Definition
On losing satellite positioning the navigator immediately notes the last known good position, the time, the log reading and the heading, and begins a manual plot from that point. Thereafter course, log, leeway and tidal data are recorded at fixed intervals, commonly every 15 to 30 minutes coastal, and an EP is carried forward. Cross-checking against soundings, radar ranges and any visual position lines rebuilds confidence, and the plot continues until an independent fix restores certainty.
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