introduction
In the field of Geographic Information Systems (GIS), spatial connections and geographic computing are the core capabilities in processing geographic data. GeoPandas, the most powerful geodata analytics library in the Python ecosystem, provides a wealth of tools and methods to perform these operations. This article will explore the spatial connection and geographic computing functions in GeoPandas in depth, and explain how to apply these technologies to solve practical problems through practical cases.
1. Environment configuration
First, make sure that the necessary libraries are installed:
# Install the necessary libraries!pip install geopandas matplotlib contextily rtree shapely # Import libraryimport geopandas as gpd import pandas as pd import numpy as np import as plt import contextily as ctx from import Point, LineString, Polygon
2. Basic concepts of spatial connection
2.1 What is spatial connection
Spatial connection is the operation of merging data sets based on spatial relationships between geographic objects. Unlike traditional database connections that use common key values, spatial connections use geometric relationships (such as intersection, inclusion, overwrite) as connection conditions.
2.2 Types of spatial connections
GeoPandas provides a variety of spatial connection methods:
- Left join: Keep all records of DataFrame on the left
- Right join: Keep all records of DataFrame on the right
- Inner join: Only records that satisfy spatial relationships on both sides
2.3 Common spatial relationships
GeoPandas supports the following spatial relationship types:
-
intersects
: There is any intersection between two geometric objects -
contains
: A geometric object completely contains another -
within
: One geometric object is completely inside another -
touches
: The boundaries of two geometric objects come into contact but do not intersect inside -
crosses
: Two geometric objects have partial but do not overlap completely -
overlaps
: Two geometric objects overlap partially and have the same dimensions
3. Actual cases-Analysis of urban POI and administrative divisions
3.1 Loading data
Let's load some sample data:
# Load administrative division datadistricts = gpd.read_file("") # Create POI point datapoi_data = { 'name': ['Coffee Shop A', 'Restaurant B', 'Mall C', 'School D', 'Hospital E', 'Park F', 'Library G', 'Supermarket H'], 'type': ['FOOD', 'FOOD', 'Shopping', 'educate', 'Medical', 'Career', 'culture', 'Shopping'], 'latitude': [39.91, 39.92, 39.93, 39.89, 39.91, 39.88, 39.90, 39.94], 'longitude': [116.41, 116.42, 116.39, 116.38, 116.44, 116.43, 116.41, 116.40] } # Create point geometrygeometry = [Point(xy) for xy in zip(poi_data['longitude'], poi_data['latitude'])] pois = (poi_data, geometry=geometry, crs="EPSG:4326")
3.2 Spatial connection between points and polygons
We spatially connect POI points with administrative divisions to determine which administrative district each POI point is located:
# Ensure the coordinate system is consistentdistricts = districts.to_crs() # Perform spatial connection - where is the point locatedjoined_data = (pois, districts, how="left", predicate="within") print(f"The connected data contains {len(joined_data)} OK,This includes point information and area")
3.3 Results visualization
# Draw the bottom mapfig, ax = (figsize=(12, 10)) # Draw the area boundaries(ax=ax, color='black', linewidth=1) # Use categorical variables to draw different types of POIs(ax=ax, column='type', cmap='viridis', legend=True, markersize=100, categorical=True) # Add a title('POI distribution and administrative division', fontsize=15) # Add background imagectx.add_basemap(ax, crs=.to_string(), source=) plt.tight_layout() ()
4. Advanced space connection operation
4.1 Spatial connection of different predicates
We can use different spatial relationship predicates to perform spatial connections:
# Use different spatial relationships to connectwithin_join = (pois, districts, how="inner", predicate="within") intersects_join = (pois, districts, how="inner", predicate="intersects") print(f"withinConnection results: {len(within_join)} OK") print(f"intersectsConnection results: {len(intersects_join)} OK") # For point data, "within" and "intersects" usually produce the same results# But for line or surface data it is different
4.2 Combining spatial connection and attribute filtering
We can use spatial connections in conjunction with regular data filtering:
# Filter specific types of POIs and determine their administrative regionsrestaurant_pois = pois[pois['type'] == 'FOOD'] restaurant_districts = (restaurant_pois, districts, how="left", predicate="within") # Statistics the number of catering POIs in each administrative regionpoi_count_by_district = restaurant_districts.groupby('district_name').size() print("Statistics on the number of catering POIs in each administrative region:") print(poi_count_by_district)
5. Core operations of geographic computing
5.1 Geometric Operations-Buffer Analysis
Buffer analysis is one of the most commonly used operations in geospatial analysis, which creates regions around geometric features:
# Create a 500m buffer for each POI# First convert the data into a projection coordinate system to use meterspois_projected = pois.to_crs(epsg=3857) # Web Mercator Projectionpois_buffered = pois_projected.copy() pois_buffered['geometry'] = pois_projected.buffer(500) # 500m buffer zone# Return to the original coordinate system for displaypois_buffered = pois_buffered.to_crs() # Draw the bufferfig, ax = (figsize=(12, 10)) (ax=ax, color='black', linewidth=1) pois_buffered.plot(ax=ax, alpha=0.5, column='type', categorical=True) (ax=ax, color='red', markersize=20) ctx.add_basemap(ax, crs=.to_string(), source=) ('Analysis of 500 meters service scope of POI point', fontsize=15) plt.tight_layout() ()
5.2 Overlay analysis-region coverage calculation
We can calculate the overlay between buffer zones and administrative divisions:
# Intersection operation between buffer zone and administrative divisiondistricts_projected = districts.to_crs(epsg=3857) pois_buffered_projected = pois_buffered.to_crs(epsg=3857) # Select a specific area for exampletarget_district = districts_projected.iloc[0] # Calculate the intersection of this area and each POI bufferintersections = [] for idx, poi_buffer in pois_buffered_projected.iterrows(): if poi_buffer.(target_district.geometry): intersection = poi_buffer.(target_district.geometry) ({ 'poi_name': poi_buffer['name'], 'poi_type': poi_buffer['type'], 'geometry': intersection, 'area': # square meters }) # Create an intersection GeoDataFrameintersections_gdf = (intersections, crs=pois_buffered_projected.crs) # Calculate coveragedistrict_area = target_district. total_coverage_area = ([geom['geometry'] for geom in intersections]).unary_union.area coverage_ratio = total_coverage_area / district_area * 100 print(f"Region name: {target_district['district_name']}") print(f"Total area: {district_area/1e6:.2f} Square km") print(f"POIService coverage area: {total_coverage_area/1e6:.2f} Square km") print(f"Coverage: {coverage_ratio:.2f}%")
5.3 Distance calculation and nearest neighbor analysis
Calculate the distance matrix and nearest facilities between POIs:
# Calculate the distance matrix (in meters) between all POIsdef calculate_distance_matrix(gdf): n = len(gdf) dist_matrix = ((n, n)) for i in range(n): for j in range(i+1, n): dist = [i].([j].geometry) dist_matrix[i, j] = dist dist_matrix[j, i] = dist return (dist_matrix, index=, columns=) # Calculate the distance matrixdistance_matrix = calculate_distance_matrix(pois_projected) # Find the nearest neighbor of each POInearest_neighbors = {} for idx in : distances = distance_matrix[idx].drop(idx) # Exclude yourself nearest = () nearest_neighbors[[idx, 'name']] = { 'nearest_poi': [nearest, 'name'], 'distance_meters': () } print("Nearest neighbor facilities for each POI:") for poi, info in nearest_neighbors.items(): print(f"{poi} -> {info['nearest_poi']} (distance: {info['distance_meters']:.2f}rice)")
6. Advanced geospatial analysis cases
6.1 Hot Spot Density Analysis
Hotspot analysis using kernel density estimation:
# Use KDE for hot spot analysisfrom import gaussian_kde # Extract POI coordinatesx = pois_projected. y = pois_projected. positions = ([x, y]) # Calculate KDEkernel = gaussian_kde(positions) # Create a grid for evaluationx_grid, y_grid = [():():100j, ():():100j] positions_grid = ([x_grid.ravel(), y_grid.ravel()]) # Calculate densityz = kernel(positions_grid).reshape(x_grid.shape) # Visualize the resultsfig, ax = (figsize=(12, 10)) districts_projected.(ax=ax, color='black', linewidth=1) contour = (x_grid, y_grid, z, cmap='viridis', levels=20, alpha=0.75) pois_projected.plot(ax=ax, color='red', markersize=20) (contour, ax=ax, label='density') ('POI Hot Spot Density Analysis', fontsize=15) plt.tight_layout() ()
6.2 Spatial clustering analysis
Spatial clustering using DBSCAN algorithm:
from import DBSCAN # Extract coordinatescoords = ((pois_projected., pois_projected.)).T # Use DBSCAN for clusteringclustering = DBSCAN(eps=1000, min_samples=2).fit(coords) # At least 2 points within a range of 1000 meters form clustering# Add clustering results to original datapois_projected['cluster'] = clustering.labels_ # Visualize clustering resultsfig, ax = (figsize=(12, 10)) districts_projected.(ax=ax, color='black', linewidth=1) pois_projected.plot(ax=ax, column='cluster', categorical=True, legend=True, markersize=100) ('POISpatial clustering analysis (DBSCAN)', fontsize=15) plt.tight_layout() () # Statistics the number of POIs for each clustercluster_stats = pois_projected.groupby('cluster').size() print("Number of POIs in each cluster:") print(cluster_stats)
6.3 Network accessibility analysis
Assuming we have road network data, we can analyze the network accessibility of POI:
# Note: This requires pre-preparation of road network data and networkx librariesimport networkx as nx # Loading road network dataroads = gpd.read_file("") # Create a network diagramG = () # Build a network from road datafor idx, road in (): coords = list() for i in range(len(coords) - 1): G.add_edge(coords[i], coords[i+1], weight=, road_id=road['id']) # Find the nearest road node to each POInearest_nodes = {} for idx, poi in pois_projected.iterrows(): min_dist = float('inf') nearest_node = None for node in (): dist = (Point(node)) if dist < min_dist: min_dist = dist nearest_node = node nearest_nodes[idx] = nearest_node # Calculate the shortest path between two POIsorigin_idx = 0 # POI index from the starting pointdest_idx = 3 # Endpoint POI indexorigin_node = nearest_nodes[origin_idx] dest_node = nearest_nodes[dest_idx] try: # Calculate the shortest path shortest_path = nx.shortest_path(G, origin_node, dest_node, weight='weight') path_length = nx.shortest_path_length(G, origin_node, dest_node, weight='weight') print(f"from {[origin_idx, 'name']} arrive {[dest_idx, 'name']} The shortest path length: {path_length:.2f}rice") # Visualize the path path_coords = shortest_path path_line = LineString(path_coords) path_gdf = ({'geometry': [path_line]}, crs=pois_projected.crs) fig, ax = (figsize=(12, 10)) (ax=ax, color='gray', linewidth=1) path_gdf.plot(ax=ax, color='red', linewidth=3) pois_projected.iloc[[origin_idx, dest_idx]].plot(ax=ax, color='blue', markersize=100) (f'from {[origin_idx, "name"]} arrive {[dest_idx, "name"]} The shortest path to', fontsize=15) plt.tight_layout() () except : print(f"无法找arrivefrom {[origin_idx, 'name']} arrive {[dest_idx, 'name']} The path")
7. Performance optimization skills
7.1 Spatial index accelerates query
GeoPandas uses R-tree index to speed up spatial queries:
# Make sure the rtree library is installed# pip install rtree # Create a spatial indexdistricts = districts.set_index('district_id', drop=False) districts_sindex = # Use spatial index to speed up querydef fast_sjoin_points_to_polygons(points_gdf, polygons_gdf): # Create a result list results = [] # traverse points for idx, point in points_gdf.iterrows(): # Use spatial index to find possible intersection polygons possible_matches_idx = list(polygons_gdf.()) possible_matches = polygons_gdf.iloc[possible_matches_idx] # Exactly check whether the point is inside the polygon precise_matches = possible_matches[possible_matches.contains()] # If a match is found if len(precise_matches) > 0: for match_idx, match in precise_matches.iterrows(): result = point.to_dict() ({ 'district_id': match['district_id'], 'district_name': match['district_name'] }) (result) if results: return (results, crs=points_gdf.crs) else: return ([], crs=points_gdf.crs) # Use optimized functions for spatial connectionimport time start_time = () optimized_result = fast_sjoin_points_to_polygons(pois, districts) end_time = () print(f"Optimized space connection time-consuming: {end_time - start_time:.4f}Second") # Compare standard sjoinstart_time = () standard_result = (pois, districts, how="left", predicate="within") end_time = () print(f"Time-consuming for standard space connections: {end_time - start_time:.4f}Second")
7.2 Processing large-scale data in parallel
For large datasets, parallel processing can be used to accelerate the calculation:
from joblib import Parallel, delayed # Parallel processing of buffer calculationsdef parallel_buffer(gdf, buffer_distance, n_jobs=-1): # Define a single geometry buffer calculation function def buffer_geom(geom): return (buffer_distance) # Parallel execution buffered_geoms = Parallel(n_jobs=n_jobs)( delayed(buffer_geom)(geom) for geom in ) # Create a new GeoDataFrame result = () result['geometry'] = buffered_geoms return result # Create a buffer using parallel processingstart_time = () pois_buffered_parallel = parallel_buffer(pois_projected, 500) end_time = () print(f"Time-consuming for parallel buffer calculation: {end_time - start_time:.4f}Second") # Comparison standard processingstart_time = () pois_buffered_standard = pois_projected.copy() pois_buffered_standard['geometry'] = pois_projected.buffer(500) end_time = () print(f"Time-consuming for standard buffer calculation: {end_time - start_time:.4f}Second")
8. Practical application scenarios
8.1 Traffic Accessibility Analysis
Analyze the number of people covered by different transportation facilities:
# Assume there is population datapopulation = gpd.read_file("population_grid.geojson") # Select a transportation facility POItransport_pois = pois[pois['type'].isin(['Bus Station', 'metro station', 'TRAIN STATION'])] # Create a traffic buffer zone (500 meters walking distance)transport_pois_projected = transport_pois.to_crs(epsg=3857) transport_buffers = transport_pois_projected.copy() transport_buffers['geometry'] = transport_pois_projected.buffer(500) # Spatial connection with population gridpopulation_projected = population.to_crs(epsg=3857) population_covered = (population_projected, transport_buffers.to_crs(population_projected.crs), how="inner", predicate="intersects") # Calculate the total population coveredtotal_population = population_projected['population'].sum() covered_population = population_covered['population'].sum() coverage_percentage = (covered_population / total_population) * 100 print(f"Total population: {total_population}") print(f"Public Transport500Rice covers the population: {covered_population}") print(f"Coverage: {coverage_percentage:.2f}%")
8.2 Commercial site selection analysis
Evaluation of commercial site selection suitability based on multiple factors:
# Suppose we have the following data layer# - Population density# - Competitor position# - Traffic Accessibility# - Business Center# Create a grid evaluation systemfrom import box # Create a study area gridxmin, ymin, xmax, ymax = districts_projected.total_bounds cell_size = 500 # 500m gridrows = int((ymax - ymin) / cell_size) cols = int((xmax - xmin) / cell_size) grid_cells = [] for i in range(cols): for j in range(rows): x1 = xmin + i * cell_size y1 = ymin + j * cell_size x2 = xmin + (i + 1) * cell_size y2 = ymin + (j + 1) * cell_size grid_cells.append(box(x1, y1, x2, y2)) grid = ({'geometry': grid_cells}, crs=districts_projected.crs) # Calculate the scores of each factor# 1. Population density scoregrid['pop_score'] = (1, 10, size=len(grid)) # Simulate data# 2. Competitor Distance Scorecompetitors = pois_projected[pois_projected['type'] == 'FOOD'] grid['comp_dist'] = ( lambda g: min([(comp) for comp in ]) if len(competitors) > 0 else 0 ) grid['comp_score'] = grid['comp_dist'] / grid['comp_dist'].max() * 10 # 3. Traffic Accessibility Scoretransit = pois_projected[pois_projected['type'].isin(['Bus Station', 'metro station'])] grid['transit_dist'] = ( lambda g: min([(t) for t in ]) if len(transit) > 0 else float('inf') ) grid['transit_score'] = 10 - (grid['transit_dist'] / grid['transit_dist'].max() * 10) # 4. Business Center Distance Scorebusiness_centers = pois_projected[pois_projected['type'] == 'Shopping'] grid['biz_dist'] = ( lambda g: min([(bc) for bc in business_centers.geometry]) if len(business_centers) > 0 else float('inf') ) grid['biz_score'] = 10 - (grid['biz_dist'] / grid['biz_dist'].max() * 10) # Calculate comprehensive scoresgrid['total_score'] = ( grid['pop_score'] * 0.4 + grid['comp_score'] * 0.2 + grid['transit_score'] * 0.2 + grid['biz_score'] * 0.2 ) # Visualize the resultsfig, ax = (figsize=(12, 10)) districts_projected.(ax=ax, color='black', linewidth=1) (ax=ax, column='total_score', cmap='RdYlGn', alpha=0.7, legend=True, legend_kwds={'label': 'Site selection suitability score'}) pois_projected.plot(ax=ax, color='blue', markersize=10) ('Commercial site selection suitability evaluation', fontsize=15) plt.tight_layout() () # Find the highest scorebest_locations = grid.sort_values('total_score', ascending=False).head(3) print("The best 3 locations to open a new store:") for idx, loc in best_locations.iterrows(): centroid = print(f"Location {idx}: coordinate ({}, {}), Score: {loc['total_score']:.2f}")
9. Summary and Advanced Suggestions
In this article, we dive into the spatial connection and geocomputing capabilities in GeoPandas. We learned how to:
- Perform different types of space connection operations
- Perform geometric operations such as buffer analysis
- Calculate spatial distance and nearest neighbors
- Conduct hot spot analysis and spatial clustering
- Optimize geospatial processing performance
- Apply these technologies to actual scenarios such as traffic analysis and commercial site selection
Advanced learning path
If you want to learn geospatial analysis more deeply, you can consider the following directions:
- Spatial Statistics: Exploring advanced statistical methods such as spatial autocorrelation and geographic weighted regression
- Network Analysis: Complex road network analysis using NetworkX and OSMnx
- Rasterio data processing: Learn to use rasterio for rasterio
- Spatial-temporal data analysis: Exploring the combination of time and space dimensions
- 3D GIS: Visualization and Analysis of Three-Dimensional Spatial Data with Python
Recommended resources
- "Bonnici, Erik" Guide for Geospatial Analysis of Python (Bonnici, Erik)
- GeoPandas official documentation:/
- Shapely Documentation:/
- Practical Guide to Spatial Data Science:/book/
By mastering these spatial connections and geocomputing techniques, you will be able to handle a variety of complex geospatial data analysis tasks, from simple spatial relationship queries to complex multi-factor geographic modeling.
The above is the detailed content of Python's implementation of spatial connection and geographical computing through Geopandas. For more information about Python's Geopandas spatial connection and geographical computing, please pay attention to my other related articles!