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Spatial utilities

PocketScope provides a small, dependency-free spatial helper module at src/pocketscope/data/spatial.py that implements common mapping operations and minimal GeoJSON ↔ WKB conversion so geometries can be stored in SQLite without an external spatial extension.

Key utilities

  • haversine_miles(lat1, lon1, lat2, lon2) -> float

    • Great-circle distance in statute miles between two WGS‑84 points.

  • approx_bbox_for_radius(lat, lon, radius_miles) -> (min_lon, min_lat, max_lon, max_lat)

    • Fast approximate lon/lat bounding box surrounding a given radius. Used for inexpensive spatial filtering prior to accurate distance checks.

  • polygon_centroid(rings) -> (lon, lat)

    • Compute centroid of a polygon exterior (rings is a sequence of rings).

  • geometry_to_wkb(geometry) -> bytes

    • Convert a GeoJSON-like geometry mapping (Point, Polygon, MultiPolygon) to a minimal WKB-like byte format used by the ingestion tool and DB.

  • wkb_to_geometry(blob) -> dict

    • Read back the WKB bytes produced above into a GeoJSON-like dict.

  • register_haversine(conn)

    • Register a SQL function HAV_MILES(lat1, lon1, lat2, lon2) on a sqlite3.Connection to enable distance calculations inside SQL queries.

WKB format notes

This project uses a lightweight binary encoding for the small set of geometries we need. The format is intentionally minimal and not a full implementation of the OGC WKB spec; it is intended only to allow storing and retrieving Points, Polygons and MultiPolygons in an SQLite BLOB column without external dependencies.

Ingestion CLI

The repository includes a small CLI pocketscope.data.ingest_geojson_to_sqlite that ingests three GeoJSON files (airports, runways, US states) into a spatially indexed SQLite database. It performs light validation, converts geometries to WKB, computes bounding boxes and centroids, and writes insert-ready rows into the DB schema found beside the ingestion module.

Example

python -m pocketscope.data.ingest_geojson_to_sqlite \
  --airports assets/airports.json \
  --runways assets/runways.json \
  --states assets/states.geojson \
  --out build/map.db --replace

The resulting map.db is suitable for the application's map provider which queries nearby airports, runways and states by bounding box and distance.

Notes and limitations

  • The WKB implementation here is intentionally minimal and optimized for simplicity and performance; it is not a full OGC-compliant implementation.
  • The approximate bounding box is intentionally conservative and should be combined with an accurate haversine distance check for exact filtering.