# make plot of etopo bathymetry/topography data on
# lambert conformal conic map projection, drawing coastlines, state and
# country boundaries, and parallels/meridians.
from matplotlib.toolkits.basemap import Basemap, shiftgrid
from pylab import *
import cPickle
# read in topo data from pickle (on a regular lat/lon grid)
# longitudes go from 20 to 380.
topodict = cPickle.load(open('data/etopo20.pickle','rb'))
topoin = topodict['data']; lons = topodict['lons']; lats = topodict['lats']
# shift data so lons go from -180 to 180 instead of 20 to 380.
topoin,lons = shiftgrid(180.,topoin,lons,start=False)
# setup of basemap ('lcc' = lambert conformal conic).
m = Basemap(-145.5,1.,-2.566,46.352,\
resolution='c',area_thresh=10000.,projection='lcc',\
lat_1=50.,lon_0=-107.)
# transform to nx x ny regularly spaced native projection grid
nx = int((m.xmax-m.xmin)/40000.)+1; ny = int((m.ymax-m.ymin)/40000.)+1
topodat,x,y = m.transform_scalar(topoin,lons,lats,nx,ny,returnxy=True)
# set up figure with same aspect ratio as map.
xsize = rcParams['figure.figsize'][0]
fig=figure(figsize=(xsize,m.aspect*xsize))
ax = fig.add_axes([0.1,0.1,0.7,0.7])
# plot image over map with imshow.
im = m.imshow(topodat,cm.jet)
# use pcolor (looks very similar to imshow, but slower).
#p = m.pcolor(x,y,topodat,shading='flat')
# plot contour lines over map (colors is a list so neg contours will
# not be dashed).
#levels, colls = m.contour(x,y,topodat,15,linewidths=0.5,colors=['k','k'])
# fill the contours.
#levels, colls = m.contourf(x,y,topodat,15,cmap=cm.jet,colors=None)
cax = axes([0.875, 0.1, 0.05, 0.7]) # setup colorbar axes
colorbar(tickfmt='%d', cax=cax) # draw colorbar
axes(ax) # make the original axes current again
# plot blue dot on boulder, colorado and label it as such.
xpt,ypt = m(-104.237,40.125)
m.plot([xpt],[ypt],'bo')
text(xpt+100000,ypt+100000,'Boulder')
# draw coastlines and political boundaries.
m.drawcoastlines()
m.drawcountries()
m.drawstates()
# draw parallels
delat = 20.
parallels = arange(0.,90.+delat,delat).tolist()+\
arange(-delat,-90.-delat,-delat).tolist()
m.drawparallels(parallels,labels=[1,1,0,1]) # labels on left, right, bottom.
# draw meridians
delon = 30.
meridians = arange(10.,360.,delon)
m.drawmeridians(meridians,labels=[1,1,0,1]) # labels on left, right, bottom.
title('ETOPO Topography - Lambert Conformal Conic')
show()
