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What is Reverse Geocoding?

Background

When we talk about physical locations globally, there are typically two ways of identifying them: addresses and coordinates. An address is a discrete identifier, usually for a building or specific plot of land. For example, you can go to 123 Main Street or 124 Main Street, but there probably is no valid address between them. Valid addresses are typically maintained by the government in which they exist. A coordinate, however, is continuous and agnostic to political boundaries. Coordinates are represented by latitude and longitude values, where the latitude specifies the north-south position (-90° to 90°), and the longitude specifies the east-west position (-180° and 180°). When put together, these coordinates can specify an exact location anywhere on the surface of the Earth regardless of whether or not that location is a valid postal address. 

So why have two systems? Well, each has its benefits. Addresses are beneficial for organization and governance. They are an intuitive way of labeling a place with official semantic meaning (buildings, apartments, land parcels, etc.). They can indeed get complex, but they are created with an organizational scheme that follows prescribed rules (e.g., if you’re at 50 Main Street, you know the numbers will increase in one direction and decrease in the other). Addresses are readable, intuitive, and easy to converse about.

On the other hand, coordinates are relatively meaningless to the human eye; you probably can’t tell where “40.7484° N, 73.9857° W” is just by looking at it. There are several use-cases, though, where coordinates are pretty powerful. Coordinates cover every possible location globally rather than just the official addresses. The format and added precision mean you can quickly determine distances between locations or what timezone a location is in. Their lightweight nature means they are easily stored, analyzed by computer systems, or displayed to users on something like a map. 

So What is Reverse Geocoding?

Reverse Geocoding is the process of converting coordinates into a valid address. It is the opposite of geocoding, which is, as imagined, the process of converting addresses into geographic coordinates. **insert a link to geocoding KB article here**. Reverse geocoding allows the identification of nearby street addresses, places, and/or areal subdivisions such as neighborhoods, county, state, or country. It does so by systematically interpolating the street address from a range of other address data points. It uses the given coordinates to find that aforementioned range that already exists.

Uses of Reverse Geocoding

Building programs that can systematically reverse geocode coordinates can allow businesses and organizations to have real-time data on where their product is located. One of the most common uses is location-based services on your phone. This will enable applications to see where you are, enabling them to better serve you through their software or service. For example, if Yelp knows that you are in a location close to Denver, Colorado, it can provide you with the ten best sushi restaurants to visit. Google leverages GPS data to tell you how busy a restaurant might be at the moment.

When you call an Uber to your current location, the app uses reverse geocoding to take your raw geographic location and turn it into an address that the driver can find. Calling 911 works the same way – your geographic coordinates are obtained from your phone and then reverse geocoded into an address that emergency response personnel can be sent to.

Not every application comes with a built-in GPS, so the integration and utilization of APIs have allowed more companies to benefit from reverse geocoding than ever before. The end-user needs to enter their current coordinates, and API programs can return the closest addresses. This functionality will continue to allow location-based services to gain popularity and profitability