On Wed, 19 Jan 2005 17:24:31 GMT, otnmbrd
wrote:

Rodney Myrvaagnes wrote:


It would seem interesting to investigate what caused the errors in the
charting systems. My experience with non-charting WAAS receivers is
much tighter. At the slip we have used for the past few years, the GPS
not only tells us we are in our own slip, and not either adjacent, but
whether we are bow or stern in.

You did say the source for chart data was unknown.

I haven't purchased a charting system because I would still have to
keep paper charts even if I did. I am interested to read of your
experiences, and thank everyone for this thread.



Rodney Myrvaagnes

I have a strong feeling that much the the information we all gather as
to possible anomalies in GPS fixes versus plotted positions/chart
plotter positions/actual positions will for the most part end up as very
case specific.
We will also need to know who's charts the plotter data is based on
(NOAA/British Admiralty) and is it up to date; who created the plotter
program; are all the components matched and compatible; is the error
consistent; etc. (much of this need some tech types to rule out or
confirm system problems versus charting problems).
Nowadays, all of what I'm seeing is very Port specific and not of much
help to the average boater, other than to say the possibilities exist.
I do note that I've seen a great improvement over the years that I've
been using chart plotters for this port, to the point that in some cases
I consider the units "right on", G with reservations.
Again, and as always on this subject ..... never rely exclusively on one
system, especially in confined waters.

otn
In this connection I should say where I got these tight results. It is
a marina just south of the Holland Tunnel on the NJ side of the North
(Hudson) River. The chart survey is new, since it shows the floating
docks that were only built in 1989.

I use charts in Maine that use 18th and 19th Century surveys, and will
probably never get redone. The situation there is not the same as in
NY Harbor, where many charts are sold every year.

In Maine, I use the GPS the way I formerly used Loran C, for
repeatibility, in places I have already visited.



Rodney Myrvaagnes NYC J36 Gjo/a


"Be careful. The toe you stepped on yesterday may be connected to the ass you have to kiss today." --Former mayor Ciancia