Measuring the elevation

Using the excellent Google Chart API, we can quickly build a nice elevation profile chart showing how the elevation changes across the route:

# Build the elevation chart using the Google Charts API
log.info("Creating elevation profile chart")
chart = SimpleLineChart(600, 300, y_range=[min(elvs), max(elvs)])

# API quirk -  you need 3 lines of data to color
# in the plot so we add a line at the minimum value
# twice.
chart.add_data([min(elvs)]*2)
chart.add_data(elvs)
chart.add_data([min(elvs)]*2)

# Black lines
chart.set_colours(['000000'])

# fill in the elevation area with a hex color
chart.add_fill_range('80C65A', 1, 2)

# Set up labels for the minimum elevation, halfway value, and max value
elv_labels = int(round(min(elvs))), int(min(elvs)+((max(elvs)-min(elvs))/2)), \
                 int(round(max(elvs)))

# Assign the labels to an axis
elv_label = chart.set_axis_labels(Axis.LEFT, elv_labels)

# Label the axis
elv_text = chart.set_axis_labels...