Research
The effects of local street network characteristics on the positional accuracy of automated geocoding for geographic health studies
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* Corresponding author: Dale L Zimmerman dale-zimmerman@uiowa.edu
1 Department of Statistics and Actuarial Science, University of Iowa, Iowa City, IA 52242, USA
2 Department of Biostatistics, University of Iowa, Iowa City, IA 52242, USA
3 Center for Health Policy and Research, University of Iowa, Iowa City, IA 52242, USA
International Journal of Health Geographics 2010, 9:10 doi:10.1186/1476-072X-9-10
Published: 16 February 2010Abstract
Background
Automated geocoding of patient addresses for the purpose of conducting spatial epidemiologic studies results in positional errors. It is well documented that errors tend to be larger in rural areas than in cities, but possible effects of local characteristics of the street network, such as street intersection density and street length, on errors have not yet been documented. Our study quantifies effects of these local street network characteristics on the means and the entire probability distributions of positional errors, using regression methods and tolerance intervals/regions, for more than 6000 geocoded patient addresses from an Iowa county.
Results
Positional errors were determined for 6376 addresses in Carroll County, Iowa, as the vector difference between each 100%-matched automated geocode and its ground-truthed location. Mean positional error magnitude was inversely related to proximate street intersection density. This effect was statistically significant for both rural and municipal addresses, but more so for the former. Also, the effect of street segment length on geocoding accuracy was statistically significant for municipal, but not rural, addresses; for municipal addresses mean error magnitude increased with length.
Conclusion
Local street network characteristics may have statistically significant effects on geocoding accuracy in some places, but not others. Even in those locales where their effects are statistically significant, street network characteristics may explain a relatively small portion of the variability among geocoding errors. It appears that additional factors besides rurality and local street network characteristics affect accuracy in general.