A choke ring antenna is a particular form of omnidirectional antenna for use at high frequencies (VHF & UHF). It consists of a number of concentric conductive cylinders around a central antenna. Choke ring antennas are notable for their ability to reject multipath signals from a source. Since the path that a signal takes from a transmitter to receiver can be used to measure the distance between the two, this makes it highly suited for GPS and radar applications. In a GPS ground-based receiver, a choke ring antenna can provide millimeter precision measurements for use in surveying and geological measurements.