basemap

[Jennifer Adams]

Hi, Tess --
The basemap.gs script is drawing a lot of polygons that fit exactly
inside (or outside) the continental outlines. The database of polygon
coordinates was generated by running another script manually -- it was
a painstaking process that required the effort of several summer
interns. Unfortunately, some of the polygons in the database cross
over latitude circles and this spoils the look of some circular polar
stereographic plots because these polygons do not get clipped. There
are a couple of options:
1. Try changing your latitude limits -- maybe there are no polygons
crossing the 65N line...
2. Use low resolution instead of medium -- I think these polygons are
better behaved
3. (Best option, I think) Change your lat range to 50 90, but then use
'set mpvals 0 360 70 90' to zoom into the area of interest -- this
will result in a square plot instead of a circular one, but basemap
will work properly. You can rotate the plot by changing the min/max
lon values in the 'set mpvals' command.

Jennifer


On Mar 15, 2009, at 9:05 PM, Tess Parker wrote:

> List - I am using the script basemap.gs to produce a north pole
> stereographic map with land areas shaded grey. I am using medium
> resolution.
> My grads commands are:
>
> 'open avestn.ctl'
> 'enable print 'test_ave.gmf'
> 'set grads off'
> 'set mproj nps'
> 'set lon 0 360'
> 'set lat 70 90'
> 'set digsize 0.09'
> 'set dignum 1'
> 'set stid on'
> 'set stnprint on'
> 'set mpdset mres'
> 'set map 1 1 3'
> 'd press'
> 'basemap L 15 0 M'
> 'draw title Monthly Mean SLP'
> 'print'
> 'disable print'
>
> The problem I have is that there are a couple of shaded areas which
> extend
> outside my map; do I need to use another command such as mpvals or
> something
> to get rid of these? There are three biggish blocks of grey outside
> the 60
> lat circle. Any help much appreciated.

--
Jennifer M. Adams
IGES/COLA
4041 Powder Mill Road, Suite 302
Calverton, MD 20705
jma at cola.iges.org



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