Sailing in Scottish Islands

dunedin said:
As others have said, if you have observed any issues with Antares Charts then you should report them back to Antares so they can be checked.
I am not familiar with Gometra North Harbour, but Antares looks to be consistent with but much more detailed than the official Admiralty chart. So not sure what you feel is “odd”.

I have been into and out of Arisaig a few times using Antares and not noticed any discrepancies, having checked depth by going directly over a few spot soundings in the approach to check actual tide height (although stuck to a narrow channel so not explored a lot). But I don’t see why you say Antares “significantly underestimates the depths” in the narrow channel - i.e. you are saying it is in fact deeper than Antares indicates. But from what I can see:
- Navionics gives no detail, so take your choice of minimum depth between drying 1.5m and drying 0.2m
- Admiralty BA2207 again gives no detail, with minimum depth of drying 0.2 - but before relying on this, it is difficult to tell exactly which source but looks like the survey was leadline type between 1857 and 1866 !! (Do you feel lucky)
- The old Martin Lawrence Guide didn’t seem to commit to a depth but implied could find about 1m if zig zagged round drying rocks
- Current CCC suggests a minimum depth of 0.4m - but probably now based on Antares data rather than 19th Century surveys
- Antares shows a route “technically” with minimum 2m depth, but strongly advises not assuming this but 0.4m controlling depth, as deeper gap far too narrow to keep in reliably with tide.
On this basis Antares, rather than underestimating, is showing a tiny bit more depth than other sources. But all best done with a couple of metres or more of height of tide to be on the safe side.
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I wholly agree with you re Arisaig. I am familiar with Acarsaid Mor Gometra, and haven't found Antares Charts different to what I have found by personal experience over the past fifty years. As it happens I have a 1966 copy of the CCC SDs to hand, in which a "correction" states that, "it is reported (1968) that this anchorage is silting up, and 6ft at LW is the maximum anywhere". At the time I thought that was wrong, and always could, and still can find considerably more water. But anyway, that particular Acarsaid Mor (other spellings are available) has a clean and gradually shallowing sandy bottom, and apart from the approach to the entrance, is totally devoid of any nasty surprises. A wee bit of application of the twelfths rule, and a glance at the sounder is all that's needed. One change that has taken place, is that it is now much less encumbered by long and thick masses of thong weed.

If JD feels that the Antares details are "rather odd", and if he can be more detailed, I would earnestly encourage him to report his findings to Antares.
 
dunedin said:
As others have said, if you have observed any issues with Antares Charts then you should report them back to Antares so they can be checked.
I am not familiar with Gometra North Harbour, but Antares looks to be consistent with but much more detailed than the official Admiralty chart. So not sure what you feel is “odd”.
Click to expand...

I'm going from hazy memory here, but I think we found the pool to be a lot bigger (ie a larger proportion of the surface area) than he suggests.

I have been into and out of Arisaig a few times using Antares and not noticed any discrepancies, having checked depth by going directly over a few spot soundings in the approach to check actual tide height (although stuck to a narrow channel so not explored a lot). But I don’t see why you say Antares “significantly underestimates the depths” in the narrow channel - i.e. you are saying it is in fact deeper than Antares indicates.
Click to expand...

The issue I found wasn't in the narrow channel, but in the notoriously shallow reef across it about halfway in. I had been in there a couple of times before Antares covered it, using the hardback CCC book directions, so when I went in the next time I kept a careful eye open: the reef is there, but I don't think it comes nearly as far up as he suggests:

M86444G.png


Please don't get me wrong: the charts are generally very good and a remarkable undertaking and I believe that a couple of the Clyde locations were my suggestion. It's simply that constructing accurate contours using limited data in areas of rapid change is very, very hard and at the scales Bob works at this is bound to cause problems. Users of the charts should be aware of this, and follow Bob's disclaimer to the letter.
 
Back in #16 I mentioned the Penguin club. Curiosity got the better of me and I searched to see if the club had updated its gazeteer - Penguin Bolt Holes.
I was surprised to find that my snapshot of their document (which I had plagiarised/added to for my own benefit back in 2007) was available on the web.

http://www.bluemoment.com/downloads/penguinboltholes.pdf

But I couldn't find an update. Anyone know if any updates were ever produced?

Looking through the document, I'm even sadder that I am currently confined to Lake Solent.

Cheers
Bob
PS my email reference in the document has been defunct for years
PPS I have no connection to who or what Bluemoment is.
 
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