1. GENERAL REQUIREMENTS 



19 



usage. Where published names diflfer from 

 local usage, the hydrographer should ascer- 

 tain how well established the local name is 

 and, if possible, the origin of it. When prac- 

 ticable, the field party should submit a spe- 

 cial report on geographic names to cover the 

 entire project area, or the portion surveyed 

 during the season (see 7-14). 



1-55 Landmarks for charts. — A report 

 on landmarks for charts on Form 567 is 

 required from nearly all hydrographic sur- 

 vey parties. Landmarks on charts are for 

 the aid of the mariner in navigating adjacent 

 waters and should be selected with this in 

 mind. Where a large number of objects are 

 available, only the most conspicuous ones 

 should be selected for charting. An inspec- 

 tion should be made from the water area 

 to determine the value of the objects re- 

 ported. The report on landmarks should 

 cover the entire area surveyed during the 

 season. A similar report is required for 

 charted landmarks which no longer exist or 

 which should be deleted from the charts for 

 other reasons. When a landmark is also used 

 as a control station for hydrography, the 

 word "landmark" in black ink shall be 

 placed in parentheses below the station name 

 (see 2-39 and 7-18, 19). 



1-56 Deficiencies in surveys. — The pri- 

 mary purpose of a hydrographic survey is to 

 acquire data for the publication of a nautical 

 chart. The information must be complete 

 and accurate. Mistakes in recorded data can 

 usually be reconciled when the survey is 

 smooth plotted, but omissions cannot be rec- 

 tified, or inadequate data supplemented after 

 the survey party has left the project area 

 (see 5-75). 



After a survey has been smooth plotted, it 

 is verified and reviewed in the Washington 

 Office. Errors in the survey and in smooth 

 plotting are frequently discovered by the 

 verifier (see 6-74). Adherence to instruc- 

 tions and standards in both phases of the 

 operation, proper evaluation of the data, and 

 a reasonable amount of care in smooth plot- 

 ting will eliminate most of these deficiencies. 

 The hydrographer should keep a day-to-day 



record of events to supplement the sounding 

 record. Explanatory notes should be made 

 on the boat sheet where necessary. 



The following is not a complete list of 

 deficiencies, but it does include those which 

 cause most trouble during verification. 



(a) Shoran calibrations are inadequate or 

 have been incorrectly applied. Shoran dis- 

 tances have not been corrected for attenua- 

 tion or passage over intervening land. 



(b) Fathograms have been poorly and in- 

 completely scanned as shown by failure to 

 record least depths which occur at irregular 

 intervals. 



(c) Fathograms have not been correctly 

 interpreted in areas of kelp or grass and 

 there is a lack of supporting lead line or 

 pole soundings in such areas. 



(d) Strays have been recorded as true 

 depths and shoal indications provided by 

 side echoes have not been investigated. 



(e) Echo sounders are carelessly operated 

 or are in need of repair as shown by incor- 

 rect speed and lack of adjustment. 



(f) Failure of agreement at crossings, or 

 unnatural depth curves are indications that 

 errors exist, and these indications are fre- 

 quently ignored on the boat sheet and smooth 

 sheet. 



(g) The hydrographer has failed to rec- 

 oncile differences between the photogram- 

 metric manuscript and the hydrographic 

 survey with respect to position or elevation 

 of offshore rocks. 



(h) Reducers are incorrect or are not cor- 

 rectly applied. 



1-57 International accuracy standards 

 for hydrographic surveys. — The American 

 Nations, meeting in Mexico City in 1955 at 

 the 7th Cartographic Consultation of the 

 Pan American Institute of Geography and 

 History, adopted accuracy standards for the 

 conduct of hydrographic surveys. At the 7th 

 International Hydrographic Conference in 

 Monaco, 7-17 May 1957, the United States 

 proposed that the International Hydrograph- 

 ic Bureau States Members adopt the same 

 standards. 



The standards are stated as follows : 



I. Measurement of Depth : 



