Strickland Matthew J, Siffel Csaba, Gardner Bennett R, Berzen Alissa K, Correa Adolfo
National Center on Birth Defects and Developmental Disabilities, Centers for Disease Control and Prevention, Atlanta, Georgia, USA.
Environ Health. 2007 Apr 4;6:10. doi: 10.1186/1476-069X-6-10.
The Metropolitan Atlanta Congenital Defects Program (MACDP) collects maternal address information at the time of delivery for infants and fetuses with birth defects. These addresses have been geocoded by two independent agencies: (1) the Georgia Division of Public Health Office of Health Information and Policy (OHIP) and (2) a commercial vendor. Geographic information system (GIS) methods were used to quantify uncertainty in the two sets of geocodes using orthoimagery and tax parcel datasets.
We sampled 599 infants and fetuses with birth defects delivered during 1994-2002 with maternal residence in either Fulton or Gwinnett County. Tax parcel datasets were obtained from the tax assessor's offices of Fulton and Gwinnett County. High-resolution orthoimagery for these counties was acquired from the U.S. Geological Survey. For each of the 599 addresses we attempted to locate the tax parcel corresponding to the maternal address. If the tax parcel was identified the distance and the angle between the geocode and the residence were calculated. We used simulated data to characterize the impact of geocode location error. In each county 5,000 geocodes were generated and assigned their corresponding Census 2000 tract. Each geocode was then displaced at a random angle by a random distance drawn from the distribution of observed geocode location errors. The census tract of the displaced geocode was determined. We repeated this process 5,000 times and report the percentage of geocodes that resolved into incorrect census tracts.
Median location error was less than 100 meters for both OHIP and commercial vendor geocodes; the distribution of angles appeared uniform. Median location error was approximately 35% larger in Gwinnett (a suburban county) relative to Fulton (a county with urban and suburban areas). Location error occasionally caused the simulated geocodes to be displaced into incorrect census tracts; the median percentage of geocodes resolving into incorrect census tracts ranged between 4.5% and 5.3%, depending upon the county and geocoding agency.
Geocode location uncertainty can be estimated using tax parcel databases in a GIS. This approach is a viable alternative to global positioning system field validation of geocodes.
大亚特兰大先天性缺陷项目（MACDP）在分娩时收集患有出生缺陷的婴儿和胎儿的母亲住址信息。这些住址已由两个独立机构进行地理编码：（1）佐治亚州公共卫生部健康信息与政策办公室（OHIP）；（2）一家商业供应商。利用地理信息系统（GIS）方法，借助正射影像和税 parcel 数据集对两组地理编码中的不确定性进行量化。
我们对1994年至2002年期间在富尔顿或格温内特县分娩的599名患有出生缺陷的婴儿和胎儿进行了抽样。税 parcel 数据集来自富尔顿和格温内特县的税务评估办公室。这些县的高分辨率正射影像由美国地质调查局获取。对于599个住址中的每一个，我们试图找到与母亲住址对应的税 parcel。如果找到了税 parcel，则计算地理编码与住址之间的距离和角度。我们使用模拟数据来描述地理编码位置误差的影响。在每个县生成5000个地理编码，并为其分配相应的2000年人口普查区。然后，每个地理编码以随机角度移动一个从观察到的地理编码位置误差分布中抽取的随机距离。确定移动后地理编码的人口普查区。我们重复这个过程5000次，并报告解析为错误人口普查区的地理编码的百分比。
OHIP和商业供应商的地理编码的中位位置误差均小于100米；角度分布似乎是均匀的。相对于富尔顿（一个既有城市又有郊区的县），格温内特（一个郊区县）的中位位置误差大约大35%。位置误差偶尔会导致模拟的地理编码被移动到错误的人口普查区；解析为错误人口普查区的地理编码的中位百分比在4.5%至5.3%之间，具体取决于县和地理编码机构。
可以使用GIS中的税 parcel 数据库来估计地理编码位置的不确定性。这种方法是对地理编码进行全球定位系统实地验证的一种可行替代方法。
