River Trieux and c map

[Laysula]

I have a plotter which uses a c map card. This has been dead accurate up to now and I have always been confident of my position. However we have just been up the river Trieux form Lezardrieux to Pontrieux and about half way from Lezardrieux to the lock our position went completely off and it stayed off position until we were half way back. We are now sitting on the visitors pontoon at Lezardrieux and the plotter is spot on position wise. Has anyone had a similar experience using a plotter going up the Trieux.

 

[Cockaigne]

I have a plotter which uses a c map card. This has been dead accurate up to now and I have always been confident of my position. However we have just been up the river Trieux form Lezardrieux to Pontrieux and about half way from Lezardrieux to the lock our position went completely off and it stayed off position until we were half way back. We are now sitting on the visitors pontoon at Lezardrieux and the plotter is spot on position wise. Has anyone had a similar experience using a plotter going up the Trieux.

Sorry, I can't help you. The only navigational instrument I have ever used on the Trieux is a depth sounder. I'd rather enjoy the scenery than look at a plotter.

 

[Arcady]

I had the same problem some years ago using a C-Map cartridge dating from early 2000’s. It’s possible (I hope) that the error has been fixed in later variants. I have not seen that error repeated with my Raymarine/Navionics combo.

 

[Hadenough]

The Trieux beyond Lezardrieux bridge is not surveyed so none of the systems will give an accurate plot. I have been up and down from Lezardireux five times this winter using Garmin and Navionics charts. Neither were accurate. Beyond the La Roche we were in ploughed fields. It is a contour line navigation anyway and changes more often than the Deben Bar so I really wouldn't rely on a plotter to keep me off the mud.. Your first (hopefully successful) plotter track is useful though as long as you can cope with it taking you over the green bits according to your plotter chart. Fantastic place though, lovely people and highly recommended.
Edit:
Get a Google Earth print out of the river track. The current one shows it at low water so displays the bits to avoid. Do it on a rising tide and it is not a problem.

 

[James_Calvert]

The current Reeds Almanac states that official charts do not extend much further S than Lezardrieux but a useful river guide/map is available from the Harbour Master. My old Shell Channel Pilot advises commonsense pilotage is applicable round the bends.

Always been glad of my echosounder to confirm my commonsense was up to the mark.

It would be surprising if official and accurate electronic charting was available. But surprising also that you can just fall off the edge of the chart without any warning.

 

[Laysula]

Thanks for that. It was a bit unnerving at first but we ignored the plotter and as you say followed common sense and the sounder. Return trip was a bit awkward though as we had quite thick mist after the first bend but we did have a bit more water.