Iowa Department of TransportationThe Horizontal surface is a plane 150' above the established airport elevation. The perimeter of which is constructed by swinging arcs of specified radii from the center of each end of the primary surface and connecting adjacent arcs by lines tangent to those arcs.ArcGIS FeatureLayerhttps://hub.arcgis.com/datasets/a56a8a7952fa441bb3681050a48ea2c4_0engIowa Department of TransportationPublicAirport Horizontal Surface [Iowa]Web servicesIowaLast Modified: 2020-06-11