OpenSeaMap is a software project to collect freely usable nautical information and geospatial data to create a worldwide nautical chart . This chart is available on the OpenSeaMap website, and can also be downloaded as an electronic chart for offline applications. [1]

The project is part of OpenStreetMap . OpenSeaMap uses the same database, and complements the spatial data with nautical information. Such data may be used in conjunction with the Open Database License . This ensures integration into printed materials, websites and applications is possible, without being limited by restrictive licenses , or having to pay fees.


The idea for the project Was Born at an OpenStreetMap developer conference in autumn 2008 at the Linux Hotel in Essen , Germany . A group of boaters and programmers decided to extend the coverage of OpenStreetMap to the seas and fresh water bodies. From the start the project has been worldwide and multilingual. By the end of 2009, the design and architecture of the project had been created, and a sample harbor ” Warnemünde ” was created to serve as an example chart. Since autumn 2009, a dedicated server has been available and the project is engaged in several collaborations with other free projects and organizations. In January 2010 OpenSeaMap Düsseldorf , Europe’s largest boat show,

Contents of the chart

Charts will show lighthouses , lateral buoy , cardinal marks and other navigational aids . In the ports, facilities will be mapped (port wall, pier, walkways, docks, fueling stations, loading cranes, access roads, railway lines, ferry lines). Similarly, public authorities, shipbuilders and repairers, as well as sanitation and utility facilities will be displayed. The navigational attributes correspond to the international standard IHO S-57.

Water depths are not limited to three-dimensional coordinates. However, the plan is to eventually integrate a bathymetric model to describe the seabed .

The data are presented in multiple levels with OpenLayers on the base map of OpenStreetMap. The base map contains all possible objects from OpenStreetMap. [2] OpenSeaMap includes additional layers such as ports and temporary racing events.


The chart is for sailing and boat trips. It will also be useful as a guide for tourists. It is not intended to replace official charts .

Online Map
The website. This map is updated daily.
Offline Map
The map can be loaded aussi one local data storage and can be used On Any PC without internet access. Garmin and Lowrance, phones, and PDAs. The off-map is regularly updated, usually every week.
App for iPad, iPhone, iPod touch
The free App for OpenSeaMap works on iPad , iPhone and iPod touch. [3] The actual position is shown on the chart. Each downloaded chart is cached on the device and can be used without internet connection. With internet connection the app checks if there is a newer version of the chart. The Apple location search finds the fitting map section. The app works worldwide.
With certain navigation programs, it is possible to display the current position directly on the chart via a connected GPS device, tracking a vessel’s movement. An NMEA interface can run an autopilot and thus control the ship. Also, the display of AIS signals on the chart is possible. SeaClear, OpenCPN and GPSANGLER .


The site is translated into six languages: English, German, French, Italian, Spanish and Russian. The tools and the legends are available with a German, English and French interface. On the map the place is always written in local language and script. The geographical coverage is worldwide. Depending on the region and the active cartographers , the coverage varies but is growing daily.


Data is stored in the database as soon as it is available. The hotel is located in the heart of the city. Navigational data is currently (2010) visible on the chart.

Editing tools

JOSM Editor
JOSM Offline Editor with navigational enhancements
JOSM is the default editor for OpenStreetMap. It has been extended for use on a charter with a plugin . It is written in Java and runs on multiple desktop platforms [4]

To edit you must register with a verified email address. Registration is free and will encourage high data quality. Read access does not require registration.

Other programs can access the XML-RPC OpenSeaMap data.

Harbor pilots

On the map are the port , marina and anchorage . Via a pop-up window. This guide is organized as a Wiki and is shaped by the users. Included is the free wikiproject “SkipperGuide”. [5] 5000 ports are accessible worldwide, including detailed descriptions of 600 marinas.

Weather information

Air pressure

In worldwide weather charts there are shown weather conditions like wind speed, air pressure (isobars), etc., each time updated to two times.

For each harbor there is a meteogram with detailed wind forecasts and weather information for eight days. Available weather data for wind direction, wind speed, air temperature, air pressure, relative humidity, cloudiness, precipitation. From here you can see the weather forecast.

Bathymetric data

Bathymetric data

Worldwide, depths between 100 and 10,000 m are shown in a blue color scale of 23 steps, together with depth shading. Higher zoom levels at depth contours are displayed aussi. GEBCO_08-database The data is given through cooperation with GEBCO and its bathymetric.

See also OSMDCON .

Water depths by crowdsourcing

Depth tracks near Palma (ES)
OpenSeaMap Data Logger

OpenSeaMap measurements water depths by Crowdsourcing . Sailors, motor boaters, commercial shipping, various, fishermen collect water depths between 0 and 100m with sounder and GPS. Various work with a dive computer . Coastal water, lakes and rivers are surveyed. Result of the elevation model and derived depth lines. [1] [6] Uploaded tracks are shown in the chart. [7] There is a discussion how crowd sourcing can support and enrich the systematic official measuring.

Wikipedia articles on the map

OpenSeaMap and Wikipedia

By “View Wikipedia-Links” OpenSeaMap displays all georeferenced Wikipedia articles worldwide as Icon, and optionally as gallery of all pictures from Commons. Until now 1.7 Mio. Georeferenced articles are shown, in 41 languages, 260’000 in German and 740’000 in English (9.2011). By mouseover a popup is opened with title of the article and an informative picture. By clicking you will get the answering Wikipedia-article.


  1. ^ Jump up to:b International Hydro: OpenSeaMap – the Free Nautical Chart
  2. Jump up^ map elements “Map Features”
  3. Jump up^ App for OpenSeaMap for iPhone, iPad and iPod touch
  4. Jump up^ JOSM Editor
  5. Jump up^ port manual “SkipperGuide”
  6. Jump up^ OpenSeaMap – Wassertiefen per Crowdsourcing. Hydrographische Nachrichten 95, 30. Jahrgang, Juni 2013, Seiten 23-27.
  7. Jump up^ Water depths by crowd sourcing (Chart)

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