PREFACE 



This edition of the Hydrographic Manual is issued to serve as a guide in 

 the execution and processing of hydrographic surveys. Since Special Pub- 

 lication 143 was issued in 1942 there has been rapid development in control 

 systems and echo sounders which renders that work obsolete in some 

 respects. Although parts of the present text are carried forward from 

 Special Publication 143, much useful information has not been repeated 

 and copies of the 1942 edition should not be destroyed but should be re- 

 tained for reference purposes. 



The subject matter in this manual is identified by a numbering system 

 in which the first number identifies the chapter and the second number 

 identifies the section in the chapter. Cross references are entered by num- 

 bers in the same manner; for example the notation (see 1-26) refers to 

 Chapter 1, Section 26. 



This edition of the Hydrographic Manual has been compiled with the 

 assistance and advice of many officers and personnel in the office and the 

 field. Special credit is due Mr. G. F. Jordan who wrote the first draft of 

 Chapter 6. The Smooth Sheet; to Mr. R. H. Carstens who reviewed a large 

 part of the manual and contributed much valuable information ; to per- 

 sonnel from the Electronics Laboratory for their contributions to Chapter 

 3; to the officers who reviewed the manuscript; and to Mr. C. E. Cook for 

 his assistance in preparing the index. 



