I do not know much about the electronic charts format but I thought that you
might want to download a few S-57 charts to play with. The US Office of
Coast Survey has them on their website for free download.

See: http://nauticalcharts.noaa.gov/MCD/enc/download.htm

Thanks,

This will be a good place to get charts to test against. Sadly
I haven't found any decent documentation on the S-57 format yet.
And if I don't find any soon I'll have to write to first version
with raster charts.

Josce