The Master Address Repository (MAR) serves as the source repository for addressing information in the District. The MAR provides District agencies with an authoritative single source for accurate address data within the District of Columbia. Each address contained in the Master Address Repository is linked to a specific geographic feature that is contained within the DC GIS central database.

Agencies are encouraged to adhere to the following guidelines when creating or appending geospatial data by geocoding addresses:

• Use the MAR (point geocoding against address points) as the primary method for geocoding.
• If the above method fails, use the MAR to validate individual address components (street name, quad, zip code, etc) and rerun.
• Use interpolation between address points as the secondary method of geocoding.
• Use street centerlines address ranges as the tertiary method of geocoding.
• Note in the record which of the above methods was used to geocode each point.
• If geocoding against the MAR was successful, store the AID (address identification number) returned by the MAR in your local database.
• If the MAR fails or returns suspect results, report them to DC GIS.