how accurate is mapsource bluecharts

HEY
How accurate are bluechart mapsource?
ive located some wrecks last summer with it and some i didn't
my gps was accurate to about 10 ft
ive cross reverenced some wrecks on google earth and ether one is out by 400ft or so, im wondering witch one?
im using "bluechart atlantic v9.5"
for instance the bailey lighthouse on the south bull is in the middle of the sea according to google earth!
ive downloaded the new downloads for bluechart on the garmin site and noticed a new wreck has popped up on the south burfourd not far from the other one.

ive checked on admiralty charts of Dublin bay and the wrecks not there!
any one any ideas

thanks
anto

Mapsource is as accurate as you will find. You will find that the charted positions of wrecks are not necessarily correct. We have found the charted position to be “out” by as much as half a mile.
These positions are generally the “last reported position” of the wreck.

I think there is an accuracy problem with Google earth. It is a pity. I had some great ground located via Google but it was nowhere near accurate.

I’m afraid I would have no experience of the Buford but maybe the Admiralty chart is older?

no the burford is clean of wrecks but just past the south burford there is a wrecked marked on a chart i have but ive looked for it many times but to no avail.
the kish bank on the other hand is littered with them