Interpreting channels and harbour entrances

An entrance can combine laterals, safe-water mark, cardinal, leading line, sectors and local signals. They are not competing elements from which the most familiar colour is chosen. Each communicates something particular: lateral limit, axis reference, danger, directional relationship or local information. The figure separates layers in fictional panels, not a European harbour entrance or track to follow. Its purpose is understanding that identifying one buoy does not independently answer every channel question. Appearance, documented meaning and suitability for an actual vessel must remain separate.

Laterals relate to a defined channel and conventional direction. Two marks do not make every part between them equally deep. A channel can include bends, junctions, dredged areas and documented obstructions, whose geometry is not deduced from red and green. A special mark can indicate a particular-interest area without replacing general laterals or cardinals. Charts and local documents supply spatial information missing from category identity. Distinguishing these roles avoids drawing a broad approved corridor between familiar colours while ignoring what the bed actually contains.