During the initial reconstruction of the Gaia, formally known as Earth before the war, the World Government assigned the remaining countries a numerical identifier for simple communication.

  Examples:

  

  
• Sector 9 = Japan


  
• Sector 1 = United Kingdom


  
• Sector 5 = United States


  
• Sector 8 = China


  

  To identify individual cities within a sector, a directional tag was added:

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• A = North


  
• B = East


  
• C = South


  
• D = West


  

  This creates combined identifiers:

  

  
• Sector 1C = United Kingdom, South (London)


  
• Sector 9B = Japan, east (New Tokyo)


  

  Each directional tag is further subdivided into smaller units called outposts.

  For example, the city of Blackreach is assigned the numerical value 7, with the directional tag A (North). Following this logic:

  

  
• Outpost 7A, Sector 9B is located in East Japan, north of New Tokyo.