A C-Map must always be considered like you would consider a 2-year-old
chart.....out of date. The longer you use it, the more out-of-date it
becomes. But, the day you bought it wasn't the current chart. It sat
on someone's shelf for months waiting for a buyer. Before that it
took time to produce and distribute. They are sold like everything
else on the shelf.....sell the oldest product first...."stock
rotation". Your marine store doesn't have a EPROM burner to update
them.

Even the charts aren't well up-to-date for obstructions like you see.
The only way it gets updated is if someone REPORTS it to the
cartographer, a long, arduous, bureaucratic sequence of desks. The
guy drawing the map only has what someone told him at the moment to go
by......sometimes very inaccurately.

When was the last time anyone here took the time to actually report a
new shoal or rock that got put on a chart? Would that be NEVER?



On Sun, 14 Sep 2003 12:17:00 +0100, "Graham Stephen"
wrote:

I have had a nice shiny Raymarine Chart plotter with the C-Map Cartography
for a year of so. Generally I am delighted. One issue that irritates me
seriously is the large number of rocks that have suddenly appeared in the
water that I have sailed for years.

They appear on the plotter as the + symbol (IHO 421.2 apparently) which
indicates "Underwater rock over which the depth is unknown, but is
considered dangerous to surface navigation". Cross referencing to my paper
charts the original symbol was R which that the Nature of the Seabed is
Rock. This is not helpful and causes hairloss to the navigator.

I also come across some soundings of 60+ metres have been charted with the +
symbol.


I am unique in suffering this problem? Is the the cartography that is
faulty or is the Raymarine unit that is causing the problem.

Any comments welcome.

Graham




Larry W4CSC

3600 planes with transponders are burning 8-10 million
gallons of kerosene per hour over the USA. R-12 car air
conditioners are responsible for the ozone hole, right?