Structure :
location absolute elevation 0d0 abs_elev1 loc2 abs_elev2 ...... ...... pipe lengh abs_elevN
Example :
0.d0 0.d0
20.d0 20.d0
1000.d0 20.d0
4000.d0 40.d0
6000.d0 40.d0
7000.d0 20.d0
10000.d0 20.d0