3.2 Gridding of arbitrarily spaced data

Except in the situation above when a gridded file is available, we must convert our data to the right format readable by GMT before we can make contour plots and color-coded images. We distinguish between two scenarios:

1. The (x, y, z) data are available on a regular lattice grid.

2. The (x, y, z) data are distributed unevenly in the plane.

The former situation may require a simple reformatting (using xyz2grd), while the latter must be interpolated onto a regular lattice; this process is known as gridding. GMT supports three different approaches to gridding; here, we will briefly discuss the two most common techniques.

All GMT gridding programs have in common the requirement that the user must specify the grid domain and output filename:

-–Rxmin/xmax/ymin/ymax	The desired grid extent
-–Ixinc[m$\vert$c][/yinc[m$\vert$c]]	The grid spacing (append m or c for minutes or seconds of arc)
-–Ggridfile	The output grid filename