NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Using sun compass for calibrating boat compass
From: Bill B
Date: 2014 May 08, 13:35 -0400
From: Bill B
Date: 2014 May 08, 13:35 -0400
On 5/8/2014 9:51 AM, Greg Rudzinski wrote: > The way I see this is that Hc is based on an assumed position not the > actual position so that the azimuths will differ slightly. Not an issue > for the LOP plot. But if an accurate fiber optic gyro were to be checked > to it's precision then I would use Ho (not Hc or Hs)to calculate azimuth > to the tenth of a degree. Sean and Greg Thanks for your input. I do see your points, but still feel like a puppy chasing its own tail. If I understand correctly, in the following formula I would still be working from an assumed position as the LHA is derived from the GHA and AP longitude, so your caveats are still valid: Tan Z = sin LHA / ((cos LHA sin lat) - (cos lat tan dec)) If tan Z is negative, add 180 to Z If hour angle is less than 180, add another 180 to Z If the scenario was similar to Greg's post from the archives, and I was working from about a known position (Ho and Hc theoretically equal), then the azimuth derived from the Hc or Ho would yield the correct azimuth. Have I caught up to my tail yet :-)
