## Re: [Matplotlib-users] A question on Basemap projection

 Re: [Matplotlib-users] A question on Basemap projection From: Jeff Whitaker - 2008-12-08 13:13:21 ```Mauro Cavalcanti wrote: > Dear Jeff, > > 2008/12/7 Jeff Whitaker : > >> Mauro: Just set the llrncrlat,urcrnrlon appropriately. For instance, >> llcrnrlon=0, urcrnrlon=360 will produce a map centered on the dateline while >> llcrnrlon=-180, urcrnrlon=180 will produce a map centered on Greenwich. >> > > Thanks! I had not figured out that the decimal coordinates used by > Basemap range from 0 to 360 (and not just from -180 to 180). Using > this tip, I could also create a map centered on the Indian Ocean. BTW, > by varying the llcrnrlat and urcrnrlat, can one also create maps > centered on the North and South poles using a Equirectangular > projection? > Mauro: I realized that this is actually possible with the Cassini projection (the transverse aspect of the cylindrical equidistant). from mpl_toolkits.basemap import Basemap import matplotlib.pyplot as plt width=20000000 m = Basemap(lon_0=0,lat_0=0,projection='cass',\ width=0.75*width,height=2*width) m.drawcoastlines() m.fillcontinents(color='coral',lake_color='aqua') m.drawparallels(range(-80,81,21)) m.drawmeridians(range(-180,181,60)) m.drawmapboundary(fill_color='aqua') plt.show() Don't know why you would actually do it though, if you want to show polar regions you should probably use the polar stereographic maps (npstere, spstere). -Jeff > With best regards, > > -- Jeffrey S. Whitaker Phone : (303)497-6313 NOAA/OAR/CDC R/PSD1 FAX : (303)497-6449 325 Broadway Boulder, CO, USA 80305-3328 ```

 [Matplotlib-users] A question on Basemap projection From: Mauro Cavalcanti - 2008-12-07 22:25:51 ```Dear Jeffrey & ALL, Are there any way to plot a Basemap using a standard Equidistant Cylindrical Projection, but centered on the Pacific Basin instead of the default plot? This can be done easily with all projections that require just a center point at lat_0, long_0 (Robinson, Mollweide, Orthographic, Geostationary) but could not figure out how to do this in projections that require a bounding rectangle to be defined (as is the case with the Equidistant Cylindrical). Thanks in advance! With best regards, -- Dr. Mauro J. Cavalcanti Ecoinformatics Studio P.O. Box 46521, CEP 20551-970 Rio de Janeiro, RJ, BRASIL E-mail: maurobio@... Web: http://studio.infobio.net Linux Registered User #473524 * Ubuntu User #22717 "Life is complex. It consists of real and imaginary parts." ```
 Re: [Matplotlib-users] A question on Basemap projection From: Jeff Whitaker - 2008-12-08 00:36:35 ```Mauro Cavalcanti wrote: > Dear Jeffrey & ALL, > > Are there any way to plot a Basemap using a standard Equidistant > Cylindrical Projection, but centered on the Pacific Basin instead of > the default plot? This can be done easily with all projections that > require just a center point at lat_0, long_0 (Robinson, Mollweide, > Orthographic, Geostationary) but could not figure out how to do this > in projections that require a bounding rectangle to be defined (as is > the case with the Equidistant Cylindrical). > > Thanks in advance! > > With best regards, > > Mauro: Just set the llrncrlat,urcrnrlon appropriately. For instance, llcrnrlon=0, urcrnrlon=360 will produce a map centered on the dateline while llcrnrlon=-180, urcrnrlon=180 will produce a map centered on Greenwich. -Jeff -- Jeffrey S. Whitaker Phone : (303)497-6313 NOAA/OAR/CDC R/PSD1 FAX : (303)497-6449 325 Broadway Boulder, CO, USA 80305-3328 ```
 Re: [Matplotlib-users] A question on Basemap projection From: Mauro Cavalcanti - 2008-12-08 12:14:50 ```Dear Jeff, 2008/12/7 Jeff Whitaker : > Mauro: Just set the llrncrlat,urcrnrlon appropriately. For instance, > llcrnrlon=0, urcrnrlon=360 will produce a map centered on the dateline while > llcrnrlon=-180, urcrnrlon=180 will produce a map centered on Greenwich. Thanks! I had not figured out that the decimal coordinates used by Basemap range from 0 to 360 (and not just from -180 to 180). Using this tip, I could also create a map centered on the Indian Ocean. BTW, by varying the llcrnrlat and urcrnrlat, can one also create maps centered on the North and South poles using a Equirectangular projection? With best regards, -- Dr. Mauro J. Cavalcanti Ecoinformatics Studio P.O. Box 46521, CEP 20551-970 Rio de Janeiro, RJ, BRASIL E-mail: maurobio@... Web: http://studio.infobio.net Linux Registered User #473524 * Ubuntu User #22717 "Life is complex. It consists of real and imaginary parts." ```
 Re: [Matplotlib-users] A question on Basemap projection From: Jeff Whitaker - 2008-12-08 12:53:57 ```Mauro Cavalcanti wrote: > Dear Jeff, > > 2008/12/7 Jeff Whitaker : > >> Mauro: Just set the llrncrlat,urcrnrlon appropriately. For instance, >> llcrnrlon=0, urcrnrlon=360 will produce a map centered on the dateline while >> llcrnrlon=-180, urcrnrlon=180 will produce a map centered on Greenwich. >> > > Thanks! I had not figured out that the decimal coordinates used by > Basemap range from 0 to 360 (and not just from -180 to 180). Mauro: I just updated SVN basemap so you can specify just lon_0 for all cylindrical projections (cyl,gall,merc,mill) to get a global map centered on lon_0 (implying llcrnrlat=-90,urcrnrlat=90,llcrnrlon=lon_0-180,urcrnrlon=lon_0+180). > Using > this tip, I could also create a map centered on the Indian Ocean. BTW, > by varying the llcrnrlat and urcrnrlat, can one also create maps > centered on the North and South poles using a Equirectangular > projection? > No. Cylindrical projections can't cross the poles. -Jeff > With best regards, > > -- Jeffrey S. Whitaker Phone : (303)497-6313 NOAA/OAR/CDC R/PSD1 FAX : (303)497-6449 325 Broadway Boulder, CO, USA 80305-3328 ```
 Re: [Matplotlib-users] A question on Basemap projection From: Mauro Cavalcanti - 2008-12-08 13:22:10 ```Dear Jeff, 2008/12/8 Jeff Whitaker : > Mauro: I just updated SVN basemap so you can specify just lon_0 for all > cylindrical projections (cyl,gall,merc,mill) to get a global map centered on > lon_0 (implying > llcrnrlat=-90,urcrnrlat=90,llcrnrlon=lon_0-180,urcrnrlon=lon_0+180). Excellent! Will however have to change my Basemap installation to the SVN repository. > No. Cylindrical projections can't cross the poles. Just figured this out, by trial-and-error. BTW, these explorations led me to comment that biogeographers (almost all of them biologists like myself) have seldom (or never!) paid attention to the question of map projections! This by itself should merit a scientific paper! So, Basemap may also be lending to scientific insights... Exciting, isn't it? More soon.... ;-) Best wishes, -- Dr. Mauro J. Cavalcanti Ecoinformatics Studio P.O. Box 46521, CEP 20551-970 Rio de Janeiro, RJ, BRASIL E-mail: maurobio@... Web: http://studio.infobio.net Linux Registered User #473524 * Ubuntu User #22717 "Life is complex. It consists of real and imaginary parts." ```
 Re: [Matplotlib-users] A question on Basemap projection From: Jeff Whitaker - 2008-12-08 13:13:21 ```Mauro Cavalcanti wrote: > Dear Jeff, > > 2008/12/7 Jeff Whitaker : > >> Mauro: Just set the llrncrlat,urcrnrlon appropriately. For instance, >> llcrnrlon=0, urcrnrlon=360 will produce a map centered on the dateline while >> llcrnrlon=-180, urcrnrlon=180 will produce a map centered on Greenwich. >> > > Thanks! I had not figured out that the decimal coordinates used by > Basemap range from 0 to 360 (and not just from -180 to 180). Using > this tip, I could also create a map centered on the Indian Ocean. BTW, > by varying the llcrnrlat and urcrnrlat, can one also create maps > centered on the North and South poles using a Equirectangular > projection? > Mauro: I realized that this is actually possible with the Cassini projection (the transverse aspect of the cylindrical equidistant). from mpl_toolkits.basemap import Basemap import matplotlib.pyplot as plt width=20000000 m = Basemap(lon_0=0,lat_0=0,projection='cass',\ width=0.75*width,height=2*width) m.drawcoastlines() m.fillcontinents(color='coral',lake_color='aqua') m.drawparallels(range(-80,81,21)) m.drawmeridians(range(-180,181,60)) m.drawmapboundary(fill_color='aqua') plt.show() Don't know why you would actually do it though, if you want to show polar regions you should probably use the polar stereographic maps (npstere, spstere). -Jeff > With best regards, > > -- Jeffrey S. Whitaker Phone : (303)497-6313 NOAA/OAR/CDC R/PSD1 FAX : (303)497-6449 325 Broadway Boulder, CO, USA 80305-3328 ```
 Re: [Matplotlib-users] A question on Basemap projection From: Mauro Cavalcanti - 2008-12-08 13:33:20 ```Dear Jeff, 2008/12/8 Jeff Whitaker : > Mauro: I realized that this is actually possible with the Cassini > projection (the transverse aspect of the cylindrical equidistant). > > Don't know why you would actually do it though, if you want to show polar > regions you should probably use the polar stereographic maps (npstere, > spstere). I had not yet had time to try Cassini's before receiving your posting. As Scott already pointed out, no doubt the polar projections are more adequate to representing the poles (pretty obvious!). I just intended to try making the most parsimonious use of the Basemap parameters :-). The polar stereographic are nice, but what about the polar azimuthal, that also look good? Just curious. Best regards, -- Dr. Mauro J. Cavalcanti Ecoinformatics Studio P.O. Box 46521, CEP 20551-970 Rio de Janeiro, RJ, BRASIL E-mail: maurobio@... Web: http://studio.infobio.net Linux Registered User #473524 * Ubuntu User #22717 "Life is complex. It consists of real and imaginary parts." ```