Global Land Cover Characteristics Database

The U.S. Geological Survey (USGS), the University of Nebraska-Lincoln (UNL), and the European Commission's Joint Research Centre (JRC) have generated a 1-km resolution global land cover characteristics database for use in a wide range of environmental research and modeling applications. The global land cover characteristics database was developed on a continent-by-continent basis for Africa, Australia Pacific, Eurasia, North America, and South America. All continental databases share the same map projections (Interrupted Goode Homolosine and Lambert Azimuthal Equal Area), have 1-km nominal spatial resolution, and are based on 1-km Advanced Very High Resolution Radiometer (AVHRR) data spanning April 1992 through March 1993. Each database contains unique elements based on the geographic aspects of the specific continent. In addition, a core set of derived thematic maps produced through the aggregation of seasonal land cover regions are included in each continental database. The continental databases are combined to make six global data sets, each representing a different landscape based on a particular classification legend.

There are now two versions of the Global Land Cover Chacteristics Database available. The first version (Version 1.2) of the Global Land Cover Characteristics database was released to the public in November, 1997. Version 1.2 was produced as an International Geosphere Biosphere Programme-Data and Information System (IGBP-DIS) initiative lead by the Land Cover Working Group and has been subjected to a formal accuracy assessment (the IGBP DISCover classification). Since this version was released, over 200 gigabytes of land cover data have been distributed from the EROS Data Center's anonymous ftp site. Many of the users of the land cover data set have provided feedback (that is, suggestions for additions and improvements). EROS Data Center now offers a revised version of the database (Version 2.0). A formal accuracy assessment has not been conducted for the revised land cover data. The global documentation at [http://edcdaac.usgs.gov/glcc/globdoc2_0.html] provides further information about the validation exercise and the differences between these versions of the Global Land Cover Characteristics Database. The What's New page at [http://edcdaac.usgs.gov/glcc/whatsnew.html] provides information on a new classification schemes, new categories, and a new projection.

The following derived data sets are now available in a global geographic projection with 30 arc second grid cell size:

* Global Ecosystems (Olson, 1994a, 1994b)

* International Geosphere Biosphere Programme Land Cover Classification (DISCover) (Belward, 1996)

* U.S. Geological Survey Land Use/Land Cover System (Anderson and others, 1976)

* Simple Biosphere Model (Sellers and others, 1986)

* Simple Biosphere 2 Model (Sellers and others, 1996)

* Biosphere-Atmosphere Transfer Scheme (Dickinson and others, 1986)

* Vegetation Lifeforms (Running and others, 1995)

The legends for each of these derived data sets can be found in Appendices 1-7 in the global documentation at [http://edcdaac.usgs.gov/glcc/globdoc2_0.html].

美国地质调查局（U.S. Geological Survey, USGS）、内布拉斯加大学林肯分校（University of Nebraska-Lincoln, UNL）与欧盟委员会联合研究中心（European Commission's Joint Research Centre, JRC）共同构建了一套1km分辨率的全球土地覆盖特征数据库，可广泛应用于各类环境研究与模拟建模任务。该全球土地覆盖特征数据库按大洲分块开发，涵盖非洲、澳大利亚-太平洋区域、欧亚大陆、北美洲及南美洲。所有大洲级数据库采用统一的地图投影（中断古德等面积投影（Interrupted Goode Homolosine）与兰伯特方位等面积投影（Lambert Azimuthal Equal Area）），标称空间分辨率均为1km，数据基础为1992年4月至1993年3月期间的1km先进甚高分辨率辐射计（Advanced Very High Resolution Radiometer, AVHRR）观测数据。每个大洲级数据库均包含针对对应大洲地理特征的独有要素，此外各数据库还集成了通过聚合季节性土地覆盖区域得到的核心专题地图集。将所有大洲级数据库整合后，可生成六套全球数据集，每套数据集均基于特定分类图例表征不同的景观类型。

目前全球土地覆盖特征数据库共有两个公开版本。第一版（版本1.2）于1997年11月向公众发布，该版本是由土地覆盖工作组主导的国际地圈生物圈计划-数据与信息系统（International Geosphere Biosphere Programme-Data and Information System, IGBP-DIS）项目成果，已通过正式的精度评估（即IGBP DISCover分类体系）。自该版本发布以来，地球资源数据中心（EROS Data Center）的匿名FTP站点已累计分发超过200吉字节的土地覆盖数据。诸多用户反馈了数据改进相关的建议，因此该中心推出了修订版数据库（版本2.0），该修订版尚未经过正式的精度评估。关于验证工作细节以及两个版本的差异信息，可查阅全球文档：[http://edcdaac.usgs.gov/glcc/globdoc2_0.html]。更新说明页面[http://edcdaac.usgs.gov/glcc/whatsnew.html]则介绍了新版分类体系、新增类别与新投影方式。

以下衍生数据集现已以30角秒网格单元尺寸的全球地理投影格式发布：
* 全球生态系统（Olson, 1994a, 1994b）
* 国际地圈生物圈计划土地覆盖分类（DISCover）（Belward, 1996）
* 美国地质调查局土地利用/土地覆盖系统（Anderson等, 1976）
* 简单生物圈模型（Sellers等, 1986）
* 简单生物圈2号模型（Sellers等, 1996）
* 生物圈-大气传输方案（Dickinson等, 1986）
* 植被生活型（Running等, 1995）

各衍生数据集的分类图例可在上述全球文档的附录1至7中查阅。