Accuracy of Garmin Blue Charts

[Master_under_Dog]

This is where I need some experienced advice. I have noticed that the position of buoys on my Garmin Chartplotter is at variance with their actual position. For example as I kept to port of the starboard hand buoys going down river past Burnham my position was given as being in the main channel, i.e. to starboard of the buoys. Similarly on the chartplotter the buoys marking the cable crossing east of Burnham were quite a long way upstream of the actual buoys. I know that GPS is not accurate to a metre or two but these discrepancies are much larger than that. Does anyone else have this experience?

Michael

 

[sailorman]

my C-MapNT charts show us tracking through locks thats accuarate enough,linked into a Raymarime RC80+

 

[Habebty]

My Bluechart plotter even puts me on the right berth in Ipswich Haven Marina. Generally very good, but NTMs must be taken into account for bouy movements of course. Another obvious point is to check in your GPS settings menu that it is set to the correct datum - WGS84 perhaps.

 

[moondancer]

My c-map NT plus chartplotter also shows discrepancies on the Crouch. All physical features are spot on but some of the buoys are out, particularly the racing marks. I put this down to the normal movement of buoys and my chartplotter catridge needing updating.

 

[FulmarJeddo]

My Garmin GPS550 seems spot on in the Swale and Medway. Buoys seem to be exactly where the plotter shows them. My mooring at Lower Halstow completely dries, I can follow the narrow creek that is little more than a ditch across the mud and appears as a dotted line on the plotter as the tide is coming in. If I wander off the line the echo sounder changes rapidly.
I had some problems transfering waypoints from my handheld GPS to the IMRAY charts on my PC, they were a long way out. That was due to having the Chart datum set wrong.