About Airport Boundaries
From X-Plane Wiki
Boundary Polygon in apt.dat and Global Scenery
When we make the global scenery, we apply special processing to the surface area of airports, as defined by their boundary.
- The elevation of the airport area is pre-processed to remove bumps and radar spikes (flattened)*.
- The terrain type is set to airport grass.
Before the apt.dat 850 file format, the airport boundary was calculated by taking all of the airport pavement and adding a buffer region. But with the apt.dat 850 file it is possible for an author to draw the airport boundary by hand.
Guidelines for drawing the airport boundary:
- The airport boundary should match a visual boundary between cleared airport area and surrounding terrain.
- The airport boundary should include any airport-related buildings, so that the elevation near terminals is well-controlled.
- The airport boundary does not need to be very detailed - the boundary is slightly blended in the DSF file.
This picture shows a possible boundary for BWI. Note that the forest areas are probably on the property of the airport legally, but are not part of the airport boundary in the diagram so that the trees are not replaced with grass when the airport is built.
If you make an X-Plane 850 airport layout, you should create a boundary polygon to indicate where the global scenery should stop and the airport should start.
Drawing a Boundary in WED
See the Airport Creation tutorial for information on drawing an airport boundary in World Editor.