NINearbyObject.VerticalDirectionEstimate.unknown An indication that the nearby object resides at an unknown vertical location. Declarationcase unknown See AlsoRelative vertical locationNINearbyObject.VerticalDirectionEstimate.sameNINearbyObject.VerticalDirectionEstimate.aboveNINearbyObject.VerticalDirectionEstimate.belowNINearbyObject.VerticalDirectionEstimate.aboveOrBelow