Abstract
Many studies examining the food retail environment rely on geographic information system (GIS) databases for location information. The purpose of this study was to validate information provided by two GIS databases, comparing the positional accuracy of food service places within a 1 km circular buffer surrounding 34 schools in Ontario, Canada. A commercial database (InfoCanada) and an online database (Yellow Pages) provided the addresses of food service places. Actual locations were measured using a global positioning system (GPS) device. The InfoCanada and Yellow Pages GIS databases provided the locations for 973 and 675 food service places, respectively. Overall, 749 (77.1%) and 595 (88.2%) of these were located in the field. The online database had a higher proportion of food service places found in the field. The GIS locations of 25% of the food service places were located within approximately 15 m of their actual location, 50% were within 25 m, and 75% were within 50 m. This validation study provided a detailed assessment of errors in the measurement of the location of food service places in the two databases. The location information was more accurate for the online database, however, when matching criteria were more conservative, there were no observed differences in error between the databases.
Highlights
The built environment in which people live can have a major influence on obesity and its behavioral determinants, physical activity and diet [1]
The proportion of all categories of food service places found within the 1 km buffer was higher for the Yellow Pages database, with the exception of convenience stores (Table 1)
For urban schools, the proportion of limited-service restaurants in the Yellow Pages database that were within 100 m of their true location was 77%; 53% were within 50 m and only
Summary
The built environment in which people live can have a major influence on obesity and its behavioral determinants, physical activity and diet [1]. Many of the existing studies classified food service places as present or absent at their listed address, rather than measuring distances between the true and reported locations. This approach does not provide information on whether the true location of the food service place is a few meters or several meters away from the listed location. This has important implications for whether people can access the food service places by walking. Our study objective was to evaluate the positional accuracy of the geocoded addresses of food service places provided by two GIS databases in urban and non-urban areas
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