> calculations are done on earth-centered coordinates IIRC. BTW, if > only three satellites are visible, then the receiver will _assume_ > your current altitude (based on the most recent determination) and > use that. Hence the greater uncertainty with only three satellites. ... and the current altitude is normally zero for a kayaker, :-) same as his recent altitude, or am I missing something? *************************************************************************** PaddleWise Paddling Mailing List - Any opinions or suggestions expressed here are solely those of the writer(s). You must assume the entire responsibility for reliance upon them. All postings copyright the author. Submissions: PaddleWise_at_PaddleWise.net Subscriptions: PaddleWise-request_at_PaddleWise.net Website: http://www.paddlewise.net/ ***************************************************************************
On 29 Aug 2004 at 15:11, alex wrote: > ... and the current altitude is normally zero for a kayaker, :-) same > as his recent altitude, or am I missing something? Not if you're in a place with significant tides or if it's your first reading on the water since you were on land. When I first got my GPS back in late '96, I remember getting a couple of readings based on only three satellites, but lately I always see the better part of a dozen. Mike *************************************************************************** PaddleWise Paddling Mailing List - Any opinions or suggestions expressed here are solely those of the writer(s). You must assume the entire responsibility for reliance upon them. All postings copyright the author. Submissions: PaddleWise_at_PaddleWise.net Subscriptions: PaddleWise-request_at_PaddleWise.net Website: http://www.paddlewise.net/ ***************************************************************************
> > ... and the current altitude is normally zero for a kayaker, :-) same > > as his recent altitude, or am I missing something? > > Not if you're in a place with significant tides or if it's your first > reading on the water since you were on land. > > When I first got my GPS back in late '96, I remember getting a couple > of readings based on only three satellites, but lately I always see > the better part of a dozen. Well, tides are quite significant here in BC (I've heard they are 50 years record, both high and low). I noticed an errror once, - previously marked landing spot happend to be covered with water, about 150 ft offshore. But this was cosistent with tidal activity (I've marked it not at the highest tide). May be with 3 satellites the location error would be greater, and would be affected by a few ft altitude change as well, but in last cuple of years (since I've bought a GPS) I don't remember them being less than 5 or 6 at a time, in this area and on open water. Honestly, I don't have much use for it in routine weekend trips, may be I will in a sudden fog or when forced to paddle in darkness. Btw, GPS uploadable or built-in tidal tables - they are probably for the USA only, not for Canada or Mexico? *************************************************************************** PaddleWise Paddling Mailing List - Any opinions or suggestions expressed here are solely those of the writer(s). You must assume the entire responsibility for reliance upon them. All postings copyright the author. Submissions: PaddleWise_at_PaddleWise.net Subscriptions: PaddleWise-request_at_PaddleWise.net Website: http://www.paddlewise.net/ ***************************************************************************
Quoting alex <al.m_at_3web.net>: > ... and the current altitude is normally zero for a kayaker, :-) same as his > recent altitude, or am I missing something? Not on Lake Superior, which has an altitude a little over 600 feet. Chuck Holst *************************************************************************** PaddleWise Paddling Mailing List - Any opinions or suggestions expressed here are solely those of the writer(s). You must assume the entire responsibility for reliance upon them. All postings copyright the author. Submissions: PaddleWise_at_PaddleWise.net Subscriptions: PaddleWise-request_at_PaddleWise.net Website: http://www.paddlewise.net/ ***************************************************************************
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