Two code multipath reduction technologies, namely MET#8482; and MEDLL#8482;, were tested in DGPS shipborne mode to determine their effectiveness in this environment. The MET#8482; and MEDLL#8482; technologies are designed to reject multipath delays of 15m or more and their performance will be a function of the surrounding environment at the reference station and on the ship. In addition to intercomparing the MET#8482; and MEDLL#8482; approaches, each was compared to the standard C/A Code wide correlator spacing and the semicodeless Y Code approach. The MET#8482; and MEDLL#8482; technologies are used in NovAtel's receivers. A pair of Ashtech Z-12 receivers were used to provide the C/A code and semicodeless results. The tests were carried out on a 1,600 tonne Department of National Defence vessel off the coast of Vancouver Island in May 1995 over a period of several days. All receivers performed well and, for each receiver pair, the integer ambiguities were resolved to obtain a reference trajectory at the cm-level These reference trajectories were then used to assess the code and carrier phase smoothed code solutions obtained with the above technologies. Under the prevailing multipath conditions, the code and carrier phase smoothed code position results with MET#8482; and MEDLL#8482; were found to be more than twice as good as the corresponding standard C/A code results in terms of rms agreement. MET#8482; and MEDLL#8482; outperformed the semicodeless Y1 derived positions by some 25 to 70. MEDLL#8482; was found to outperform MET#8482; by about 15 in term of rms agreement.
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