Page 25 



PRELIMINARY 



1362 



be placed on the chart and shifted about until the best position for the sheet is deter- 

 mined. In a simple area it will be easy to lay out successive sheets by this method to 

 cover the entire area of the project. Wliere the area is complex it is frequently neces- 

 sary to try various successive layouts of sheets before the most practicable and eco- 

 nomical one is found. As the best position for each sheet is determined, the four corners 

 may be pricked through the tracing with dividers and joined by straight lines on the 

 layout. 



Table 1. — Scale equivalents for laying out sheets 



Scale 



One inch equals 



One centimeter 

 equals 



One nautical mile 

 equals 



One statute mile 

 equals 



2,500 



5,000 



10,000_.. 

 20,000--. 

 40,000--. 

 60,000--. 

 80,000--- 

 100,000-- 

 120,000-. 

 200,000-. 

 400,000-. 

 500,000-- 

 1,000,000 



Nautical 



miles 



0.034 



.069 



. 137 



. 274 



. 548 



. 822 



1. 096 



1. 371 



1. 645 



2. 741 

 5.482 

 6. 853 



13. 706 



Statute 



miles 



0.039 



.079 



. 158 



. 316 



. 631 



. 947 



1. 263 



1. 578 



1. 894 



3. 157 



6. 313 



7. 891 

 15. 783 



Nautical 

 miles 



0. 013 

 . 027 

 . 054 

 . 108 

 . 216 

 . 324 

 . 432 

 . 540 

 . 648 



1. 079 



2. 158 

 2. 698 

 5. 396 



Statute 

 miles 

 0.016 

 .031 

 . 062 

 . 124 

 . 249 

 . 373 

 . 497 

 . 621 

 . 746 



1. 243 



2. 485 



3. 107 

 6. 214 



Inches 



29. 185 



14. 593 



7. 296 



3. 648 



1. 824 



1. 216 



0. 912 



. 730 



. 608 



. 365 



. 182 



. 146 



.073 



Centi- 

 meters 

 74. 13 

 37. 06 

 18. 53 

 9. 27 

 4. 63 

 3. 09 

 2. 32 

 1.85 

 1. 54 

 93 

 . 46 

 . 37 

 . 18 



Inches 



25. 344 



12. 672 



6. 336 



3. 168 



1. 584 



1. 056 



792 



. 634 



. 528 



. 317 



. 158 



. 127 



. 063 



Centi- 

 meters 

 64. 37 

 32. 19 

 16. 09 

 8.05 

 4.02 

 2. 68 

 2. 01 

 1. 61 

 1. 34 

 0.80 

 . 40 

 . 32 

 . 16 



The area that will be included on a sheet of given dimensions at a specified scale 

 may be readily determmed from table J. by multiplying the dimensions of the sheet by 

 the number of miles at the selected scale. For example, a sheet 31 by 53 inches on a 

 scale of 1 : 20,000 will include an area 8.5 by 14.5 nautical miles. 



1362. Sheet Orientation 



All hydrographic sheets shall be laid out so that the projection lines are approxi- 

 mately parallel with the sides of the sheet, except when such a layout is extremely 

 uneconomic or impracticable (see 1361). The reason for this is that a cloth-mounted 

 sheet distorts almost uniformly along its axes and if a sheet is laid out with the pro- 

 jection lines parallel to the edges, distortion is comparatively easy to compensate for 

 in chart compilation. With a skewed projection it is much more troublesome and in 

 addition such a sheet is inconvenient to handle. 



1363. Sheet Size 



The standard size for all hydrographic smooth sheets shall be 31 by 53 inches and 

 they shall ordinarily not exceed this size, except for offshore surveys. The maximum 

 size, which shall never be exceeded under any circumstances, is 42 by 72 inches (see 

 712). In the original layout of the project these limits need not be strictly adhered to, 

 and it is sometimes of advantage to plan the boat sheets on a size somewhat larger than 

 the anticipated limits of the smooth sheets and with more overlap. Frequently it is 

 only after part of the survey has been completed that the smooth sheets can be laid 

 out most economically. 



465382—44 4 



