Contact

GlossaryGeography and community profiles

Geocoding

Geocoding turns an address or place description into a map location. Learn why a successful match can still be approximate.

Geocoding assigns a map location to an address or other place description. It commonly produces latitude and longitude coordinates and may identify the geographic areas containing the matched location. The result is a match produced by a method; it is not automatically a direct measurement of where an event occurred.

How an address becomes a point

Different geocoders use different reference information and matching rules. The Census Geocoder, for example, returns coordinates based on matching an address to its geographic reference data. Its user guide explains that coordinates can be interpolated—estimated along an address range—and that a possible address number does not establish an actual structure exists there. Census Geocoder User Guide.

This distinction matters when a dashboard places a small dot on a large-scale map. The dot is a display symbol for the supplied coordinate. Its apparent precision may exceed the location detail in the original record.

Example

Hypothetical: A report lists an address on a street segment. A geocoder matches the street and estimates a coordinate partway along the segment. The dashboard then assigns the point to a neighborhood boundary.

The match may be sufficient for a broad neighborhood summary. It does not necessarily identify a building entrance, a room, or the exact spot where the incident occurred. If the point lies close to a neighborhood boundary, a small positional difference could also change the assigned neighborhood.

Common confusion

Geocoding differs from location masking. Geocoding finds a location representation; masking deliberately changes or reduces location detail for privacy or release purposes. A record may undergo both processes.

Reverse geocoding starts with coordinates and returns an address or place description. That output is also a geographic interpretation, not independent proof of an incident's exact address.

A failed match does not establish that a place is fictitious. Incomplete addresses, spelling differences, new streets, and the reference dataset can affect matching. Unmatched records remain part of the source unless the analysis explicitly excludes them.

Checking a mapped dataset

Look for the matching method, reference-data version, match quality, and number of unmatched records. Distinguish the address originally submitted from the address the geocoder matched. They may differ in meaningful ways.

A public map should state whether locations are exact, approximate, or generalized. When describing a point, use the precision the source supports rather than turning an estimated coordinate into a claim about a specific property.

Sources