This command to refine the appearance of the map lines.
set mpt type off
... or ...
set mpt type color <style <thickness>>
The type is
the map type; it can be a number from 0 to 255,
or it can be an asterick(*) to indicate this command applies to all the
type values.
The color argument may be one of the 16 GrADS default colors, a new color defined with set rgb, or it can be set to -1, in which
case GrADS will use the set
map settings for this map type.
Options for style are:
1 - solid
2 - long dash
3 - short dash
4 - long dash, short dash
5 - dotted
6 - dot dash
7 - dot dot dash
The thickness option must be an integer in the range of 1 to 12 (or 256 for version 2.1 and later.)
The lowres map data set has only one option for type:
1 -- coastlines
For the mres and hires data sets, there are three options for type:
0 -- coastlines
1 -- political boundaries (sorry, in some places these are out of date)
2 -- US state boundaries
Other map files may have more type options.
Changes to the map characteristics 'stick' until reset by a new
execution of set mpt, or when a reset or reinit command is issued.
When using GrADS version 2.0.2 and earlier, for the X window display and the image output (e.g. PNG), a thickness setting between 1 and 5 will result in map lines approximately one pixel wide; a thickness between 6 and 11 will result in map lines two pixels wide, and a thickness of 12 will give map lines approximately three pixels wide.
For the vector graphics output (e.g. PostScript and Encapsulated PostScript) the map line thickness will increase with each increment in the thickness value.
If using GrADS version 2.1 and later with the Cairo graphics library enabled,
then each thickness setting will increment the map line thickness, for the X window display and all hardcopy output formats.
The default line widths for thickness settings between 1 and 12 are: 0.6, 0.8, 1.0, 1.25, 1.5, 1.75, 2.0, 2.2, 2.4, 2.6, 2.8, 3.0. The units (pixels or points) will depend on the surface being drawn to. In GrADS version 2.1 and later, there is a new command, set lwid, that allows the user to define a new line thickness setting if the 12 default widths are unsatisfactory.
Suppose you are using the hires data set.
This will result in a map with coastlines and political boundaries, but no US state boundaries:
set mpt 2 off
These will plot the coastlines and political boundaries with thick light gray solid lines, and US state boundaries with thinner white dashed lines:
set mpt 0 15 1 6
set mpt 1 15 1 6
set mpt 2 1 3 3