geo-l1-tokyo-busstop-buffer

Rerun

import geopandas as gpd

def main():
    # Load the input connectors
    input_file = 'tokyo_connectors.geojson'
    output_file = 'tokyo_stop_catchments.geoparquet'
    buffer_dist = 400  # meters

    print(f"Reading {input_file}...")
    gdf = gpd.read_file(input_file)

    # Check CRS
    if gdf.crs is None:
        print("Warning: Input has no CRS. Assuming WGS84 (EPSG:4326).")
        gdf.set_crs(epsg=4326, inplace=True)
    
    # We need to buffer in meters, so project to a metric CRS.
    # For Tokyo, EPSG:3857 (Web Mercator) or a local UTM zone is appropriate.
    # EPSG:6677 (JGD2011 / Japan Plane Rectangular CS VI) is often used for Tokyo.
    # Let's use EPSG:3857 for simplicity if we don't want to guess the exact zone, 
    # but EPSG:6677 is better for local accuracy.
    # Actually, let's check if we can use a more appropriate one or just 3857.
    # Since it's a 400m buffer, 3857 is usually "good enough" for general catchments,
    # but let's try to be professional.
    
    print("Projecting to metric CRS for buffering...")
    # EPSG:6677 is JGD2011 / Japan Plane Rectangular CS VI (covers Tokyo area)
    # Alternatively, EPSG:3857 is safe and common.
    gdf_metric = gdf.to_crs(epsg=6677)

    print(f"Buffering by {buffer_dist}m...")
    # Apply buffer
    gdf_metric['geometry'] = gdf_metric.buffer(buffer_dist)

    # Ensure we keep connector_id and project back to WGS84 if the original was 4326
    # Or just keep the metric CRS if that's preferred? 
    # Usually, ridership tables are in WGS84. Let's check original CRS.
    original_crs = gdf.crs
    print(f"Original CRS: {original_crs}")
    
    gdf_buffer = gdf_metric.to_crs(original_crs)

    # Ensure connector_id is preserved. 
    # The buffer operation on a GeoSeries preserves the index, so the columns are kept.
    # The prompt says: "one Polygon or MultiPolygon row per input connector"
    # buffer() returns a single geometry per row.

    print(f"Saving to {output_file}...")
    gdf_buffer.to_parquet(output_file)
    print("Done!")

if __name__ == "__main__":
    main()