1333 HYDROGRAPHIC MANUAL Page 20 



1333. Weather Conditions 



No part of planning is more important than that based on the prevalent weather 

 conditions in different seasons. In northern areas, or other areas where bad weather 

 prevails during a large part of the year, it is necessary to utilize to the fullest extent 

 the season during which survey operations may be conducted economically. It is 

 essential that the survey party arrive on the scene of operations as early as practicable 

 and remain there until survey operations are no longer economical. 



Special attention should be given to selecting an appropriate part of the season 

 during which to conduct those operations requiring unusually favorable weather con- 

 ditions. When the season of most favorable weather for certain operations is known 

 in advance, economy will result if the entire project is planned so that these can be 

 undertaken at that time. 



Where the project is located in a region with which the Chief of Party is unfamiliar, 

 he should study in advance the available information regarding the prevalent weather 

 conditions in the area. Meteorological data may be available, but if not, much infor- 

 mation of value may be found in the reports of survey or exploratory parties who have 

 previously operated in this or similar adjacent areas. 



Exceptionally clear weather is needed for certain operations such as triangulation 

 observations, the control of offshore hydrography by visual fixes, and sun-azimuth 

 observations between buoys. Exceptionally smooth weather is needed for other oper- 

 ations, among which are landings on very exposed portions of the outer coast, the 

 installation of tide gages, the establishment and location of buoy control, and the 

 installation of hydrophones and cable laying if R.A.R. shore stations are used. Some 

 of the above operations must necessarily be performed at the beginning of the season 

 or prior to certain other operations, but when there is a choice, they should be planned 

 for that part of the season during which prevalently good weather for those operations 

 may be expected. (See also 145.) 



1334. Anchorages 



Before proceeding to the project area, it is desirable to determine in advance 

 whether or not safe anchorages are available at which the survey vessel may base. 

 If the area is well known, a selection can be made without difficulty. There may be 

 many possibilities, the choice often depending merely on the facility of obtaining 

 supplies and the adequacy of the mail and communication service. 



When the project is in an area where dangerous weather conditions may be expected, 

 the work must be planned so that a protected anchorage is always accessible, and 

 ordinarily such anchorages can be selected in advance from a knowledge of the area. 



134. Operational Plan 



From the study of the project, a general advance plan should be formulated for 

 the accomplishment of the early operations of the project. This plan should be based 

 on the results to be attained, the size of the party and the various units which may be 

 organized, the weather conditions, and other factors that may affect the operations. 

 Such a general plan will, of course, be subject to frequent change as the work progresses. 



Where the area to be surveyed extends offshore from the coast and various zones 

 of the project are to be surveyed by separate hydrographic units and by different 

 methods of control, the hydrography should be planned so that the various units may 

 be given the limits to which their surveys are to extend. 



