NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: I knew where we were, but where are we now?
From: George Huxtable
Date: 2006 Jun 26, 22:46 +0100
From: George Huxtable
Date: 2006 Jun 26, 22:46 +0100
Recently, Peter Fogg has been particularly free with his words of advice. He responded to Lu Abel's correct statement- | > If you look at Chapter 24 of Bowditch as mentioned in my previous post, | > the most accurate sailing is a Mercator sailing. | > Mercator Sailings rely on Table 6 of Bowditch, Meridional Parts. with | Almost correct. The most accurate uses tables of meridional parts AND | meridional distances. I ask Peter to inform us about this "Table of meridional distances", that he regards as so essential. Where are we to find it, and what is done with it, under what circumstances? | Having said that, if Guy wants to concentrate on one calculation method, | then he could do worse than settle on Middle Latitude. In certain limited circumstances, not specified by Peter, yes. In many other situations, no. In general, the procedure that gives precise answer under all circumstances is the Mercator sailing method, using meridional parts. |But nobody has | mentioned the other quick and reliable method that is accurate enough for | practical purposes, and offers other advantages that calculation methods | cannot. | | Plot it. On the chart if you must (barbarian). Preferably on the succession | of plotting sheets that track your progress. The big advantage is that it | provides a picture (quite literally) thus showing you just where you are in | a spatial two-dimensional sense: much more valuable than numbers that you | are then most likely to plot onto paper anyway. I think of plotting as a | primary method and calculation as a back-up or check method. It depends entirely what sort of sailing you are doing. In the sort of sailing that I do (and Peter does too, I bet) there's no call for any Mercator calculation. Middle latitude is perfectly adequate, as is plotting on a chart. But if he travelling great distances (as some do) on ocean passages spanning a wide range of latitudes, he would be unlikely to find his simple plotting techniques practical. So in advocating a certain method he should make it clear what its limitations are. "Accurate enough for practical purposes", says Peter. But accurate enough only for some practical purposes, and not for others. I ask him to tell us what is the longest passage he has made, using the techniques he advocates. George. contact George Huxtable at george@huxtable.u-net.com or at +44 1865 820222 (from UK, 01865 820222) or at 1 Sandy Lane, Southmoor, Abingdon, Oxon OX13 5HX, UK.