Seamarks/Leading Lines

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Navigation Lines and Recommended Tracks

The tags defined on this page will render in various nautical charts.

This page defines tag values for Navigation Line and Recommended Track objects.

Type S100 seamark:type Definition Rendering
Navigation Line NAVLNE navigation_line A navigation line is a straight line extending towards an area of navigational interest and generally generated by two navigational aids or one navigational aid and a bearing. Navline.png
Recommended Track RECTRC recommended_track The recommended track is that portion of a 'navigation line' that a ship should use for navigation. Rectrack.png


Category (CATNAV) seamark:navigation_line:category Definition
Clearing line clearing A straight line that marks the boundary between a safe and a dangerous area or that passes clear of a navigational danger.
Transit line transit A line passing through one or more fixed marks.
Leading line leading A line passing through one or more clearly defined objects, along the path of which a vessel can approach safely up to a certain distance off.

Category (CATTRK) seamark:recommended_track:category Definition
Based on a system of fixed marks fixed_marks A straight route (known as a recommended track, range or leading line), which comprises at least two structures (usually beacons or daymarks) and/or natural features, which may carry lights and/or top-marks. The structures/features are positioned so that when observed to be in line, a vessel can follow a known bearing with safety.
Not based on a system of fixed marks no_fixed_marks A route (known as a recommended track or preferred route) which is not based on a series of structures or features in line.

Navigation lines and recommended tracks are mapped as ways (usually just two nodes) laying along the path where the objects are to be displayed. The way should carry the tags for correct rendering. Nodes belonging to other objects, such as leading lights, may be used. The following illustration shows two navigation lines and two recommended tracks. The latter carry seamark:recommended_track:orientation=... tags in order for the bearing to be displayed. The values are decimal numbers, representing the bearing in degrees true.

Do not use these objects to map fairway centrelines. Remember, these objects are straight lines and should normally have only two nodes. Both types must project to a pair of transit objects or other directional object, otherwise they are not navigationally useful. Fairways should be mapped as areas and should not have a separately mapped centreline.

Leading Lines.png


Seamark Tag Values
Seamark Objects
Seamark Attributes
INT-1 Cross Reference