matplotlib-users

[Matplotlib-users] draw track across the Dateline in Basemap

[fatuheeva <fat...@ya...>]

Hello,
I am wondering if Basemap has the ability to plot a track across the Dateline? Plotting longitudes that go across the Dateline (e.g., [175,177,179,-179,-176]) wraps the track back around the globe when it goes from 179 to -179. Instead, I want them directly connected. My Basemap instance looks like:

m = Basemap(projection='merc',llcrnrlat = 10,urcrnrlat = 30,llcrnrlon = 160,\
                urcrnrlon = -160,lat_ts = 20,resolution = 'l',lon_0 = 180)

Am I screwed on this one?
Thanks,

Mike

Re: [Matplotlib-users] draw track across the Dateline in Basemap

[Jeff W. <jef...@no...>]

On 7/3/12 11:39 AM, fatuheeva wrote:
> Hello,
> I am wondering if Basemap has the ability to plot a track across the 
> Dateline? Plotting longitudes that go across the Dateline (e.g., 
> [175,177,179,-179,-176]) wraps the track back around the globe when it 
> goes from 179 to -179. Instead, I want them directly connected. My 
> Basemap instance looks like:
>
> m = Basemap(projection='merc',llcrnrlat = 10,urcrnrlat = 30,llcrnrlon 
> = 160,\
>                 urcrnrlon = -160,lat_ts = 20,resolution = 'l',lon_0 = 180)
>
> Am I screwed on this one?
> Thanks,
>
> Mike

Mike:  There's no automagical way to do this. You either have to shift 
your map so the dateline is in the middle, or split you track into two 
segments.

-Jeff

-- 
Jeffrey S. Whitaker         Phone  : (303)497-6313
Meteorologist               FAX    : (303)497-6449
NOAA/OAR/PSD  R/PSD1        Email  : Jef...@no...
325 Broadway                Office : Skaggs Research Cntr 1D-113
Boulder, CO, USA 80303-3328 Web    : http://tinyurl.com/5telg

Re: [Matplotlib-users] draw track across the Dateline in Basemap

[fatuheeva <fat...@ya...>]

Thanks Jeff. I'll explore those options and see what I can do.

Mike



________________________________
 From: Jeff Whitaker <jef...@no...>
To: mat...@li...; fat...@ya... 
Sent: Tuesday, July 3, 2012 11:21 AM
Subject: Re: [Matplotlib-users] draw track across the Dateline in Basemap
 

On 7/3/12 11:39 AM, fatuheeva wrote:

Hello,
>I am wondering if Basemap has the ability to plot a track across the Dateline? Plotting longitudes that go across the Dateline (e.g., [175,177,179,-179,-176]) wraps the track back around the globe when it goes from 179 to -179. Instead, I want them directly connected. My Basemap instance looks like:
>
>
>m = Basemap(projection='merc',llcrnrlat = 10,urcrnrlat = 30,llcrnrlon = 160,\
>                urcrnrlon = -160,lat_ts = 20,resolution =
          'l',lon_0 = 180)
>
>
>Am I screwed on this one?
>Thanks,
>
>
>Mike
>
Mike:  There's no automagical way to do this. You either have to
    shift your map so the dateline is in the middle, or split you track
    into two segments.

-Jeff

-- 
Jeffrey S. Whitaker         Phone  : (303)497-6313
Meteorologist               FAX    : (303)497-6449
NOAA/OAR/PSD  R/PSD1        Email  : Jef...@no... 325 Broadway                Office : Skaggs Research Cntr 1D-113
Boulder, CO, USA 80303-3328 Web    : http://tinyurl.com/5telg 

Re: [Matplotlib-users] draw track across the Dateline in Basemap

[Eric F. <ef...@ha...>]

On 07/03/2012 08:21 AM, Jeff Whitaker wrote:
> On 7/3/12 11:39 AM, fatuheeva wrote:
>> Hello,
>> I am wondering if Basemap has the ability to plot a track across the
>> Dateline? Plotting longitudes that go across the Dateline (e.g.,
>> [175,177,179,-179,-176]) wraps the track back around the globe when it
>> goes from 179 to -179. Instead, I want them directly connected. My
>> Basemap instance looks like:
>>
>> m = Basemap(projection='merc',llcrnrlat = 10,urcrnrlat = 30,llcrnrlon
>> = 160,\
>>                 urcrnrlon = -160,lat_ts = 20,resolution = 'l',lon_0 = 180)
>>
>> Am I screwed on this one?
>> Thanks,
>>
>> Mike
>
> Mike:  There's no automagical way to do this. You either have to shift
> your map so the dateline is in the middle, or split you track into two
> segments.
>
> -Jeff

If I am reading the original message correctly, what is needed is for 
the longitudes that are to be plotted to be unwrapped as well, as in the 
unwrap_lon (and unwrap) function here:

http://currents.soest.hawaii.edu/hg/pycurrents/file/2851d48cd865/data/navcalc.py

Eric

>
> --
> Jeffrey S. Whitaker         Phone  : (303)497-6313
> Meteorologist               FAX    : (303)497-6449
> NOAA/OAR/PSD  R/PSD1        Email  :Jef...@no...
> 325 Broadway                Office : Skaggs Research Cntr 1D-113
> Boulder, CO, USA 80303-3328 Web    :http://tinyurl.com/5telg
>
>
>
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