7113 HYDROGRAPHIC MANUAL PaGE 658 



When paper other than Wliatman's standard is used, the smooth sheet shall have 

 noted in the margin the maker's name and the trade name or number of the particular 

 paper, if these are known. Some papers have this information imprinted at regular 

 intervals along the margin but if this imprint does not contain all the desired data or 

 if the entire imprint does not appear on the smooth sheet, it must be noted thereon 



in ink. 



7113. Defective Paper 



Drawing paper is purchased by the Federal Government in accordance with stand- 

 ard specifications. These require generally that paper be free of surface imperfections, 

 that it be subject to a minimum dimensional change, that it permit inked lines to be 

 drawn without spreading or feathering, and that it permit several successive erasures, 

 with rubber or steel, in the same spot, on which lines can be subsequently inked with 

 little or no spreading or feathering. In addition, the paper must not be so stiff and 

 rigid that it will not withstand a reasonable amount of rolling and flexing without 

 cracking. 



Notwithstanding the specification requirements, considerable variation in the 

 quality of smooth-sheet paper is found in practice. Paper which does not comply to 

 a reasonable degree with the above general requirements shall not be used for smooth 

 sheets and the Washington Office shall be notified of the specific fault in a letter stating 

 the maker's name, the trade name of the paper, and the date of shipment to the party, 

 if these are laiown. 



7114. Paper Distortion 



Drawing paper, not mounted on metal, does not exist which is free of distortion 

 under varying conditions of temperature and humidity. This distortion is a decided 

 nuisance to the surveyor in his field work and to the cartographer who subsequently 

 uses the smooth sheet in the Office. The distortion is more troublesome in rainy 

 climates and in localities where there are rapid and large changes in humidity. Because 

 of this distortion, distances once laid off cannot be assumed to retain their correct 

 length. If distances are plotted for use at some future date, it is necessary to verify 

 them before use. 



The best quality of smooth-sheet paper is manufactured so that the percentage 

 of contraction or expansion is nearly equal in all directions. Such distortion can be 

 compensated for, especially if it occurs after the survey has been completely plotted, 

 because the effect is merely a change in scale. Where the percentage distortion is not 

 uniform in all directions, as is the case with many grades of paper, its effect is relatively 

 easy to compensate for, promded certain precautions are taken in laying out projections 

 (see 1362). 



One test for distortion made in the field in Alaska in 1931 showed a maximum di- 

 mensional change in a standard Whatman sheet of 1.12 percent in length and 0.62 per- 

 cent in width; the sheet assuming its greatest dimensions on a foggy day when the sheet 

 was damp and its minimum on a clear day when the sheet was quite dry. 



Recent tests in the Washington Office show that the following distortions may be 

 expected for the various papers listed: 



