I have learned much from this forum so thought I would contribute. The Jan/Feb 2007 JOF, which arrived here yesterday, has an article (beginning on Pg 9) entitled Performance Comparison of Low-Cost Mapping Grade GPS Receiver and Consumer Grade GPS Receiver under Dense Forest Canopy. Here's the abstract (abbreviated & appended here by me): We compared the measurement accuracy and reliability of a low-cost (they used SXBlue, cost $2,000) mapping grade GPS receiver to a consumer grade (Garmin V) GPS receiver while operating under a very dense forest canopy. The mapping grade GPS collected both autonomous (uncorrected) GPS measurements and measurements that were differentially corrected in real time through the WAAS. Although we found average measurement accuracies of 7.2 m for uncorrected data and 7.8 m for differentially corrected data for the mapping grade GPS, these differences were not statistically significant. Ther overall positional error for the consumer grade GPS was larger (8.9m) but the consumer grade GPS collected data more efficiently, and for about half of all points collected, with smaller measurement errors. (end of abstract) The analysis preceded addition of WAAS satellites in 2006. JOF is a publication of Society of American Foresters, and carried by many libraries and most university libraries.
