# 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 matplotlib.toolkits.basemap import Basemap
from pylab import title, colorbar, show, axes, cm, load, arange, \
figure, ravel, meshgrid
# read in topo data (on a regular lat/lon grid)
# longitudes go from 20 to 380.
etopo = load('etopo20data.gz')
lons = load('etopo20lons.gz')
lats = load('etopo20lats.gz')
print 'min/max etopo20 data:'
print min(ravel(etopo)),max(ravel(etopo))
# 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 = -20.
elif hem == 'North':
lon_0 = -90.
lon_0_ortho = lon_0
lat_0 = 90.
bounding_lat = 20.
# loop over projections, one for each panel of the figure.
fig = 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)
# compute native map projection coordinates for lat/lon grid.
x,y = m(*meshgrid(lons,lats))
ax = fig.add_subplot(2,2,npanel)
# make filled contour plot.
cs = m.contourf(x,y,etopo,20,cmap=cm.jet)
# draw coastlines.
m.drawcoastlines()
# draw parallels and meridians.
m.drawparallels(arange(-80.,90,20.))
m.drawmeridians(arange(0.,360.,60.))
# draw boundary around map region.
m.drawmapboundary()
# draw title.
title(hem+' Polar '+projname,y=1.05,fontsize=12)
print 'plotting '+hem+' Polar '+projname+' basemap ...'
show()
