Program sfsamplowmat | Sample the lowrank propagation matrix 
[SYNOPSIS]
sfsamplowmat < velocity.rsf > mat.rsf dt= nz= dz= z0= nx= dx= x0=
[PARAMETERS]
        | dt | = |   | 	
        | dx | = |   | 	
        | dz | = |   | 	
        | nx | = |   | 	
        | nz | = |   | 	
        | x0 | = |   | 	
        | z0 | = |   | 	
[DIRECTORY]
user/jingwei
