OpenSeaMap/Lights Data Model
Contents |
Lights
A luminous or lighted aid to navigation. (adapted from IHO Dictionary, S-32, 5th Edition, 2766)
Usage
These definitions relate to node tags in the OSM database which will render on the OpenSeaMap charts. Web site: OpenSeaMap.org
Tagging Lights
When deciding on the tagging of lights, one should balance the navigational significance of the light with its visual impact on the map. It is important to avoid a cluttered rendering, particularly where the density of lights is high, such as in port areas. As a general rule, use the least decorated set of attributes whilst keeping the navigational function of the light obvious. Also it is important to not obscure land features that may be important to navigators.
The following guidelines provide a set of criteria for tagging lights and lighted objects:
- Minor Light
- This should be the default classification. It is rendered with the small star symbol at zoom levels 13 and above, therefore is the least obtrusive. These object indicate simple navigational information such as to warn of the presence of an obstruction, or to indicate safe paths such as harbour entrances, approach channels (leading lights), etc.
- Major Light
- This classification should be for those lights that either indicate more complex navigational information or are intended to be visible for an extended distance. It should be the default for sectored lights, since they obviously meet the first criterion.
- Lighthouse
- This classification should be applied if, in addition to meeting those of a major light, its structure is that of a classical lighthouse. These structures are often confused with beacon towers, since they can have similar appearances. A test to apply is: does it have integral or adjacent living quarters?
- Lighted Beacon
- If the body of the structure is painted in navigationally significant colours, or has a topmark/daymark, then it should be classified as a beacon of the the appropriate type. Otherwise, the object should be classified as either a minor or major light according the the criteria above. Since the word "beacon" is commonly understood to mean a structure supporting a light, do not classify it as such if it does not meet the stated criteria, even if other (non-OpenSeaMap) tags describe it as a beacon.
Use of Sector Arcs
Careful consideration should be given to the use of and the radius of sector arcs. A map can become overly cluttered if these are used carelessly or in excess.
Data Structure
The OSM data scheme is related to the IHO-S-57 [1] standard.
The data scheme is fairly complex. It is suggested that attributes are assigned by using either the JOSM Plugin (offline) or by using the OpenSeaMap Online editor. Both come with an easy-to-use GUI.
- Objects
Three types of S-57 objects are defined on this page: LIGHTS, LITFLT & LITVES. They encompass lighthouses, major and minor lights, light floats and light vessels.
Each of these consists of at least two objects:
- The light object
- The light(s)
For sectored lights, each sector is considered to be an individual light.
Additionally, particular tags are added for the current renderer to improve rendering performance and the visual aspect.
Lighthouse
(only)
This section describes the attributes of the lighthouse building. It is based on IHO-S-57 LNDMRK (Landmarke)
seamark:type=landmark + seamark:landmark:category=* (category: tower | chimney | windmill | ... ) + seamark:landmark:name=* (name in local language) + seamark:landmark:height=##,# (height of the building without antennas) + seamark:landmark:colour=* (colour: white | red | green | yellow | brown | black | grey | red;white | ... ) + seamark:landmark:colour:pattern=* (colour pattern: vertical | horizontal | diagonal | squared ) + seamark:landmark:construction=* (material: masonry | steel | concreted | metal | ... )
Light Vessel
(only)
Basis: IHO-S-57 LITVES
A distinctively marked vessel anchored or moored at a charted point, to serve as an aid to navigation. By night, it displays a characteristic light(s) and is usually equipped with other devices, such as fog signal, submarine sound signal, and radio-beacon, to assist navigation. Also called light ship. (IHO Dictionary, S-32, 5th Edition, 2828,2829)
This type includes old-style lightships and the more modern automatic major light floats.
It is charted using the IHO_INT_1 symbol: P6
seamark:type=light_vessel + seamark:light_vessel:name=* (name in local language) + seamark:light_vessel:colour=* (hull colour: white | red | green | yellow | brown | black | grey | red;white | ... ) + seamark:light_vessel:colour:pattern=* (hull colour pattern: vertical | horizontal | diagonal | squared )
Light Float
(only)
Basis: IHO-S-57 LITFLT
A boat-like structure used instead of a light buoy in waters where strong streams or currents are experienced, or when a greater elevation than that of a light buoy is necessary (IHO Dictionary, S-32, 5th Edition, 2821).
This type refers to minor light floats.
It is charted using the IHO_INT_1 symbols: Q30-31
seamark:type=light_float + seamark:light_float:name=* (name in local language) + seamark:light_float:colour=* (colour: white | red | green | yellow | brown | black | grey | red;white | ... ) + seamark:light_float:colour:pattern=* (colour pattern: vertical | horizontal | diagonal | ... ) [+ seamark:topmark:shape=*] (Topmark shape: 33 different marks ) [+ seamark:topmark:colour=*] (Topmark colour: 13 different colours ) + seamark:light=* ( ... )
Major and Minor Lights
(only)
Basis: IHO-S-57 LIGHTS
A luminous or lighted aid to navigation. (adapted from IHO Dictionary, S-32, 5th Edition, 2766)
These are lighted structures positioned either on land or in the sea that are not one of: beacon, cardinal; beacon, isolated danger; beacon, lateral; beacon, safe water; beacon special purpose/general; buoy, cardinal; buoy, installation; buoy, isolated danger; buoy, lateral; buoy, safe water; buoy, special purpose/general; light vessel; light float.
A major light is a light with an extended function (e.g. sectored lights, elevated height, long range, etc.). They may be mounted on a beacon or attached to some other structure. NB: All active lighthouses are classed as major lights and charted as such, but few major lights are lighthouses!
A minor light is single function light not mounted on a beacon, but attached to some other structure. Minor lights can also be lights that do not have a specific navigational function other than being visible to mariners, such as jetty lights. Not all charts show these objects.
They charted using the two star symbols in IHO_INT_1: P1
seamark:type=light_major seamark:type=light_minor + seamark:light=* ( ... )
Lights and Sectors
This section describes the properties of the lights that are used for navigation. It is based on IHO-S-57 LIGHTS
Each sector is considered to be an individual LIGHTS object. The sectors are defined separately based on some common data.
Note: The bearing of sectors is always as seen from ship to light!
Light Data
+ seamark:light:character=* ( F | Fl | LFl | Q | VQ | UQ | Iso | Oc | IQ | IVQ | IUQ | Mo | AI ) + seamark:light:colour=* (colour of light: white | yellow | red | green | ... For Alternating lights (Al), two colours in the form: x;y) + seamark:light:group=* (signal groups) + seamark:light:sequence=* (sequence) + seamark:light:period=* (period) + seamark:light:category=* (category: directional | leading |rear | front| upper | lower | horiz | vert | ... [;category]) + seamark:light:height=* (height of light above see level in metres) + seamark:light:range=* (nominal range of light in nautical miles) + seamark:light:multiple=* (The number of lights of identical character that exist as a co-located group) + seamark:light:status=* (permanent | occasional | recommended | not in use ) + seamark:light:exhibition=* (24hr | day | night | fog ) + seamark:light:reference=C ####,# (international number of light) + seamark:light:information=* (important nautical information about this light)
Light Character
| F | Fix | Constant light |
| Fl | Flash | Interval < 2 sec. |
| LFl | Long Flash | Interval > 2 sec. |
| Q | Quick | Rate: ~60 / Min |
| VQ | Very Quick | Rate: 100 - 120 / Min |
| UQ | Ultra Quick | Rate: > 120 / Min |
| Iso | Isometric | Equal light and dark periods |
| Oc | Occulting | Long on and short off periods |
| IQ | Interrupted Quick | interrupted rate, 60 / Min |
| IVQ | Interrupted Very Quick | interrupted rate, 100 - 120 / Min |
| IUQ | Interrupted Ultra Quick | interrupted rate, > 120 / Min |
| Mo | Morse | Character from Morse alphabet group |
| FFl | Fixed/flash | Constant light with flashing light |
| FLFl | Fixed/Long flash | Constant light with long flashing light |
| FlLFl | Flash/Long flash | Flash alternating with Long flash |
| OcFl | Occulting/Flash | Occulting alternating with Flash |
| Q+LFl | Quick flash plus Long flash | Quick flash group followed by Long flash |
| VQ+LFl | Very quick flash plus Long flash | Very quick flash group followed by Long flash |
| UQ+LFl | Ultra quick flash plus Long flash | Ultra quick flash group followed by Long flash |
| Al | Alternating | Alternating colours |
| Al.Oc | Occulting alternating | Alternating colours |
| Al.LFl | Long flash alternating | Long flash alternating colours |
| Al.Fl | Flash alternating | Flash alternating colours |
| Al.F | Fixed alternating | Fixed alternating colours |
| Al.FFl | Fixed and Flash alternating | Fixed plus Flash alternating colours |
| Al.Iso | Isophase alternating | Isophased alternating colours |
Sectors
A sectored light consists of at least one sector. "seamark:light:#:*" defines a single sector (e.g. "seamark:light:1:*" defines sector 1, "seamark:light:2:*" defines sector 2,...). Each sector has a starting and an ending bearing, seen from ship to shore.
+ seamark:light:#:sector_start=###.# (anticlockwise-most bearing) + seamark:light:#:sector_end=###.# (clockwise-most bearing) + seamark:light:#:colour=* (colour of light: white | red | green , green;white for Alternating lights (Al)) + seamark:light:#:range=## (nominal range in nautical miles)
Leading Lights
Leading lights consist of a pair of lights set some distance apart; a rear or upper light and a front or lower light. The correct approach bearing is when both lights become aligned vertically (a 'transit').
- Upper (rear) light
+ seamark:light:category=upper (Upper leading light) or + seamark:light:category=rear (Rear leading light)
- Lower (front) light
+ seamark:light:category=lower (Lower leading light) or + seamark:light:category=front (Front leading light)
Directional Lights
These lights perform a similar function to pairs of leading lights. They consist of a single light with a very narrow sector angle, such that it is only visible when approached on the correct bearing.
- Directional light
+ seamark:light:category=directional + seamark:light:orientation=###.#
Rendering Sector Arcs
To control the radius of sector arcs in the map, the following tag should be used for each sector:
- Sectors
+ seamark:light:#:radius=###.## │ │ │ └─> radius at which this sector should be displayed on the map in NM. └─> number of sector If this tag is not present, the default radius of 0.2NM will be rendered
The appearance and radius of the arc can be changed within a sector to improve the rendering. To achieve this, the sector is divided into a number of segments, each with its own radius and style. The radius tag value is specified as a semi-colon separated list of tuples, each with three colon-separated parameters. The arc styles are solid (default), dashed and suppressed. See OpenSeaMap/smfilter for further details.
seamark:light:#:radius=segment;segment;... where: segment=radius:style:span radius=###.# (decimal Nautical Miles) style="solid"|"dashed"|"suppress" span=###.# (decimal degrees) Individual tuple parameters can be omitted, but the colons must be present. The missing parameter is taken to be that of the previous segment The span value of the last tuple can be a negative value to indicate a span from the end of the sector back towards the start.
Further Properties
Radar Reflector
+ seamark:radar_reflector=yes (Radar reflector)
Radar Transponder
+ seamark:radar_transponder:category=* (Category: Ramark | Racon | Leading ) + seamark:radar_transponder:group=* (Morse letter transmitted) + seamark:radar_transponder:period=* (Repeat time of transmissions)
Fog Horn
+ seamark:fog_signal:category=* (Category: Horn | Bell | Whis | Gong | Siren | Dia | Explos) + seamark:fog_signal:group=* (Morse letter transmitted) + seamark:fog_signal:period=* (Period in seconds)
Additional Information
+ seamark:information=* (To define any important information about all objects at this location) + seamark:light:information=* (To define any important information about the light or lights at this location) + seamark:light:#:information=* (To define any important information about the individual light sector)
