2. PLANS AND PREPARATIONS 



2-1 Purpose of a hydrographic survey. — 



The principal object of all hydrographic 

 surveying by the Coast and Geodetic Survey 

 is to obtain information concerning the wa- 

 ter areas and adjacent coast for the compila- 

 tion of nautical charts, coast pilots and 

 related publications. Hydrography is defined 

 as that branch of surveying which embraces 

 the determination of the configuration and 

 composition of the bottom of the ocean, a 

 harbor or other body of water ; the depth of 

 the water; and the position of channels and 

 shoals. A hydrographic survey party is gen- 

 erally required to perform a variety of other 

 survey operations which may include: astro- 

 nomic observations, triangulation, topo- 

 graphic surveys, and magnetic surveys. 

 Therefore, the activities of a hydrographic 

 party are termed "combined operations." 



2—2 Survey manuals. — This manual is 

 one of a series of Coast and Geodetic Survey 

 manuals and publications designed to de- 

 scribe the methods and equipment used and 

 to state the requirements for various survey 

 operations. Since this manual deals pri- 

 marily with hydrographic methods only, the 

 combined operations party needs continually 

 at hand several manuals covering other 

 phases of the work. Depending on the na- 

 ture of the project, the following should be 

 available : 



Special 

 Pub. No. TMe 



5 ...Tables of Polyconic Projections. 



Ser. 166.- Directions for Magnetic Measure- 

 ments. 



20-1 Wire Drag Manual. 



239 Manual of Geodetic Leveling. 



8 ...Formulas and Tables for the Com- 

 putation of Geodetic Positions. 



247- Manual of Geodetic Triangulation. 



196 .Manual of Tide Observations. 



215_ Manual of Current Observations. 



249 .Topographic Manual — Part II. 



256A EPI Manual. 



H.O. 226 -...Handbook of Magnetic Compass 



Adjustment and Compensation. 



H.O. 607 -..-Instruction Manual for Oceano- 



graphic Observations. 



H.O. 614 Processing Oceanographic Data. 



25-1...^ ....Coast Pilot Manual. 



In addition to the numbered publications 

 listed above, the survey party should have 

 service manuals for equipment being used, 

 as : echo sounders, Shoran, Raydist, etc. 



2-3 Project defined. — The field opera- 

 tions of a survey party in a specified area 

 are considered a project and each project is 

 assigned a number, as CS-406, the letters 

 being the abbreviation for Coastal Surveys. 

 All correspondence and reports relating to 

 the project should include reference to the 

 project number. 



Field examinations and surveys of very 

 limited extent are called special surveys, for 

 purposes of record, and are not assigned 

 project numbers. They are identified thus: 

 Special Survey 4-58, indicating the 4th spe- 

 cial survey in 1958. 



Surveys accomplished at the request of 

 other agencies and financed by the request- 

 ing agency are assigned numbers which 

 reflect the cost accounting symbol assigned 

 to reimbursable projects. 



Each combined operations project is de- 

 veloped on the basis of requirement for a 

 specific chart or as part of a long-range 

 charting program. 



2-4 Project instructions. — Instructions 

 are written for each project to supplement 

 the published manuals. The details of the 

 instructions vary from specific to general 

 depending on the locality and nature of the 

 survey. The Chief of Party shall suggest 

 changes in specific instructions when, in his 

 opinion, such amendments should be made in 

 the interest of safety of personnel or prop- 

 erty, for reasons of real economy, or on the 

 basis of valid engineering principles. Ordi- 



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