The new node spacing may be determined in one of several ways by specifying the grid spacing, number of nodes, or resolution. No space between the option flag and the associated arguments. Use upper case for the option flags and lower case for modifiers. Selects the map projection. More details can be found in the psbasemap manpages.
Options -D Set the grid spacing for the new grid.
Append m for minutes, c for seconds. Set the resolution for the new grid in dots pr inch. Do the Inverse transformation, from rectangular to geographical. Set the number of grid nodes in the new grid. To get a full grid back, your input grid may have to cover a larger area than you are interrested in.