Galileo, the European global satellite navigation system,

[barnakiel]

Originally Posted by Benz

My biggest question is: when will actual surveys of physical places happen so that the position fix from the satellites can be accurately plotted on a chart? I have been to many places where the GPS may be totally accurate but the charts are not, and boats go hard aground because the plotter showed them to be in a channel when they weren't.
It seems this is a more pressing concern that having "more accurate satellite signals"
Ben
zartmancruising.com

Perhaps when govt agencies apply sat derived measurements to their products.

We have been places where an island was X miles off on the official chart but it was right where it was on Google Earth.

However, many such places do not have relevant govt agencies. Hence at places the answer is probably 'never'.

b.

[bcn]

Originally Posted by Dockhead

That means that accuracy of position data of better than 2 meters is not at all overkill. I would be really happy to see something more like 30cm, which is theoretically possible. Of course in this range and even at 2 meters EPE, the position of the antenna inside the vessel becomes important, and we don't have the ability to account for that in most of our consumer-grade chartplotting gear. It would be nice if we could have a real sized own ship icon (to be used at high zoom levels), with the antenna position determined within those dimensions. I believe that ECDIS systems used in ships already have this.

With EGNOS (and other similar correction sources via satellite) you can get down to 60-80cm precision under optimal conditions.
From there on you need differential corrections in real time from a base station that should be in a range of 10nm. Then it is doable to get a 1-2cm precision.
L1/L2 RTK.

OpenCPN allows parameters for the position of the GNSS antenna if you use the own ship icon, and you will even see a point indicating the antenna position. And the icon gets re-sized for scaling as well.