Sea Map is a map viewer that supports both online Maps and offline Open Sea Maps for planning and light navigation purposes. Check www.openseamap.org for the quality and availabilty of the maps.
Sea Map comes with a preinstalled set of community created open source navigational maps which can be used, even when you have no data network available.
This means that you can navigate, without the roaming charges that come with the use of online maps.
But Sea Map does not just support any map, it supports sea maps! Since means you have additional features such as lights and buoy markers that are not visible on the normal map.
What can and cant you do with Sea Map?
Every mariner knows you should use certified charts for navigation, and since the nature of community charts is by definition not official, you should not rely on Sea Map to be your primairy and only source of chart material.
That beeing said, Sea Map is a great utility and the power of open source community maps may very well lead to better and faster updated charts for particular areas.
You can use Sea Map to check features and to quickly find your way, and it will prove to become your chart table in your pocket.
Why is there no (good)map for my region?
Sea Map is a viewer for community sea charts. If there is no map for your region, you can help in creating it by joining openseamap. Check for quality and availability on their website, it is under rapid community development.
How can I get a better/newer map?
You can join the mailing list and request maps from there. We follow the releases of openseamap closely and will provide updates (free of charge) with the latest maps. You can also send in your maps and they will be added to the server for the benefit of all.