5. Data quality

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Lineage
Positional accuracy
Attribute accuracy
Logical consistency
Completeness

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

Lineage

Lineage describes the history of the linkage 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 digital files.

Sources

The sources used to derive the Postal Codes^OM by Federal Ridings File (PCFRF) are as follows:

• The November 2014 Postal Code^OM Conversion File (PCCF) links postal codes^OM (provided by Canada Post Corporation [CPC] on the Address Lookup File updated to November 2014) to geographic codes for all 2011 Census geographic areas, including province and federal electoral district 2003 Representative Order codes. The November 2014 PCCF contains over 1.7 million postal code^OM records linked to the geographic areas used in the 2011 Census. These geographical areas have a reference date of January 1, 2011, except for the Federal electoral district – 2003 Representation Order.
• The PCFRF contains postal code^OM data under license from Canada Post Corporation. The most recent Canada Post Corporation file from which this data is copied is dated November 2014.
• Federal electoral district (FED) names are derived from the Statistical Registers and Geography Division's Spatial Data Infrastructure. The source of the geographic names and codes of federal electoral districts is the 2013 Representation Order of the Chief Electoral Office, Elections Canada. The Spatial Data Infrastructure contains a table with the name of each federal electoral district and its associated identification code. This table is updated based on name changes provided by Elections Canada. Where changes to the electoral boundaries have been provided by Elections Canada, the correspondence between the federal electoral district and postal codes^OM is updated.
• The 2011 Census of Population is used as a source for deriving the weights. When a postal code^OM is linked in the PCFRF to more than one FED, the number of persons reporting the postal code^OM in the census may be used to derive the weights.

Method of derivation

The updated Postal CodesOM by Federal Ridings File (PCFRF) was created by converting the existing federal electoral districts (2003 Representation Order) and their linked postal CodesOM to the new federal electoral districts (2013 Representation Order), transferring the postal CodesOM linkages. The conversion process was accomplished using 2011 Census Dissemination Blocks and a best fit methodology for dissemination blocks that were found in more than one federal electoral district. During the conversion process, in cases where dissemination blocks overlapped two or more federal electoral districts (2013 Representation Order), a complete allocation was made of the dissemination block to one FED based on the population count or the area of the dissemination block found in each FED.

Positional accuracy

Not applicable

Attribute accuracy

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

The attribute accuracy of the PCFRF is dependent on the accuracy of the geocodes for the dissemination blocks and dissemination areas in the PCCF. The linkage of the dissemination blocks or dissemination areas to the FEDs is based on the boundaries of the FEDs as found in the Spatial Data Infrastructure.

The accuracy of the weight variable is based on the linkage to the FED in the PCFRF, the population reporting the postal code^OM in the census as well as address range data in Canada Post's Address Lookup File.

The population on which the weight variable in the PCFRF is based was derived from the total population data of the 2011 Census. Population counts are determined according to the 'de jure' method. This means that people are enumerated at their usual place of residence, regardless of where they may have been on Census Day, May 10, 2011. For more information on the quality of 2011 Census data, see Appendix C in the 2011 Census Dictionary.

If a postal code^OM is linked to more than one FED in the PCFRF and was not reported in the census, address range data from the Address Lookup File is used to estimate the weight. This is the case for about 1% of the postal codes^OM in the PCFRF. Because large populations residing in apartments or collective dwelling units may be represented by only one address, this method can underestimate the weight associated with these populations.

Logical consistency

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

Of the 845,603 active postal codes^OM found on this file, there are 843,128 active postal codes^OM uniquely linked to one federal electoral district and 2,475 active postal codes^OM that are linked to two or more federal electoral districts. The following table summarizes them.

Table 5.1
Count of postal codes^OM linked to federal electoral districts Table summary
This table displays the results of Table 5.1 Count of postal codes linked to federal electoral districts. The information is grouped by Number of federal electoral districts (appearing as row headers), Active postal codes and Number of records (appearing as column headers).

Number of federal electoral districts	Active postal codesOM	Number of records
1	843,128	843,128
2	2,126	4,252
3	292	876
4	25	100
5	19	95
6	13	78
Total	845,603	848,529

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.

Completeness in the context of the PCFRF is the degree to which all valid postal codes^OM are accounted for. Almost all postal codes^OM, valid and active as of November 2014 according to Canada Post Corporation, have been linked to census geography.

There are 338 FEDs in the 2013 Representation Order of the Chief Electoral Office, Elections Canada. All of these FEDs are included in the PCFRF.