5. Data quality

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Lineage
Positional accuracy
Attribute accuracy
Logical consistency
Consistency with other products
Completeness

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

Lineage

Lineage describes the history of the 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 file.

General methodology

The National Geographic Database (NGD) is a joint Statistics Canada-Elections Canada initiative to develop and maintain a spatial database which serves the needs of both organizations. The focus of the NGD is the continual improvement of quality and currency of spatial coverage using updates from provinces, territories and local sources. The native file used for the creation of the 2011 Census Geographic Attribute File resides on Statistics Canada's Spatial Data Infrastructure (SDI) which was derived directly from data stored in the NGD environment.

In creating the 2011 Census Geographic Attribute File, all dissemination blocks were extracted from the SDI along with data for the higher level standard geographic areas in which dissemination blocks are located.

Geographic areas, unique identifiers, names, types and classes

Statistics Canada disseminates 2011 Census statistical data by standard geographic area. These areas are either administrative or statistical.

Administrative areas are defined, with a few exceptions, by federal and provincial statutes. These include:

• Canada (CAN)
• province and territory (PR)
• federal electoral district (FED) (2003 Representation Order)
• census division (CD)
• census subdivision (CSD)
• designated place (DPL)

Statistical areas are defined by Statistics Canada and are used to collect and disseminate Census statistical data. These include:

• economic region (ER)
• census consolidated subdivision (CCS)
• census metropolitan area (CMA), census agglomeration (CA) and census metropolitan influenced zone (MIZ)
• census tract (CT)
• population centre (POPCTR) and rural area (RA)
• dissemination area (DA)
• dissemination block (DB)

Geographic names refer to the names given to standard geographic areas. Geographic names, however, are not given to all standard geographic areas. Named standard geographic areas include provinces and territories, economic regions, census divisions, census consolidated subdivisions, census subdivisions, census metropolitan areas, census agglomerations, designated places, populations centres and federal electoral districts. Although census tracts do not have alphabetic names, they do have numeric names consisting of seven characters, which include leading zeros, a decimal point and trailing zeros.

For provinces and territories, the 2011 Census Geographic Attribute File contains both English and French names. The sources used for the names of the provinces and territories are the statutes of the respective provinces and territories.

The source of the geographic names of federal electoral districts is the 2003 Representation Order, Elections Canada.

For those census divisions and census subdivisions that respect the administrative fabric within the provinces and territories, the sources of the names and types are the provincial and territorial governments. Statistics Canada receives input from the provincial and territorial governments concerning all boundary, name and type changes to their respective municipal structures. The 2011 Census reflects the administrative structure within provinces and territories that was in effect on January 1, 2011, the geographic reference date of the 2011 Census.

Where no provincial or territorial administrative areas exist, census divisions and census subdivisions and their associated names and types are created in consultation with provincial and territorial authorities. The names of Indian reserves and settlements are provided to Statistics Canada by Aboriginal Affairs and Northern Development Canada (formerly Indian and Northern Affairs Canada).

For census consolidated subdivisions, names are derived from their component census subdivisions. Census consolidated subdivision names coincide with the name of the census subdivision component with the largest land area within the consolidated census subdivision.

Census metropolitan area and census agglomeration names are usually based on the largest population centre(s) within the census metropolitan area or census agglomeration.

Information on the delineation criteria for 2011 Census standard geographic areas as well as the sources of geographic names is provided in the 2011 Census Dictionary (Catalogue no. 98-301-X) and the 2011 Census Illustrated Glossary (Catalogue no. 92-195-X).

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 file or product after all transformations.

The only positional data contained within the 2011 Census Geographic Attribute File are the representative point coordinates of dissemination areas. Within Statistics Canada's Spatial Data Infrastructure, representative point coordinates were generated using ArcGIS^® software in conjunction with dissemination area boundaries. The most detailed hydrography available was used in identifying cartographic boundaries and calculating representative point coordinates in Statistics Canada's native format. Efforts were made to ensure that representative point coordinates do not fall in water, where possible. The representative point coordinates were initially calculated based on the Lambert Conformal Conic projection; they were then transformed to latitude and longitude coordinates.

Attribute accuracy

Attribute accuracy refers to the accuracy of the quantitative and qualitative information attached to each feature (such as population counts for dissemination blocks, census subdivision unique identifiers, names and types).

The geographic unique identifiers, names, types and classes contained within the 2011 Census Geographic Attribute File, along with the relationships between all standard geographic areas, were verified against Statistics Canada's Spatial Data Infrastructure. The hierarchy of standard geographic units for dissemination, 2011 Census (Appendix B) illustrates the relationships between all geographic units.

Blank fields are displayed within the 2011 Census Geographic Attribute File where population and dwelling counts have been suppressed due to incompletely enumerated Indian reserves and Indian settlements. Population counts for Indian reserve refusal census subdivisions are not included in any census counts, therefore the blank population at the census subdivision, dissemination area and dissemination block levels are consistent with the 2011 Census statistical data.

2011 Census land area

Land area data for 2011 Census standard geographic areas reflect the boundaries in effect on January 1, 2011, the geographic reference date for the 2011 Census.

The data were derived from the Spatial Data Infrastructure (SDI), including selected hydrographic polygon layers. The Lambert Conformal Conic projection was transformed to the Albers equal-area conic projection, since the property of equal area is appropriate for calculating land area. The same projection parameters (two standard parallels, central meridian and latitude of projection origin) were used for each province or territory. Land area was calculated using ArcGIS^® software.

Users should note that even when the boundaries of standard geographic areas did not change between the 2006 and 2011 Censuses, calculated land areas may differ due to geometry shifts. Geometric shifts are caused by a change in the underlying land and hydrography features and by improvements in the absolute positional accuracy within areas.

Logical consistency

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

Internal consistency

Consistency between data at various geographic levels was verified. Verification procedures ensured that counts at lower geographic levels sum to higher geographic levels.

Population and dwelling count data

The 2011 Census population and dwelling count data were verified to ensure that they sum properly to all higher level 2011 Census standard geographic areas.

Consistency with other products

The population and dwelling count data in the 2011 Census Geographic Attribute File are consistent with those disseminated in other 2011 Census products.

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.

The 2011 Census Geographic Attribute File contains one record for each of the 493,345 dissemination blocks. It also contains the appropriate geographic units for each standard geographic level. Appendix C indicates the number of geographic units by province and territory for the 2011 Census. These data were verified within the 2011 Census Geographic Attribute File.