Sorry - I failed to make my point clear - Somewhere in the digitisation the
symbol for a rock bottom that is way deeper than the draught of any
conventional surface vessel has turned in to the symbol for a rock that is
dangerous to surface navigation.

I am a sad person who corrects his paper charts, so I know that they are
slightly out of date rather than very out of date. I am still trying to
work out a policy that I can afford for updating the electronic charts.
Effectively paying two license fees for the same information irritates me.
(I am a Scot)

My patch is in a area where the legend "Unsurveyed" appears on charts.
Other parts of the chart may have been surveyed by a man, who might have
sailed under Nelson in his childhood, in small boat with a lump of lead on a
piece of string. He certainly did not have the luxury of GPS when he made
the chart so we cannot rely heavily on the accuracy of our own systems.

My charts regularly get updated with NMs where people have reported
"uncharted features". I have done this myself. There is a form H.102 for
doing it. They are not usually very significant as no master of ship would
take his ship anywhere on a 150 year old survey where there is any risk of a
surprise (hopefully!)

I am still unsure whether the problem is a C-Map or Raymarine issue - I
suspect the former. I would not risk my life on the electronic charts!!!

Graham




"Larry W4CSC" wrote in message
...
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out of date. The longer you use it, the more out-of-date it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?