Do you need...
Some people like to be able to overlay their chart onto Google Earth, or vice versa, and there are chartplotters, such as Fugawi Marine ENC,
that will do that. This feature may be quite useful when going
into a poorly surveyed harbor. There are sailors who feel it helps them
get an overall sense of a new destination.
There are chartplotters that will combine surface navigational charts
with either Google Earth or land topographic maps, and create a
three-dimensional view of the land and sea. This is most useful with
poorly charted harbors.
It may be useful to have street maps available, to know where to go
when you get off the boat in a new port. Products that support
these include Fugawi Marine ENC. If you opt for this feature, you may want a printer on board so you can take directions with you.