Overview - ISO 19128:2005 (Web map server interface)
ISO 19128:2005 defines the Web Map Service (WMS) interface for producing spatially referenced maps dynamically from geographic information. It specifies how a WMS exposes service metadata, how clients request rendered maps, and how a server can answer queries about features displayed on a map. The standard applies to pictorial renderings (raster or vector image outputs) and is explicitly not intended for retrieval of raw feature datasets or coverage data values.
Key facts:
- Protocol version used by implementations: 1.3.0
- Primary operations: GetCapabilities (mandatory), GetMap (mandatory), GetFeatureInfo (optional)
- Output formats commonly supported: PNG, GIF, JPEG, and optionally SVG or WebCGM
- Emphasis on named Layers and predefined Styles (user-defined symbolization is outside the standard; OGC SLD is referenced for that)
Key topics and technical requirements
- Service operations and request/response rules
- Defines URL-based HTTP requests (parameters passed in URLs) and XML-based service metadata.
- Requires inclusion of protocol version in service metadata and requests (supports negotiation).
- Conformance classes
- Two classes: Basic WMS (GetCapabilities + GetMap) and Queryable WMS (adds GetFeatureInfo). Each class has client and server subclasses.
- Map portrayal and output
- Maps are digital image files for display; multiple maps using identical geographic and size parameters must be overlay-compatible (supports transparency).
- Coordinate Reference Systems (CRS)
- Specifications govern coordinate handling and CRS definitions (Annex B) - important for accurate georeferencing and overlays.
- Service metadata and XML schemas
- Service capabilities described in XML; normative XML schemas and UML model included (Annexes E and F).
- Testing and compliance
- Conformance tests and abstract test suites provided (Annex A).
Practical applications and users
Who benefits:
- GIS software vendors and map server implementers building WMS-compliant services
- Web and mobile web mapping developers integrating distributed map layers
- Government and commercial geospatial data providers publishing maps over HTTP
- System integrators creating composite maps by overlaying tiles from multiple WMS servers
Common use cases:
- Delivering on-demand map images for web mapping portals
- Serving base maps or thematic layers for clients that do not need raw feature downloads
- Enabling interoperable composition of maps from distributed servers using consistent CRS and styling
Related standards
- ISO 19111 (Spatial referencing by coordinates)
- ISO 19115 (Geographic metadata)
- ISO 8601 (Date/time representation)
- OGC specifications: Styled Layer Descriptor (SLD), Web Feature Service (WFS), Web Coverage Service (WCS)
ISO 19128:2005 is essential for interoperable, standards-based map rendering over the web and remains a foundation for web GIS integrations and map server implementations.