Re: [python-users] Displaying GOES in mercator projection

• To: "Weber, Jim" <Jim.Weber@xxxxxxx>
• Subject: Re: [python-users] Displaying GOES in mercator projection
• From: Ryan May <rmay@xxxxxxxx>
• Date: Thu, 18 Nov 2021 12:53:00 -0700

Hi Jim

So when you type:

    ax.set_extent([-135, -60, 10, 65], crs=ccrs.Mercator())

You are telling cartopy "set the extents of the axes to a box with lower
left corner (-135, 10) and upper right corner (-60, 65); those points are
native coordinates in the Mercator() projection". You essentially specified
a 75m x 55m box. To plot with Mercator you want:

    # Tell cartopy the axes we're plotting on should be in Mercator
    ax = fig.add_subplot(1, 1, 1, projection=Mercator())
    # Specify the extent as lat/lon
    ax.set_extent([-135, -60, 10, 65], crs=ccrs.PlateCarree())

Hope this helps!

Ryan

On Thu, Nov 18, 2021 at 11:54 AM Weber, Jim <Jim.Weber@xxxxxxx> wrote:

> Below is a snippet of code from Brian Blaylock’s True Color Recipe.  I am
> trying to instead display imagery in a Mercator projection. I thought I
> would do this with a line such as:
>
> mc=cartopy.ccrs.Mercator(*central_longitude=0.0*, *min_latitude=-80.0*,
> *max_latitude=84.0*, *globe=None*)
>
>
>
> and then have lines:
>
> ax = fig.add_subplot(1, 1, 1, projection=mc)
>
> ax.set_extent([-135, -60, 10, 65], crs=ccrs.Mercator())
>
>
>
> but this does not work. Can someone point out what I am doing wrong or
> point me to the correct resource so I might understand my problem better?
>
>
>
>
>
> Thanks, Jim
>
>
>
> ------ Code snippet ---------
>
>
>
>
>
> fig = plt.figure(figsize=(15, 12))
>
>
>
> # Generate an Cartopy projection
>
> lc = ccrs.LambertConformal(central_longitude=-97.5,
> standard_parallels=(38.5,
>
>
> 38.5))
>
>
>
> ax = fig.add_subplot(1, 1, 1, projection=lc)
>
> ax.set_extent([-135, -60, 10, 65], crs=ccrs.PlateCarree())
>
>
>
> ax.imshow(RGB, origin='upper',
>
>           extent=(x.min(), x.max(), y.min(), y.max()),
>
>           transform=geos,
>
>           interpolation='none')
>
> ax.coastlines(resolution='50m', color='black', linewidth=0.5)
>
> ax.add_feature(ccrs.cartopy.feature.STATES, linewidth=0.5)
>
>
>
> plt.title('GOES-16 True Color', loc='left', fontweight='bold', fontsize=15)
>
> plt.title('{}'.format(scan_start.strftime('%d %B %Y %H:%M UTC ')),
> loc='right')
>
>
>
> plt.show()
>
>
>
>
>
>
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-- 
Ryan May, Ph.D.
Software Engineer
UCAR/Unidata
Boulder, CO

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  • Re: [python-users] Displaying GOES in mercator projection
    • From: Weber, Jim

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  • [python-users] Displaying GOES in mercator projection
    • From: Weber, Jim