Building Your Airport4 min read
Ground cover
Ground cover is a free natural-surface polygon laid under your whole airport. It replaces the aerial photo beneath your runways and aprons - which is often ugly, mismatched, or shows the farm that used to be there - with clean, consistent ground. It never draws from your materials.
What it is
Press Gto open the Ground tool. The satellite imagery under a new airport rarely matches what you're building: seams between photo passes, old field boundaries, roads that no longer make sense. Ground cover paints over all of it with one natural surface, so runways and aprons sit on ground that belongs to them. Because it's a free layer, use it on every airport - there is no reason not to.
Controls
- Enable ground cover - the master checkbox.
- Surface swatch - pick from the free natural surfaces: grass, dirt, or gravel.
- Corner rounding- slider from 0 (sharp) up to the maximum; softens the outline's corners.
- Edge blend - a feather slider that fades the cover into the surrounding terrain. 0 gives a hard edge.
- Margin around features- in auto mode, how much breathing room the boundary keeps around everything you've built.
Shaping the boundary
By default the boundary is automatic: a rectangle sized around everything you've built, plus the margin. As your airport grows, it grows.
Going custom
Drag any green corner and the boundary switches to a custom outline you fully control. Grab the + handle on an edge to add a corner - useful for routing the cover around something you want to keep, like a real pond. Alt-click removes a corner. Clicking a corner opens a per-corner rounding override: This corner sets its own radius, Follow boundary slider returns it to the global setting.
Changed your mind? Reset to auto throws away the custom outline and returns to the automatic rectangle.
What happens automatically
Separate from the cover polygon, every airport gets ground preparation on by default:
- Terrain flattening with a 35 m falloff, so the field sits level and eases back into the landscape at its edge.
- Clutter exclusion across the whole buildable circle: auto-generated buildings, vegetation, roads and their traffic, street lights, powerlines, and parked cars are all removed, so your field sits on clean ground instead of streaming-photogrammetry debris.
Making it look hand-laid
A sharp-cornered rectangle with a hard edge reads as stamped onto the world. Some corner rounding plus a generous edge blend makes the same field look hand-laid - the cover fades into the surrounding terrain instead of ending at a fence line that isn't there. It's the cheapest realism upgrade in the builder, because it costs nothing at all.