Geocoding is a method of distinguishing one type of geographic information from other geographic information. By using known locations, such as street addresses or property information, it is possible to extrapolate coordinates. These coordinates can then be added to a global positioning or navigation system. Geocoding is vital to certain types of modern emergency response systems and decentralized navigation platforms. Geocoding has, however, generated controversy surrounding certain methods of its use.
Geocoding generally works via two methods, interpolation and triangulation. An interpolated location is common when dealing with cities and addresses. If an address is required and the system already knows an address to either side on the same street, it can use that information to find the required location. Since addresses numbers are a set distance from one another and alternate down the street, the program simply calculates how many numbers the required address is from the known addresses. This is why many global positioning systems (GPS) specifically target intersections.
Interpolation is common in emergency response systems. These systems know the caller’s address from the computer system. The address is then entered into a geocoding system where other known addresses are used to find its coordinates. This information is then entered into a navigation system that sends the emergency team where they need to go. Cell phones use reverse geocoding — it provides coordinates and the software finds its location.
The second common method is triangulation. This method is typically used in locations where there aren’t any linear connection points. In this case, the exact location is determined through other nearby spots. The software takes nearby known coordinates and triangulates the position of the new spot. The more nearby locations the system knows, the more accurate the results.
Triangulation based geocoding is a common feature in most handheld GPS receivers. These systems use the chip within the unit to find the base coordinates. These coordinates are then verified using a triangulation of other known coordinates in the area. This form of geocoding also works well when planning wilderness trips, as coordinates can be identified before entering the area allowing for easier navigation to a desired destination.
Geocoding, particularly interpolation, allows users to gain a surprising amount of personal information. Using these systems, combined with other open databases, it becomes possible to track a person quite easily. This is particularly common for individuals who have committed crimes that require local registration. As a result, several watchdog groups feel that geocoding, and many other geographic systems, invade people’s privacy and need tighter regulations.