libspatialite

libspatialite is an open-source C library that extends SQLite with spatial capabilities. It implements the SpatiaLite extension, enabling SQLite databases to store, index, and query vector spatial data following the OGC Simple Features specification.

The library provides geometry data types such as POINT, LINESTRING, POLYGON and their multi- counterparts, stored in SQLite as binary blobs, along with metadata describing geometry columns and spatial reference systems. It offers a broad set of spatial functions and predicates for spatial queries, measurement, and relational operations. To enable full functionality, libspatialite integrates with external libraries such as PROJ for coordinate reference systems and GEOS for geometry operations, and uses an R-tree based spatial index to speed up queries.

Data model and extension usage: applications load the mod_spatialite extension into SQLite; libspatialite supplies the runtime and API. Typical workflows include creating a geometry column with AddGeometryColumn, initializing metadata with InitSpatialMetaData, and creating a spatial index with CreateSpatialIndex. Spatial data are stored with associated entries in geometry_columns and spatial_ref_sys.

Usage and impact: libspatialite is widely used in GIS applications and data workflows that require portable, lightweight spatial data storage. It is commonly used as a data source in QGIS and other desktop and mobile GIS software for offline projects and small-to-medium datasets.

Development and licensing: libspatialite is open-source software with ongoing development and community support, reflecting the long-standing SpatiaLite project that began in the mid-2000s as an extension to SQLite.