Adam Mercer wrote:
> Hi
>
> I'm running into a problem using the mollweide projection, with the
> following simplified code, my actual code doesn't use random data for
> values but this is a clearer example to the problem I'm experiencing:
>
> lon = numpy.arange(0, 361, 1)
> lat = numpy.arange(90, 91, 1)
> x, y = numpy.meshgrid(lon, lat)
> values = numpy.random.random((181, 361))
>
> map = basemap.Basemap(projection='moll', lon_0=0, resolution='c')
> map.drawcoastlines()
> map.drawcountries()
> map.drawmapboundary()
> map.drawmeridians(numpy.arange(0,360,30))
> map.drawparallels(numpy.arange(90,90,30))
>
> X, Y = map(x, y)
>
> map.contourf(X, Y, values)
>
> I get the following error:
>
> WARNING: x coordinate not montonically increasing  contour plot
> may not be what you expect. If it looks odd, your can either
> adjust the map projection region to be consistent with your data, or
> (if your data is on a global lat/lon grid) use the shiftgrid
> function to adjust the data to be consistent with the map projection
> region (see examples/contour_demo.py).
>
> And the resulting map is incorrect due to the horizontal trends, see
> http://tier2.ihepa.ufl.edu/~ram/files/moll.jpg
>
>
> but if I use the orthographic projection ie:
>
> map = basemap.Basemap(projection='ortho', lat_0=20, lon_0=30, resolution='c')
>
> Then there are no errors, and the map is displayed as expected, see
> http://tier2.ihepa.ufl.edu/~ram/files/ortho.jpg
>
> I am unsure as to why I am receiving this error for the mollweide
> projection, as my coordinate grid is covering the entire surface. I
> am clearly doing something wring here but I don't know what  does
> anyone know what is causing this issue?
>
> Cheers
>
> Adam
>
Adam: I assume your data is on a latitudelongitude grid? You've asked
for a mollweide projection centered on the Greenwich meridian. Your
data is not centered on Greenwich  but the error message is trying to
say that you can shift your grid (with the shiftgrid function) so that
is has the same orientation as the map projection region. This only
comes into play with global projections that 'wraparound' at the edges,
like the mollweide and mercator projections. The orthographic
projection does not 'wrap around'  hence you don't get the error message.
Jeff

Jeffrey S. Whitaker Phone : (303)4976313
Meteorologist FAX : (303)4976449
NOAA/OAR/PSD R/PSD1 Email : Jeffrey.S.Whitaker@...
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