Professional Station Pointer
Also known as a 3 arm protractor. The station pointer is used to determine location of a ship. The navigator first identifies three visible objects ashore and then separates the legs by the angles between the adjacent objects. He positions the station pointer on the chart and lines up the three arms with the objects ashore. There is only one solution to the procedure and that is that the ship’s location on the chart is the intersection of the three arms (the center of the protractor). The ship’s position is marked by a pin prick on the chart or a pencil may be used through a center hole. This process is especially useful in coastal surveys when charting soundings. This same procedure can be used on land to determine the location of the point where the observer is located.
The Station Pointer has a 5 inch diameter aluminum protractor graduated in degrees and three 13.4 inch metal legs radiating from the center of the protractor. The middle leg is fixed to the protractor; the other two are free to rotate to any angle (greater than 5° from zero) relative to the fixed middle leg. High precision to within 1 minute of arc is provided by a micrometer drum with worm gear attached to each movable leg. There is a release lever to allow quick re-positioning of the legs. The unit comes with three connector arms which extend the leg lengths to 24.8 inches if desired. The entire unit is stored in a handsome wooden case. Total weight is 3.3 lbs. SW 6 lbs..