NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Life raft questions - knowing only GHA and sun's rising or setting
From: Brad Morris
Date: 2018 Nov 8, 13:50 -0500
From: Brad Morris
Date: 2018 Nov 8, 13:50 -0500
Tony
Virtually all life raft "navigation" has been obsoleted. The very specific reason is that it is irrelevant. Life rafts aren't navigated, piloted, sailed or otherwise directed. The life raft is designed to keep you afloat, hydrated and modestly nourished. Your PLB or EPIRB will provide your position to SAR. They will come and get you.
If you wish to amuse yourself, while waiting, I suppose you could determine your position by tables, watches and etc, OR you could simply look at any number of displays that directly provide your position. For example "ACR Aqualink View PLB". Not only does this show you your lat & long on a display, it provides that position to the SAR satellites on 406 MHz. It also broadcasts on 121 MHZ to be used as a homing beacon once SAR gets close.
Many modern life rafts/boats do not even contain any way to power the craft. No motor. No sails. Nothing. It drifts with wind and current. What good will knowing your position do in these circumstances? Far better that SAR know your position.
Brad
On Thu, Nov 8, 2018, 1:17 PM Tony Oz <NoReply_TonyOz@fer3.com wrote:
Dear Ed,
You said:
...you could also estimate at sun rise or set the sun is six hours local time but that depends on your latitude and time of year. So this is subject to some big errors...
Such table (to estimate one's latitude from daylight duration and date) is included in the Harold Gatty's Raft Book - with the auxiliary interpolation tables. This table also lists the LMT of sunrise/sunset along with the azimuths to those points. Was all this obsoleted on modern life rafts?
Regards,
Tony
60°N 30°E
