What is a road?

My recent adventures in GPS have me returning to the warm embrace of MapServer, the open source mapping server that I first implemented for the Province of PEI, and later for Yankee. It’s a wonderful project: well supported, well documented, and very powerful.

One of the neat feature of MapServer is its ability to pull map layers from remote WMS servers. Olle asked me “what is a wms server?” and I replied “Think ‘webserver for GIS layers’,” which pretty much covers it.

Here in Canada we benefit from a pleasantly progressive and technically savvy group of mapocrats who consider it their responsibility to spread mapping data far and wide; one result of their efforts is GeoBase, a project that describes itself as existing to “ensure the provision of, and access to, a common, up-to-date and maintained base of quality geospatial data for all of Canada.” That’s pretty cool.

The GeoBase WMS server has a fulsome collection of GIS layers available, including the nascent National Road Network (“the representation of a continuous accurate centerline for all non-restricted use roads in Canada”). Inside the cryptic XML file that describes the capabilities of the GeoBase WMS server, you find the following description of what a “Road Segment” is:

A linear section of the earth designed for or the result of vehicular movement.

It’s a very elegant description, I think — especially the “or the result of” part, which admits that sometimes roads are roads because drivers drive places.