Technical documentation of Geoportal API

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Prerequisites

Information found in this documentation heavily rely on the knowledge of Information Technology and Geographical Information. Amongst these technologies, one can find :

Programming languages

Technologies involved in the 2D API are based on Internet technology. Information streams are coming from different servers bringing data to the browser ;

  • browser's programming languages : API based web pages are dynamic web pages that mainly use the following three technologies :
    • HyperText Markup Language (HTML) : one has to know how to write an HTML page ;
    • Cascading Style Sheet (CSS) : one has to know how to design the look and feel of an HTML page ;
    • ECMA-262 and alike (JavaScript [1] / ActionScript [2]) : these are the core languages of the WEB 2D API and its components (like OpenLayers). One has to know how to write scripts with at least one of these languages.

Standards

International de jure standards from ISO (International Organization for Standardization), de facto standards from OGC (Open Geospatial Consortium) and OSGeo (Open Source Geospatial Fundation) : geographical services use these standards, on has to have some knowledge about how they work :

  • Web Map Tile Service (WMTS) : this standard is close to the WMS. However, instead of generating an image for each request as in the case of WMS, the WMTS returns pre-generated small pictures (tiles) or reuses images previously created for the same request (cache).
  • Web Map Service - Cached (WMS-C) : as ISO/OGC did not provide us with a high performances Web Mapping Service, we have chosen this proposal from MetaCarta. This may change when this OGC's RFC becomes a standard ;
  • Web Map Service (WMS) : maps on the network, this service mainly publishes images (but not only). While the browser is a WMS client through the API, a GIS application can also be a WMS client ;
  • Web Feature Service (WFS) : it acts as a database connector and heavily uses the Geographic Markup Language (GML) for transferring geographical data between the service and its clients. Again, the browser is a WFS client through the API, a GIS application can also be a WFS client ;
  • Keyhole Markup Language (KML) : this language is being adopted by OGC. It is well known when used with Google Earth application. OpenLayers supports it ;
  • GPS eXchange Format (GPX) : this language, also supported by the API, is used to interchange GPS tracks, routes or waypoints.

Mapping libraries

  • OpenLayers 2 : a pure JavaScript library for displaying map data in most modern web browsers, with no server-side dependencies. The Javascript WEB 2D API is based on it.
  • OpenScales : an open source (LGPL) mapping framework written in ActionScript 3 and Flex that enables developers to build Rich Internet Mapping Applications. The Flex WEB 2D API is based on it.

The above technologies are not the only ones to know in the field of geomatics ...


N1 JavaScript is a trademark of Sun MicroSystems Inc.

N2 ActionScript is a trademark of Adobe Inc.