Coordinates stored with six or more decimal places of precision

Storing latitude and longitude with fewer than 6 decimal places introduces systematic positional error. At 4 decimal places the precision is approximately 11 meters — enough to place a marker across the street or in an adjacent building. At 2 decimal places it is roughly 1.1 kilometers, which can misplace a marker in the wrong neighborhood entirely. CWE-681 (Incorrect Conversion between Numeric Types) applies when floating-point coordinates are truncated into low-precision columns. ISO 25010:2011 functional-suitability is violated because the directory cannot reliably represent the physical location of a listing. For delivery, navigation, and accessibility use cases, 11-meter error is operationally significant.

Define latitude and longitude columns with at least 8 decimal places, or use a PostGIS geography type which stores full double-precision coordinates internally.

-- Option 1: explicit decimal columns
ALTER TABLE listings
  ADD COLUMN latitude DECIMAL(10, 8),
  ADD COLUMN longitude DECIMAL(11, 8);

-- Option 2: PostGIS geography (preferred for spatial queries)
ALTER TABLE listings
  ADD COLUMN location GEOGRAPHY(POINT, 4326);

DECIMAL(10, 8) gives 8 decimal places (approximately 1.1mm accuracy). If columns already exist with low precision, migrate the type: ALTER TABLE listings ALTER COLUMN latitude TYPE DECIMAL(10, 8). Verify existing data after migration — low-precision values will not gain precision retroactively and may need re-geocoding.