Re: [Matplotlib-users] display a filled lat/lon basemap rectangle.

[Mathew Y. <mat...@gm...>]

lets say I want  to shade the area with lat/lon corners 34.-117  and 35,-116

but my map was created with projection='aeqd'

The shade area will not be a rectangle. In fact the edges will be curved.
See the basemap code for "tissot". I think every point on the boundary of
the lat/lon box has to projected to a line segment.  The collection of
resulting segments forms an irregular polygon.

Mathew



On Wed, Apr 7, 2010 at 6:24 PM, Jeff Whitaker <js...@fa...> wrote:

> Mathew Yeates wrote:
>
>> I think this will only work with some projections but not all. I looked at
>> the code for tissot. It's pretty hairy but it almost does what I want. (It
>> draws projected circles
>> instead of projected  rectangles.
>>
> Mathew:
>
> You said you wanted a NxN degree polygon - that's what I gave you.  What
> exactly do you want?  A rectangle in map projection coordinates?  A
> rectangle in lat/lon coordinates?  A circle?
>
> -Jeff
>
>>
>>
>> On Wed, Apr 7, 2010 at 1:54 PM, Jeff Whitaker <js...@fa...<mailto:
>> js...@fa...>> wrote:
>>
>>    Yeates, Mathew C (388D) wrote:
>>    >
>>    >
>>    >
>>    > Hi
>>    >
>>    > What is the simplest way to fill  in a 1 degree by 1 degree
>>    rectangle
>>    > on a basemap projection?
>>    >
>>    >
>>    >
>>    > Mathew
>>    >
>>
>>    Mathew:  Try this (for a 10x10 rectangle, but you get the idea)
>>
>>    from matplotlib.patches import Polygon
>>    import matplotlib.pyplot as plt
>>    from mpl_toolkits.basemap import Basemap
>>    map = Basemap(projection='moll',lon_0=0)
>>    x1,y1 = map(-10,-10)
>>    x2,y2 = map(-10,10)
>>    x3,y3 = map(10,10)
>>    x4,y4 = map(10,-10)
>>    p = Polygon([(x1,y1),(x2,y2),(x3,y3),(x4,y4)],\
>>       facecolor='red',edgecolor='blue',linewidth=2)
>>    plt.gca().add_patch(p)
>>    map.drawcoastlines()
>>    map.drawmapboundary()
>>    plt.show()
>>
>>    -Jeff
>>    >
>>
>>
>>
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