Square Map Distance

In Freeciv, Square Map Distance is a shortcut measurement for mechanics that measure in Euclidean Distance. Square Map Distance is simply (Euclidean Distance)2. By avoiding square roots required in Euclidean distance formulas, the use of Square Map Distance can model the exact same results while avoiding 1) decimal places, 2) slower CPU calculations with floating point arithmetic, and 3) extra CPU processing when needing to take a square root for every calculation. 
Square Map Distance is simply a proxy for measuring the exact same thing as Euclidean Distance. A player of the game should simply think of Square Map Distance as (Euclidean Distance)2. For example, a Square Map Distance of 5 represents: 
SMD = 22 +12 = 5 
* In other words, the distance when the destination tile is a distance of (1,2) or (2,1). The true or Euclidean distance of this is √5. 
Please see the article on Euclidean Distance for more info.