What is a specified geographic surface used for facilitating coordination and deconfliction between units called?

The term used for a specified geographic surface that facilitates coordination and deconfliction between units is referred to as an "Area."

In military operations, an "Area" is designated to provide a clear spatial understanding for units involved in the planning and execution of missions. This allows for effective coordination and reduces the risk of overlap or confusion between units operating in close proximity. The concept of an area is significant in ensuring that each unit has a defined space to operate within, which aids in command and control as well as maintaining situational awareness.

While "Zone," "Sector," and "Region" may describe different geographic or operational spaces, they do not specifically capture the intended purpose of facilitating coordination and deconfliction between units as effectively as "Area" does. Each of those terms has its own context and application within military operations, but "Area" is the most precise for the function described in the question.