Openstreetmap maps in Python

I figured out a simple way to present data on a map in Python.

	from urllib2 import urlopen
	from pylab import imshow, imread, show
	lon = [49.5,50.35]
	lat = [18.6,20.2]
	scale = 700000
	# open an openstreetmap export png file via http
	url = urlopen('http://parent.tile.openstreetmap.org/cgi-bin/export?'
	'bbox={lat1:.2f},{lon1:.2f},{lat2:.2f},{lon2:.2f}&'
	'scale={scale:d}&format=png'.format(lat1=lat[0],
	lat2=lat[1],
	lon1=lon[0],
	lon2=lon[1],
	scale=scale))
	# plot the map
	imshow(imread(url), extent=lat+lon, aspect='equal')
	# plot other data here
	show()

view raw openstreetmap.py hosted with ❤ by GitHub

Openstreetmap server often experiences heavy loads (everyone wants access to these tiles, including me). A little more code to handle denials:

	from urllib2 import urlopen
	from pylab import imshow, imread, show
	lon = [49.5,50.35]
	lat = [18.6,20.2]
	scale = 700000
	print "Downloading map... "
	tries = 0
	url = None
	while tries < 60:
	tries += 1
	print 'Try {}...'.format(tries)
	try:
	url = urlopen('http://parent.tile.openstreetmap.org/cgi-bin/export?'
	'bbox={lat1:.2f},{lon1:.2f},{lat2:.2f},{lon2:.2f}&'
	'scale={scale:d}&format=png'.format(lat1=lat[0],
	lat2=lat[1],
	lon1=lon[0],
	lon2=lon[1],
	scale=scale))
	except HTTPError:
	sleep(5)
	continue
	else:
	print 'Map successfully downloaded.'
	break
	if url is None:
	print 'Failed to download a map.'
	else:
	m = imread(url)
	imshow(m, extent=lat+lon, aspect='equal')
	show()

view raw openstreetmap.py hosted with ❤ by GitHub

Combined with matplotlib's hexbin one can create nice density plots.

By the way: hexbin has an amazing parameter C (lacking in every other density plot function I've encountered). According to documentation:

If C is specified, it specifies values at the coordinate (x[i],y[i]). These values are accumulated for each hexagonal bin and then reduced according to reduce_C_function, which defaults to numpy’s mean function (np.mean).

 My data is counts (of Geiger-Mueller counter) per minute versus geographic position. I want to plot an average counts per minute value in each bin, not total, as other systems I've tried would have me do. Some would even limit me to number of data entries.