OpenSeaMap

OpenSeaMap is a starting OpenStreetMap subproject to create some free nautical map with contributions both from official public data (with no copyright) and passionated individuals.

As the backend structure for the data is based on the s-57 vector format (used by official ENC), it could be a good tool to :

• develop some cartographic online interface for implementing the info from the official Notices to Mariners (NTMs) which provides timely marine safety information for the correction of all the official navigation paper charts
• use the power of collaborative crowdsourcing for implementing nautical POI such as port information, marinas, repair shops, shipchandlers, marine electronic dealers...

Of course, this interesting initiative can't be a 'competitor' of the official Hydrographic Services which are using sophisticated technical means (multibeam, RTK GPS, Lidar...) in order to propose nautical charts more increasingly accurate.

In this way, as the final result is open to all, why not imaging some OpenSeaMap layer in the Marine GeoGarage to get official chart corrections from NTMs and a complementary marine local guide ?

What about Google Earth and Marine GeoGarage ?

Demo movie

Example of kml network link to Marine GeoGarage for viewing seamless all the NOAA raster chart dataset in Google Earth (GE).

Unfortunately GE does not react well to big dataset such as several thousands maps, even with the advanced and fancy features of the network links. We tried two different techniques and GE either ends up by struggling with the amount of data or showed ugly stuff while (slowly) refreshing.

Right now the other question is to know if there are some applications for users for this overlay and in this case how to distribute it.

About Physical layer

The 'Physical' layer which can be selected in the 'background' layers such as Google Maps, Satellite/Aerial imagery and Terrain layers has been created as a composite imagery got from several sources of data :

• 30 arc second global elevations grid model (bathymetry) from GEBCO,
• high-resolution Shoreline (GSHHS) from NOAA/SOEST and
• NGA vmap0 layers (lakes, rivers, political boundaries, green and relief areas...)

Contrary to nautical maps which are pre-processed and directly accessible on our servers, the raster tiles from this Physical layer are created on-the-fly by our map contour rendering engine in our servers.

This explains the display is much longer than for nautical layers.

More users will play with this layer in all regions of the world and for different levels of scales, more tiles will be created on our server, so available for all.

In the same time, the cache memory of the web browser will help to refresh faster when the user will display the same area.

Online live vessel traffic system

The GeoGarage team is leading some experimentation about the display of AIS live tracking online.

Using some specific hardware connected to a AIS receiver for sending AIS raw data automatically to the GeoGarage server (no need of additional PC), we have the following displays :

• Nantes/Saint Nazaire harbor with nautical maps overlay courtesy from SHOM (authorization for reproduction n°140/2008 for charts #7395 and 7396)
• Pointe à Pitre (Guadeloupe) harbor with nautical maps overlay courtesy from SHOM (authorization for reproduction n°409/2009 for chart #6948 and 7100)

Note : these two data flow are sent to MarineTraffic by GeoGarage for its own use

By the way, Marine GeoGarage is also studying the impact of nautical chart overlay on other Live AIS website such as :

• San Francisco bay ship traffic

About nautical chart updates frequency

The main advantage of the Marine GeoGarage server is to provide up to date nautical charts.

At this stage of the project, the time planning for the updates which depends on the distribution methods used by the different Hydrographic Services (HS) is the following :

• NOAA : every 2 months (today 1024 charts / 2223 including sub-charts)
• UKHO : every 3 months (today 667 charts / 1293 including sub-charts)
• Linz : every month (today 323 charts)
• Brazil : every month (today 242 charts)

* sub-chart : a paper chart might include a number of smaller detailed charts inset inside of it.

Note : in a future version of the Marine GeoGarage backend application, this scheduling will be reduced to match the update rating proposed the different HS servers (using automated distribution infrastructure provided by NOAA for example)