add 'round' keyword for pole-centered plots

Changelog

@@ -1,4 +1,10 @@
 version 1.0.3 (not yet released)
+           * clip coastlines for nplaea,npaeqd,splaea,spaeqd in stereographic
+             coordinates to avoid S. America disappearing in some south polar
+             plots.
+           * add 'round' keyword to Basemap.__init__ for pole-centered
+             projections to make them round (clipped at boundinglat) instead
+             of square.
            * fix broken daynight terminator function.
            * added kav7 (Kavrayskiy VII) and eck4 (Eckert IV) projections
              (https://github.com/matplotlib/basemap/issues/9).

examples/polarmaps.py

@@ -5,7 +5,7 @@
 
 # illustrates special-case polar-centric projections.
 
-from mpl_toolkits.basemap import Basemap
+from mpl_toolkits.basemap import Basemap, cm
 import numpy as np
 import matplotlib.pyplot as plt
 
@@ -26,15 +26,17 @@
 # showing all four polar projections.
 for hem in ['North','South']:
     if hem == 'South':
-        lon_0 = 130.
+        lon_0 = -130.
         lon_0_ortho = lon_0 - 180.
         lat_0 = -90.
-        bounding_lat = -20.
+        #  Lambert Azimuth bounding lat must not extend into opposite hem.
+        bounding_lat = -0.01
     elif hem == 'North':
-        lon_0 = -90.
+        lon_0 = 130.
         lon_0_ortho = lon_0
         lat_0 = 90.
-        bounding_lat = 20.
+        #  Lambert Azimuth bounding lat must not extend into opposite hem.
+        bounding_lat = 0.01
     # loop over projections, one for each panel of the figure.
     fig = plt.figure(figsize=(8,8))
     npanel = 0
@@ -51,17 +53,18 @@
                        resolution='c',area_thresh=10000.,lat_0=lat_0,lon_0=lon_0_ortho)
         else:
            m = Basemap(boundinglat=bounding_lat,lon_0=lon_0,\
-                       resolution='c',area_thresh=10000.,projection=projection)
+                       resolution='c',area_thresh=10000.,projection=projection,round=True)
         # compute native map projection coordinates for lat/lon grid.
         x,y = m(*np.meshgrid(lons,lats))
         ax = fig.add_subplot(2,2,npanel)
         # make filled contour plot.
-        cs = m.contourf(x,y,etopo,20,cmap=plt.cm.jet)
+        cs = m.contourf(x,y,etopo,np.linspace(-7500,4500,41),cmap=cm.GMT_haxby)
         # draw coastlines.
         m.drawcoastlines()
         # draw parallels and meridians.
         m.drawparallels(np.arange(-80.,90,20.))
-        m.drawmeridians(np.arange(0.,360.,60.))
+        #labels = [l,r,t,b]
+        m.drawmeridians(np.arange(0.,340.,30.),labels=[1,1,1,1],fontsize=7)
         # draw boundary around map region.
         m.drawmapboundary()
         # draw title.

examples/round.py

@@ -0,0 +1,70 @@
+# make plots of etopo bathymetry/topography data on
+# various map projections, drawing coastlines, state and
+# country boundaries, filling continents and drawing
+# parallels/meridians
+
+# illustrates special-case polar-centric projections.
+
+from mpl_toolkits.basemap import Basemap
+import numpy as np
+import matplotlib.pyplot as plt
+
+# read in topo data (on a regular lat/lon grid)
+# longitudes go from 20 to 380.
+etopo = np.loadtxt('etopo20data.gz')
+lons = np.loadtxt('etopo20lons.gz')
+lats = np.loadtxt('etopo20lats.gz')
+
+print 'min/max etopo20 data:'
+print etopo.min(),etopo.max()
+
+# these are the 4 polar projections
+projs = ['laea','stere','aeqd','ortho'] # short names
+# long names
+projnames = ['Lambert Azimuthal Equal Area','Stereographic','Azimuthal Equidistant','Orthographic']
+# loop over hemispheres, make a 4-panel plot for each hemisphere
+# showing all four polar projections.
+for hem in ['North','South']:
+    if hem == 'South':
+        lon_0 = 130.
+        lon_0_ortho = lon_0 - 180.
+        lat_0 = -90.
+        bounding_lat = -1.
+    elif hem == 'North':
+        lon_0 = -90.
+        lon_0_ortho = lon_0
+        lat_0 = 90.
+        bounding_lat = 1.
+    # loop over projections, one for each panel of the figure.
+    fig = plt.figure(figsize=(8,8))
+    npanel = 0
+    for proj,projname in zip(projs,projnames):
+        npanel = npanel + 1
+        if hem == 'South':
+            projection = 'sp'+proj
+        elif hem == 'North':
+            projection = 'np'+proj
+        # setup map projection
+        # centered on Australia (for SH) or US (for NH).
+        if proj == 'ortho':
+           m = Basemap(projection='ortho',
+                       resolution='c',area_thresh=10000.,lat_0=lat_0,lon_0=lon_0_ortho)
+        else:
+           m = Basemap(boundinglat=bounding_lat,lon_0=lon_0,\
+                       resolution='c',area_thresh=10000.,projection=projection,round=True)
+        # compute native map projection coordinates for lat/lon grid.
+        x,y = m(*np.meshgrid(lons,lats))
+        ax = fig.add_subplot(2,2,npanel)
+        # make filled contour plot.
+        cs = m.contourf(x,y,etopo,20,cmap=plt.cm.jet)
+        # draw coastlines.
+        m.drawcoastlines()
+        # draw parallels and meridians.
+        m.drawparallels(np.arange(-80.,90,20.))
+        m.drawmeridians(np.arange(0.,360.,60.))
+        # draw boundary around map region.
+        m.drawmapboundary()
+        # draw title.
+        plt.title(hem+' Polar '+projname,y=1.05,fontsize=12)
+        print 'plotting '+hem+' Polar '+projname+' basemap ...'
+plt.show()