Open Access Highly Accessed Methodology

Accuracy of city postal code coordinates as a proxy for location of residence

C Jennifer D Bow24, Nigel M Waters24, Peter D Faris4, Judy E Seidel34, P Diane Galbraith4, Merril L Knudtson14, William A Ghali134* and the APPROACH Investigators

Author Affiliations

1 Department of Medicine, University of Calgary, 3330 Hospital Drive NW, Calgary, AB, T2N 4N1, Canada

2 Department of Geography, University of Calgary, 2500 University Drive NW, Calgary, AB, T2N 1N4, Canada

3 Department of Community Health Sciences, University of Calgary, 3330 Hospital Drive NW, Calgary, AB, T2N 4N1, Canada

4 Centre for Health and Policy Studies, Faculty of Medicine, Department of Community Health Sciences, University of Calgary, 3330 Hospital Drive NW, Calgary, AB, T2N 4N1, Canada

For all author emails, please log on.

International Journal of Health Geographics 2004, 3:5  doi:10.1186/1476-072X-3-5

Published: 18 March 2004

Abstract

Background

Health studies sometimes rely on postal code location as a proxy for the location of residence. This study compares the postal code location to that of the street address using a database from the Alberta Provincial Project for Outcome Assessment in Coronary Heart Disease (APPROACH©). Cardiac catheterization cases in an urban Canadian City were used for calendar year 1999. We determined location in meters for both the address (using the City of Calgary Street Network File in ArcView 3.2) and postal code location (using Statistic Canada's Postal Code Conversion File).

Results

The distance between the two estimates of location for each case were measured and it was found that 87.9% of the postal code locations were within 200 meters of the true address location (straight line distances) and 96.5% were within 500 meters of the address location (straight line distances).

Conclusions

We conclude that postal code locations are a reasonably accurate proxy for address location. However, there may be research questions for which a more accurate description of location is required.

Keywords:
Geographic Location; Postal Code; GIS (Geographical Information Systems)