[gradsusr] Basemap with polar projection in circle frame

[Jennifer M Adams]

Yeah, when I was creating the polygons for the basemap script ~18 years ago, I was unaware of the consequences if some of them crossed latitude circles. The polygons that extend outside your specified domain don’t get clipped because of the circular frame — clipping only works with the square frame. —Jennifer

> On Sep 11, 2018, at 5:45 AM, David Nielsen <davidnielsen at id.uff.br> wrote:
> 
> Dear Grads users,
> 
> I am trying to use a north polar stereographic projection with basemap to cover land areas in Grads. 
> 
> Using the combination of set lat/lon and mproj suggested in basemap's script, I get a nice map framed with a square: 
> 
> 'set lat 0 90'
> 'set lon -180 180'
> 'set mproj nps'
> 'set mpvals -180 180 50 90'
> ...
> 'set rgb 88 200 200 200'
> 'basemap L 88 1 L' 
> 
> <image.png>
> 
> No problem there. Now, I would like to get rid of the corners of the square, setting the minumin latitude to 50 and using the "set frame" command, aiming to get a circle-shaped figure:
> 
> 'set lat 50 90'
> 'set lon -180 180'
> 'set mproj nps'
> 'set mpvals -180 180 50 90'
> 'set frame circle'
> ...
> 'set rgb 88 200 200 200'
> 'basemap L 88 1 L'
> 
> But then I get some pieces of land streching out of the circle:
> 
> <image.png>
> 
> Trying other mpdset and basemap resolutions doesn't solve the problem.
> 
> It can get even more messy with different map domains:
> 
> <image.png>
> 
> 
> Has someone run into this or found a solution to this bug?
> 
> Many thanks in advance,
> David
> 
> 
> 
> 
> 
> 
> 
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--
Jennifer Miletta Adams
Center for Ocean-Land-Atmosphere Studies (COLA)
George Mason University