Press Release

OpenGIS adopt Cadcorp proposal for Coordinate Transformation

Stevenage, December 21 2000. At the recent OpenGIS meeting in San Rafael, California, an OpenGIS interface specification proposal for Coordinate Transformation Services (CT IS Version 1.0) from British GIS software company Cadcorp was unanimously adopted by the OpenGIS Consortium (OGC). A second proposal for raster images (Gridded Coverage Interface - GC IS Version 1.0), a joint effort between Cadcorp and Canadian company PCI Geomatics, was also unanimously adopted.

These interface specifications are now made public for utilisation and are available at www.opengeospatial.org/datasheets

Up until now a lack of a coordinate transformation interface standard has prevented users from easily overlaying maps or earth images that have been created and referenced to the earth using different datums, ellipsoids, and units. Coordinate reference systems are complex and diverse. This is one reason why geographic information systems (GIS) have required too much expertise to become part of mainstream computing.

Many people assume that latitude and longitude are universal and sufficient for positioning maps and geospatial information. However, there are a number of distinctly different longitude-latitude spatial reference systems regularly in use. These differences result mainly from the use of different ellipsoids which describe the non truly spherical shape of the Earth; 2) different datums which link a coordinate system to a real place upon the Earth; and 3) different projections, or 2D representations of the Earth’s 3D surface. Furthermore, there are other spatial reference systems in common use whose coordinates are different from longitude and attitude.

Applied mathematics addresses these issues and provides an established computational foundation for coordinate transformation. With today’s software, converting a set of coordinates in one spatial reference system to a set of coordinates in another spatial reference system can usually be accomplished with acceptably small loss of accuracy. The European Petroleum Survey Group (EPSG) maintains a registry of most of the commonly used coordinate reference systems along with the coordinate transformation parameters which provide a basis for these calculations. The EPSG registry provides a starting point for the OpenGIS Coordinate Transformation Services Specification.

In May 1999, the OGC issued a request for a Coordinate Transformation proposal. Cadcorp submitted their first proposal in November 1999. This was approved in February 2000 and finally adopted and published at the December meeting in San Rafael.

The Coordinate Transformation Services (CTS) Specification, as it is known, provides common interfaces for general positioning, coordinate systems, and coordinate transformations. The OpenGIS Coordinate Transformation Services (CTS) Specification is expressed in Universal Modeling Language (UML), The Unified Modeling Language (UML) is a graphical language for visualizing, specifying, constructing and documenting the artifacts of software systems. Profiles have been created in COM, CORBA and Java. Cadcorp has already fully implemented the COM profile of the CTS specification.

The CTS specification consists of two major packages:

Coordinate System package
Coordinate Transformation package

Coordinates can have any number of dimensions. So the Cadcorp specification can handle 2D and 3D coordinates, as well as 4D (space + time), 5D etc. The Coordinate System package will extend and replace the 2D Spatial Reference package contained in the 1998 OpenGIS Simple Features Specification, (the Simple Features specification defines the handling of standard GIS data structures such as points, lines and polygons). However, it has been designed to work in conjunction with Simple Features during any transition period.

The Coordinate Transformation package allows points to be transformed between any coordinate system. There are also hooks for allowing the same coordinate transformations to be used for transforming arbitrary geometries and images, with full and robust support for warping and tearing.

The illustrations on the right show an image grabbed from an OpenGIS Web Mapping server, and transformed using Cadcorp's implementation of the OpenGIS Coordinate Transformation Specification. Notice the warping and tearing in the second image.

This is yet further evidence of the ground-breaking work being carried out in GIS by Cadcorp and follows in the wake of Cadcorp SIS – Spatial Information System software being certified Open GIS compliant for Simple Features, and work in the Open GIS Web-mapping Testbed (WMT).

About Cadcorp

Established in 1991, Cadcorp are a leading developer of Geographic Information Systems (GIS) software. Based in the UK and USA, the Cadcorp distribution and VAR network stretches worldwide. Cadcorp play a pivotal technical role in the OpenGIS Consortium. Cadcorp SIS - Spatial Information System is a range of modules covering spatial data viewing, data management, data editing, data modelling and analysis. Cadcorp SIS ActiveX components are available for embedding into third party systems. Cadcorp ASC is Internet/Intranet developer toolkit designed for Web based GIS solutions. Cadcorp SIS applications exist in Local Government, Central Government, National Mapping Agencies, Emergency Services, Mapping and Surveying, Commerce, Broadcasting and many others.

About OGC

The Open GIS Consortium, Inc. (OGC) is an international, not-for-profit industry organisation dedicated to the full integration of geospatial data and geoprocessing resources into mainstream computing. In addition to developing the Open GIS Specification in the OGC technical committee, OGC works to inform the geoprocessing community about open geoprocessing issues and developments and promotes the widespread use of interoperable, commercial geoprocessing software, on a world-wide basis. OGC currently has some 300 members, split roughly 50/50 between the USA and the rest of the world. Members include geoprocessing software developers, IT industry leaders and government agencies, including the UK’s Ordnance Survey.

ENDS

For further information, contact: Chris Holcroft, Tel: 01438 747996, e-mail: chrish@cadcorp.com

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