4. CONTROL AND SIGNAL BUILDING 



123 



most suitable in good holding ground. When 

 anchored in 15 fathoms or less, %-inch boat 

 chain with a scope of approximately 3 to 1 

 and a 30-pound Danforth anchor will be ade- 

 quate for the standard buoy. In depths of 

 15 to 50 fathoms the cable should be com- 

 posed of %-inch chain and %-inch wire rope 

 with a total length equal to approximately 

 twice the depth. The length of the wire 

 rope should be a few fathoms less than the 

 depth of the water. A %-inch swivel should 

 be used at each end of the wire rope to pre- 

 vent snarls and kinks in the wire. Other 

 connections should be made with screw-pin 

 shackles and the pins secured by seizing 

 wire. 



4-36 Position of a buoy. — It is custom- 

 ary to lower the buoy to the water and back 

 away from it as the anchor cable is paid 

 out. The anchor is then released from a posi- 

 tion over the side by a releasing hook or 

 small line. The position of the buoy is de- 

 termined at the instant the anchor is dropped. 

 If sextant angles are used, a check angle or 

 sum angle should be observed and the fix 

 should be observed at the anchor. If the 

 position is observed eccentrically, appro- 

 priate corrections shall be applied to reduce 

 the observed position to the position of the 

 anchor. 



4-37 Control station na«ies. — A triangu- 

 lation station is generally named for the 

 locality or for the topographic feature on 

 which it is established. The name of the 

 property owner is often used. In either case, 

 the spelling of the name must be correct. 



It is good practice to assign names of five 

 or more letters to triangulation and traverse 

 stations. One or two syllables of a long name 

 may be used when the station is used in a 

 three-point fix. Marked or recoverable topo- 

 graphic stations should be assigned four- 

 letter names, and all supplemental stations 

 should be assigned three-letter names. 



To avoid confusion in the records, names 

 should be selected which can be pronounced 

 and spelled only one way. For example, 

 AID and TOE should not be used because 

 they are pronounced the same as ADE and 

 TOW. Names which may be confused with 



numbers, such as TOO and FOR, should be 

 avoided. 



In the assignment and use of such names, 

 the following general principles should be 

 observed : 



(a) All references to a station shall be by 

 the name assigned to it. 



(b) The same name shall be used for a 

 station during its existence or as long as it 

 is used. 



(c) Different names shall not be assigned 

 to the same station even in different surveys. 



(d) Recovered stations used in a survey 

 shall always retain the original names as- 

 signed to them. 



(e) A duplication of names must be avoid- 

 ed in the same locality and shall never occur 

 within the limits of the same hydrographic 

 sheet. 



(f) Station names shall be assigned in 

 alphabetical order across the sheet from a 

 list of acceptable names compiled for this 

 purpose, such as the list of station names 

 shown in Table 6. 



4-38 Shore station shelters. — When an 

 electronic system is to be used to control the 

 survey and shelters for instruments and 

 housing for personnel are not available at 

 the selected station, temporary structures 

 must be built. The amount of construction 

 required varies with the equipment used and 

 the nature of the installation. At temporary 

 shoran stations established for launch hy- 

 drography in a limited area, the equipment 

 may be housed in a prefabricated portable 

 shelter about six feet square (Figure 49). 

 The several parts of the shelter can be as- 

 sembled and bolted together at the site and 

 the unit be placed in operation in a few 

 hours. In such cases, the electronics tech- 

 nician is at the station during periods of 

 operation only. 



Raydist shore station equipment is fur- 

 nished in weather proof containers and may 

 be used without a shelter. If the station is 

 to be used for more than a few days, it is 

 advisable to provide some type of shelter in 

 order that servicing or repair may be ac- 

 complished during periods of inclement 

 weather. The portable shelter described 

 above is suitable for this purpose. 



