Transcript Web mapping services for biological data

Web mapping services for biological data
SVG Sniplet Server
Francisco Hernandez, Bart Vanhoorne, Roeland T’Jampens, Edward Vanden Berghe
When marine data is being shared online through the web, often the need rises for interactive mapping tools. Whether it is for displaying data, or for providing geographical selection options
for this data, whether for biological parameters (distribution records) or for abiotic, oceanographic parameters: a nice, interactive map gives a clear added value to the application. At VLIZ
we have several of these online databases running, and over the last few years we have developed a certain amount of program code. This paper describes our experiences, the tools
developed so far, and how they will be made available to the larger scientific community.
After some experiments with clickable bitmaps we chose for an SVG based technology, because of some clear benefits: SVG is an W3C specification, it is Open source, thus free and has
very good scripting possibilities. However, when using SVG for something more than a simple, one-file-application, several problems arise. The generation and documentation of base
maps, the need for different geographical projection systems and the performance issues when using higher resolution maps are some of the problems that need to be solved.
Our solution to these problems is the ‘Svg Sniplet Server’. What we basically did is upload our charts into an SQL database, and install a webservice application that queries the database,
projects the retrieved coordinates and generates small pieces of SVG code (called sniplets) that can be combined to form one SVG file.
In a next phase we want to investigate the possible interaction with other standards like GML, other ISO 191xx standards, and the forthcoming MarineXML standard.
upload
ESRI shapefile
Avenue script
SVG sniplet server
S3 database
XML format
SQL query
webservice call
generate
PHP script
Database
WEB client
SVG viewer
S3 server
WEB server
Application database
SVG sniplet
assemble
SQL query
http request
PHP / java script
SVG
The S3 database is populated by uploading shaprefiles that where converted to
XML. The Sniplet are generated on the fly, depending on the projection and
resolution required. The sniplets are cached. The assembly process is
application specific.
The web client requests http content from the application webserver, and svg
content from the S3 server.
The svg viewer parses stylesheets to render the objects according to application
specific content.
Different applications can share the same sniplets, because they only encode
the geometries. Style and scripting is added at the application level.
Projections on the fly are handled by the svg sniplet server. The geometries in
the database are stored in unprojected coordinates.
Smart zooming in SVG : because the S3 server generates sniplets of different resolution, it can be
used to load better resolution maps when the user zooms in.
Flanders Marine Institute, Vismijn Pakhuis 49 , 8400 Oostende Belgium