Trace Address Search Issues

Address Found in the Wrong City

In some cases, an address search in OsmAnd may return results for a different city than expected. These issues arise due to how city boundaries are defined and processed in OpenStreetMap (OSM). If a user searches for a street name or a street with a house number without specifying a city, the full-text search algorithm may return a match from another city.

Related Issues

Instances of incorrect city assignments have been reported in the following GitHub issues: 10679, 10677, 10699, 10921.

How OsmAnd Identifies City Boundaries

OsmAnd determines a city’s boundary using its administrative relation in OpenStreetMap. For a boundary to be considered valid, it must meet the following criteria:

• The boundary relation must include the tags:

  • boundary = administrative or postal_code
  • place = [city, town, village, hamlet, etc.]

• The boundary relation must contain a relation member:

  • label
  • admin_centre or admin_center

• The name of the boundary relation must exactly match the place-node name.

• If these conditions are not met, the boundary relation is not recognized as a city boundary.

• Among overlapping boundaries, OsmAnd selects the largest boundary.

• The relation ways define the boundary. OsmAnd supports both inner and outer ways.

Exact Name Matching

For accurate address processing, street names must match exactly, including:

• Differences in diacritic marks (e.g., Rue André Chenier vs. Rue André Chénier).
• Variations in prefixes and abbreviations.

If a mismatch occurs, one of the following issues may arise:

• The house is assigned to the wrong street.
• The same street appears multiple times in different city boundaries.

See GitHub issue 10036 for an example.

Possible Causes of Incorrect City Assignments

Issues in OpenStreetMap

1. Broken or missing city boundaries.

   • If city boundaries are incomplete, incorrect, or missing, address assignments may be unreliable.
   • Solution: Follow the OSM boundary fixing guide.
   • Example: 10699.

2. City boundaries do not correctly overlap.

   • If a street belongs to two cities but is mapped incorrectly, OsmAnd may not recognize the overlap.
   • Solution: Adjust city boundaries in OpenStreetMap to ensure they correctly encompass shared streets.

3. Missing required tags in the boundary relation.

   • If a relation lacks essential tags such as boundary=administrative or place=city, it will not be used.
   • Examples:
     • Issue 10921 (missing tags).
     • Issue 12548 (Erfstadt boundary issue).

Issues in OsmAnd

Addresses assigned to neighboring cities.

• Cities, towns, villages, or suburbs in proximity may incorrectly inherit addresses due to boundary overlaps or missing boundaries.
• This is common when cities are divided into administrative areas but lack clearly defined OSM relations.
• See related reports: 10559, 10679, 10730.

Verification Methods

To verify and troubleshoot city boundary issues, compare results from different map tools.

Using OpenStreetMap

Example: Address searched: Wolności 223, Zabrze

1. Open OpenStreetMap (OSM).
2. Search for Zabrze and select the result associated with an administrative boundary.
3. View the city boundary to confirm whether the address is correctly assigned.

Using Nominatim

Example: Address searched: Wolności 223, Zabrze

1. Search for the street and house number without specifying the city.
2. If the search result places the address in another city, note the suggested city name.
3. Enter the found city name in Nominatim.
4. Check the Address Rank value:
   • Example: Wolności, Maciejów
   • If Maciejów is listed as suburb/hamlet (rank 20), it is a smaller administrative division of another city.

Important: Be cautious when selecting search results, as cities with similar names may exist in different regions or countries.

US Address Search and TIGER Data

OsmAnd uses OpenStreetMap data for address searches, with additional data sources such as TIGER (Topologically Integrated Geographic Encoding and Referencing System) from the U.S. Census Bureau. This dataset is range-based and does not contain precise house numbers. Some addresses may be missing or inaccurate.

Solving issues with U.S. addresses:

1. The entered address is split into components: [House Number] [Street Name], [City], [State], [ZIP Code]

2. The system first checks OSM for an exact match with house numbers and streets.

3. If no match is found in OSM, the system searches TIGER data, which includes:

   • Street names and classifications.
   • Interpolated house number ranges.
   • Administrative boundaries.

4. If a house number is missing, OsmAnd estimates its location based on nearby data.

5. Returning results:

   • If the address exists in OSM, an exact match is displayed.
   • If only TIGER data is available, an approximate result is provided.
   • If neither source contains the address, the search fails.

Types of Address Data in TIGER

TIGER Data Type	Usage in OsmAnd
Street names	Used for name-based searches.
House number ranges	Provides approximate address locations.
ZIP Codes	Helps associate addresses with correct postal areas.
Administrative boundaries	Determines city and state locations.

When an Address is Found vs. Not Found

Search Scenario	Result in OsmAnd
Address exists in OSM with house number and street	✅ Exact match
Address exists in TIGER but lacks house numbers	⚠️ Approximate match using interpolation
Address exists in TIGER but contains incorrect data	⚠️ Partial match with errors
Address is missing from both OSM and TIGER	❌ No result

Limitations of TIGER Data in OsmAnd

Several factors affect the accuracy of address searches in the TIGER-based system:

• Missing house numbers. Many addresses in TIGER rely on interpolation, leading to approximate locations.

• Outdated street names. Road names in TIGER may not reflect current naming conventions in OSM.

• ZIP Code mismatches. Boundaries in TIGER may be incorrect, causing incorrect ZIP code assignments.