60 



NAUTICAL CHAKT MANUAL 



III 

 Depth Curves and Tints 



DEPTH CUEVES (Fig. 1) (R) 



The configuration of the ocean floor can be adequately revealed only by the proper use 

 of depth curves. The character and form of the ocean bottom, completeness of the siuT^eys, 

 the draft of vessels using the charts, and the now frequent use of the echo sounder in navigation, 

 all have an important bearing on the selection of the depth curves to be charted. 



Wherever necessary, additional depth curves should be added to existing charts at the 

 time extensive hydrographic corrections are made, but the Chief of Branch will determine 

 which curves are to be added. The depth curves to be used on new or reconstructed charts 

 will be given in the Specifications. 



Continuous, solid depth curves in black shall be used on all new or reconstructed charts. 

 All depth curves shall be labeled clearly in the same unit as the soundings. 



The cartographer must be constantly on the alert to add or omit curves, other than 

 standard, which will bring out more clearly the features of value to navigation. By the proper 

 use of depth cmres, dangers and dangerous areas can be made to stand out clearly. On the 

 smaller scale charts, it will be necessary to generahze cutrves to some extent. However, care 

 must be taken not to close or seriously reduce the width of a navigable channel. 



Depth curves appUed from surveys by this Bureau are to be charted as close as possible 

 to the positions shown thereon, except where sufl&cient curves for fathometer navigation have 

 not been drawn on the older sm^eys. In such cases, additional depth ciirves should be drawn 

 as necessary. In converting detached soundings to fathoms and fractions, additional curves 

 or revisions to curves may also be required. Before depth curves are appUed to a chart from 

 siureys plotted in feet and tenths, they should be redrawn on the survey sheet to include 

 within their limits the appropriate soundings with fractions of 0.2 foot. 



Depth curves shall include within their limits all soundings of the same depth as the 

 curve. They should not touch the sounding figures. 



When curves on existing charts are revised, they shaU be made continuous solid lines, in 

 black, as illustrated below. 



HYDROGRAPHIC SURVEY 



CHART 



