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mankoff opened this issue Sep 10, 2014 · 7 comments
Open

ortho projection w/ limits crashes #164

mankoff opened this issue Sep 10, 2014 · 7 comments

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@mankoff
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mankoff commented Sep 10, 2014

Basemap documentation states that ortho projection can take ll/ur crnr limits. The following code seems like it should work (mpl 1.4.0), but does not:

from mpl_toolkits.basemap import Basemap
m = Basemap(projection='ortho',lon_0=0,lat_0=0,llcrnrlat=-10,llcrnrlon=-10,urcrnrlat=10,urcrnrlon=10)

Error:

---------------------------------------------------------------------------
AttributeError                            Traceback (most recent call last)
<ipython-input-5-98fbf042abb9> in <module>()
----> 1 m = Basemap(projection='ortho',lon_0=0,lat_0=0,llcrnrlat=-10,llcrnrlon=-10,urcrnrlat=10,urcrnrlon=10)

/Users/mankoff/Library/Enthought/Canopy_64bit/User/lib/python2.7/site-packages/mpl_toolkits/basemap/__init__.pyc in __init__(self, llcrnrlon, llcrnrlat, urcrnrlon, urcrnrlat, llcrnrx, llcrnry, urcrnrx, urcrnry, width, height, projection, resolution, area_thresh, rsphere, ellps, lat_ts, lat_1, lat_2, lat_0, lon_0, lon_1, lon_2, o_lon_p, o_lat_p, k_0, no_rot, suppress_ticks, satellite_height, boundinglat, fix_aspect, anchor, celestial, round, epsg, ax)
   1032         self.area_thresh = area_thresh
   1033         # define map boundary polygon (in lat/lon coordinates)
-> 1034         blons, blats, self._boundarypolyll, self._boundarypolyxy = self._getmapboundary()
   1035         self.boundarylats = blats
   1036         self.boundarylons = blons

/Users/mankoff/Library/Enthought/Canopy_64bit/User/lib/python2.7/site-packages/mpl_toolkits/basemap/__init__.pyc in _getmapboundary(self)
   1464             # circular region.
   1465             thetas = np.linspace(0.,2.*np.pi,2*nx*ny)[:-1]
-> 1466             rminor = self._height
   1467             rmajor = self._width
   1468             x = rmajor*np.cos(thetas) + rmajor

AttributeError: 'Basemap' object has no attribute '_height'
> /Users/mankoff/Library/Enthought/Canopy_64bit/User/lib/python2.7/site-packages/mpl_toolkits/basemap/__init__.py(1466)_getmapboundary()
   1465             thetas = np.linspace(0.,2.*np.pi,2*nx*ny)[:-1]
-> 1466             rminor = self._height
   1467             rmajor = self._width

ipdb>
@mankoff mankoff mentioned this issue Sep 10, 2014
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@jswhit
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jswhit commented Sep 10, 2014

you can use lcrnrx,llcrnry,urcrnrx,urcrnry (corners in map projection coords) but not lat/lon.

@mankoff
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mankoff commented Sep 10, 2014

Ok. Then perhaps consider this a documentation bug. The current docs here: http://matplotlib.org/basemap/api/basemap_api.html state,

For ortho... the lat/lon values of the corners may be specified, or the x/y values of the corners...

@PBrockmann
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Not sure to understand because indeed without lat_0 and lon_0

from mpl_toolkits.basemap import Basemap
m = Basemap(projection='ortho',llcrnrlat=-10,llcrnrlon=-10,urcrnrlat=10,urcrnrlon=10)

it gives

 ValueError: must specify lat_0 and lon_0 for Orthographic basemap

@mankoff
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mankoff commented Jan 8, 2015

@PBrockmann I'm not sure what your comment has to do with this bug. With lat_0 and lon_0 specified, it says that corners may be specified in lon/lat coordinates, but that is not correct, they must be in x,y coords. We aren't discussing the presence/absence of the lat_0,lon_0 arguments.

@PBrockmann
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The "but not lat/lon" from jswhit push me to try without lat_0 and lon_0.
Sorry for the missunderstanding and thank you for the clarification.

@WeatherGod
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I would like to clean up any documentation bugs soon. Could someone please suggest a revised line? Even better, could someone put together a PR with the documentation correction?

Also, ideally, I would want to produce a better error message in this case, so a suggested error message would be useful, too.

full discloser, I don't work in ortho projections, so I have no clue what is/isn't allowed.

@ImportanceOfBeingErnest
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Can someone please comment on how to obtain
lcrnrx,llcrnry,urcrnrx,urcrnry given that I have llcrnrlat=-10,llcrnrlon=-10,urcrnrlat=10,urcrnrlon=10?
Usually you may get x,y as x,y = m(lon,lat); however, if you need to know these already when instantiating the Basemap, you cannot use the Basemap to calculate the values to input in its initialisation method.

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5 participants
@mankoff @WeatherGod @jswhit @PBrockmann @ImportanceOfBeingErnest