The horizontal angles from the boat between A and B and B and C, the stations on the shore are respectively `theta_1 and theta_2`. The distances AB = L1 and BC = L2. For calculating the angle`alpha_2` at C between the boat and station B is obtained by using the following formula: where (`beta` is horizontal angle between A and C at B).
P and Q are two stations on the shore line at distance d. If the angle between Q and the boat O and P is a and the angle between P and Q at boat O is `beta`, the x and y. Coordinate along PQ and perpendicular to PQ from O are :