SWASH expects all quantities that are given by the user to be expressed in S.I. units:
m, kg, s and composites of these with accepted compounds, such as Newton
(N) and Pascal (Pa). Consequently, the water level and water depth are in m,
flow velocity in m/s, etc. For wind, (incident) wave and flow direction both the
Cartesian and a nautical convention can be used (see below). Directions and spherical
coordinates are in degrees (0) and not in radians.
SWASH operates either in a Cartesian coordinate system or in a spherical coordinate system, i.e. in a flat plane or on a spherical Earth. In the Cartesian system, all geographic locations and orientations in SWASH, e.g. for the bottom grid or for output points, are defined in one common Cartesian coordinate system with origin (0,0) by definition. This geographic origin may be chosen totally arbitrarily by the user. In the spherical system, all geographic locations and orientations in SWASH, e.g. for the bottom grid or for output points, are defined in geographic longitude and latitude. Both coordinate systems are designated in this manual as the problem coordinate system.
In the input and output of SWASH the direction of wind, (incident) wave and current are defined according to either