RULES AND PRACTICES 17 



BLUEPRINT CLARIFICATION FOR MICROFILM 



When applying a rock, wreck, obstruction or the least depth on a shoal from Blueprints 

 to Aid Proofs or chart Drawings, a detailed enlargement of the feature being charted shall be 

 indicated in the margin or other clear area on the Blueprint. A leading line shall be drawn 

 from the enlargement to the feature. This is necessary so that the feature's position and 

 value can be clearly read from a microfilm copy of the Blueprint. 



LOGARITHMIC SPEED SCALE 



The logarithmic speed scale (fig. 37) is to be shown on all charts of 1:40,000 and larger 

 scales. 



ANCHORAGE CHART FILE 



Compilers should consult U.S. Naval Oceanographic Office anchorage charts on file in 

 Standards Section and use chart copy as a guide to avoid interference between anchorage 

 overprint data, charted details and corrections added to the base chart Drawing. 



OVERLAPPING CHARTS 



Minor aids and other details on small-scale charts should be omitted when such information 

 is completely shown on larger scales. This procedure makes it necessary for the mariner to use 

 the more adequate large-scale chart. A note calling attention to the fact that such information 

 has been omitted should be prominently shown. Removal of this information from existing 

 charts may be made only with prior approval of the Branch Chief. 



Overlapping portions of charts of the same scale should be identical as far as is possible. 



Hydrographic detail is not ordinarily shown in a body of water outside the area for which 

 the chart is to be used or when the entrance is omitted from the chart. It is, however, shown 

 in areas not covered by other charts of the same or larger scale. In all cases, the high water 

 line must be shown. 



REFERENCES TO INTRACOASTAL WATERWAY CHARTS 



A reference note regarding the Intracoastal Waterway charts should be charted in black on 

 the 1:80,000 scale Atlantic and Gulf Coast charts through which the Intracoastal Waterway 

 passes. For example, the note on chart 1246 reads as follows: 



INTRACOASTAL WATERWAY 

 Use chart 845-SC. The depths and 

 channel markers are not shown hereon. 



