Grid Point Code

An address for every door, stall and gate

A shared prefix is a shared cell.

Where streets have no numbers, directions stand in for an address: beside the tea stall, behind the blue gate. Ten characters give every door its own, worked out on any phone with no network.

Khan el-Khalili, Cairo, Egypt30.047489, 31.262223

Without a code
Khan el-Khalili, Cairo, and then directions
Said aloud
Khan el-Khalili 66194

Level 4 · Metropolitan area40.01 km × 53.43 km

Ten characters, ten levels

Every character after the first selects one cell of a five-by-five division of the cell before it. Read the code from the left and the world closes in at a constant rate, which is what makes a prefix mean something.

  1. Level 1Block of the world5,001 km × 6,679 km
  2. Level 2Country1,000 km × 1,336 km
  3. Level 3Region200 km × 267.2 km
  4. Level 4Metropolitan area40.01 km × 53.43 km
  5. Level 5District8.002 km × 10.69 km
  6. Level 6Suburb1.6 km × 2.137 km
  7. Level 7A few streets320 m × 427 m
  8. Level 8Building64 m × 85.5 m
  9. Level 9Entrance12.8 m × 17.1 m
  10. Level 10Doorway2.56 m × 3.42 m