32 



HYDROGRAPHIC MANUAL 



Lalunching a boat through breakers is 

 a more difficult and exhausting opera- 

 |;ion, though not necessarily a more 

 dangerous one, than making a landing 

 under similar conditions. 



Arj entirely different technique is re- 

 quired on a steep rocky shore from that 

 required on a gently sloping sand 

 beach. 



2-34 Leases of station sites. — When 

 electronic equipment is to be used for control 

 of hydrography, suitable locations for es- 

 tablishing shore stations should be selected 

 and station marks located prior to beginning 

 the field season. It may be necessary to lease 

 private property for this purpose. Such leases 

 should be executed and cleared through the 

 Washington Office well in advance of estab- 

 lishment of the station. If the station is to 

 be located on Federally-owned land, use per- 

 mits should be obtained and forwarded to 

 the office. 



The area required for each station will 

 vary with the type of equipment used. A 

 portable Raydist station, or Shoran station 

 with a short mast, can be set up on a lot as 

 small as 50 feet square ; but a Raydist com- 

 plex o| towers will require a space approxi- 

 mately 800 by 300 feet. The site should be 

 clear apd approximately level. 



2-35 Selection of station sites. — There 

 are several factors which should be considered 

 when selecting a site for establishment of 

 shore stations for electronic control: 



(a) Adequacy of coverage for the area to 

 be surveyed. The stations should be located 

 so as to provide strong intersections of dis- 

 tance arcs. Approximate limits of adequate 

 service can be defined as : maximum distance 

 offshore equal to twice the length of the 

 baseline (distance between stations), and the 

 closest approach to the center of the base 

 line equal to one-fourth of the baseline. 



(b) The station should be at, or near, a 

 triangulation station. If this is not possible, 

 the mast should be visible from two or three 

 triangulation stations nearby (see 1-19). 



(c) The site should be selected so that 

 there will be little or no land intervening 



between the stations and the service area, 

 and, in the case of Raydist, there should be 

 little land between the stations. 



(d) The availability of commercial sources 

 of power is desirable but not essential. 



(e) Problems of housing and supplying 

 personnel at the station. 



(f) If Shoran is to be used, the station 

 must be sufficiently elevated to provide line- 

 of-sight coverage for the maximum distance 

 required. It should not be so high that dis- 

 tance corrections are required for inshore 

 surveys. 



(g) Operation of the equipment should not 

 interfere with, or be affected by, other 

 electronic or radio facilities in the area. 



2-36 Coast Pilot reports.— The Coast 

 Pilots of the Coast and Geodetic Survey are 

 a series of volumes containing information 

 of importance to the navigator which cannot 

 be shown conveniently on nautical charts 

 and is not readily available elsewhere. A 

 new edition of a pilot is published at inter- 

 vals which may vary from 5 to 12 years. 

 Supplements to each Pilot are published 

 annually and contain corrections, changes and 

 new information. Each supplement is com- 

 plete for the period between the date of 

 publication of the Pilot and the date of the 

 supplement. 



Coast Pilot reports from field parties are 

 among the most important sources of infor- 

 mation. All hydrographic parties shall collect 

 Coast Pilot data and furnish at the end of 

 each season a special report on this subject 

 (see 1-53). This report should include in- 

 formation obtained while en route to and 

 from the project area as well as that gathered 

 on the working ground. A mere revision of the 

 published text of the Pilot is not all that is 

 required, but additional new information 

 should be obtained that will enhance its value. 



The report should be submitted in dupli- 

 cate, the information to be contained therein 

 and the manner in which it should be fur- 

 nished being described in the Coast Pilot 

 Manual. Such data should not be made a 

 part of the descriptive reports. 



Important information and especially any- 

 thing affecting the safety of navigation 



