// Returns null if the runway or the opposite runway cannot be found.
public static double?GetSlopePercent(this IAirport a, string runway)
{
var rwy = a.FindRwy(runway);
if (rwy == null)
{
return(null);
}
var oppositeId = RwyIdentConversion.RwyIdentOppositeDir(runway);
if (oppositeId == null)
{
return(null);
}
var opposite = a.FindRwy(oppositeId);
if (opposite == null)
{
return(null);
}
return((opposite.ElevationFt - rwy.ElevationFt) * 100.0 / rwy.LengthFt);
}