Geocoding Summary

Output file:
US_DC_Sample_geocoded.csv

What was added:
- longitude
- latitude
- geocode_source
- geocode_precision
- geocode_status
- geocode_match_address
- Census audit fields
- Nominatim/OpenStreetMap audit fields

Results:
- 249 total records
- 204 records matched through the U.S. Census Geocoder
- 45 records used city-level fallback coordinates from Nominatim/OpenStreetMap
- 0 records are missing coordinates
- Final CSV has 38 columns with consistent row width

Precision notes:
- Census matches are marked geocode_precision=address_range.
- Census coordinates are interpolated address-range coordinates, not guaranteed rooftop or building-centroid coordinates.
- Nominatim fallback records are marked geocode_precision=city.
- City-level fallback coordinates should not be treated as facility-level locations.

Status values:
- census_match: Census returned a usable address match.
- census_no_match_city_fallback: Census did not match the submitted street address, so city-level fallback coordinates were used.
- census_tie_city_fallback: Census returned a tie, so city-level fallback coordinates were used instead of selecting one ambiguous address.
- no_street_city_fallback: No usable street address was available, so city-level fallback coordinates were used.

Repair note:
Before geocoding, 3 records were repaired where a street address existed in source_address but had not been parsed into street_address.

Supporting audit files:
- census_address_results.csv
- nominatim_city_cache.csv
- US_DC_Sample_geocoding_base.csv
- census_address_input.csv

Source documentation:
- U.S. Census Geocoder API:
  https://geocoding.geo.census.gov/geocoder/Geocoding_Services_API.html
- Nominatim/OpenStreetMap usage policy:
  https://operations.osmfoundation.org/policies/nominatim/

Attribution note:
If the Nominatim/OpenStreetMap fallback coordinates are published or distributed, include appropriate OpenStreetMap attribution.