Yourbestsail · video

What this video covers

Two fundamental navigation concepts — bearing (demora) and relative bearing (marcación) — are defined and related through a single formula: magnetic bearing equals magnetic heading plus relative bearing.1:54

Marcación is the angle to an observed object measured from the boat's centerline (crujía).0:41 Demora is the same angle measured from magnetic north.1:15 The two are linked by the boat's heading.1:47 A key regional note: Spanish and European usage reverses the terminology used in Argentina, where the two terms swap meanings.2:40

The practical application covered is collision-course detection.3:14 If either measurement stays constant while another vessel approaches, a collision course exists.3:23 For recreational boats, demora is the more reliable check: heading on a small boat shifts constantly with wave action, which causes marcación to fluctuate even when the geometry hasn't changed.3:23 Demora, referenced to north rather than the centerline, is unaffected by those heading oscillations.4:32 The instrument used to take this measurement is the compás de demora (bearing compass).3:52 The instructor notes that the bearing compass has additional navigation uses covered in his offshore navigation courses.5:03

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