Turn the ring until the time meridian offset scale.
旋转这个环直到时间子午线偏移刻度。
Loosen the setscrew that secures the ring with the time meridian indicator.
松开固定时间子午线指示环的定位螺丝。
Greenwich thus became established as the location of the prime meridian of longitude, and the base line for calculating time zones around the world.
由此格林威治不仅作为起初子午线的所在地，也成为全球计算时区的基准线。
应用推荐