Thursday, October 18, 2007

Wrestling Xerces on MINGW - Qgis GML support

With all the fuss about using XML based standards, GML is becoming increasingly popular as the medium of vector data representation in the GIS community. For the rest there is always KML /KMZ and for the old-timers Shapefiles. The zip and gzip compression algorithms compress text very well and compressed XML based formats are less bandwidth hungry compared to binary formats. GeoServer can produce all these formats for distribution from various datasources, GML is the primary format. GML2-GZIP fares best in terms of size and speed of creation.
After struggling for weeks to link GDAL with Xerces-C on MINGW I ran across this little nugget, a compiler flag that simply and cleanly allowed static linking to parse GML. Xerces-C is not the most elegant, lean and fast XML library, but it is used in GDAL and conversion to another library, possibly Expat which is also a GDAL dependency will require developer resources not currently available. So finally after all the fiddling around I have GML loading in QGIS and hopefully better luck with WFS servers providing it.
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