3^. Referring to Figure lU, an interval to be crossed is divided into 

 segments or boxes, by transverse lines. The spacing, R, of the lines is 

 arbitrarily set as a ratio of the distance, J, between the contours. For 

 the complete interval to be crossed, Cp/C-, is computed or found from Table f 

 of Appendix D (Note: C2/C1 not 0.-^/^2^* 



36. On the template (Figure 12) is a graph showing orthogonal angle 

 txirnings (Aa ) at the center of a box, plotted as a function of the C2/C-|_ 

 value of any contour interval for various values of the R/J ratio, which 

 may be chosen, 



37. The orthogonal is brought into the middle of the box, Aa is read 

 from the graph, and the orthogonal turned by that angle. The procedure is 

 repeated for every box until a at a plotted or interpolated contour becomes 

 less than 80°, At this point this method of orthogonal construction must 

 be stopped or error will result. The dots on the graph of Figure 12 are 

 those used to determine values for the example on Figure lU. 



J = Distance between contours at turning points, • 



R = Distance along orthogonal 



T = 12 seconds 



Lo= 737 ft. 



For contour interval from 40fm to 30fm C /C = 1.045, C /C =0.957 



12 '21 



A* = 2*- 25 



REFRACTION DIAGRAM USING -j METHOD 

 FIGURE 14 



2k 



