CHAP, v.] USE OF THE SHIP FOR TRIANGULATION 143 



ILLUSTRATING THE USE OF THE SHIP FOR 

 TRIANGULATION. 



Example X. — Given the angles and lengths of the sides of 

 a well-executed trigonometrical survey, with stations near the 

 coast from 20 to 25 miles apart, successively visible from 

 each other, intermediate points may be fixed with all the pre- 

 cision necessary for a coast survey, by means of angles from 

 the ship tautly moored in positions where the receiving angle 

 from two of the trigonometrical stations is not greater than 

 110°. In Fig. 33, A and B being two trigonometrical stations 



near the coast, the ship is shot up in three suitably selected 

 positions, F, G, H, by observers at the two main stations. 

 Angles are in each case observed simultaneously at the ship to 

 an intermediate station E on the coast-line, which, if possible, is 

 so placed as to see one of the two main stations. This inter- 

 mediate station may then be used in conjunction with either 

 of the two main stations for shooting up the ship in such 

 positions as are necessary to fix coast-marks for sounding, etc. 

 The intermediate station is desirable on account of the dis- 

 tance at which the ship must necessarily place herself from one 

 or other of the maiii .stations in order to fix the coast-marks. 



