土地覆盖和土地覆盖的自然变更，在地球系统的气候和生物化学全球尺度模式中扮演着重要角色，对全球生态环境产生着巨大的影响。
Land cover and its natural alteration, which play an important role in climate system and biochemistry pattern in globe scale, have brought tremendous effect to global entironment.
本文系统地介绍了GPS应用于精密测地和天文地球动力学的基本模式、原理和误差。
In this paper, the basic models, principle and error sources of GPS applied to precise geodesy and astro-geodynamics are introduced systematically.
数字地球是网络环境下高效利用地理信息的一种设想，也是未来地理信息系统的模式之一。
Digital Earth envisions the development of geographic information system in a networked environment, and is considered to be a model of the future geographic information system.
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