Accuracy of residential geocoding in the Agricultural Health Study

Table 4 Distribution of positional error (meters) ^a of geocoded addresses in Iowa and North Carolina from two subcohorts within the Agricultural Health Study, overall and by rural status

				Positional Error (m)
GPS vs. Address-Matched Geocode	N	%	Min	Mean	SD	Median (IQR)	Max	IQR	Percent ≤100 m	Percent ≥1000 m
Overall
Iowa	1917	73.1	1	348	1178	131 (65–287)	28556	222	39	4
North Carolina	707	26.9	5	272	1189	99 (53–210)	20695	156	50	4
Rural ^b
Iowa	1583	82.6	6	406	1288	153 (84–344)	28556	260	30	5
North Carolina	637	90.1	5	262	981	105 (57–218)	20695	161	48	4
Non-rural
Iowa	334	17.4	1	77	125	49 (29–82)	1673	53	81	0
North Carolina	70	9.9	9	362	2362	55 (24–112)	19830	88	71	1

^aPositional error was determined by comparing global positioning system (GPS) coordinates taken at the entrance to the home to geocoded address coordinates using the NAVTEQ street database.
^bRural status was based on GPS location.

ISSN: 1476-072X