Simple Features

Simple Features
Name	Simple Features
Developer	Open Geospatial Consortium; multiple vendors
Released	2001
Latest release	ongoing
Programming language	C, C++, Java, Python, R, SQL
Operating system	Cross-platform
License	Various (open source and proprietary)

Simple Features

Simple Features is a specification for the representation and exchange of vector spatial data using a concise set of geometry types and attribute bindings. Originating in the early 2000s under standards bodies, the model defines how points, lines and polygons are encoded, queried and manipulated across databases, GIS software, and programming libraries. The specification emphasizes interoperability between systems such as PostGIS, ESRI, QGIS, GDAL/OGR and database engines like Oracle Database and Microsoft SQL Server.

Definition and Scope

The specification provides a normative definition for spatial objects, coordinate reference handling and topology assumptions adopted by implementations like PostGIS and vendors such as ESRI. It focuses on vector geometries rather than raster formats used by projects like GDAL, and it standardizes operations that are exposed by interfaces such as ODBC, JDBC and spatial SQL in PostgreSQL and SQLite. The scope includes geometry primitives, spatial predicates, spatial relationships inspired by work like the DE-9IM model, and well-known encodings promoted by organizations such as the Open Geospatial Consortium and the International Organization for Standardization.

Data Model and Geometry Types

The model defines a compact set of geometry types: Point, LineString, Polygon, MultiPoint, MultiLineString and MultiPolygon, plus GeometryCollection. Implementations extend these primitives with dimensionality (2D, 3D, measured) and closedness constraints found in systems like ESRI ArcGIS and PostGIS. Coordinate Reference Systems are referenced via identifiers from registries such as the EPSG registry, and spatial indexing uses structures like R-trees implemented in SQLite's spatial extension and in PostGIS via GiST. Topological predicates and relationships mirror concepts formalized in works by the Open Geospatial Consortium and research groups at institutions like University College London and MIT.

Standards and Specifications

The core normative documents include standards published by the Open Geospatial Consortium and ISO standards adopted by the International Organization for Standardization that specify Well-Known Text and Well-Known Binary encodings, SQL bindings, and geometry operator semantics. Related specifications referenced by implementers include the Simple Features Access standards for SQL, the Well-Known Text and Well-Known Binary formats, and the DE-9IM matrix for spatial relations. Other influential documents include profiles and best-practice notes from organizations like OGC member companies such as Esri, Oracle Corporation and open source communities around MapServer and GeoServer.

Implementations and Libraries

A wide ecosystem implements the specification. Database systems with spatial extensions include PostgreSQL with PostGIS, Oracle Spatial, and Microsoft SQL Server. Libraries that parse and manipulate Simple Features representations include GDAL/OGR, GEOS (geometry engine), JTS Topology Suite for Java, Shapely for Python, and sf (R package) for R. Desktop and server GIS software adopting the model include QGIS, ArcGIS Pro, GeoServer and MapServer. Client and web mapping frameworks such as OpenLayers and Leaflet interoperate with Simple Features through vector tiles and GeoJSON produced by servers like Mapbox and Carto.

Use Cases and Applications

Simple Features underpins a variety of applications: cadastral mapping systems operated by agencies like Ordnance Survey and National Land Survey of Sweden; routing engines used by OpenStreetMap-based services and companies such as HERE Technologies; environmental modeling workflows in research institutions like USGS and NIH projects; urban planning tools used by municipal governments exemplified by deployments in New York City and London; and asset management solutions in utilities operated by firms such as Siemens and Schneider Electric. It is also central to web mapping platforms powering services from organizations like Mapbox and community projects hosted by GitHub.

Interoperability and Extensions

Interoperability is achieved through standardized encodings (WKT, WKB, GeoJSON) and SQL-based bindings that allow geometry data to move between systems like PostGIS, Oracle Spatial and Spatialite; tooling such as GDAL/OGR and drivers for ODBC and JDBC facilitate these transfers. Extensions address shortcomings: topology-enabled models such as those in TopoJSON and PostGIS Topology add network and adjacency semantics; 3D and temporal extensions are promoted by standards groups and research programs at institutions like NASA and European Space Agency; and vertical industry profiles are defined by consortia including INSPIRE for European spatial data infrastructures and national clearinghouses like Data.gov. Emerging work integrates Simple Features with graph databases (e.g., Neo4j spatial plugins) and big-data ecosystems such as Apache Spark via connectors and libraries developed by vendors and communities.

Category:Geographic information systems