Example 14. GMT supports several gridding algorithms. Perhaps the most used is the continuous curvature splines in tension algorithm which was used in this example to grid the data shown in example 12. Also shown is a comparison of the gridded surface and a low order polynomial trend surface. Several GMT modules were used to make this figure: blockmean and surface prepared the grid from non-uniformly spaced data, psxy and pstext drew points, lines, and text, grdcontour did the contouring, grdtrend determined a bicubic trend surface, and grdtrack sampled both the grid and trend surface along an arbitrary track.