    0.         100.               upper surface
 2000.         100.
 3000.         200.
 4000.         100.
 5000.         100.
10000.         100.
13000.        -500.
15000.           0.
18000.         100.
    1.      -99999.               end of upper surface
    0.         600.               interface 1
18000.         600.               ...
    1.      -99999.               end of interface 1
    0.        1000.               interface 2
 3000.        1000.               ...
 6000.        1500.
10000.        1000.
15000.         900.
18000.         800.
    1.      -99999.               end of interface 2
