Joe Pylka wrote (regarding 3-minute discrepancies between GPS receivers): > Almost always, this sort of discrepancy is due to setting the wrong > reference datum into the receiver. ... Actually, this can't possibly be the explanation. There are no areas in North America for which the discrepancy between reference datums--such as NAD27 and WGS84--is as large as 3 minutes (or 3 nautical miles). I know of only two possible explanations for such large discrepancies: (1) multipath error, or (2) a serious problem with the GPS receiver. Multipath error could be the cause if the placement of the remote antenna for the console-mounted receiver is such that it is subject to reflected signals. This can lead to very large errors (as much as the 3 nautical miles that were observed). The way to check to see if this is the problem is to hook up a handheld receiver (with an external antenna connector) into the antenna that the console-mounted unit is using, and see if the problem is repeated for the new receiver. I think that this explanation, while possible, is unlikely based on your description, since multipath errors are variable and somewhat random (as the ship changes position). The second possibility--a faulty receiver--is more likely to be the problem. Again, hooking up a different receiver to the antenna should help to identify if the problem lies with the antenna placement or with the receiver. Dan Hagen *************************************************************************** PaddleWise Paddling Mailing List Submissions: paddlewise_at_lists.intelenet.net Subscriptions: paddlewise-request_at_lists.intelenet.net Website: http://www.gasp-seakayak.net/paddlewise/ ***************************************************************************Received on Sat Mar 13 1999 - 19:30:27 PST
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