Perspective views

Our final undertaking in this tutorial is to examine three-dimensional perspective views. GMT is currently limited to vantage points at infinity; thus we are unable to do fly-by's through canyons etc. The GMT module that produces perspective views of gridded data files is grdview . It can make two kinds of plots:

1.

Mesh or wire-frame plot (with or without superimposed contours)

2.

Color-coded surface (with optional shading, contours, or draping).

Regardless of plot type, some arguments must be specified; these are

1.

relief_file; a gridded data set of the surface.

2.

–-J for the desired map projection.

3.

–-JZheight for the vertical scaling.

4.

-–Eazimuth/elevation for vantage point.

In addition, some options may be required:

 

Table 4.5: The most useful options in grdview 

Option	Purpose
-–C cptfile	The cptfile is required for color -coded surfaces and for contoured mesh plots
-–G drape_file	Assign colors using drape_file instead of relief_file
-–I intens_file	File with illumination intensities
-–Qm	Selects mesh plot
-–Qs[ m]	Surface plot using polygons; append m to show mesh. This option allows for -–W
-–Qi dpi[ g]	Image by scan-line conversion. Specify dpi; append g to force gray-shade image. -–B is disabled.
-–W pen	Draw contours on top of surface (except with -–Qi)