7327 



HYJDROGRAPHIC MANUAL 



Page 672 



\2V," 



lV2 



V2" 



38 ^2'^ 



.iK- 



the northeast to the southwest corner through the construction center with the cor- 

 responding distance from the northAvest to the southeast corner. 



The verification must be made the same day that the projection is constructed and, 

 if practicable, immediately following the construction. 



7327. Ruling Machine Projections 



Hand-ruled projections, carefully constructed, are usually of as great accuracy as is 

 warranted when drawn on cloth-mounted paper. The Coast and Geodetic Survey 

 has a projection ruling machine designed especially for ruling precise projections on 

 mediums subject to little or no dimensional change, such as aluminum-mounted paper, 



aluminum plates, copper, and glass 

 h ^ ^" i negatives. If practicable, all pro- 

 jections on such mediums should be 

 made on the machine. It is not 

 necessar3'- to describe the details of 

 the machine, except to say that pro- 

 jections of any type can be ruled on 

 it, limited in size to 38}^ by 56)^ 

 inches and limited approximately by 

 the curvature required in a 1:500,000 

 scale conic projection. 



Chiefs of Party who wish machine- 

 ruled projections should forward 

 their requests sufficiently in advance 

 to reach the Washington Office at 

 least 3 weeks prior to the date they 

 wish them shipped to the party. 

 Such requests must always be accom- 

 panied by rough layout sketches 

 showing the sheet limits by latitude 

 and longitude, the scale, and the 

 orientation of the projection if it is 

 not parallel with the sheet edges. 

 The poly conic projection will be as- 

 sumed unless otherwise specified. 



The size of a projection that can be 

 drawn on the ruling machine is lim- 

 ited by a rectangle 38)2 by 56 }2 inches 

 whose sides are parallel to the pro- 

 jection lines. The sheet itself, how- 

 ever, can extend somewhat beyond these limits, but ordinarily should not exceed 42 by 

 60 inches (see fig. 147). In special cases a sheet 46 by 65 inches can be used. When 

 projections larger than 38K by 56K inches are required, the lines must be extended by 

 hand from the part ruled on the machine, which cannot be centered. 



Where a skewed projection is to be ruled, the size of paper is also limited by the 

 above dimensions, i. e., measured parallel to the projection lines, diagonally opposite 

 corners of the sheet cannot be separated more than 46 inches in one direction nor 65 

 inches in the other direction (see fig. 147). 



M'^ 



:f- 



! I 



-'-f- 



J 



-42"- 



Preferred maximum limits of sheet 



. Extreme limits of sfieet 



Skewed projection (note limitation of size and ruled area) 



Figure 147. — Sheet limits for ruling-machine projections. 



