What Is Reverse Geocoding?

Reverse geocoding is the process of turning a pair of coordinates into a human-readable description of the place, such as a street address, a neighbourhood or a landmark name. It is the mirror image of geocoding, which starts with text and ends with coordinates.

How it works

A reverse geocoder takes a latitude and longitude and searches a reference dataset for the closest matches. The dataset may include:

• Address points for individual buildings
• Road segments with house-number ranges
• Place and neighbourhood boundaries
• Postcode areas, towns, regions and countries

The service picks the nearest suitable feature, or several of them, and assembles a label. The result might be a full address, or only a street and town when no building is nearby.

What you usually get back

Typical outputs include:

• A formatted address line
• Individual parts such as street, locality, region, postcode and country
• A type that says what was matched, for example building, street or area
• A distance or confidence value, depending on the provider

Where it is used

• Showing the address after you drop a pin on a map
• Labelling where a photo was taken or where a delivery was made
• Pre-filling an address form from a phone's current position
• Mapping a position to a country or region, which also helps decide whether a service is available there

Limits to keep in mind

Reverse geocoding returns the closest thing the database knows, not necessarily the address of that exact point. In places with sparse address data, the result may be a road name only, or a street some distance away. Near the borders of neighbouring properties, the nearest address may belong to the building next door. A related guide, reverse-geocoded address vs real address, explores this in detail.

Accuracy also depends on the quality of the input coordinates. A reading that is off by 30 m because of urban canyon effects will produce an address for the wrong place.

How it relates to location codes

A location code and a reverse-geocoded address answer different questions. The code identifies a specific 3 m by 3 m cell and is the same however the surrounding addresses are written. The address is a label that humans and delivery staff are used to reading. UPCS can show both, and the embeddable map returns an address value alongside the code, but the code is the exact-location part.