OpenOSX: GrassPro: GMT Masks

psclip	Use polygon files to define clipping paths. Several files may be read to create complex paths consisting of several non-connecting segments, the polygons "direction" may be reversed which determines the inside and outside of the paths
grdlandmask	Creates a "wet-dry" mask .grd file from shoreline data base, it will read the selected shoreline database and uses that information to decide which nodes in the specified grid are over land or over water.
psmask	Create an overlay to mask out regions on maps; uses specified xyz data to determine which grid cells are reliable. Only gridcells which have one or more data points are considered reliable. As an option, you may specify a radius of influence. Then, all gridcells that are within radius of a data point are considered reliable, with an option to reverse the sense of the test. Having found the reliable/unreliable points, psmask will either paint tiles to mask these nodes, or use contouring to create polygons that will clip out regions of no interest.
grdmask	Creates mask .grd files from xy paths with two modes of operation: 1. It reads one or more xy-files that each define a closed polygon, the nodes defined by the specified region and lattice spacing will be set equal to one of three possible values depending on whether the node is outside, on the polygon perimeter, or inside the polygon. The resulting mask grdfile may be used in subsequent operations involving grdmath to mask out data from polygonal areas. 2. The xy-files simply represent data point locations and the mask is set to the inside or outside value depending on whether a node is within a maximum distance from the nearest data point. If the distance specified is zero then only the nodes nearest each data point are considered "inside".