Dual frequency (L1/L2) Choke Ring Antennas provide geodetic-quality GPS measurements for surveying, mapping, and research applications. Typical dual-frequency choke ring antennas maintain a stable phase center that has less than 1 mm of drift. The choke ring antenna is based on the geodetic research standard and features aluminum choke rings and a Dorne Margolin antenna element. These antennas are durable, have a low power consumption, and have excellent multipath rejection characteristics.