[Sdi-northamerica] Canadian National Road Network defines state of the art for national datasets

[Kate Lance]

http://www.esri.com/news/arcnews/winter0708articles/canadian-national-road.html
Canadian National Road Network defines state of the art for national datasets
A strategy to build a national road dataset was envisaged in Canada in the 1990s. The initial goal was to build a simple framework dataset with accurate geometry and basic attributes to support topographic mapping, but the vision also included the ability for partners to extend and enhance the base data to support numerous application needs.
The National Road Network (NRN) program was defined by Natural Resources Canada, the national mapping organization in Canada, in partnership with federal, provincial, local, and aboriginal partners to provide this freely available road information. Currently, datasets can be downloaded in shapefile and GML formats by province/territory for the entire country at www.geobase.ca .
At the heart of NRN is a simple geometric data model and identification scheme. A road segment connects two road junctions, and a junction is placed at every point where there is a physical (not necessarily legal) turning option. The geometric model follows the ISO Geographic Data Files (GDF) standard.
Along with the spatial model, unique National Identifiers (NIDs) are assigned to features and junctions. Early in the design process, a more elaborate system for storing attribute information along road segments was defined, but at this point, a simpler segmented model has been implemented with a set of standard attributes stored directly on each feature. As a result, roads are split between junctions where there are changes in attribute values.


      
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