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Section 4 Data quality
Archived Content
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Postal code characteristics
Lineage
Attribute accuracy
Logical consistency
Consistency with other products
Completeness
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 elements include an overview describing the purpose and usage, as well as specific quality elements reporting on the lineage, attribute accuracy, logical consistency and completeness. This information is provided to users for all linkage data products disseminated for the census.
Postal code characteristics
Before using the Postal Codes by Federal Ridings File (PCFRF) with administrative files containing postal codes, users should be aware of some characteristics of postal codes that may affect their linkage to federal electoral districts on the PCFRF.
Postal delivery areas do not respect federal electoral district boundaries
A postal delivery area (as represented by the six-character postal code) may straddle one or more federal electoral district boundaries. This means that, in the Postal Code Federal Riding File, the same postal code may be linked to two or more (adjacent) federal electoral districts. Most federal electoral districts are affected in this way in both urban and rural areas. Refer to Logical consistency later in this section for further details.
Postal codes may be associated with post office boxes at a postal station that is not in the same federal electoral district as the client using the post office box
The postal code associated with a lock box (post office box) may be geocoded to the physical location of the associated postal installation (post office). This could be located in a federal electoral district that is different from the ultimate destination of the mail delivery – the residential, industrial, or commercial location of the client renting the lock box.
Canada Post Corporation (CPC) regularly retires postal codes and may also reactivate retired postal codes for use again
Users of the PCFRF must keep in mind that the file contains only the postal codes from CPC that are active as of July 2009.
If the addresses of postal codes in a user's administrative file are not updated to July 2009, there may be non-matches with the PCFRF because some of the postal codes in the user’s file may have been retired, or may even have been reactivated and re-assigned by CPC to another range of addresses outside the riding where they had previously been used.
Statistics Canada maintains an audit trail of the birth dates and retirement dates of postal codes in the PCCF. Users may wish to consult the Postal Code Conversion File (PCCF), Reference Guide (Catalogue no. 92-153-GWE), available on the Statistics Canada website. An updated version of the file including July 2009 postal codes is released in January 2010.
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 PCFRF are as follows:
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The July 2009 PCCF links postal codes (provided by CPC on the Address Lookup File updated to July 2009) to geographic codes for all 2006 Census geographic areas, including province and federal electoral district 2003 Representative Order codes. It also provides the geographic point coordinates representing the postal codes. The July 2009 PCCF contains over 1.6 million postal code records linked to the geographic areas used in the 2006 Census. These geographical areas have a reference date of January 1, 2006, except for the Federal electoral district – 2003 Representation Order.
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The PCFRF contains postal code data under license from Canada Post Corporation. The most recent Canada Post Corporation file from which this data is copied is dated July 2009.
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Federal electoral district names are derived from Geography Division’s Spatial Data Infrastructure. The source of the geographic names and codes of federal electoral districts is the 2003 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 is updated.
- The 2006 Census of Population is used as a source for deriving the weights. When a postal code is linked in the PCFRF to more than one FED, the number of persons reporting the postal code in the census may be used to derive the weights.
Method of derivation
The PCFRF is created by extracting the active postal codes and the related FED codes included in the July 2009 PCCF, containing July 2009 postal codes. Each FED code in this file is linked to the list of federal electoral districts – 2003 Representation Order codes and names. The linkage to the FED on the July 2009 PCCF is based on the dissemination block or dissemination area geocoded in the PCCF.
The resulting PCFRF file contains 834,954 active postal code records of which 819,505 are unique links to one federal electoral district. In total, 7,372 active postal codes (15,449 records) are linked to more than one federal electoral district (further details are provided in Logical consistency later in this section). The number of postal code records by federal electoral district and whether those postal codes are linked to other FEDs is provided in Appendix B, Postal codes by federal electoral district.
The unique link variable is derived based on the postal code and FED codes in the PCFRF. If the postal code is linked to only one FED, the unique link is assigned a value of 1, otherwise it is assigned a value of 2.
The ‘weight’ estimates the proportion of the population of a postal code that resides within each FED.
If a postal code is linked to only one FED in the PCFRF, the weight is equal to 1. If the postal code is linked to more than one FED and is reported in the 2006 Census, the weight is equal to the proportion of the population that reported the postal code in each of the FEDs. If the postal code was not reported in the census, the weight is estimated using the address ranges in the service area of the postal code as found in the Address Lookup File from Canada Post Corporation. If necessary, the weights for a postal code are normalised and adjusted using the Single Link Indicator variable in the PCCF so that the sum of weights equals 1.0.
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 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 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 2006 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 16, 2006. See Appendix E for notes on the quality of the 2006 Census data.
If a postal code 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 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 834,954 active postal code records found on this file, there are 819,505 active postal codes uniquely linked to one federal electoral district and 7,372 active postal codes that are linked to two or more federal electoral districts. The following table summarizes them.
Table 4.1 Count of postal codes linked to federal electoral districts (FEDs)
Consistency with other products
Data contained in the PCFRF are consistent with all 2006 Census related geographic products with the exception of the 2006 Census Forward Sortation Area Boundary File (Catalogue no. 92-170-XWE, XCE), which represents only the forward sortation areas reported in the 2006 Census. The PCFRF is derived from the Postal Code Conversion File (PCCF), and is consistent with that file.
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 are accounted for. All postal codes, valid and active as of July 2009 according to CPC, have been linked to census geography.
There are 308 FEDs in the 2003 Representation Order of the Chief Electoral Office, Elections Canada. All of these FEDs are included in the PCFRF.
The data files are named using a file naming convention described in Section 5, Technical specifications. Each file contains the following number of active postal code records:
Table 4.3 lists abbreviations for the region names used in the data file names and the province and territories that they represent.
