Page 695 the smooth sheet 756 



756. Methods of Transfer 



There are five methods of transferring topographic detail from one sheet to another 

 depending on the respective scales of the two sheets, the degree of accuracy sought, 

 and the mstrument equipment available. These are: (a) by tracing paper; (6) by 

 projector; (c) by pantograph; (d) by the method of squares; and (e) by the radial-line 

 method. The projector and pantograph are generally not available to field parties 

 nor to Processing Offices and these methods are, therefore, not described in this section. 

 A description of the projector is given in 4854 and of the pantograph in 4853. 



7561. Tracing-Paper Method 



Where the topographic and hydrographic surveys are on the same scale, the simplest 

 method of transfer is by means of tracing paper. Tracing cloth must not be used. As 

 explained in 7413 the topographic details are traced at the same time that the topo- 

 graphic control is pricked through, making the adjustments for distortion by small 

 shif tings of the tracing on the topographic sheet. The transfer to the smooth sheet 

 can be accomplished in several ways. The preferred method is to use a letter-size 

 sheet of thin transfer paper, which is prepared in advance by dusting with red offset 

 chalk powder (Kiel), or dry powdered graphite, rubbing it lightly over the surface with 

 a small rag until an even coating is produced. Red is preferable because of its contrast 

 with penciled or inked detail that may be on the smooth sheet. These materials are 

 needed in very small quantities and will be furnished by the Office on request. Ver- 

 milion dry pigment should not be used because it is slightly greasy. In an emergency 

 black or red carbon paper can be used. 



The actual transfer is made by superposing the tracing on the smooth sheet so that corresponding 

 projection intersections are in exact coincidence. The transfer paper is then placed, coated side 

 down, between the tracing and the smooth sheet and with a stylus or sharp hard pencil the detail on 

 the tracing is gone over. This leaves a sharp outline on the smooth sheet. The transfer paper is 

 moved to an adjoining portion of the sheet and the procedure repeated. It is of the utmost importance 

 that the tracing does not slip during the transfer process. This should be checked as each portion is 

 transferred. The transferred detail is subsequently inked or penciled as explained in 752 to 755 

 inclusive. 



Where a small amount of transfer is involved, the reverse side of the tracing itself may be coated, 

 applying the powdered chalk only in the vicinity of the topographic details. Another method is to 

 smear the underside of the tracing paper with the lead of a soft pencil, using the side of the lead for 

 the purpose. Special care must be taken with the latter method because of the danger of distorting 

 the tracing paper during the rubbing. 



In transferring detail by the tracing-paper method excessive pressure must not be used on the 

 tracing, as this will engrave the lines in the smooth sheet. A slight pressure is generally sufficient to 

 ensure a satisfactory impression. 



The tracing or tracings used in the transfer shall be forwarded to the Washington 

 Office with the boat sheet (see 8351). 



7562. Method of Squares 



This method is not sufficiently accurate for the transfer of topographic detail to 

 the smooth sheet, but may be used to transfer the shoreline to the boat sheet or in 

 other cases. 



In the method of squares (fig. 156), common points on the two surveys are selected— usually 

 intersections of meridians and parallels. Referred to these common points, sets of corresponding 

 squares or rectangles are constructed lightly in pencil, which are identical when referred to the actual 



