There are multiple ways to define a coordinate system for Earth coordinates; some are better for particular purposes than others.
有多种方式来定义地面坐标系统；有一些在某些用途方面比其他的更好。
The study of multiple satellite scheduling that satisfies complicated satellite observation requirements is of great importance in improving the supporting capability of an earth observation system.
研究面向复杂任务需求的多卫星联合下的任务规划技术，对于提高对地观测系统的保障能力具有重要意义。
This system adopts satellite linking route to realize on-the-spot teaching and use IP network on the earth to realize multiple modes of interaction between students and tutors.
该系统采用卫星链路实现教学现场的直播，采用地面IP网实现师生间多模式的交互。
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