I was concerned about that much error, too, so I ran an interesting experiment with my Garmin 12XL last weekend. I took it out on the front porch to mark the location using position averaging. Got some poor signal messages, so I moved it a few feet further out onto the lawn where it could see more of the sky, though it was still under a couple of big oak trees, and then left it on about 15 minutes or so before saving the position. When I downloaded the data to Street Atlas USA 5.0 and TOPO!GPS, both maps showed the position approximately in the same place: in the street, about 100 feet SW of its actual position. The TOPO! map also showed the track caused by SA and, possibly, by poor reception. Most of of the track excursions caused by SA were pretty small, but there was one long excursion about 1000 feet to the SW that placed our house in a pond on the other side of Hwy. 280. I think the long excursion was probably caused by poor reception, and that it might also have dragged the average position in that direction. I didn't think to check the map datums until I had closed TOPO!, but I believe they were at default -- probably WGS84. I did try to find out what map datum Street Atlas USA was using, but couldn't find anything in the online help. That was all I had time for last weekend. I'll try repeating it in a few days and see if I get the same results. Chuck Holst -----Original Message----- From: Bob Denton [mailto:BDenton_at_aquagulf.com] Sent: Friday, May 28, 1999 4:06 PM To: Chuck Holst; 'Paddlewise' Subject: RE: [Paddlewise] FW: Download to Garmin When they were searching for the A6 that flew into the Rockies, SA was turned off. I marked my position on the beach, then a few hours later I decided to paddle in "on instruments" and followed the GPS to the beach. I landed on my footprints. That was with a 12XL. .12 miles is 633 feet. Way too much of an error and I'd be calling Garmin if I were you. Cya -----Original Message----- From: owner-paddlewise_at_lists.intelenet.net [mailto:owner-paddlewise_at_lists.intelenet.net] On Behalf Of Chuck Holst Sent: Friday, May 28, 1999 10:07 AM To: 'Paddlewise' Subject: [Paddlewise] FW: Download to Garmin 12X Good question. Last weekend I carefully marked a waypoint at my takeout before putting in upriver, using about a minute of waypoint averaging. When I returned by river to the same spot, my Garmin 12XL told me I was .12 miles west of the waypoint! This was all done without maps, so the culprit must be selective availability. *************************************************************************** PaddleWise Paddling Mailing List Submissions: paddlewise_at_lists.intelenet.net Subscriptions: paddlewise-request_at_lists.intelenet.net Website: http://www.gasp-seakayak.net/paddlewise/ ***************************************************************************
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