178 



HYDROGRAPHICAL SURVEYING [chap. vi. 



Modified 

 Running 

 Survey. 



that have sunk or not yet risen above the horizon of the 

 deck. 



Compass-bearings are of great use, as direction of valleys, 

 etc., may be noted without making a position. 



The whole course of a running survey will have to be one 

 of compromise between discordant results, and only long 

 practice will enable the surveyor to decide what to throw out 

 and what to accept. 



It may often occur in a survey, that a portion of the coast 

 is inaccessible for landing by reason of heavy surf ; or the 

 shore is so chffy or densely thick with jungle that stations 

 cannot be made without loss of more time than they are worth. 

 A running survey of this piece may be as much as is requisite, 

 but the probability is that we shall be able to fix on some main 

 points from the triangulation of the other and more important 

 part of the survey, and these will greatly help us to make 

 the best chart of the portion we can under the circumstances. 



In such a case, the best course to pursue is to pass along 

 the coast at some distance, stopping at convenient positions, 

 where the ship can get station-pointer fixes by the main points, 

 anchoring, if possible, for this purpose, and cutting in from 

 these positions other secondary points nearer together, and 

 nearer the coast than the first. Then pass along again closer 

 to the land, and fix points on the shore itself, using the 

 seoondary points to fix the ship with. Boats may then be 

 sent to sound, if required, or to sketch in more details of little 

 bays, etc., if they can get near enough. Compromise will be 

 required here too, probably, in plotting the points, as, unless 

 the ship is absolutely motionless, it is unhkely the angles will 

 intersect exactly, but it is astonishing what good results can 

 be obtained with a number of officers taking angles at the 

 same time, with the ship's way stopped, each being told off 

 to take two or three angles as quickly as possible ; the most 

 important angles, and those that change most rapidly, being 

 taken first. 



Advantageous use may be made of beacons in a running 

 survey. 



As an example, we will give some details of a method 

 employed with success on the south-east coast of Africa on 

 an open coast, beacons being dropped in from 20 to 60 fathoms. 



