Most modern charts are good in areas that have heavy shipping traffic,
but who wants to sail there? It doesn't take long before you realize how far
off charts can be. We noticed ourselves on land more than once within 500
miles of the US/Mexico boarder. Other regions that are notoriously bad
include the eastern portions of Fiji (7/10 of a mile off), Kiribati, and
Tuvalu (2 miles off) and those places have reefs everywhere. In fact, we
watched one boat sail right by the lagoon thinking that there was no way it
could be THAT off. The detail in Google earth is amazing and you can use
it offline as long as you prepare the data ahead of time.
Throughout Indonesia we frequently found ourselves looking for a patch of
sand to drop the hook in. The anchorages on the eastern side are typically
on small shelves close to land that drop from 40' to 500' rather quickly.
The electronic charts didn't have enough detail to find anything reasonable,
but Google Earth (GE) showed us plenty of options. We even entered poorly
charted areas using GE as a guide with me on the bow as a lookout. Google
Earth stores data (cache) on
your computer so that you don't have to wait so long to see an image the
next time you visit the same location. If you disconnect your computer from the internet and
try re-starting Google Earth, you'll get an error message about not being
able to connect.. do you want help? select no and it will continue to load
your cache data. Some online KML links will give errors but all the critical
graphical data is there. I
save copies of this cached data based on regions and I copy the data I'm
interested in viewing into the correct place so that Google Earth will see it.
(Google for Google Earth offline use for more details). If you have navigation software that has
an interface to Google Earth you can check your waypoints and routes against
the Satellite data. The most I've ever seen GE off is 100 feet and that was
probably the GPS not GE.