Definition
All almanac tabulations are argued on UT1, referred to in practice as GMT and closely tracked by UTC, which is kept within 0.9 seconds of it. Since the sun's geographical position sweeps west at about 0.25 minutes of arc per second of time, a timing error of four seconds displaces a longitude line by roughly one nautical mile at the equator. Watch error and watch rate must therefore be logged and applied.
Want to apply this on the water?
Ask Saily out loud for an example, a scenario or a simpler explanation.
Talk to Saily