Range-Dependent SSP File


If you select option 'Q' (quadrilateral elements) for the SSP interpolation, BELLHOP will read a range-dependent SSP from an SSPFIL. The format of the SSPFIL is as follows:

Range-dependent SSP

Syntax:

NPROFILES
RPROF( 1 )  RPROF( 2 ) ...  RPROF( NPROFILES )
C( 1, 1 )   C( 1, 2 )  ...  C( 1, NPROFILES )
C( 2, 1 )   C( 2, 2 )  ...  C( 2, NPROFILES )
 
.
 
.
 .
C( NZ, 1 )  C( NZ, 2 )     ...  C( NZ, NPROFILES )

Description:

NPROFILES:   Number of profiles.
NZ:          Number of depth points where SSP is sampled
RPROF():     Range of each profile in km.
C():         Sound speed. c( iz, iprof ) is the sound speed at the depth point, iz, in profile, iprof.

Example:


8
0.0     12.5     25.0    37.5    50.0    75.0    100.0   125.0
1536    1536     1536    1536    1536    1536    1536    1536
1506    1508.75  1511.5  1514.25 1517    1520    1524    1528
1503    1503     1503    1502.75 1502.5  1502    1502    1502
1508    1507     1506    1505    1504    1503    1501.5  1500
1508    1506.6   1505    1503.75 1502.5  1500.5  1499    1497
1497    1497     1497    1497    1497    1497    1497    1497
1500    1500     1500    1500    1500    1500    1500    1500
1512    1512     1512    1512    1512    1512    1512    1512
1528    1528     1528    1528    1528    1528    1528    1528
1545    1545     1545    1545    1545    1545    1545    1545


Note: The main BELLHOP envfil must contain a dummy SSP with NZ depth points. Those depths points are used to interpret the depths in the above SSP matrix.

You should also include an altimetry or bathymetry file with points at each of the profile ranges. The altimetry or bathymetry can be flat. However, BELLHOP uses the altimetry and bathymetry points to define segements in range, and it adjusts the ray step size to always land on the profile boundaries (which is good for the accuracy of the ray trace). I didn't implement similar logic for the SSP so using the altimetry/bathymetry data is a simple trick to accomplish the same thing.

See the example in at/tests/Gulf.