If there is a line passing the top of the ruler, and parallel to the equator, then the Angle between the line and the ruler is equal to the latitude here.

如果有一条线和赤道线平行，而且经过尺的顶端，这条线和尺的夹角就等于纬度。

The utility model discloses a collapsible ruler, which is formed by the combination of two rulers glidingly assembled into integration; the two rulers face each other and are parallel mutually.

本实用新型公开了一种可伸缩尺，该伸缩尺由两个滑动装配成一体的直尺组合而成，两直尺相互正对且相互平行。