The United States Patent Office issued a patent (# 6,751,467) that covers the combination of radio modem and GPS technologies in ways that reduce cost and improve performance of a GPS system used in survey and other precision applications. This patent was issued to Pacific Crest Corporation on June 15, 2004.
Pacific Crest Corporation is a manufacturer of wireless data communication equipment. Founded in 1994 and with headquarters in Santa Clara, California, Pacific Crest Corporation maintains a strong international presence in the GPS survey and environmental monitoring industries.
Source: Pacific Crest, July 13, 2004