next up previous contents
Next: Block IV: Environmental Model Up: Block II: OASP options Previous: Block II: OASP options

Block III: Source Frequency

FRC is the source center frequency. As the source convolution is performed in PP, FRC is not used in OASP, but will be written to the transfer function file and become the default for PP.

COFF is the complex wavenumber integration contour offset. To be specified in , where is the wavelength at the source depth SD. As only the horizontal part of the integration contour is considered, this parameter should not be chosen so large, that the amplitudes at the ends of the integration interval become significant. In lossless cases too small values will give sampling problems at the normal modes and other singularities. For intermediate values, the result is independent of the choice of COFF, but a good value to choose is one that gives 60 dB attenuation at the longest range considered in the FFT, i.e.


where the maximum FFT range is


This value is the default which is applied if COFF is specified to 0.0.

Doppler shift

By specifying option d in OASP V.1.7 and higher, radial Doppler shift is accounted for using the theory developed by Schmidt and Kuperman [9]. The source pulse and the radial projections of the source and receiver velocities must be specified in the input file following the specification of the centre frequency and the contour offset (Block II), i.e.

Standard For option d
FRC COFF IT VS VR

IT is a number identifying the source pulse as described in Sec.16. VS and VR are the projected radial velocities in m/s of the source and receiver, respectively, both being positive in the direction from source to receiver. Since this option requires incorporation of the source function in the wavenumber integral, the PP post-processor must subsequently be used with source pulse -1 (impulse response).


next up previous contents
Next: Block IV: Environmental Model Up: Block II: OASP options Previous: Block II: OASP options
henrik schmidt
1999-08-25