CHAP. XXL] PREPARATION OF THE ANGLES 489 



SECTION IX. 



PREPARATION OF THE ANGLES FOR CALCULATING 

 AND PLOTTING. 



On board the directing ship X the angles as obtained at the 

 beacons will have now been dealt with by the two or more 

 computers, working in pairs, and the angles corrected for the 

 various false stations involved before being tabulated for 

 future use. 



This at first sight might appear a laborious process, and of 

 doubtful utility, but in actual practice it is not so, for it is 

 necessary in any case to close the various triangles involved 

 in the plotting, and this cannot be done without first treating 

 the various false stations, some of which may be of large amount. 

 We shall not require corrections nearer than 1' of arc, and these 

 quantities can be readily obtained by inspection from a sub- 

 tended angle table, and appUed by the well-known method 

 given at p. 90. To enable this to be done, time will be saved 

 if the sextant angles at each position are expressed as theodoUte 

 angles from some convenient zero, the approximate bearing of 

 which can be taken from the plot. 



SECTION X. 



RAPID PLOTTING. 



The angles received from the co-operating vessels should be 

 treated in a similar way on board the directing ship, and it is 

 perhaps better that they should be transmitted in their original 

 form, as any discrepancy can then be more readily discovered, 

 and at once cleared up. 



Dependent upon the care that has been taken, the various 

 triangles, which must be made up correctly for calculation or 

 plotting, should close with a total error that should not exceed 

 10', and will be generally less in practice. 



If we require a rapid provisional plot, which is often the case, 

 in order that the circumstances of the day may be taken full 

 advantage of, it will be generally quite sufficient to plot the 

 beacons in their order, adopting the provisional scale which has 

 now been fully settled upon (see Section III.). 



