If you've done much searching for locations using web tools--and who hasn't by now--you've likely discovered some errors along the way. Sometimes a map marker is down the street from the actual location. Geocoding, the process of converting an address to latitude/longitude coordinates, can be an inexact science. A new geocoding service from MapQuest (our MapQuest API profile) aims to help you improve where you place that marker with Address Point Data.
MapQuest Product Manager Antony Pegg explains how geocoding without point data works:
Regular geocoding data does not actually contain every single address on a road. Instead, it normally contains the length of the road, and the range of house numbers along the length or the road (e.g: 1-99 Main Street). So if you looked for 50 Main Street, math would be used to work out the approximate location of where #50 probably is between #1 and #99
The post also contains several images that show how different regular geocoding can be from point data geocoding. For example, in the image above, the red star represents a regular geocoded result. The green star shows the more accurate point (the smaller blue star), connected to the green one, is the center of that address' land parcel.
Google lets users of its Maps product edit address points. It is not clear whether this data makes it back to developers via the geocoder in the Google Maps API, or whether Google keeps the data only for its own use. One could argue it wouldn't be a good idea for Google to pass along unverified information as fact. The fact that this feature exists highlights the challenges all mapping providers face in real-world geolocation.
MapQuest's point data is based on the parcels, making it reliable data at that level. Like many new developer features from MapQuest like their real-time traffic data, its new geocoder is in beta. If you want to add more accurate geocoding to your applications, give it a try and let them know how it works for you.