132 HYDROGRAPHIC MANUAL Page 18 



132. Nautical Charts 



Copies of the largest-scale nautical charts of the project area, of the latest print 

 dates, should always be on board the survey vessel during its operations. It is not 

 sufficient to have charts of the most recent edition. The print dates are located in the 

 lower left-hand corner of the chart and the latest is the right-hand one of a consecutive 

 series of dates (see 1127). In all Descriptive Reports, special reports, and correspond- 

 ence, in which a comparison is made between the field data and the published chart, 

 this print date must be stated. This is the only positive means of reference to the 

 data which were on the chart when the comparison was made. 



1321. Confidential Charts 



When survey vessels are operating in an area of which confidential charts have been 

 pubHshed, copies of these are obtained from the United States Navy Department for 

 use on board the vessels during the survey operations. Each chart contains a serial 

 number. Chiefs of Party are responsible for the custody of the confidential charts 

 sent to them and must render a semiannual report, on March 31 and September 30, 

 hsting these with their serial numbers. This report shall be made on Form N.H.O. 

 698a, and be forwarded to the Director. (See also 125.) 



1322. Complimentary Copies of Charts 



At the request of a Chief of Party complimentary copies of new charts or new edi- 

 tions extensively corrected from a survey will be furnished for distribution to members 

 of the crew who had a responsible part in the survey operations. Officers engaged on 

 the survey will be furnished such copies on request. It must be realized that there is 

 often a considerable lapse of time between the date of the survey and the issuance of 

 new charts or new editions embodying the results of the survey. 



133. Project Study 



As soon as the project instructions and the accompanying survey data have been 

 received, a preliminary study of the project should be made in as great detail as is 

 possible from the available data in order to formulate a general plan of operations. 

 If the project is of an unsurveyed and comparatively little known area, recourse must 

 be had to reconnaissance survey data. Much of value in planning the operations can 

 often be found in published exploratory and other reports of scientific expeditions which 

 have operated in the area. 



1331. Study of Charts and Prior Survey Data 



If the project is for the resurvey of an area, a thorough study of the published 

 charts and the photographic copies of prior survey data shall be made in order to plan 

 the operations effectively and economically. These data may be used to determine the 

 approximate limits of the area to be surveyed by each unit of the party and the probable 

 limit to which the hydrography may be controlled by the various methods. 



If the project instructions call for new triangulation in the area, a paper recon- 

 naissance can be made for use as a general layout for the scheme, and froni which the 

 actual stations can be selected after the party has arrived in the immediate locality. 

 If the existing charts of the area are based on reconnaissance surveys or sketches, little 

 confidence can be placed in the charted data for such a pifrpose, because, even though 



