NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: sight reduction with GPS receiver
From: Bill B
Date: 2005 Mar 21, 19:05 -0500
From: Bill B
Date: 2005 Mar 21, 19:05 -0500
Frank wrote: > Wow. Very interesting (btw, for those of you who were dismissive of HP's > point, I would like to make clear that I, at least, think it's worth > considering). I thought it worth consideration as well, and as posted used Paul's coordinates but came up with 2229 nm for an Hc of 52d 51!0 instead of predicted Hc of 52d 48!3. Paul's 2232 would be closer at 52d 48'. This is where I get lost in the jargon. Does "calculate geodesics on the Earth as shortest distance arcs on the ellipsoid" mean that corrections for the fact the Earth is not a perfect sphere are included? Is this "GCD?" This would be more accurate than calculations that assume the Earth is a sphere, correct? Given Paul's nm figure converted to HC is closer to correct than mine, does it appear my late 2001 Garmin 76, firmware 2.06, WGS84 datum is treating the Earth as a perfect sphere? I also have not resolves the question posted earlier: "My confusion is that 132d is the starting course of a great-circle route. I am having trouble understanding why that would be my azimuth. (spherical trig is still a plug-and-chug function for me). Bill