| Publishing larger geographic datasets on the
web did require expensive GIS or commercial database software in the past. While
commercial systems had been able to handle large databases, the file-formats delivered to
the client had been either standard-based and non-interactive (raster-based tiles) or
highly proprietary but would allow for interactivity. Most commercial systems that allow
client-side interactivity base their clients on proprietary platform-dependent plug-ins or
Java-Applets, which often includes the use of proprietary and undocumented data formats.
Additionally, many commercial products lack (carto)graphical quality and have severe
limitations when it comes to interactivity and flexibility. With the rise
of open W3C standards as well as open source scripting solutions, databases and
GIS-extensions, developers and cartographers have a more affordable and highly flexible
solution at hand. Delivering larger geographic datasets requires that a map-server is able
to extract subsets of existing spatial datasets. A server-client solution using PostGIS,
an open-source extension to the free SQL database PostgreSQL, in conjunction with
PHP-scripts on the serverside will be presented. The presented database holds various
scale-levels of the vector datasets provided by the Swiss Federal Office of Topography.
Depending on the scale and extent requested by the map-client, the server can deliver
different datasets and symbolize the data appropriate to the map-scale. An interactive SVG
and ECMA-Script based map client can display and query spatial datasets and do simple
analysis. |
