I carried my trusty Tamaya for many thousands of miles but only used it for diversion (the chess analogy is apt). Still the backup aspect is very real. I have only done two ocean crossings; on both my sextant had an LCD watch on the handle, set to UTC before departure, along with the marine
tables plus the appropriate almanac pages. Of course it was not likely that either the GPS
system would drop or my multiple GPS
units would fail, including the AA battery
powered handheld, just while I was out in the middle of the ocean. It is comforting nonetheless.
I have spent far more time coastwise and island hopping, and GPS has indeed failed me at critical moments. I am not about to forget the week number rollover problem that struck when I was on the Markermeer heading to Amsterdam
- the marina that evening was full of sailors trying to get their GPSs to work. I have also enjoyed local blackouts courtesy of Navy
tests of their jamming equipment
(announced on Navtex and the local Notices to Mariners, which everyone is following, right?). The prudent mariner never relies on any one system - even one as good as GPS.
My first line of defense (after multiple, independent GPS receivers) is my other electronic gear
, depth sounder
, heading sensor, etc. I have known vessels to lose all electronic gear
, including GPS, when struck or nearly struck by lightning
. So my second line of defense is an adjusted (swung) compass
, a trailing log, lead line, and my sextant. Unfortunately the compass
is not immune to error caused by the field of a lightning
strike but there are no guarantees in life. Finally, being a little paranoid and recording position data in potentially dodgy situations (fog, rain, gales, out of sight of land, etc) doesn't hurt.
I would recommend carrying a sextant as a backup, but only after a lot of other backup and safety equipment
has been acquired first. Unless you are someone who just wants to go back to the old ways, in which case more power to you.
And for the record
, a lot of marine
publications that are published in both the US and the UK (including the Nautical Almanac) are actually a collaboration - an error in one will be in the other as well. Conspiracy theorists can have fun with that.