I you take the position shown from your GPS on the displayed chart -- is it where it is supposed to be if you were plotting it from "features" or known marks? (i.e., like you were plotting it on your paper chart using bearings.)

Then, is it an issue that the channels are in different place or that the bottom just isn't what it says? (i.e., is it just shifted or is it that depths are just not correct?)

I've heard of the chart being "right" but the LAT/LON being wrong, I'm sure that bottoms change due to normal shifing or special occurances (like hurricanes).

Oh, Happy New Year, Chris. I enjoy your posts.