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OpenSeaMap logo
Web address .orgopenseamap
Slogan The Free Nautical Chart
Commercial? No
Registration only required for contributors
Available in English, German, French, Italian, Spanish, Russian
Owner Community
Created by members of the OpenSeaMap and OpenStreetMap community
Launched 2009

OpenSeaMap is a software project collecting 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 for use as an electronic chart for offline applications.

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 accordance 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 naming of OpenSeaMap as a data source is required for data sharing.


  • History 1
  • Contents of the chart 2
  • Applications 3
  • Internationalization 4
  • Timeliness 5
  • Editing tools 6
  • Harbor pilots 7
  • Weather information 8
  • Bathymetric data 9
  • Water depths by crowdsourcing 10
  • 11 WorldHeritage articles on the map
  • References 12
  • External links 13


The idea for the project was born at an OpenStreetMap developer conference in autumn 2008 at the Linux Hotel in boot Düsseldorf, Europe's largest boat show, allowing volunteers to present the project to a large audience of specialists for the first time.

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 yet covered, because the database is not designed for 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 the possible objects from OpenStreetmap.[1] OpenSeaMap includes additional layers such as aids to navigation, ports and temporary racing events.


The chart is for planning 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 map is available to any computer with an internet connection from the website This map is updated daily.
Offline Map
The map can also be loaded on local data storage and can be used on any PC without internet access. This map will also permit use on other devices, such as GPS devices from 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 und iPod touch.[2] The actual position is showed 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. Appropriate navigation tools from the open source area are SeaClear and OpenCPN.


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 names are 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 has been entered, and is immediately available worldwide. Base map data is visible on the map after a few minutes. Navigational data is currently (2010) visible on the chart about two days after it has been entered.

Editing tools

JOSM Editor
Offline Editor JOSM with navigational enhancements
JOSM is the default editor for OpenStreetMap. It has been extended for use on navigational charts with a plugin. It is written in Java and runs on multiple desktop platforms [3]

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 interface to the data on the server in order to read and write OpenSeaMap data.

Harbor pilots

On the map are the world Wiki and is shaped by the users. Included is the free wikiproject "SkipperGuide".[4] 5000 ports are accessible worldwide, including detailed descriptions of 600 marinas.

Weather information

Air pressure

In worldwide weather charts there are shown weather data like wind speed, air pressure (isobars), etc., each actualised two to three times per day, and with weather forecast up to three days.

For each harbour there is a Meteogram with detailed wind forecasts and weather informations for eight days. Available weather data for wind direction, wind speed, air temperature, air pressure, relative humidity, cloudiness, precipitation. From this worldwide available data the captains can predict the marine weather.

Bathymetric data

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

Water depths by crowdsourcing

Depth tracks near Palma (ES)

OpenSeaMap measures water depts by Crowdsourcing. Sailors, motor boaters, commercial shipping, divers, fishermen collect water depths between 0 and 100m with sounder and GPS. Divers work with a dive computer. Coastal water, lakes and rivers are surveyed. Result wil be an elevation model and derived depth lines.[5] Uploaded tracks are showed in the chart.[6] There is a discussion how crowd sourcing can support and enrich the systematic official measuring.

Another project cooperating with OpenSeaMap that uses crowdsourcing to generate marine data is TeamSurv.[7] TeamSurv concentrates on bathymetric charts. In a similar way its members record both position data from the GPS, and depth information from their depth sounder, and once uploaded to the server the depth data is corrected for tides and other factors to reduce it to chart datum.

WorldHeritage articles on the map

OpenSeaMap and WorldHeritage

By "View WorldHeritage-Links" OpenSeaMap displays all georeferenced WorldHeritage articles worldwide as Icon. 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 click you will get the responding WorldHeritage-article.


  1. ^ map elements "Map Features "
  2. ^ App for OpenSeaMap for iPhone, iPad and iPod touch
  3. ^ JOSM Editor
  4. ^ port manual "SkipperGuide"
  5. ^ Wolfgang Bosch, Markus Bärlocher: OpenSeaMap – Wassertiefen per Crowdsourcing (PDF; 7,2 MB). Hydrographische Nachrichten 95, 30. Jahrgang, Juni 2013, Seiten 23-27.
  6. ^ Water depths by crowd sourcing (Chart)
  7. ^ TeamSurv

External links

  • Official website
  • OpenSeaMap-Wiki
  • Charts to Download
  • OpenSeaMap open source project on SourceForge


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