Maps and map projections
Data files for some examples
Example pages containing:
NCL map outlines
NCL has three resolutions of map outline databases available through
can take one of four values:
- "LowRes" - the default prior to NCL V6.4.0;
recommended for global maps and not for regional areas
- "MediumRes" - recommended for regional maps; has more up-to-date
- "HighRes" - a high-resolution coastline database; cannot be used
for global maps as it will not be drawn correctly. Requires a "RANGS"
database that you need to download and install. Go to
the RANGS page for more
- "Dynamic" - new default behavior introduced with NCL V6.4.0;
the LowRes database is used unless either of mpFillBoundarySets
or mpOutlineBoundarySets is set to something other
than "Geophysical", in which case the MediumRes database is used. (see
example 6 below).
To turn NCL map outlines on or off, set
the mpOutlineOn resource to True or
False. You can also turn map fill on and off by setting
mpFillOn resource to True or False
to turn on/off map fill.
There are many resources for customizing the look of your map outlines.
You can see the full list
of map resources here. Here's a sample:
In some cases, NCL's map outlines may not give you the outlines
or resolution you desire. We recommend that people use
, which you can
find numerous, free examples of using a web browser search.
The Global Administrative Database (GADM)
) offers various
levels of outlines for many countries in the shapefile format. See
the shapefiles examples
page for more
This page shows you various comparisons of the three map databases, as well
as how to add your own map outlines via shapefiles or simple polyline draws
Shows how to draw the Changjiang and Huanghe Rivers on
a zoomed in map of China, using
The script was contributed by Dr. Xiao-Feng Li of the Institute of
Atmospheric Physics (IAP), Chinese Acadmey of Sciences (CAS), modified
from a GrADS code from Dr. Pinwen Guo (NUIST) and NCL code of Dr. Jun
This script is similar to the mapoutlines_5.ncl one above, except it
includes the "HighRes
database, if installed. It produces two panel plots, so you can
compare the various map outlines.
This script illustrates new default map database behavior introduced in NCL V6.4.0
and shows how to override the defaults. As with prior versions of NCL, the default
map database is LowRes, unless either of the boundary-set resources
to anything other than "Geophysical", in which case the MediumRes database is used. This
represents a balance between performance and accuracy for common use-cases. The LowRes database
is more than adequate for global scale maps depicting land/ocean boundaries, whereas the
more detailed MediumRes database is preferred for its more up-to-date political boundaries.
The default behavior can be overriden by explicitly setting mpDataBaseVersion to
the desired database name.
example is another one showing the difference between map outlines in
NCL and map outlines added from a shapefile. The first plot in the
panel shows the counties of Colorado as plotted from NCL, and the
second plot shows the counties as plotted from the USA_adm2 shapefile
The left image is from running
NCL V6.3.0 on this
script. The right image is from running
In NCL versions 6.3.0 and earlier, the NCL outlines will not show the
county of Broomfield or the updated counties around Denver. In NCL
version 6.4.0, the NCL map databases were updated to reflect the
current Colorado counties.