A system comprising: an unmanned aerial vehicle ; and an altimeter disposed on the unmanned aerial vehicle, the altimeter including an ultra-wideband radar antenna disposed orthogonally to a plane of straight and level flight of the unmanned aerial vehicle and having an omnidirectional azimuthal beam pattern orthogonal to the plane of straight and level flight of the unmanned aerial vehicle, the altimeter configured to determine an altitude of the unmanned aerial vehicle above a target surface based on time of flight of radar pulses between the ultra-wideband radar antenna and the target surface; wherein the ultra-wideband radar antenna includes: a first major face having a width extending along a first axis and a length extending along a second axis that is perpendicular to the first axis; a second major face opposite the first major face, the second major face having the width extending along the first axis and the length extending along the second axis; and a thickness extending between the first major face and the second major face along a third axis that is orthogonal to both the first axis and the second axis; wherein the second axis is parallel to the plane of straight and level flight of the unmanned aerial vehicle; and wherein the omnidirectional azimuthal beam pattern circumscribes the first major face and the second major face about the second axis. an unmanned aerial vehicle ; and an altimeter disposed on the unmanned aerial vehicle, the altimeter including an ultra-wideband radar antenna disposed orthogonally to a plane of straight and level flight of the unmanned aerial vehicle and having an omnidirectional azimuthal beam pattern orthogonal to the plane of straight and level flight of the unmanned aerial vehicle, the altimeter configured to determine an altitude of the unmanned aerial vehicle above a target surface based on time of flight of radar pulses between the ultra-wideband radar antenna and the target surface; wherein the ultra-wideband radar antenna includes: a first major face having a width extending along a first axis and a length extending along a second axis that is perpendicular to the first axis; a second major face opposite the first major face, the second major face having the width extending along the first axis and the length extending along the second axis; and a thickness extending between the first major face and the second major face along a third axis that is orthogonal to both the first axis and the second axis; a first major face having a width extending along a first axis and a length extending along a second axis that is perpendicular to the first axis; a second major face opposite the first major face, the second major face having the width extending along the first axis and the length extending along the second axis; and a thickness extending between the first major face and the second major face along a third axis that is orthogonal to both the first axis and the second axis; wherein the second axis is parallel to the plane of straight and level flight of the unmanned aerial vehicle; and wherein the omnidirectional azimuthal beam pattern circumscribes the first major face and the second major face about the second axis. <EOS>