2. PLANS AND PREPARATIONS 

 Table 5. — Scale equivalents for laying out survey sheets 



27 



Scale 



2,500 



5,000 . . . 

 10,000. . . 

 20,000. . . 

 :!0,000. . . 

 40,000 

 50,000. . 

 00,000. . . 

 80,000. . . 

 100,000. . 

 120,000. . 

 200,000. . 

 ■100,000. . 

 500,000. . 

 1,000,000 



One inch equals 



Nautical 

 miles 



o.o:h 



.00!) 



.i:i7 



.274 



.411 



. 549 



.080 



.82:{ 



1 007 



l.:{72 



1.040 



2.74:? 



5.480 



0.858 



13.715 



Statute 

 miles 



o.o:?<) 



.079 



.1.58 



.Md 



.473 



.0:51 



.78!) 



.!)47 



203 



578 



8!)4 



157 



313 



8!)2 



783 



One centimeter 

 equals 



Nautical 

 miles 



013 



027 



.054 



.108 



.162 



.210 



270 



324 



.432 



.540 



.048 



1.080 



2.1t)0 



2.700 



5.400 



Statute 

 miles 



0.010 

 .031 



002 

 .124 

 .180 



24!) 

 .311 

 .373 

 .4!)7 

 .021 

 .740 



1 243 



2 486 

 3.107 

 0.214 



One nautical mile 

 equals 



Inches 



20.105 



14.582 



7.2!)1 



3 . 040 



2.430 



.823 

 .458 

 .215 

 .!)1I 

 .729 

 .608 

 . 305 

 .182 

 .140 

 .073 



Centi- 

 meters 



74.08 



37.04 



18.52 



9 . 26 



6.17 



4.03 



3.70 



3.09 



2 31 



1.85 



1.54 



.93 



.40 



.37 



.19 



One statute mile 

 equals 



Inches 



25.344 



12 ()72 



6.336 



3.168 



2.112 



1.584 



1.267 



1.056 



.792 



.634 



.528 



.317 



.158 



.127 



.063 



Centi- 

 meters 



64.37 



32.19 



16.09 



8.05 



.36 

 .02 

 .22 

 .68 

 .01 

 .61 

 34 

 .80 

 .40 

 .32 

 .16 



1 Nautical mile 

 1 Statute mile = 



z 6,076.10 ft. or 1852.0 m. 

 5,280 ft, or 1609.3 m. 



tiplying the dimensions of the sheet by the 

 number of miles at the selected scale. For 

 example, a sheet 36 by 54 inches on a scale 

 of 1 :20,000 will include an area 9.8 by 14.8 

 nautical miles. 



If planetable topographic or graphic con- 

 trol surveys are required, the location of the 

 sheets should be shown in the sheet layout. 



2-21 Sheet orientation. — All hydro- 

 graphic sheets shall be laid out so that the 

 projection lines are approximately parallel 

 with the sides of the sheet, except when such 

 a layout is extremely uneconomic or imprac- 

 ticable. The reason for this is that a cloth- 

 mounted sheet distorts almost uniformly 

 along its axes and if the sheet is laid out 

 with the projection lines parallel to the 

 edges, distortion is comparatively easy to 

 compensate for in chart compilation. With 

 a skewed projection it is much more trouble- 

 some and, in addition, such a sheet is in- 

 convenient to handle. North shall always be 

 considered the top of the sheet, whether or 

 not the projection lines are parallel to the 

 edges of the sheet. 



2-22 Sheet sizes. — The standard size for 

 all hydrographic sheets shall be 36 by 54 

 inches and they shall ordinarily not exceed 



this size (see 1-8 and 6-3). Chiefs of Party 

 are authorized to increase the sheet size to 

 36 by 60 inches in exceptional cases, but ap- 

 proval must be obtained from the Director 

 before using a sheet larger than 36 by 60 

 inches. Flat sheets 36 by 60 or 42 by 60 

 inches will be furnished on requisition to the 

 Washington Office and shall be used for boat 

 sheets and smooth sheets. Use of other types 

 of paper for this purpose is not authorized. 

 The 42-inch width may be used when con- 

 siderations of control make it advisable; 

 however, hydrography should be limited to 

 an area 30 inches wide in order that the 

 sheet may be trimmed after verification and 

 review. 



Calibration sheets should be constructed 

 on grained aluminum or aluminum-mounted 

 paper sheets which can be furnished in var- 

 ious thicknesses and sizes as large as 38 by 

 59 inches. Drawing paper mounted on alu- 

 minum sheets or foil is the most satisfactory 

 solution to the distortion problem if the 

 sheets are not unduly exposed to moisture. 

 The paper must be mounted on both sides 

 of the aluminum, otherwise the paper will 

 contract or expand, and warp the sheet. 



Unless otherwise instructed, all planetable 

 topographic or graphic control surveys shall 



