Plot Lines In Folium

In this post I show you how to plot lines in Folium - the python module for plotting leaflet maps.

Add PolyLine to Map

Like ‘markers’, lines are added to folium map objects with the add_to() method

folium.PolyLine(points).add_to(my_map)

where “points” is a list of tuples containing latitude and longitude information, and “my_map” is a folium map object. By default this will give an output similar to:

default polyline

Adjust Line Properties

We can alter the line properties (colour, weight and opacity) with:

folium.PolyLine(points, color="red", weight=2.5, opacity=1).add_to(my_map)

Plot Lines In Folium - thin red line

Plot Lines and Markers

It can also be useful to plot both lines and markers on the same map. This can be easily done by using the Marker.add_to() method, and looping over each of the coordinate pairs in our list:

#add markers
for each in points:
    folium.Marker(each).add_to(my_map)
#add lines
folium.PolyLine(points, color="red", weight=2.5, opacity=1).add_to(my_map)

Plot Lines In Folium - line and markers

An Example

Here’s an example involving loading in GPX coordinates from a GPS device. You can also download the code here.

import gpxpy
import gpxpy.gpx
import folium
gpx_file = open('path_to_gpx_file.gpx', 'r')
gpx = gpxpy.parse(gpx_file)
points = []
for track in gpx.tracks:
    for segment in track.segments:
        for point in segment.points:
            points.append(tuple([point.latitude, point.longitude]))
print(points)
ave_lat = sum(p[0] for p in points)/len(points)
ave_lon = sum(p[1] for p in points)/len(points)
# Load map centred on average coordinates
my_map = folium.Map(location=[ave_lat, ave_lon], zoom_start=14)
#add a markers
for each in points:
    folium.Marker(each).add_to(my_map)
#fadd lines
folium.PolyLine(points, color="red", weight=2.5, opacity=1).add_to(my_map)
# Save map
my_map.save("./gpx_berlin_withmarker.html")