TS-630 Marine Three-Arm Protractor

1.Marine three-arm protractor cooperates with sextant to measure the marine position

2.Threepoint-two-angle method to measure the marine position on the chart

Three-arm protractor consists of cupreous graduated circle(180 degrees on the left and right), 3 surveyor's poles(fixed pole in the center and movable pole on the left and right), micro drum wheel and indicators, needle in the center and worm gear screw rod, etc.