28 



HYDROGRAPHIC MANUAL 



be done on aluminum-mounted sheets. The 

 size used is 24 by 31 inches, which is identi- 

 cal with the size of the planetable board. 



2-23 Subplans. — Sheets containing small 

 detached areas of hydrography shall be 

 avoided, if practicable. This can usually be 

 accomplished by placing a subplan, or inset, 

 on the boat and smooth sheets at the same 

 or an enlarged scale (see 6-6). If it is 

 impracticable to include, in the original sheet 

 layout, an entire area on several standard- 

 sized sheets, and a small section remains that 

 is necessary for effecting a junction with a 

 prior survey, it is frequently practicable to 

 include such area as a subplan on an unused 

 portion of the adjacent sheet. Such subplans 

 must alway§ be included on the sheet of 

 comparable scale closest to the area. 



Where a small harbor, anchorage, or other 

 area needs to be surveyed at a larger scale 

 than the remainder of the inshore coastal 

 waters, it likewise may frequently be in- 

 cluded as a subplan on the sheet which in- 

 cludes the area. 



It is to be noted that the boat sheets are 

 not necessarily similar in layout to the 

 smooth sheets and there is no objection, and 

 in many cases there is a decided advantage, 

 in surveying the area on separate boat sheets. 

 The results of several small boat sheets may 

 be included on one smooth sheet. 



2-24 Dog-ears. — It is sometimes imprac- 

 ticable to determine in advance the exact 

 limits of a hydrographic sheet. Because of 

 developments during progress of a survey or 

 the location of control, it is occasionally de- 

 sirable or necessary to use a control station 

 which falls a short distance beyond the limits 

 of the sheet as originally laid out. This is 

 accomplished by adding a small section of 

 paper, called a "dog-ear," to the boat sheet 

 and plotting the station thereon. While there 

 is no objection to the use of dog-ears on boat 

 sheets, there is serious objection to their use 

 on smooth sheets, and they are not to be 

 tolerated on the latter except in emergency 

 (see 6-5). 



2-25 Shore party operations. — It is fre- 

 quently more efficient to assign a portion of 



the work, especially triangulation and topog- 

 raphy, to one or more shore parties operat- 

 ing independently but responsible to the 

 Chief of Party. In well-developed areas 

 these parties can generally use trucks for 

 transportation during progress of the work 

 and for changing base of operations. Pho- 

 togrammetrists are usually assigned to assist 

 hydrographic parties in the United States, 

 and are self-sufficient. The party will usually 

 have an office-trailer, one or two trucks, and 

 a small boat which can be launched from a 

 trailer when needed. 



Where launch hydrographic surveys, or 

 other operations requiring the use of boats, 

 are made by a party based ashore, the camp 

 sites or anchorages must be chosen so that 

 time required for runs to and from the work- 

 ing ground will be at a minimum, and at 

 the same time provide safe anchorage for 

 the floating equipment. 



When electronic distance measuring equip- 

 ment is used to control hydrography, it will 

 be necessary to establish a small unit at 

 each shore station. Since all shore-based 

 units must be supplied at regular intervals, 

 the locations selected should be such that 

 landings can be made under all conditions 

 of sea and weather, if possible. 



2-26 Radio communications with de- 

 tached units. — Most launches, and shore par- 

 ties operating from a ship, will be equipped 

 with radiophones and will be in communica- 

 tion with the Chief of Party at regular inter- 

 vals. The Radio Regulations of the Interna- 

 tional Telecommunications Conference are 

 very specific with respect to procedures to 

 be employed when radiophones are used. The 

 Chief Electronics Technician, or other re- 

 sponsible person on each party, shall train 

 all users of radio communications equipment 

 in order that infractions of the regulations 

 will be avoided. Copies of the regulations 

 are furnished without request as they are 

 issued. 



2-27 Weather. — Few operations in a hy- 

 drographic survey can be conducted with 

 efficiency and accuracy during periods of 

 stormy weather and much of the work re- 



