简介：
GADM database of Global Administrative AreasGADM is a spatial database of the location of the world's administrative areas (or adminstrative boundaries) for use in GIS and similar software. Administrative areas in this database are countries and lower level subdivisions such as provinces, departments, bibhag, bundeslander, daerah istimewa, fivondronana, krong, landsvæðun, opština, sous-préfectures, counties, and thana. GADM describes where these administrative areas are (the "spatial features"), and for each area it provides some attributes, foremost being the name and variant names.
The current version is 1.0
The data are available as shapefile, ESRI geodatabase, RData, and Google Earth kmz format. Shapefiles can be used for most mapping and "GIS" software (you can download a free program such as Q-GIS or DIVA-GIS. The RData files can be used in R with the 'sp' package loaded.
Here is more information on formats and their limitations.
You can download country level files (recommended) or files covering the entire world
Our goal is to map all administrative areas of all countries, at all levels, at any time period. We use a high spatial resolution, and of a extensive set of attributes for each spatial feature. This is a never ending project, but we are happy to share what we have so far. The current version of GADM maps 226,439 administrative areas (or 167,176 if you count only the lowest level for each country). You can see them on these maps.
Our intention is to transform this project into a global collaborative effort. We still need to work out the best way of organizing this. But please contribute in whatever way you can by sending us a message to point out errors, or even better, to send an improved file for a country of your interest.

USA Adm GIS data - In GADM, a "country" is any entity with an ISO country code. Frequently these are not sovereign states. For example Greenland is an "ISO-country", and so are the Faroe Islands, and so is Denmark. Together these three ISO-countries form the Kingdom of Denmark, a single state (or country - but not for GADM). Worse still is that the world continues to have many disputes about the sovereignty over areas. We do not wish to express any opinion about such matters and we try to map the de-facto situation.
Here is a map of all countries and their bounding boxes (when using a lat/long "projection"), highlighting those countries that cross the international date line, and for which these bounding boxes make little sense (this map is provided for entertainment only).

The coordinate reference system is latitude/longitude and theWGS84 datum.

File Formats
A "shapefile" consist of at least three actual files. This is a commonly used format that can be directly used in Arc-anything, DIVA-GIS, and many other programs. Unfortunately, non-latin characters are garbled.

An "ESRI geodatabase" is an MS Access fole that can be opened in ArcGIS (an expensive but powerful program). One of its advantages, compared to a shapefile, is that it can store non-latin characters (e.g. Cyrillic and Chinese characters).

A "Google Earth .kmz" file can be opened in Google Earth.

A "RData" file can be used in R (with the sp package loaded)

Some files have been compressed and grouped in ZIP files. You can use programs such as 7-zip, PKZIP or StuffIt to decompress the files.
GIS 数据共享机制研究
蔡爱民1 , 　查良松2
(1. 滁州学院地理系,安徽滁州　239012 ; 2. 安徽师范大学国土资源与旅游学院,安徽芜湖　241000)
摘　要:实现GIS 数据共享已成为GIS 发展的迫切需要. 分析了需要数据共享的原因,评述了当前
处理数据共享的几个途径. 认为实现GIS 数据共享的根本途径是制定全球统一的数据格式,辅之
以政府的宏观调控和引导.
关键词: GIS ;数据共享;数据格式
中图分类号:P91 　　文献标识码:A 　　文章编号:1001 - 2443 (2005) 02 - 0226 - 04