import numpy as np
import matplotlib.pyplot as plt
from matplotlib.colors import rgb2hex
from mpl_toolkits.basemap import Basemap
from numpy.random import uniform

# Plot a bunch of randomly distributed points on the earth.

# set up stereographic map centered on N. Pole.
m = Basemap(lon_0=-105,boundinglat=30.,
            resolution='l',area_thresh=10000.,projection='npstere')
# number of points to plot.
npts = 500
# generate random points on a sphere,
# so that every small area on the sphere is expected
# to have the same number of points.
# http://mathworld.wolfram.com/SpherePointPicking.html
u = uniform(0.,1.,size=npts)
v = uniform(0.,1.,size=npts)
lons = 360.*u
lats = (180./np.pi)*np.arccos(2*v-1) - 90.
z = uniform(0,100,size=npts) # this field controls color of dots.
# transform lons and lats to map coordinates.
x,y = m(lons,lats)
# plot them as filled circles on the map.
# first, create a figure.
fig=plt.figure()
# draw colored markers.
# use zorder=10 to make sure markers are drawn last.
# (otherwise they are covered up when continents are filled)
m.scatter(x,y,25,z,cmap=plt.cm.jet,marker='o',edgecolors='none',zorder=10) 
# plot colorbar for markers.
plt.colorbar()
# create a list of strings containing z values
# or, plot actual numbers as color-coded text strings.
#zn = [ '%2i' % zz for zz in z ]
## plot numbers on map, colored by value.
#for numstr,zval,xpt,ypt in zip(zn,z,x,y):
#    # only plot values inside map region.
#    if xpt > m.xmin and xpt < m.xmax and ypt > m.ymin and ypt < m.ymax:
#        hexcolor = rgb2hex(plt.cm.jet(zval/100.)[:3])
#        plt.text(xpt,ypt,numstr,fontsize=9,weight='bold',color=hexcolor)
# draw coasts and fill continents/lakes.
m.drawcoastlines(linewidth=0.5)
m.fillcontinents(color='coral',lake_color='aqua')
# color ocean areas 
m.drawmapboundary(fill_color='aqua')
# draw parallels and meridians.
delat = 20.
circles = np.arange(0.,90.,delat).tolist()+\
          np.arange(-delat,-90,-delat).tolist()
m.drawparallels(circles)
delon = 45.
meridians = np.arange(0,360,delon)
m.drawmeridians(meridians,labels=[1,0,1,1])
plt.title('Random Points',y=1.05)
plt.show()