GeoPandas

GeoPandas extends pandas to enable spatial operations on geometric types. It combines the capabilities of pandas and shapely for geospatial data analysis.

Installation

uv pip install geopandas

Optional Dependencies

# For interactive maps
uv pip install folium

# For classification schemes in mapping
uv pip install mapclassify

# For faster I/O operations (2-4x speedup)
uv pip install pyarrow

# For PostGIS database support
uv pip install psycopg2
uv pip install geoalchemy2

# For basemaps
uv pip install contextily

# For cartographic projections
uv pip install cartopy

Quick Start

import geopandas as gpd

# Read spatial data
gdf = gpd.read_file("data.geojson")

# Basic exploration
print(gdf.head())
print(gdf.crs)
print(gdf.geometry.geom_type)

# Simple plot
gdf.plot()

# Reproject to different CRS
gdf_projected = gdf.to_crs("EPSG:3857")

# Calculate area (use projected CRS for accuracy)
gdf_projected['area'] = gdf_projected.geometry.area

# Save to file
gdf.to_file("output.gpkg")

Core Concepts

Data Structures

• GeoSeries: Vector of geometries with spatial operations
• GeoDataFrame: Tabular data structure with geometry column

See data-structures.md for details.

Reading and Writing Data

GeoPandas reads/writes multiple formats: Shapefile, GeoJSON, GeoPackage, PostGIS, Parquet.

# Read with filtering
gdf = gpd.read_file("data.gpkg", bbox=(xmin, ymin, xmax, ymax))

# Write with Arrow acceleration
gdf.to_file("output.gpkg", use_arrow=True)

See data-io.md for comprehensive I/O operations.

Coordinate Reference Systems

Always check and manage CRS for accurate spatial operations:

# Check CRS
print(gdf.crs)

# Reproject (transforms coordinates)
gdf_projected = gdf.to_crs("EPSG:3857")

# Set CRS (only when metadata missing)
gdf = gdf.set_crs("EPSG:4326")

See crs-management.md for CRS operations.

Common Operations

Geometric Operations

Buffer, simplify, centroid, convex hull, affine transformations:

# Buffer by 10 units
buffered = gdf.geometry.buffer(10)

# Simplify with tolerance
simplified = gdf.geometry.simplify(tolerance=5, preserve_topology=True)

# Get centroids
centroids = gdf.geometry.centroid

See geometric-operations.md for all operations.

Spatial Analysis

Spatial joins, overlay operations, dissolve:

# Spatial join (intersects)
joined = gpd.sjoin(gdf1, gdf2, predicate='intersects')

# Nearest neighbor join
nearest = gpd.sjoin_nearest(gdf1, gdf2, max_distance=1000)

# Overlay intersection
intersection = gpd.overlay(gdf1, gdf2, how='intersection')

# Dissolve by attribute
dissolved = gdf.dissolve(by='region', aggfunc='sum')

See spatial-analysis.md for analysis operations.

Visualization

Create static and interactive maps:

# Choropleth map
gdf.plot(column='population', cmap='YlOrRd', legend=True)

# Interactive map
gdf.explore(column='population', legend=True).save('map.html')

# Multi-layer map
import matplotlib.pyplot as plt
fig, ax = plt.subplots()
gdf1.plot(ax=ax, color='blue')
gdf2.plot(ax=ax, color='red')

See visualization.md for mapping techniques.

Detailed Documentation

• Data Structures - GeoSeries and GeoDataFrame fundamentals
• Data I/O - Reading/writing files, PostGIS, Parquet
• Geometric Operations - Buffer, simplify, affine transforms
• Spatial Analysis - Joins, overlay, dissolve, clipping
• Visualization - Plotting, choropleth maps, interactive maps
• CRS Management - Coordinate reference systems and projections

Common Workflows

Load, Transform, Analyze, Export

# 1. Load data
gdf = gpd.read_file("data.shp")

# 2. Check and transform CRS
print(gdf.crs)
gdf = gdf.to_crs("EPSG:3857")

# 3. Perform analysis
gdf['area'] = gdf.geometry.area
buffered = gdf.copy()
buffered['geometry'] = gdf.geometry.buffer(100)

# 4. Export results
gdf.to_file("results.gpkg", layer='original')
buffered.to_file("results.gpkg", layer='buffered')

Spatial Join and Aggregate

# Join points to polygons
points_in_polygons = gpd.sjoin(points_gdf, polygons_gdf, predicate='within')

# Aggregate by polygon
aggregated = points_in_polygons.groupby('index_right').agg({
    'value': 'sum',
    'count': 'size'
})

# Merge back to polygons
result = polygons_gdf.merge(aggregated, left_index=True, right_index=True)

Multi-Source Data Integration

# Read from different sources
roads = gpd.read_file("roads.shp")
buildings = gpd.read_file("buildings.geojson")
parcels = gpd.read_postgis("SELECT * FROM parcels", con=engine, geom_col='geom')

# Ensure matching CRS
buildings = buildings.to_crs(roads.crs)
parcels = parcels.to_crs(roads.crs)

# Perform spatial operations
buildings_near_roads = buildings[buildings.geometry.distance(roads.union_all()) < 50]

Performance Tips

• Use spatial indexing: GeoPandas creates spatial indexes automatically for most operations
• Filter during read: Use bbox, mask, or where parameters to load only needed data
• Use Arrow for I/O: Add use_arrow=True for 2-4x faster reading/writing
• Simplify geometries: Use .simplify() to reduce complexity when precision isn't critical
• Batch operations: Vectorized operations are much faster than iterating rows
• Use appropriate CRS: Projected CRS for area/distance, geographic for visualization

Best Practices

• Always check CRS before spatial operations
• Use projected CRS for area and distance calculations
• Match CRS before spatial joins or overlays
• Validate geometries with .is_valid before operations
• Use .copy() when modifying geometry columns to avoid side effects
• Preserve topology when simplifying for analysis
• Use GeoPackage format for modern workflows (better than Shapefile)
• Set max_distance in sjoin_nearest for better performance