PECan is a Canadian N£2D/3D parabolic equation (PE) underwater sound propagation model
that was developed for matched-¯eld processing applications. It is based on standard square-root
operator and/or propagator approximations that lead to an alternating direction solution of the
3D problem. A 2D split-step Pad¶e approximation is employed for propagation in range. The 3D
azimuthal corrections are computed using either a split-step Fourier method or a Crank-Nicolson
¯nite-di®erence approximation. It features a heterogeneous formulation of the di®erential operators,
an o®set vertical grid, energy conservation, a choice of initial ¯eld including self-starter, and both
absorbing and nonlocal boundary conditions. Losses due to shear wave conversion in an elastic
bottom are handled in the context of a complex density approximation. In this paper, PECan
is described and validated against some standard benchmark solutions to underwater acoustics
problems. Subsequently, PECan is applied to several single-frequency test cases that were o®ered
for numerical consideration at the SWAM'99 Shallow Water Acoustic Modelling workshop