Google Earth at Sea...
I know it sounds strange, but we've been using satellite images to augment our electronic charts for four years now. No matter how the good the charting software is, it is limited by the accuracy of the underlying charts. Most electronic charts are very accurate around the major shipping ports and lanes of the world, but who wants to sail there. There is not a lot of work being done to upgrade the charts for our cruising grounds.
We started using Sat photos in Eastern Fiji where the charts were off 7/10 of a mile, but not a single offset.. it was random. On our trip though Tuvalu, Kiribati to the Marshalls (no Cruising Guides!!) it worked amazingly well. Check out the anchorage in Onotoa Kiribati (1.825383S, 175.543985 E). In Cmap etc it is off by a bunch and there appears to be only one outer anchorage (with a couple of random soundings). If you look on Google Earth you can see the tight entrance into the inner lagoon, you can even see the coral heads. If you load our Google Earth Track
you can see our path into the inner lagoon.
A lot of charting packages have interfaces to Google Earth (GE), if not GPS Utility (http://www.gpsu.co.uk/
) has an interface from/to pretty much everything. I use OziExplorer (you can also make/calibrate charts from screen shots or scans and it uses Nasa's Mrsid Landsat Satellite images). I create waypoints in Oziexplorer, import them into Google Earth and compare. If they need adjustment I tweak them in GE and send them back to oziexplorer.
Even if you don't want to go through the hassle of import/export to check waypoints, you can use GE to find rough ideas of spots to anchor (by looking at water color etc). We use a hand held depth sounder
in the dinghy to scope it out first. Depending on the area and the scans you can use the water color/depth to get a better idea of rough depths in the area.
Google Earth does not require an internet connection but like all things cruising, it does require planning. When GE is not connected to the internet it uses previously viewed data ("the cache") to display the images. So get connected in port, scan the areas want to have available at sea. Disconnect from the internet, select No when it asks you if you want to diagnose your connection problems and double check your work.. Presto the best satellite imagery for where YOU want!!
Some notes for those following in our track
.. Indonesia (has horrible charts with deep anchorages), it helped us find anchorage spots where we would have never even looked. The reefy areas of the Red Sea (where you want a good idea what's around) were bad; especially the coast of Sudan. If you are planning on spending any time in the Maldives, Sat Photo's will help with anchoring options. Eastern Fiji and the Island north it was a real help.
For more details check out Google Earth at Sea
in our Computers at Sea
Hope this helps..