+Alan2 Posted May 11, 2002 Share Posted May 11, 2002 Here’s the 4-month result in real geocaching GPS accuracy. The set-up was that each cache finder to a NGS benchmark, cache http://www.geocaching.com/seek/cache_details.asp?ID=10814 would report their GPS coordinates at the benchmark to the cache web page. The benchmark center was on a 7 foot wide, 2 ½ foot high granite slab. You would have to reqach to set the GPS in the center and to read it. Benchmark is in an open area although there are a couple of small trees nearby. The actual NGS coordinates are 40 44' 34.46640"(N) 073 50' 42.31409"(W) which places it in Flushing Meadow Park, Queens, NYC. The following GPS’s were reported used including my own Vista when I set up the cache. Readings were taken with 13 different GPSr’s on 12 different days between 11/25/01 and 3/24/02 at different times of the day. Weather conditions were not reported. Garmin Vista (4) Garmin etrex (2) Garmin Summit Eagle Expedition II Magellan Map 330 Magellan 300 Unknown “Cheap” Garmin Garmin Street Pilot Summary of results. Difference calculated from NGS coordinates. WGS84 coordinates in DD MM.MMM were converted to UTM using Mapsource program. Distance from benchmark calculated taking the square root of the sum of the squares of the difference between the UTM latitudes and UTM longitudes in meters and converting to feet. 12 readings under 12 feet 5 readings between 13-25 feet 1 reading at 40 feet (note that this was the Magellan 300 which is an older unit and reads to 2 decimal places only - about 50 feet accurate I’ve been told). All were single readings except for Eagle (13 readings = 3.3 feet avg.) and one of the etrexs (7 readings = 25 feet avg.). There was one WASS reading reported (my Vista at 3.3 feet). I think the results speak mountains as to the accuracy of the equipment we are using. I want to thank everyone who helped contribute the data. Hope you enjoy the cache site as well Comments on the data or results would be appreciated? Alan Quote Link to comment
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