The science of mapmaking, or cartography, is extremely valuable, as it allows players a greater sense of knowledge about the world around them by sharing the maps of other explorers. In Age of Chivalry, this is represented by a valuable effect: a civilization that researches this technology gains shared line of sight with their allies, meaning you see what your allies see as well as what your own units see. This changes with diplomacy; that is, if you gain a new ally you gain his LOS (and vice versa).
Available to: All
Researched at: Market
Effect: Shared LOS w/all allies.