1 km Global Continuous Fields Tree Cover Derived from Remote Sensing

Characterization of terrestrial vegetation from the Advanced Very High Resolution Radiometer (AVHRR) on the global to regional scale has traditionally been accomplished using classification schemes with discrete numbers of vegetation classes. Representation of vegetation into a limited number of homogeneous classes does not account for the variability within land cover, nor does the portrayal recognize transition zones between adjacent cover types. An alternative paradigm to describing land cover as discrete classes is to represent land cover as continuous fields of vegetation characteristics using a linear mixture model approach. This prototype data set, created by researchers at the Global Land Cover Facility (GLCF) at the University of Maryland, contains 1 km cells for estimating: 1) Percent tree cover; 2) Percentage cover for two layers representing leaf longevity (evergreen and deciduous); and 3) Percentage cover for two layers estimating leaf type (needleleaf and broadleaf).

Data acquired in 1992-93 from NOAA's AVHRR at a 1 km spatial resolution and processed under the guidance of the International Geosphere Biosphere Programme (IGBP) were used to derive the tree cover, leaf longevity, and leaf type maps. Each pixel in the layers has a value between 10 and 80 percent. These layers can be directly used as parameters in models or aggregated into more conventional land cover maps. For the latter, the product offers the flexibility to derive land cover maps based on user's requirements for a particular application. The product is intended for use in terrestrial carbon cycle models, in conjunction with other spatial data sets such as climate and soil type, to obtain more consistent and reliable estimates of carbon stocks.

The data are provided as UNIX compressed files in a choice of three formats: 1) BSQ binary Goode's projection, 2) BSQ binary lat/long projection (Plate Carree projection), and 3) ASCII grid lat/long projection (for Arc/Info or other GIS software). There are global coverage files as well as files for the following regions: Africa, Eurasia, Asia-Pacific, North America, and South America. Additional information and references on this data set can be found at the GLCF web site.