Spatial filtering

Spatial Filtering

Overview

Spatial filtering allows you to select features based on their location relative to other features.

Point-in-Polygon

To find points that lie inside a specific polygon:

# Assuming gdf_points and gdf_polygons are GeoDataFrames
# 1. Get a specific polygon geometry
pacific_poly = gdf_polygons[gdf_polygons['Code'] == 'PA'].geometry.unary_union

# 2. Filter points
points_in_pacific = gdf_points[gdf_points.within(pacific_poly)]

Spatial Joins

Alternatively, use sjoin for batch processing:

joined = gpd.sjoin(gdf_points, gdf_polygons, predicate='within')

Attribute-based Spatial Selection

Often you need to combine attribute filters with spatial operations:

# Find boundaries associated with the Pacific plate (PA)
pacific_boundaries = gdf_boundaries[
    (gdf_boundaries['PlateA'] == 'PA') | (gdf_boundaries['PlateB'] == 'PA')
]