Using OneGeology Services
OneGeology does not have any data, all maps viewable through the portal are provided by services, some of these services may also provide access to data downloads. OneGeology makes data from geological data providers around the world accessible to those who would like to see and use it. The majority of this data is the type that is portrayed on traditional geological maps. There are increasing amounts with different geologically related types of data such as geophysics, boreholes and hydrogeology. This data is made available by means of Open GeoSpatial Consortium OGC standard web services that can be accessesed by a number of free and commercial clients. Currently OneGeology makes use of three OGC standards: Web Map Service WMS, Web Feature Service WFS and Web Coverage Service WCS. These different service standards define different kinds of capability for examining the data.
The data is “served” directly from the provider organisation.
The provider organisation retains full ownership and responsibility and is able to change or modify data whenever necessary.
WMS provides the ability to see a map image projected to its correct geographical location in a number of map projections. This will usually be accompanied by a legend which explains the symbology used in the map. Commonly, many WMS also provide the ability to select a point on the map and get a summary in text or other format of data values for that point. The majority of OneGeology services are WMS. A small number of these WMS also provide the ability to change the symbology of the map depending on the underlying data (e.g. to highlight formations of a particular age). These are called SLD enabled WMS.
WFS provide the ability to query a service based on spatial and other criteria and return the matching data in a GML format and maybe other formats as well. It assumes the data has been structured as a collection of features with spatial and other, possibly complex properties. OneGeology is focussed on two standard formats for data exchange: GeoSciML and ERML. The data available from a given WFS may be visually portrayed in one or more related WMS layers.
WCS also provices the ability to return matching data based on spatial and other criteria but the data is structured as coverages where values of some fixed set of properties are defined for each point over some spatial domain. Although theoretically different kinds of division of spatial domain are possible, currently all coverages are based on regular grids. The properties are also simple whether numerical or categorical. As image formats generally specify colour values at regular grid cells then a WCS may return coverages that can be viewed as an image directly as well as data formats that need to be processed by some application.
In simple terms, currently WFS are used for spatial data stored in some vector format and WCS for data stored in a raster gridded format.
The following pages show how you may access services using these OGC standards (including those not part of OneGeology) in a number of popular desktop software clients and web based browser applications. We concentrate first on the web based portal provided by OneGeology itself and then cover other commonly available clients.