Page 29 hydrographic manual 142 



It is also necessary to determine the most practicable method of controlling the topo- 

 graphic surveys. 



Suitable anchorages must be selected for the protection of the ship. Possible 

 locations for campsites should be investigated to determine whether camp parties can 

 operate to advantage. If there are off -lying islands, the most practicable method of 

 establishing control stations on them should be selected. An estimate of the number 

 of tide stations needed should be made and possible locations noted. The depths 

 of the water at various distances from the shore should be investigated to determine 

 the approximate limits of launch and ship hydrography. The topography of the 

 area should be viewed to find out what natural and artificial objects are available to' 

 control the ship hydrography. The type of control should be chosen for the ship 

 hydrography beyond the range of the shore objects — whether survey or sono-radio buoys 

 can be used to advantage and to what distances offshore depend mainly on the offshore 

 depths. 



142. Personnel of Survey Units 



Each of the survey operations requires a minimmn of experienced personnel 

 in order that accurate and dependable results may be obtained. When part of the 

 personnel is inexperienced, or for purposes of training, it is obviously desirable to 

 assign additional personnel to assist in carrying out the operations. 



Table 2 gi\'es the personnel needed for the various operations, but is intended as a 

 guide only. With efficient and experienced officers and men, many of the operations 

 can be carried out with fewer personnel. 



A hydrographic survey unit engaged in handlead sounding from a small boat 

 usually consists of an officer-in-charge who observes one of the angles and plots, a 

 recorder who records and observes the other angle, a leadsman and an assistant who 

 hauls in the leadline for him, and- a helmsman. When soundings are taken rapidly, the 

 recorder may not be able to observe an angle and an additional angleman is required for 

 this duty. If the small boat is propelled by oars, two to four additional men serving as 

 oarsmen are necessary. Outboard motors are used almost exclusively in small-boat 

 hydrography, in which case the oarsmen are dispensed with and the helmsman operates 

 the outboard motor. 



The organization of a launch party is similar except that an additional officer is 

 usually required to observe one of the angles and assist the officer-in-charge by gener- 

 ally supervising the operations. It is in this position that the junior officers receive 

 their preliminary training. An engineer is also necessary. In handlead sounding the 

 coxswain and leadsman usually alternate in their duties, or if the leadsman's assistant 

 is competent he may alternate with the leadsman in heaving the lead. When a sound- 

 ing machine is used the leadsman and his assistant operate the machine. When a 

 graphic-recording echo-sounding instrimient is used in a launch, a trustworthy man is. 

 required to attend it at all times. The leadsman and his assistant may be dispensed 

 with, but there must be at least one, and preferably two, additional seamen who can 

 take occasional handlead soundings and who assist at bar checks and other duties. 



For ship hydrography it is assumed that the usual personnel composing a watch 

 at sea will be on duty, and table 2 is not intended to imply that any of these should be 

 dispensed with. The requirements for ship hydrography are very similar to those for 

 a launch unit except that the increased speed of the operations may require additional 

 personnel, since virtually all depths are measured by echo sounding with the ship pro- 

 ceeding at standard speed. Under the most favorable conditions, where the area being 



