Marc Heusser wrote:
In article
,
DaveC wrote:
I was recently off the coast of Mexico and using a Garmin
chartplotter for position.
[snipped]
Garmin reports all the specific data for a
lighthouse such as you'd find on a light list but don't actually give
the LAT/LONG for the site so ... the ASSUMPTION is that they're
correct on the chart. Is that too much to ask?

It certainly should be in the right location, but does not need to be.
[snipped]
I'd hate to have such a lousy chart (if what you describe proves true)
but it never hurts to be wary.

I have a Garmin plotter and BlueChart for the Adriatic and
have consistent GPS positional errors on some charts - even
0.5nm difference switching between charts of the same area
but different scales.

I have tried differing datums but the errors remain -
presumably transcribed from the original charts. However, a
friend with C-Map does not have those errors and I would
have thought both would have used the same source data,
either British Admiralty charts or official Italian
hydrographic institute ones.

BrianH.