2) the third and fourth grade leveling
三、四等水准
1.
Conventional triangle elevation survey replacing the third and fourth grade leveling needs backsight distance equaling foresight distance to eliminate the influence of the earth curvature and observing bilaterally to reduce atmospheric refraction is considerable,which greatly increases field work.
常规的三角高程测量代替三、四等水准测量,要求保证前后视距相等来消除地球曲率的影响,要求对向观测来消除大气折光影响,大大增加了外业工作量。
4) third leveling measurement
三等水准测量
5) third-order river-crossing leveling
三等跨河水准测量
补充资料：长等短等
1.犹言左等右等。谓等待久。
说明：补充资料仅用于学习参考，请勿用于其它任何用途。
参考词条