Thread: [Matplotlib-users] Basemap with origin within the plot

I am trying to prepare a plot on the UK national grid.  This is a =
transverse mercator projection centred on the UK with a false origin =
offset from the projection origin (lat_0, lon_0).

The Basemap coordinate system origin (0 Easting and Northing) always =
seems to be set in the lower-left corner of the plot.  The plot I need =
includes data either side of the origin so I need the origin within the =
plot area.

Is there a general way of setting the origin somewhere other than the =
lower-left corner?

I can either get basemap to plot the correct data region, in which case =
the origin is in the wrong place or I can fool Basemap by adjusting the =
axes bounds later.  However, if I do this some of the coastline isn't =
plotted because Basemap decides it isn't on the map.

Cheers,
Stephen.

Pascoe, S (Stephen) wrote:
> Thanks Jeff,
>
> Unfortunately another issue is with plotting the axes tick labels.  This
> output is for a public service where the users expect to see eastings
> and northings displayed from the official UK national grid origin.  I
> can use standard matplotlib axes to produce eastings/northings but with
> your solution the origin would be shown as in the wrong place.
>
> I can envisage solving this by creating a tick Formatter object that
> offsets the axes.  Maybe that is my solution but I was hoping for a
> simpler way.
>
> Cheers,
> Stephen.
>   

Stephen: Using a TickFormatter is probably the best solution.  -Jeff

P.S.  Could you send me an example when you're done - perhaps to include 
in the examples directory?
> ---
> Stephen Pascoe  +44 (0)1235 445980
> British Atmospheric Data Centre
> Rutherford Appleton Laboratory
>
> -----Original Message-----
> From: Jeff Whitaker [mailto:js...@fa...] 
> Sent: 12 October 2007 13:11
> To: Pascoe, S (Stephen)
> Cc: mat...@li...
> Subject: Re: [Matplotlib-users] Basemap with origin within the plot
>
> Pascoe, S (Stephen) wrote:
>   
>> I am trying to prepare a plot on the UK national grid.  This is a
>>     
> transverse mercator projection centred on the UK with a false origin
> offset from the projection origin (lat_0, lon_0).
>   
>> The Basemap coordinate system origin (0 Easting and Northing) always
>>     
> seems to be set in the lower-left corner of the plot.  The plot I need
> includes data either side of the origin so I need the origin within the
> plot area.
>   
>> Is there a general way of setting the origin somewhere other than the
>>     
> lower-left corner?
>   
>> I can either get basemap to plot the correct data region, in which
>>     
> case the origin is in the wrong place or I can fool Basemap by adjusting
> the axes bounds later.  However, if I do this some of the coastline
> isn't plotted because Basemap decides it isn't on the map.
>   
>> Cheers,
>> Stephen.
>>
>>
>>   
>>     
> Stephen:  There's no way to change the coordinate system Basemap uses.  
> To get you data to plot in the correct place, just add an offset
>
> xoffset, yoffset = map(lon_0, lat_0)
>
> to the UK national grid coordinates of the data you are plotting.
>
> HTH,
>
> -Jeff
>
>   


-- 
Jeffrey S. Whitaker         Phone : (303)497-6313
NOAA/OAR/CDC  R/PSD1        FAX   : (303)497-6449
325 Broadway                Boulder, CO, USA 80305-3328

On 10/10/2007, Pascoe, S (Stephen) <S.P...@rl...> wrote:

> Is there a general way of setting the origin somewhere other than the lower-left corner?

I've just had to deal with a similar problem, you need to use the
basemap.shiftgrid() method to shift the co-ordinate grid accordingly.

Cheers

Adam

Pascoe, S (Stephen) wrote:
> I am trying to prepare a plot on the UK national grid.  This is a transverse mercator projection centred on the UK with a false origin offset from the projection origin (lat_0, lon_0).
>
> The Basemap coordinate system origin (0 Easting and Northing) always seems to be set in the lower-left corner of the plot.  The plot I need includes data either side of the origin so I need the origin within the plot area.
>
> Is there a general way of setting the origin somewhere other than the lower-left corner?
>
> I can either get basemap to plot the correct data region, in which case the origin is in the wrong place or I can fool Basemap by adjusting the axes bounds later.  However, if I do this some of the coastline isn't plotted because Basemap decides it isn't on the map.
>
> Cheers,
> Stephen.
>
>
>   
Stephen:  There's no way to change the coordinate system Basemap uses.  
To get you data to plot in the correct place, just add an offset

xoffset, yoffset = map(lon_0, lat_0)

to the UK national grid coordinates of the data you are plotting.

HTH,

-Jeff

-- 
Jeffrey S. Whitaker         Phone : (303)497-6313
NOAA/OAR/CDC  R/PSD1        FAX   : (303)497-6449
325 Broadway                Boulder, CO, USA 80305-3328