Cardinal marks

A cardinal mark relates identity to a geographical quadrant. Its name indicates its quadrant relative to the marked point and the side where the indicated water lies. North does not mean passing ahead of our boat or depend on buoyage direction. Portuguese RBMN defines quadrants through true bearings between diagonal directions. The figure connects four names to shapes and bands without a chart, depth or usable track. These references remain the same in Regions A and B, unlike the red/green exchange of lateral identities.

North has two black cones pointing upwards, south two pointing downwards. East has their bases facing one another; west their points face one another. Clear separation helps identify two cones, rather than two triangular flags or one continuous diamond. The pillar or spar body does not independently supply this direction. The topmark is especially important by day and is used where practicable, while conditions can lead to its omission. Missing or obscured topmarks leave incomplete evidence rather than authorising a different geometry to be assumed.