[gradsusr] set shp -poly

[Jennifer Adams]

Jeff,
The shapfile interface in GrADS creates a shapefile that contains polygons that fill out the areas outlined by the shaded contours. Because of the rules in the shapefile spec regarding polygon geometry, the area inside a shaded contour is split up into many pieces so that individual polygons do not overlap and do not contain holes (no donuts). That is why you are seeing all the vertical lines. If you color in the polygons and use the same color to draw the outline, you won't see the vertical lines and the plot will look more normal (like the shaded contour plot in GrADS). 

Also, before you create the shapefile, you must be in the latlon projection (set mproj latlon). No other projection will work. It should be possible to use your GIS tool to re-project the data in the shapefile using the metadata in the file provided by GrADS. From the attachement you sent, it's difficult to tell what the problem is -- better to draw a plot of a variable such a land mask that would clearly show whether the boundaries in the data are lining up with the political boundaries (and color them in and use matching outline color). If there is an issue in the way Qgis is re-projecting the shapefile, then that may or may not be a GrADS problem.

The polygons 'connect to the outside' because they are filling in the lat/lon block defined by your dimension environment. You can't mask your shapefile according to political boundaries, but you can choose to not draw a certain contour level by using -1 instead of a color number in the 'set ccols' command. 

I can't help you any further without more specific information about what version of GrADS you're using, what the descriptor file looks like for your data, the source of your data file (so I can grab a sample), what your commands were to generate the shapefile, and what you did inside Qgis to create the display in your attachment. 
--Jennifer




On Jan 3, 2012, at 4:22 PM, Jeff Lake wrote:

> I believe there is a minor, okay major, flaw in the conversion to shape file
> here is the shape file I get when converting the RTMA GRIB over (see attachment)
> the resulting polygons all 'connect' to the outside
> this is a cint set from -30 to 140 by 5 degree's
> this is a better result then another piece of software, but still not correct..
> 
> anybody got suggestions ??
> 
> -- 
> -Jeff Lake
> MichiganWxSystem.com
> WeatherMichigan.net
> TheWeatherCenter.net
> GRLevelXStuff.com
> 
> <rtma.jpg>_______________________________________________
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--
Jennifer M. Adams
IGES/COLA
4041 Powder Mill Road, Suite 302
Calverton, MD 20705
jma at cola.iges.org



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