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zenith distance 【天文學】天頂距。

zenith telescope

According to the engineering practice , the theoretical basis and method that survey directly the horizontal distance and height difference by the total station system as fourth grade and below fourth grade control network are put forward instead of surveying slant distance and zenith distance 摘要根據工程實踐,提出了用全站儀直接測量平距、高差來代替測斜距、天頂距作四等及四等以下控制網測量的理論依據和方法,并以張河灣抽水蓄能電站施工控制網為例進行了比較計算。