matplotlib-users

[Matplotlib-users] strange error when attempting to generate a map using 'geos' projection

[Dr. P. M. F. <pfe...@ve...>]

I’ve been experimenting with basemap, and have been able to make maps using
the orthographic and polyconic projections.  When I try to generate a map
using the geostationary projection, I get the error message shown below.  I
haven’t been able to make head or tail of this message; any advice will be
appreciated.

Phillip

RuntimeError                              Traceback (most recent call last)

C:\Phillip\pmap.py in <module>()
   6163
   6164       # Create basemap object:
-> 6165       map= Basemap(**map_parms)
   6166       ax= fig.add_axes([0.1,0.08,0.7,0.82])
   6167

C:\Python25\lib\site-packages\mpl_toolkits\basemap\__init__.pyc in
__init__(self, llcrnrlon, llc
rnrlat, urcrnrlon, urcrnrlat, llcrnrx, llcrnry, urcrnrx, urcrnry, width,
height, projection, res
olution, area_thresh, rsphere, lat_ts, lat_1, lat_2, lat_0, lon_0, lon_1,
lon_2, no_rot, suppres
s_ticks, satellite_height, boundinglat, fix_aspect, anchor, ax)
    680
    681         # initialize proj4
--> 682         proj =
Proj(projparams,self.llcrnrlon,self.llcrnrlat,self.urcrnrlon,self.urcrnrl
at)
    683
    684         # make sure axis ticks are suppressed.

C:\Python25\lib\site-packages\mpl_toolkits\basemap\proj.pyc in
__init__(self, projparams, llcrnr
lon, llcrnrlat, urcrnrlon, urcrnrlat, urcrnrislatlon)
    117             urcrnry = -llcrnry
    118         elif self.projection == 'geos':
--> 119             self._proj4 = pyproj.Proj(projparams)
    120             # find major and minor axes of ellipse defining map proj
region.
    121             # h is measured from surface of earth at equator.

C:\Python25\lib\site-packages\mpl_toolkits\basemap\pyproj.pyc in
__new__(self, projparams, **kwa
rgs)
    146                     kvpairs.append(kvpair+' ')
    147             projstring = ''.join(kvpairs)
--> 148         return _Proj.__new__(self, projstring)
    149
    150     def __call__(self, *args, **kw):

C:\Python25\lib\site-packages\mpl_toolkits\basemap\_proj.pyd in
_proj.Proj.__cinit__ (src/_proj.
c:587)()
     23
     24
---> 25
     26
     27

RuntimeError: unknown prime meridian conversion id
WARNING: Failure executing file: <pmap.py>

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Re: [Matplotlib-users] strange error when attempting to generate a map using 'geos' projection

[Jeff W. <js...@fa...>]

Dr. Phillip M. Feldman wrote:
> I’ve been experimenting with basemap, and have been able to make maps using
> the orthographic and polyconic projections.  When I try to generate a map
> using the geostationary projection, I get the error message shown below.  I
> haven’t been able to make head or tail of this message; any advice will be
> appreciated.
>
> Phillip
>
> RuntimeError                              Traceback (most recent call last)
>
> C:\Phillip\pmap.py in <module>()
>    6163
>    6164       # Create basemap object:
> -> 6165       map= Basemap(**map_parms)
>    6166       ax= fig.add_axes([0.1,0.08,0.7,0.82])
>    6167
>
> C:\Python25\lib\site-packages\mpl_toolkits\basemap\__init__.pyc in
> __init__(self, llcrnrlon, llc
> rnrlat, urcrnrlon, urcrnrlat, llcrnrx, llcrnry, urcrnrx, urcrnry, width,
> height, projection, res
> olution, area_thresh, rsphere, lat_ts, lat_1, lat_2, lat_0, lon_0, lon_1,
> lon_2, no_rot, suppres
> s_ticks, satellite_height, boundinglat, fix_aspect, anchor, ax)
>     680
>     681         # initialize proj4
> --> 682         proj =
> Proj(projparams,self.llcrnrlon,self.llcrnrlat,self.urcrnrlon,self.urcrnrl
> at)
>     683
>     684         # make sure axis ticks are suppressed.
>
> C:\Python25\lib\site-packages\mpl_toolkits\basemap\proj.pyc in
> __init__(self, projparams, llcrnr
> lon, llcrnrlat, urcrnrlon, urcrnrlat, urcrnrislatlon)
>     117             urcrnry = -llcrnry
>     118         elif self.projection == 'geos':
> --> 119             self._proj4 = pyproj.Proj(projparams)
>     120             # find major and minor axes of ellipse defining map proj
> region.
>     121             # h is measured from surface of earth at equator.
>
> C:\Python25\lib\site-packages\mpl_toolkits\basemap\pyproj.pyc in
> __new__(self, projparams, **kwa
> rgs)
>     146                     kvpairs.append(kvpair+' ')
>     147             projstring = ''.join(kvpairs)
> --> 148         return _Proj.__new__(self, projstring)
>     149
>     150     def __call__(self, *args, **kw):
>
> C:\Python25\lib\site-packages\mpl_toolkits\basemap\_proj.pyd in
> _proj.Proj.__cinit__ (src/_proj.
> c:587)()
>      23
>      24
> ---> 25
>      26
>      27
>
> RuntimeError: unknown prime meridian conversion id
> WARNING: Failure executing file: <pmap.py>
>
>   
Philip:  That's an error from the proj4 c library saying that it didn't 
like one of the parameters you used to define the projection.  Since you 
didn't include the parameters you used, I can't say which one is the 
culprit.

-Jeff

Re: [Matplotlib-users] strange error when attempting to generate a map using 'geos' projection

[Dr. P. M. F. <pfe...@ve...>]

Jeff Whitaker wrote:
> 
> <snip>
> Philip:  That's an error from the proj4 c library saying that it didn't 
> like one of the parameters you used to define the projection.  Since you 
> didn't include the parameters you used, I can't say which one is the 
> culprit.
> 
> -Jeff
> 

I've boiled the code down to something small that demonstrates the problem. 
Thanks!
http://old.nabble.com/file/p27297693/temp.py temp.py 
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Re: [Matplotlib-users] strange error when attempting to generate a map using 'geos' projection

[Jeff W. <js...@fa...>]

Dr. Phillip M. Feldman wrote:
> Jeff Whitaker wrote:
>   
>> <snip>
>> Philip:  That's an error from the proj4 c library saying that it didn't 
>> like one of the parameters you used to define the projection.  Since you 
>> didn't include the parameters you used, I can't say which one is the 
>> culprit.
>>
>> -Jeff
>>
>>     
>
>   
Philip: I believe that lat_0 must be zero for the geostationary 
projection (you have to be looking down on the equator).  I usually 
leave the lat_0 parameter off entirely, in which case zero is assumed.  
I'll try to catch that and raise a more insightful error message.

-Jeff

Re: [Matplotlib-users] strange error when attempting to generate a map using 'geos' projection

[Phillip M. F. <pfe...@ve...>]

Jeff Whitaker wrote:
> Dr. Phillip M. Feldman wrote:
>> Jeff Whitaker wrote:
>>  
>>> <snip>
>>> Philip:  That's an error from the proj4 c library saying that it 
>>> didn't like one of the parameters you used to define the 
>>> projection.  Since you didn't include the parameters you used, I 
>>> can't say which one is the culprit.
>>>
>>> -Jeff
>>>
>>>     
>>
>>   
> Philip: I believe that lat_0 must be zero for the geostationary 
> projection (you have to be looking down on the equator).  I usually 
> leave the lat_0 parameter off entirely, in which case zero is 
> assumed.  I'll try to catch that and raise a more insightful error 
> message.
>
> -Jeff
>

Hm.  I suppose that you are right.  "Geostationary" does imply that the 
viewer is 35786.2 km above the equator.

What would be more useful is a geosynchronous projection.  This would 
allow the viewer to be located at any latitude.  Geostationary is a 
special case of geosynchronous.

Even more useful than a geosynchronous projection is a camera projection 
that allows one to place the viewer at any location in space (i.e., any 
latitude and longitude for the nadir point, and any altitude).  (I wrote 
something like this is Fortran 25 years ago).  Generalizing the existing 
geostationary projection to turn it into a camera projection would make 
it far more useful.  I hope that someone will consider making this change.

Phillip