from numpy import *
from matplotlib.toolkits.basemap import Basemap, pyproj
from pylab import *
# add drawscale method to Basemap class.
class Basemap2(Basemap):
def drawscale(self,lon,lat,length,yoffset=None):
"""draw a fancy map scale from lon-length/2,lat-yoffset to
lon-length/2,lat-yoffset, label it with actual distance in
km"""
length = length*1000 #input length is km
#we need 5 sets of x coordinates (in map units)
#center of scale
xc,yc = self(lon,lat)
#left edge of scale
lon1,lat1 = self(xc-length/2,yc,inverse=True)
x1,y1 = self(lon1,lat1)
#quarter scale
lon2,lat2 = self(xc-length/4,yc,inverse=True)
x2,y2 = self(lon2,lat2)
#three quarter scale
lon3,lat3 = self(xc+length/4,yc,inverse=True)
x3,y3 = self(lon3,lat3)
#right edge of scale
lon4,lat4 = self(xc+length/2,yc,inverse=True)
x4,y4 = self(lon4,lat4)
if yoffset is None: yoffset = 0.1*length
#plot top line
ytop = yc+yoffset/2
ybottom = yc-yoffset/2
ytick = ybottom - yoffset/2
ytext = ytick - yoffset/2
m.plot([x1,x4],[ytop,ytop],color='k')
#plot bottom line
m.plot([x1,x4],[ybottom,ybottom],color='k')
#plot left edge
m.plot([x1,x1],[ybottom,ytop],color='k')
#plot right edge
m.plot([x4,x4],[ybottom,ytop],color='k')
#make a filled black box from left edge to 1/4 way across
fill([x1,x2,x2,x1,x1],[ytop,ytop,ybottom,ybottom,ytop],'k')
#make a filled white box from 1/4 way across to 1/2 way across
fill([x2,xc,xc,x2,x2],[ytop,ytop,ybottom,ybottom,ytop],'w')
#make a filled white box from 1/2 way across to 3/4 way across
fill([xc,x3,x3,xc,xc],[ytop,ytop,ybottom,ybottom,ytop],'k')
#make a filled white box from 3/4 way across to end
fill([x3,x4,x4,x3,x3],[ytop,ytop,ybottom,ybottom,ytop],'w')
#plot 3 tick marks at left edge, center, and right edge
m.plot([x1,x1],[ytick,ybottom],color='k')
m.plot([xc,xc],[ytick,ybottom],color='k')
m.plot([x4,x4],[ytick,ybottom],color='k')
#label 3 tick marks
text(x1,ytext,'%d' % (0),\
horizontalalignment='center',\
verticalalignment='top',\
fontsize=9)
text(xc,ytext,'%d' % (round((length/2)/1000)),\
horizontalalignment='center',\
verticalalignment='top',\
fontsize=9)
text(x4,ytext,'%d' % (round((length)/1000)),\
horizontalalignment='center',\
verticalalignment='top',\
fontsize=9)
#put units on top
text(xc,ytop+yoffset/2,'km',\
horizontalalignment='center',\
verticalalignment='bottom',\
fontsize=9)
# setup of basemap ('lcc' = lambert conformal conic).
# use major and minor sphere radii from WGS84 ellipsoid.
m = Basemap2
(llcrnrlon=-145.5,llcrnrlat=1.,urcrnrlon=-2.566,urcrnrlat=46.352,\
rsphere=(6378137.00,6356752.3142),\
resolution='l',area_thresh=1000.,projection='lcc',\
lat_1=50.,lon_0=-107.)
# draw coastlines and political boundaries.
m.drawcoastlines()
m.fillcontinents()
# draw parallels and meridians.
# label on left, right and bottom of map.
m.drawparallels(arange(0.,80,20.),labels=[1,1,0,1])
m.drawmeridians(arange(10.,360.,30.),labels=[1,1,0,1])
# draw a line from x1,y to x2,y and label it with distance in km.
length = 3000 #kilometers
x1,y1 = 0.25*m.xmax, 0.25*m.ymax
lon1,lat1 = m(x1,y1,inverse=True)
m.drawscale(lon1,lat1,length)
title('a fancy map scale')
show()
------------------------------------------------------
Michael Hearne
[EMAIL PROTECTED] <mailto:[EMAIL PROTECTED]>
(303) 273-8620
USGS National Earthquake Information Center
1711 Illinois St. Golden CO 80401
Senior Software Engineer
Synergetics, Inc.
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