Following this newer template, equation () (the ray equation) becomes
where ,,and as before M indicates slowness squared (Mx = 1/ Vx2, ,,and Mz = 1/ Vz2).
Similarly, equation () (the dispersion relation) becomes
where ,,and as before W indicates velocity squared (Wx = Vx2, ,,and Wz = Vz2).
Note that the subscript indicates moveout velocity measured for near-vertical propagation; i.e., is the square NMO velocity we use every day in surface-to-surface data processing. (If an x subscript seems confusing for a paraxial measurement about the vertical, remember that in an elliptic world it is a horizontal velocity that surface moveout measures.) The subscript indicates moveout velocity measured for near-horizontal propagation, such as might be found in a cross-borehole experiment.