Weighted geo-heatmap using gmaps

Summary: this little blog guides you to create a proper weighted heatmap using gmaps, google map API and suggest to avoid using folium in weighted geoheatmap due to an existing bug in folium, at the moment of this blog, May 2019.

Cows in Gorge, Switzerland, 2016

Plotting aggregated geolocation data points onto a map as a heatmap is a common thing to do and there are a handful of libraries supporting this. In this blog, I’ll note down my experiments in plotting weighted geoheatmap using two most common libraries: gmaps and folium.

The simplicity of folium may result it to be the first tool many people picks when it comes to plotting geoheatmap, however, the weighted heatmap is not working properly and the visualisation will give you incorrect results by ignoring the weight column in your datum. Therefore, when you need to plot weighted heatmap, pick another library like gmaps and let google map API do the rest for you, just as easy as that. Below is the post for the folium weighted heatmap bug.

heat map plugin creating incorrect output · Issue #496 · python-visualization/folium

Then I turned to gmaps and it yields correct output for weighted geo-heatmap. Minimum code is as below:

#data.csv looks like this:
+-----------+--------------------+---------------+
|   lat     |       long         |     weight    |
+-----------+--------------------+---------------+
| 64.27     | -21.65             | 100           |
| 64.27     | -21.58             | 200           |
| ...       | ...                | ...           |
+-----------+--------------------+---------------+
import gmaps
import pandas as pd
data = pd.read_csv('data.csv')
gmaps.configure(api_key="AI...") # Fill in with your API key
m = gmaps.Map()
heatmap_layer = gmaps.heatmap_layer(data[['lat','long']], weights=data['weight'],max_intensity=10000, point_radius=20.0
)
#point markers layer:
markers = gmaps.marker_layer(store_locationlist)
m.add_layer(markers)
m.add_layer(heatmap_layer)
m

To get API key from google map services is straightforward, it only requires you to use the map services from google, do note that the google map API may incur charges according to their price plan, but if you are crafting out your personal project in relatively small scale, it should fall into the free tier.

https://developers.google.com/maps/documentation/javascript/get-api-key

Voila! There you have it, a weighted geo-heatmap (Iceland as example because it’s a nice place)

Cheers!