|Introduction to the Dictionary, A to Z Index, Modifications|
Geographic Infrastructure:National Geographic Base (NGB)
Part A – Plain Language Definition
Part B – Detailed Definition
The National Geographic Base (NGB) is a new database that contains roads and boundaries of standard geographic areas in one integrated layer, as well as other physical and cultural features (such as hydrography, railroads and power transmission lines) stored as separate layers.
The NGB is an internal, maintenance database that is not disseminated. It supports a wide range of census operations, such as updating the road network and address ranges, supporting the block program, delineating the boundaries of standard geographic areas (including the automated delineation of enumeration areas, urban areas and dissemination areas), and geocoding. As well, the NGB is the source for generating many geography products for the 2001 Census, such as reference maps and Cartographic Boundary Files.
The NGB now provides 100% digital coverage of Canada, whereas previously Street Network Files were limited to the major urban centres, which covered less than 1% of the land area and 62% of the population.
The main source files for the NGB include:
In addition, portions of the NGB contain information obtained from a variety of other sources, including field operation activities.
Compared to the 1996 SNFs, the NGB has not only an improved road network geometry (since the SNF roads are now realigned to the NTDB road network), but also a greater number of street names and address ranges. Roads and boundaries are edge-matched at map tile limits, but other reference layers are not. Since the primary purpose of NGB is to support census activities, topological accuracy takes precedence over absolute positional accuracy.
The data are maintained and stored in the Lambert Conformal Conic projection based on the North American Datum of 1983 (NAD83). Links to other data holdings, such as the address register and postal code files, are incorporated into the database.
Given the improvements to the NGB, geography products for the 2001 Census allow users to geographically reference census data more accurately when compared to the 1996 Census products (e.g. Street Network Files, Digital Boundary Files and Digital Cartographic Files).
Refer to the related definitions of Block, Block-face, Cartographic Boundary Files (CBFs), Coordinate System, Datum, Geocoding, Map Projection, Road Network Files (RNFs), Reference Map and Representative Point, and to related Reference Guides (Cartographic Boundary Files and Road Network Files) (Catalogue Nos. 92F0171GIE and 92F0157GIE).
Changes Prior to the 2001 Census:
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