OK, soon I found out that m.xmax... are dependant on projection, and I
wasn't using Lambert projection
For default projection result are degrees and this way meters it sems
On Tue, Nov 8, 2011 at 9:13 PM, klo uo <klo...@gmail.com> wrote:
> from http://matplotlib.github.com/basemap/users/examples.html:
>
> ----------------------------------------
> from mpl_toolkits.basemap import Basemap, shiftgrid, cm
> import numpy as np
> import matplotlib.pyplot as plt
> from netCDF4 import Dataset
>
> # read in etopo5 topography/bathymetry.
> etopodata =\
> Dataset('http://ferret.pmel.noaa.gov/thredds/dodsC/data/PMEL/etopo5.nc')
> topoin = etopodata.variables['ROSE'][:]
> lons = etopodata.variables['ETOPO05_X'][:]
> lats = etopodata.variables['ETOPO05_Y'][:]
> # shift data so lons go from -180 to 180 instead of 20 to 380.
> topoin,lons = shiftgrid(180.,topoin,lons,start=False)
>
> # plot topography/bathymetry as an image.
>
> # create the figure and axes instances.
> fig = plt.figure()
> ax = fig.add_axes([0.1,0.1,0.8,0.8])
> # setup of basemap ('lcc' = lambert conformal conic).
> # use major and minor sphere radii from WGS84 ellipsoid.
> m =
> Basemap(llcrnrlon=-145.5,llcrnrlat=1.,urcrnrlon=-2.566,urcrnrlat=46.352,\
> rsphere=(6378137.00,6356752.3142),\
> resolution='l',area_thresh=1000.,projection='lcc',\
> lat_1=50.,lon_0=-107.,ax=ax)
> # transform to nx x ny regularly spaced 5km native projection grid
> nx = int((m.xmax-m.xmin)/5000.)+1; ny = int((m.ymax-m.ymin)/5000.)+1
> topodat = m.transform_scalar(topoin,lons,lats,nx,ny)
> ...
> ----------------------------------------
>
> Line (last but one):
> nx = int((m.xmax-m.xmin)/5000.)+1; ny = int((m.ymax-m.ymin)/5000.)+1
>
> (m.xmax-m.xmin) and (m.ymax-m.ymin) are very small compared to their
> divider 5000, so nx and ny are always 1
>
> Provided link for "etopo5.nc" is desperately slow (~20 Kb/s) so I can't
> test the code, but I tried with other dataset (ETOPO2) and I can't get what
> "topodat" varable should be. It's not clear to me from provided
> documentation.
>
> Thanks in advance for any help
>
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