Exploiting online sources to accurately geocode addresses

Many Geographic Information System (GIS) applications require the conversion of an address to geographic coordinates. This process is called geocoding. The traditional geocoding method uses a street vector data source, such as, Tigerlines, to obtain address range and coordinates of the street segment on which the given address is located. Next, an approximation technique is used to estimate the location of the given address using the address range of the selected street segment. However, this provides inaccurate results since the approximation assumes that properties exist at all possible addresses and all properties are of equal size. To address the inaccuracy of the traditional geocoding approach, we propose two new methods for geocoding using additional online data sources. The first method, the uniform-lot-size method, uses the number of addresses/lots present on the street segment to approximate the location of an address. The second method, the actual-lot-size method, takes into consideration the lot sizes on the street segment and the orientation of the lots as well. Moreover, we describe an implementation of these methods using an information mediator to obtain information about actual number of lots and sizes of the lots on the streets from various property tax web sites. We geocoded an area covering 13 blocks (267 addresses) using all three methods. Our evaluation shows that the traditional method results in an average error of 36.85 meters, while the uniform-lot-size and the actual-lot-size methods result in the average error of 7.87 meters and 1.63 meters, respectively.