The Station Pointer is a device for plotting navigation that is used for transferring horizontal sextant angles directly to nautical chart. It consists of a circular graduated 0.5° on both sides (up to 180°) with three arms radiating from the center. The central arm (OA) is fixed and serves as the zero reference, while the other two arms (OB and OC) can be moved to the desired angle and locked in place by clamps. This allows mariners to plot their ship position very accurately during a marine survey and while working on charts.
The survey-grade models are equipped with a vernier scale that allows readings to one minute of arc for angle transfer accuracy. There is a mark about 1/6 of the distance from the center leg that maintains the alignment of the arms when marking the positions on the chart. In the case of a very small right-hand angle, the instrument can be set to the smaller angle, then the pointer can be moved to the total of the two right-hand angles.
