Spatial Data Infrastructure (SDI)

Detailed definition

The Spatial Data Infrastructure (SDI) is an internal maintenance database that is not disseminated outside of Statistics Canada. It contains roads, road names and address ranges from the National Geographic Database (NGD), as well as boundary arcs of standard geographic areas that do not follow roads, all in one integrated line layer. The database also includes a related polygon layer consisting of basic blocks (BB)1, boundary layers of standard geographic areas, and derived attribute tables, as well as reference layers containing physical and cultural features (such as hydrography, railroads and power transmission lines) from the NGD.

The SDI supports a wide range of census operations, such as the maintenance and delineation of the boundaries of standard geographic areas (including the automated delineation of dissemination blocks and population centres) and geocoding. The SDI is also the source for generating many geography products for the 2011 Census, such as cartographic boundary files and road network files.


2011, 2006 (Spatial Data Infrastructure)
2001 (National Geographic Base)


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 codeOM files, are incorporated into the database.

Given the enhancements to the SDI, primarily through the integration of improved road network data from the National Geographic Database (NGD), geography products for the 2011 Census allow users to geographically reference census data more accurately when compared to the 2006 Census products (e.g., cartographic boundary files, digital boundary files, reference maps, road network files).

Product files from the SDI are available in the Geography Division's data warehouse (GeoDepot).

Refer to the related definitions of block-face; cartographic boundary files (CBFs); coordinate system; datum; digital boundary files (DBFs); dissemination block (DB); geocoding; map projection; National Geographic Database (NGD); reference map; representative point and road network file (RNF), and related reference guides.

Changes prior to the current census

For 2001, the internal database was called the National Geographic Base (NGB), which was divided into National Topographic Data Base (NTDB) map tiles.


  1. Basic blocks are the smallest polygon units in the database, and are formed by the intersection of all roads and the arcs of geographic areas that do not follow roads.
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