Tracking 45-parallel GPS channels, with an ultra sensitive high-gain internal GPS antenna and low-noise front-end amplifiers, the MobileMapper 120 boasts the fastest Time-to-First-Fix, best Under-Canopy performance and the highest accuracy available in a handheld GPS receiver. The ProMark 220 receiver is fully US and GLONASS enabled, tracking L1 + L2 + G1 + G2 with 45-channels. RTK performance with the PM220 is nearly identical to that of the ProMark 800.