38 
  
  
  
z2+(x—b)? y(x —b 2 x —b 
doe ed ze j i. dig -——, d (7a) 
X 
dx =-d 7b 
x =—dz (7b) 
ad : 
d -)ds aps (7e) 
where 
- 2 52 
0p = — e Van +5 t3 doy — (x — b)dky — 
(7d) 
— dbyy +2dbzy 
Five terrain-forms are defined by Fig. 3. In each of the nine 
points, one of following values for Az is assumed: 
TAZ , — Az' > 0 
For the points 3, 4, 5, 6, 8, and 9, (3) is valid, that is: 
»| =d+kAz 
” 
Me 
Az 7 ^ 7 
  
  
  
  
  
  
  
  
Case 1 Case 2 
  
Fig. 3. The form of the terrain in the 5 specified cases,