Draw borders from GeoJSON paths in python folium maps

Skill - Draw borders from GeoJSON paths in python folium maps

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Skills Required

• Setup python development environment
• Basic Printing in Python
• Commenting in Python
• Managing Variables in python
• Introduction to Folium for interactive maps in python

Please make sure to have all the skills mentioned above to understand and execute the code mentioned below. Go through the above skills if necessary for reference or revision

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In this post we will learn how to draw GeoJSON paths in folium maps. See this post to learn about folium libary basics

Files used in this example

Place the following files in the same folder of the python file to run this code example

• states_india.geojson
• srilanka.geojson

Create map layer with geojson data

import folium

mapObj = folium.Map(location=[22.167057857886153, 82.44140625000001], zoom_start=5)

layer1 = folium.GeoJson(
    data=(open("states_india.geojson", 'r').read()),
    name="India")
layer1.add_to(mapObj)

mapObj.save('output.html')

You can add multiple GeoJSON layers to a map

Control border and fill style of GeoJSON objects

• use the style_function input of folium.GeoJSON function to control the styling of the paths.
• style_function should be a function that returns a dictionary with styling properties specified in the documentation here
• Some of the important styling properties are
  • color - line stroke color
  • weight - line stroke width in pixels
  • opacity - line stroke opacity
  • fillColor - fill Color
  • fillOpacity - ranges between 0 to 1. 0 means transparent, 1 means opaque

import folium

mapObj = folium.Map(location=[22.167057857886153, 82.44140625000001], zoom_start=5)

# style options - https://leafletjs.com/reference-1.7.1.html#path
bordersStyle = {
    'color': 'green',
    'weight': 2,
    'fillColor': 'blue',
    'fillOpacity': 0.2
}

folium.GeoJson(
    data=(open("states_india.geojson", 'r').read()),
    name="India",
    style_function=lambda x: bordersStyle).add_to(mapObj)

mapObj.save('output.html')

Complete example

import folium

# initialize a map with center and zoom
mapObj = folium.Map(location=[22.167057857886153, 82.44140625000001],
                    zoom_start=5)

# https://leafletjs.com/reference-1.7.1.html#path
# border styles dictionary
bordersStyle = {
    'color': 'green',
    'weight': 2,
    'fillColor': 'blue',
    'fillOpacity': 0.2
}

folium.GeoJson(
    data=(open("states_india.geojson", 'r').read()),
    name="India",
    style_function=lambda x: bordersStyle).add_to(mapObj)

folium.GeoJson(
    data=(open("srilanka.geojson", 'r').read()),
    name="Srilanka",
    style_function=lambda x: bordersStyle).add_to(mapObj)

# add layer control over the map
folium.LayerControl().add_to(mapObj)

# save the map as html file
mapObj.save('output.html')

Video

The video for this post can be seen here

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References

• what is GeoJSON - https://en.wikipedia.org/wiki/GeoJSON
• GeoJSON styling options - https://leafletjs.com/reference-1.7.1.html#path
• official docs - https://python-visualization.github.io/folium/modules.html#folium.features.GeoJson

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