Thematic and Choropleth Mapping
Thematic mapping is a powerful technique in geospatial data science that enables you to visually communicate patterns and relationships in attribute data across geographic regions. Unlike general reference maps, which focus on showing physical features or boundaries, thematic maps are designed to highlight a specific subject or theme, such as population density, land use, or climate zones. Among the most widely used types of thematic maps are choropleth maps, which represent data variation by shading or coloring areas—such as countries, states, or districts—according to the values of a particular attribute.
Choropleth maps provide a straightforward way to visualize how a variable changes across space. Each area on the map is colored based on the value of a selected attribute, usually using a continuous or sequential color scale. This approach makes it easy to spot spatial trends, clusters, and outliers in the data. For example, you might use a choropleth map to display population by region, where darker shades indicate higher population counts and lighter shades indicate lower ones.
1234567891011121314151617181920212223242526import geopandas as gpd import matplotlib.pyplot as plt # Your hosted GeoJSON world_url = "https://staging-content-media-cdn.codefinity.com/courses/6fe97724-da29-4079-ab74-75a30eeb43d3/data/world_countries.geojson" # Load dataset world = gpd.read_file(world_url) # Dissolve by CONTINENT and sum POP_EST regions = world.dissolve(by="CONTINENT", aggfunc="sum")[["POP_EST", "geometry"]] # Plot choropleth fig, ax = plt.subplots(figsize=(10, 6)) regions.plot( column="POP_EST", cmap="Blues", linewidth=0.8, edgecolor="0.8", legend=True, ax=ax ) ax.set_title("Population by Continent (Choropleth Map)", fontsize=14) ax.axis("off") plt.show()
Choose color ramps that reflect the nature of your data. Sequential schemes (light to dark) work well for ordered data like population or income; diverging schemes are useful for data with a meaningful midpoint.
Do not use colors that imply meaning not present in the data (for example, red for "danger" unless appropriate).
Use statistical methods (like quantiles or natural breaks) to divide data into classes, ensuring patterns are visible and not distorted.
A well-designed legend helps viewers interpret color values correctly and improves map readability.
Use palettes that remain distinguishable for people with color vision deficiencies.
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Thematic mapping is a powerful technique in geospatial data science that enables you to visually communicate patterns and relationships in attribute data across geographic regions. Unlike general reference maps, which focus on showing physical features or boundaries, thematic maps are designed to highlight a specific subject or theme, such as population density, land use, or climate zones. Among the most widely used types of thematic maps are choropleth maps, which represent data variation by shading or coloring areas—such as countries, states, or districts—according to the values of a particular attribute.
Choropleth maps provide a straightforward way to visualize how a variable changes across space. Each area on the map is colored based on the value of a selected attribute, usually using a continuous or sequential color scale. This approach makes it easy to spot spatial trends, clusters, and outliers in the data. For example, you might use a choropleth map to display population by region, where darker shades indicate higher population counts and lighter shades indicate lower ones.
1234567891011121314151617181920212223242526import geopandas as gpd import matplotlib.pyplot as plt # Your hosted GeoJSON world_url = "https://staging-content-media-cdn.codefinity.com/courses/6fe97724-da29-4079-ab74-75a30eeb43d3/data/world_countries.geojson" # Load dataset world = gpd.read_file(world_url) # Dissolve by CONTINENT and sum POP_EST regions = world.dissolve(by="CONTINENT", aggfunc="sum")[["POP_EST", "geometry"]] # Plot choropleth fig, ax = plt.subplots(figsize=(10, 6)) regions.plot( column="POP_EST", cmap="Blues", linewidth=0.8, edgecolor="0.8", legend=True, ax=ax ) ax.set_title("Population by Continent (Choropleth Map)", fontsize=14) ax.axis("off") plt.show()
Choose color ramps that reflect the nature of your data. Sequential schemes (light to dark) work well for ordered data like population or income; diverging schemes are useful for data with a meaningful midpoint.
Do not use colors that imply meaning not present in the data (for example, red for "danger" unless appropriate).
Use statistical methods (like quantiles or natural breaks) to divide data into classes, ensuring patterns are visible and not distorted.
A well-designed legend helps viewers interpret color values correctly and improves map readability.
Use palettes that remain distinguishable for people with color vision deficiencies.
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