Appendix B: Glossary

CRS

A “coordinate reference system”. The combination of a geographic coordinate system and a projected coordinate system.

GDAL

Geospatial Data Abstraction Library, pronounced “GOO-duhl”, an open source raster access library with support for a large number of formats, used widely in both open source and proprietary software.

GML

Geography Markup Language. GML is the OGC standard XML format for representing spatial feature information.

JSON

“Javascript Object Notation”, a text format that is very fast to parse in Javascript virtual machines. In spatial, the extended specification for GeoJSON is commonly used.

JSTL

“JavaServer Page Template Library”, a tag library for JSP that encapsulates many of the standard functions handled in JSP (database queries, iteration, conditionals) into a terse syntax.

JSP

“JavaServer Pages” a scripting system for Java server applications that allows the interleaving of markup and Java procedural code.

KML

“Keyhole Markup Language”, the spatial XML format used by Google Earth. Google Earth was originally written by a company named “Keyhole”, hence the (now obscure) reference in the name.

OGC

The Open Geospatial Consortium <http://opengeospatial.org/> (OGC) is a standards organization that develops specifications for geospatial services.

OSGeo

The Open Source Geospatial Foundation <http://osgeo.org> (OSGeo) is a non-profit foundation dedicated to the promotion and support of open source geospatial software.

SFSQL

The Simple Features for SQL (SFSQL) specification from the OGC defines the types and functions that make up a standard spatial database.

SLD

The Styled Layer Descriptor (SLD) specification from the OGC defines an format for describing cartographic rendering of vector features.

SRID

“Spatial reference ID” a unique number assigned to a particular “coordinate reference system”. The PostGIS table spatial_ref_sys contains a large collection of well-known srid values and text representations of the coordinate reference systems.

SQL/MM

SQL Multimedia; includes several sections on extended types, including a substantial section on spatial types.

WFS

The Web Feature Service (WFS) specification from the OGC defines an interface for reading and writing geographic features across the web.

WMS

The Web Map Service (WMS) specification from the OGC defines an interface for requesting rendered map images across the web.

WKT

“Well-known text”. Can refer either to the text representation of geometries, with strings starting “POINT”, “LINESTRING”, “POLYGON”, etc. Or can refer to the text representation of a CRS, with strings starting “PROJCS”, “GEOGCS”, etc. Well-known text representations are OGC standards, but do not have their own specification documents. The first descriptions of WKT (for geometries and for CRS) appeared in the SFSQL 1.0 specification.