Alternative single scatter approximation for one-way wave propagation

For wave propagation in a slowly varying waveguide, approximate one-way models are widely used. The single scatter approximation improves the accuracy of the standard one-way equation involving a square root operator, but it is usually given in a discrete form. The continuous limit of the discrete single scatter approximation leads to an improved one-way equation. An alternative formulation of the discrete single scatter approximation is then introduced to avoid the difficulty related to the rational approximation of a sum of two square root operators. Numerical implementation of the alternative formulation is more convenient and achieves the same level of accuracy as the original single scatter approximation.