[nclpy-group] Thoughts on changing NCL's default map database to "MediumRes"

Mary Haley haley at ucar.edu
Tue Mar 15 10:52:54 MDT 2016


I'm writing to get the NCL advisory group's opinions on a somewhat
significant change we plan to make in NCL Version 6.4.0.

As you may know, the default map database in NCL is the "LowRes" database,
which is woefully out-of-date.  We get the feeling that people tend to use
the "MediumRes" database if they turn on political outlines or if they zoom
in on regional areas.

For the NCL V6.4.0 release, we propose making the "MediumRes" map database
the default one that is used if the user specifies any map boundaries other
than the default "Geophysical" boundaries.

We originally thought about making the "MediumRes" map database the default
in all cases, but when we ran some timing tests we saw a 57% increase in
time across our graphics test suite (this included global and regional
plots). We then decided that perhaps the default should only be changed in
the case where the user requests map outlines other than geophysical
outlines.

We also considered making the "Earth..4" database subset of the "MediumRes"
database the default, because it has much nicer outlines than the default
"Earth..2". However, this caused a 300% increase in time, and a significant
increase in the size of the graphics output files.

I've attached a script and some sample images so you can see what the
different databases look like. I used "Germany" as the focal area of
interest, since the "LowRes" database still has the East/West dividing line
<cringe>.

In a future release of NCL, we plan to incorporate shapefile outlines more
seamlessly. The changes we are proposing now are just a small step to
improve the NCL maps until then.

We would welcome any comments, positive or negative, regarding this
proposal. I will likely post this to ncl-talk before too long, but wanted
to get this group's thoughts first.

Thanks for your time,

--Mary
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