shed their leaves simultaneously in
1.112 + response to cold seasons.
1.113 +
1.114 +4 = Deciduous Broadleaf Forests: lands dominated by trees with a percent canopy
1.115 + cover >60% and height exceeding 5m. Trees shed their leaves simultaneously in
1.116 + response to dry or cold seasons.
1.117 +
1.118 +5 = Mixed Forests: lands dominated by trees with a percent canopy cover >60% and
1.119 + height exceeding 5m. Consists of tree communities with interspersed mixtures or
1.120 + mosaics of needleleaf and deciduous forest types. Neither type has <25% or >75%
1.121 + landscape coverage.
1.122 +
1.123 +6 = Woodlands: lands with herbaceous or woody understories and tree canopy cover
1.124 + of >40% and <60%. Trees exceed 5m in height and can be either evergreen or
1.125 + deciduous.
1.126 +
1.127 +7 = Wooded Grasslands/Shrublands: lands with herbaceous or woody understories and
1.128 + tree canopy cover of >10% and <40%. Trees exceed 5m in height and can be either
1.129 + evergreen or deciduous.
1.130 +
1.131 +8 = Closed Bushlands or Shrublands: lands dominated by bushes or shrubs. Bush and
1.132 + shrub percent canopy cover is >40%. Bushes do not exceed 5m in height. Shrubs
1.133 + or bushes can be either evergreen or deciduous. Tree canopy cover is <10%. The
1.134 + remaining cover is either barren or herbaceous.
1.135 +
1.136 +9 = Open Shrubland: lands dominated by shrubs. Shrub canopy cover is >10% and
1.137 + <40%. Shrubs do not exceed 2m in height and can be either evergreen or
1.138 + deciduous. The remaining cover is either barren or of annual herbaceous type.
1.139 +
1.140 +10 = Grasslands: lands with continuous herbaceous cover and <10% tree or shrub
1.141 + canopy cover.
1.142 +
1.143 +11 = Croplands: lands with >80% of the landscape covered in crop-producing fields.
1.144 + Note that perennial woody crops will be classified as the appropriate forest or
1.145 + shrubs land cover type.
1.146 +
1.147 +12 = Barren: lands of exposed soil, sand, rocks, snow or ice which never have more
1.148 + than 10% vegetated cover during any time of year.
1.149 +
1.150 +13 = Urban and Builtup: land covered by buildings and other man-made structures.
1.151 + Note that this class is not mapped from the AVHRR imagery but is developed from
1.152 + the populated places layer that is part of the Digital Chart of the World (Danko
1.153 + 1992).
1.154 +
1.155 +14 = Unclassified: Points where the ISLSCP2 land/sea mask was labeled as land and
1.156 + the UMD original data had sea and which could not be filled in from a 3 by 3
1.157 + average of surrounding cells.
1.158 +