Hello matplotlib users,

I am having trouble understanding the coordinate transformations in

Basemap and pyproj. I have gridded MODIS vegetation data, with upper

left corner and lower right corner given in projection coordinates

(meters). I want to contour the data with Basemap. The data are in a

sinusoidal projection, but the coordinates do not correspond to what

Basemap seems to expect.

The code below illustrates the problem. Proj translates the upper

left to lat/lon correctly (-92.327237416031437, 30.141972433747089),

while Basemap does not.

#-------- code --------

from mpl_toolkits.basemap import Basemap

from mpl_toolkits.basemap import pyproj

ulm = [-8895604.1573329996, 3335851.5589999999] #upper left, meters

lrm = [-7783653.6376670003, 2223901.0393329998] #lower right, meters

sinu = pyproj.Proj(proj='sinu', lon_0=0.0, x_0=0.0, y_0=0.0)

m = Basemap(projection='sinu', resolution=None, lon_0=0.0)

print "ULM: " + str(ulm)

print "Proj: " + str(sinu(ulm[0], ulm[1], inverse=True))

print "Basemap: " + str(m(ulm[0], ulm[1], inverse=True))

#----- end code --------

This gives:

ULM: [-8895604.1573329996, 3335851.5589999999]

Proj: (-92.327237416031437, 30.141972433747089)

Basemap: (-159.99950210056144, -59.99995206181125)

I'm sure I'm missing something really simple, but I've read a lot of

documentation and I'm not sure what.

Many thanks for any help.

Best,

Tim

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Timothy W. Hilton

PhD Candidate, Department of Meteorology

The Pennsylvania State University

503 Walker Building, University Park, PA 16802

hilton@...3085...