Distributed Web Mapping using Multi-layered GIFs.

[DOIG.JONATHAN@epa.nsw.gov.au]

                       http://www.epa.nsw.gov.au/soe/maps
          
          The New South Wales Environment Protection Authority (NSW EPA) 
          has developed web server mapping software which combines 
          individual map layers from multiple web sites into interactive 
          maps for viewing on standard web browsers.
          
          The approach used has a number of benefits:
          
          *    It provides a platform for integration (by overlay) of map 
               data between internet sites.
          
          *    Both source map layers and output maps are held in the 
               standard GIF89a format used throughout the web.
          
          *    The HTML form and Perl scripts developed by NSW EPA are 
               available free of charge and the back-end uses the freely 
               available ImageMagick suite.
          
          *    Because it takes GIF89a images as input, this approach 
               could be used to combine output from proprietory web map 
               servers such as MapInfo ProServer, ESRI's MapObjects 
               Internet Map Server and Genasys's Web Broker.
          
          *    With some further development of tools and standards, an 
               organisation would only need to publish a GIF map file and 
               accompanying metadata file on their website, and notify a 
               map server of its existence, in order to link their map 
               layer to the pool of existing layers for their geographic 
               area.
          
          The multi-layered GIF map interface is demonstrated in the NSW 
          State of the Environment report which is available at the NSW EPA 
          website as follows:
          
          http://www.epa.nsw.gov.au/soe/maps - list of State of Environment 
          maps. Choose any 'NSW' map to go to the mapping interface. From 
          there, either of the following options will demonstrate the use 
          of map layers sourced from remote sites:
          
          The state-wide map: Interim Biogeographical Regionalisation of 
          Australia, NSW [ERIN]
          OR
          The boundary overlay map: Catchment management unit [DLWC]
          
          The interface also links to "Technical Details of the Mapping 
          Interface" (at http://www.epa.nsw.gov.au/soe/95/tech/map.htm).
          
          Although already operational, the approach is obviously in its 
          infancy. Considerable work would be needed, for example in 
          standardising the metadata files to accompany map images, so as 
          to enable more general overlay between maps.
          
          I would be interested in comments on this approach, particularly 
          from those who may consider developing it further.
          
          
          Jonathan Doig

          
          Doig.Jonathan@epa.nsw.gov.au
          Ph: +61 2 9325 5565  Fax: +61 2 9325 5899
          Acting Webmaster
          NSW Environment Protection Authority
          http://www.epa.nsw.gov.au