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# 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:

-–R xmin/ xmax/ ymin/ ymax | The desired grid extent
-–I xinc[ m| c][/ yinc[ m| c]] | The grid spacing (append m or c for minutes or seconds of arc)
-–G gridfile | The output grid filename

- Nearest neighbor gridding
  - Exercises
- Gridding with Splines in Tension
- Preprocessing

Next: Nearest neighbor gridding Up: SESSION THREE Previous: Exercises