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First,the paper summarized and analyzed the definition of the earth prime meridian in different periods,clarified the ambiguous recognition that the earth prime meridian was the meridian passing Greenwich astronomical observatory and gave the rigorous definition about the Earth prime meridian presently.

首先对地球首子午线在不同时期的定义进行了分析和总结,进一步明确了当前对地球首子午线的严格定义,澄清了地球首子午线即过格林尼治天文台的子午线这一模糊认识。