Re: [Matplotlib-users] projections in matplotlib.toolkits.basemap Basemap vs. pyproj.Proj

Charles Seaton wrote:
> I have noticed that matplotlib.toolkits.basemap.Basemap supports a smaller
> set of projection arguments than the underlying function
> matplotlib.toolkits.basemap.pyproj.Proj and was wondering if there is a
> fundamental limitation on the functionality of Basemap that prevents it from
> handling proj arguments such as x_0, y_0, ellps, datum, and init?
>
> I would like to be able to use all of the very nice functionality built into
> Basemap on standard projections such as Oregon State Plane Coordinate
> System-North NAD27 (which can be generated using pyproj.Proj with the
> following proj arguments:
>
> orspcs_m = matplotlib.toolkits.basemap.pyproj.Proj(\
> proj='lcc',lat_1=44.33333333333334,lat_2=46,lat_0=43.66666666666666,\
> lon_0=-120.5,x_0=609601.2192024384, y_0=0,ellps='clrk66',datum='NAD27')
>
> or even more simply by
> orspcs_m = matplotlib.toolkits.basemap.pyproj.Proj(init='epsg:32026')
> or 
> orspcs_m = matplotlib.toolkits.basemap.pyproj.Proj(init='nad27:3601')
>
> but Basemap() won't accept the necessary arguments
>
> Would this be a matter of modifying the Basemap __init__ function to
> recognize a longer list of possible arguments or is there a larger issue I'm
> not seeing, or a bunch more code that would require modification?
>
> thanks,
>
> Charles Seaton
> Research Associate
> OHSU/ STC-CMOP
>   
Charles:  Unfortunately, there's more to making a map than getting the 
map projection transformation right.  There's lots of special case code 
for different projections in basemap to take care of coastline polygons 
that go over the edge of the map region, drawing of meridians and 
parallels, drawing the map projection boundary, etc.

It looks like the projection you want is lambert conformal with a 
Clark66 ellipsoid.  You should be able to use Basemap with 
projection='lcc', and rsphere set to a tuple that defines the Clark66 
ellipsoid.  Is there a reason that won't work?

-Jeff

-- 
Jeffrey S. Whitaker         Phone : (303)497-6313
NOAA/OAR/CDC  R/PSD1        FAX   : (303)497-6449
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