One of the more interesting features of Invasion is how the Defenders can observe the Invaders' movements off their initial spawns. As mentioned before, Tier 1 is much like a duck shoot where the incentive to move out of the initial Spawn Hive is created by the Defenders' Line Of Sight to those Hives. But it is the elevation that I want to discuss here and how it is used to permit the observation of the Invaders' initial movements to setup for a coordinated defense.
For Boneyard and Spire, the Defenders enjoy the elevated position looking down upon the Invaders' Spawn Hives. From that location, they can observe where the individual Fire Teams move initially. For example, does the middle team move toward Alpha or Bravo? On Breakpoint, the Invaders enjoy the elevation above the Objectives and Defenders, but again the Defenders can observe the Invaders' initial direction of movement.
In each case, those elevations enable observing over the obstacles that the Invaders use for cover as they make their approach toward the Objectives. It doesn't matter who has the elevation, but what matters is that the initial movement of the Invaders can be observed before the Invaders slip into the cover of the rocks, cliff elevations, and structures leading toward forward positions near the Objectives.
So while each map provides cover against the Defenders' Line Of Sight, they also provide elevation by which to observe the initial movements of each Invader over that same cover until the Invaders move forward.
A map that has the Invaders spawning at the same elevation as the Defenders tends to prevent or seriously hinder any Line Of Sight over the cover of the Invaders' approach. The Defenders have a very difficult time observing and reporting amongst each other what the Invaders are doing. This in turn will retard the Defenders' ability to setup for a meaningful defense. These problems of relatively flat terrain are found along side the Island and the Canyon - the very places where an Invasion map must be forged due to the enormous space requirements.
One way to compensate is to elevate the Objectives onto a platform that the Defenders spawn or operate from, like on Boneyard. Another method is to create a large rock (or two) by which a Defender can climb upon to observe over the Approach's cover. But such a position of elevation must not be too far forward, lest Defenders fear abandoning their Objectives and never use them.
Summary
1. A key Game Element to help support team work is to allow the Defenders to observe the Invaders' initial movement directions so that they can setup for a meaningful defense.
2. Elevation at one end or the other is typically the means used to enable this initial observation over the obstacles that provide cover for the Invaders as they approach the Objectives.
3. Any position of elevation to observe Invader's initial movements out of their Spawn Hive must not be too far from the Defenders' Objective lest many simply be too afraid to ever use them.