4. Data quality

Lineage
Positional accuracy
Attribute accuracy
Logical consistency
Completeness

Spatial data quality elements provide information on the fitness-for-use of spatial data by describing why, when and how the data are created, and how accurate the data are. The elements include an overview describing the purpose and usage, as well as specific quality elements reporting on lineage, positional accuracy, attribute accuracy, logical consistency and completeness. This information is provided to users for all spatial data products disseminated for the census.

Lineage

Lineage describes the history of the spatial data, including descriptions of the source material from which the data were derived, and the methods of derivation. It also contains the dates of the source material, and all transformations involved in producing the final map products.

Source materials

Census division and census subdivision names, types, codes and boundaries are those that were in effect on January 1, 2006 (the geographic reference date of the 2006 Census). Where notification from provincial or territorial authorities was not received or was received after March 1, 2006, the name, type and/or limits of the census division and census subdivision may not correspond with those recognized by provincial or territorial authorities.

The vector base map information (coastlines, rivers, and lakes) was taken from the National Geographic Database. Water toponymy (river names, lake names, names of bays, oceans, gulfs, straits, seas and islands) was taken from the Canadian Geographical Names Data Base maintained by Natural Resources Canada. The map projection for all maps is Lambert conformal conic with different parameters for each province and territory. The latitude/longitude graticule was generated using ArcGIS^® Version 9.1 software.

The geographic area boundaries, names, types and codes, and the relationships among the various geographic levels are found on Statistics Canada's Spatial Data Infrastructure. These data for administrative areas are updated intercensally using information from provincial and territorial sources. These data for statistical areas are updated using the results of the previous census, as well as input from users.

Method of derivation

The census divisions and census subdivisions reference maps were generated from digital geographic files using ArcGIS^® Version 9.1, a geographic information system (GIS) software produced by Environmental Systems Research Institute (ESRI).

For hydrography, ranked water layers were used, allowing for the display of an appropriate number of water features given the map scale.

The national reference maps were generated from digital geographic files using ArcGIS^® Version 9.1, a geographic information system (GIS) software produced by Environmental Systems Research Institute (ESRI).

Positional accuracy

Positional accuracy refers to the absolute and relative accuracy of the positions of geographic features. Absolute accuracy is the closeness of the coordinate values in a dataset to values accepted as or being true. Relative accuracy is the closeness of the relative positions of features to their respective relative positions accepted as or being true. Descriptions of positional accuracy include the quality of the final product after all transformations.

The Spatial Data Infrastructure is not Global Positioning System (GPS)-compliant. However, every possible attempt is made to ensure that the geographic area boundaries maintained in the Spatial Data Infrastructure respect the limits of the administrative entities that they represent (e.g., census division and census subdivision) or on which they are based (e.g., census metropolitan area/census agglomeration). The positional accuracy of these limits is dependent upon source materials used by Statistics Canada to identify the location of limits. In addition, due to the importance placed on relative positional accuracy, the positional accuracy of other geographic data (e.g., road network data and hydrographic data) is considered when positioning the limits of the geographic areas.

Initial text placement of labels for census divisions, census metropolitan areas, census agglomerations and census subdivisions was automated. Interactive editing was then performed to enhance label placement.

The national map showing the location of the census metropolitan areas and census agglomerations across Canada was produced using point symbols that were interactively positioned to portray the urban centres' proximity to major hydrographic features and the Trans-Canada Highway.

Attribute accuracy

Attribute accuracy refers to the accuracy of the quantitative and qualitative information attached to each feature (such as population for an urban area, street name, census subdivision name, type and code).

As noted under Lineage, the attributes (names, types and codes) for all geographic areas displayed on the maps were sourced from Statistics Canada's Spatial Data Infrastructure. The names and types for administrative geographic areas were updated from the 2001 Census using source materials from provincial and territorial authorities.

River and lake names in the National Geographic Database were sourced from the Canadian Geographical Names Data Base. Names of water features having 'pan-Canadian' significance, as identified by the Geographical Names Board of Canada, are provided in both official languages.

Logical consistency

Logical consistency describes the fidelity of relationships encoded in the data structure of the digital spatial data.

Internal consistency

The geographic area boundaries align to the hydrographic features of the National Geographic Database water layers. The only hydrographic features that do not align to geographic area boundaries are the external features (water falling outside of national limits) derived from generalized layers.

Consistency with other products

Census reference maps show the location of the geographic areas for which census data are tabulated and disseminated. The main information depicted includes the boundaries, names, types and codes of census geographic areas, and major physical and cultural features such as roads, coastlines, rivers and lakes.

Completeness

Completeness refers to the degree to which geographic features, their attributes and their relationships are included or omitted in a dataset. It also includes information on selection criteria, definitions used, and other relevant mapping rules.

This series contains all 288 census divisions and 5,418 census subdivisions, as well as all 33 census metropolitan areas and 111 census agglomerations as defined in the 2006 Standard Geographical Classification. Names of hydrographic features and names of 'pan-Canadian' significance are included if they fit on the map.

The base map features selected for display on the national maps include only the major rivers and lakes and the Trans-Canada Highway.