NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: John D. Howard
Date: 2017 Jan 2, 10:15 -0800
David,
Yes, there is sloppy use of time termonogly. I have seen people and web sites and apps talk about GPS time, Internet time, atomic time, and the most common mistake is GMT.
All these and many others are not offically defined - they are colocial ( s ) no more official than Alexander's Rag Time ;-)
Take the common term Grenwitch Mean Time ie. GMT. It has not been offically used for over 50 years or so yet every navigator will know what you mean if you say 1230 GMT.
If you relate whatever time you get from any good source to UTC than you can not go wrong.
Don't try to make cel-nav into a GPS. We only record time to the second when we take a shot. If you and your mate are standing next to one another on the beach and you record your time as 13:15:05 UTC and he records his time as 13:15:06 then the Nautical Almanac will show your GHA sun as 0.2 or 0.3 minutes different! You cannot get any more accurate than that because the Almanac is only garenteed to .25 minutes of arc.
John H.
