Thine eyes deceiveth thee.....

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Telo
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Thine eyes deceiveth thee.....

Postby Telo » Tue Jun 10, 2008 11:34 pm

Maybe it's just me, but until I'm familiar with an anchorage, I feel that it is much smaller than it really is, and that the slightest breath of wind will have us cast onto the rocks.

I was thinking about this when I dug out a pic after reading a comment by Silkie about Gylen Castle on Kerrera in another thread.

Image

From the boat, it really felt as though the rocky point (below and to the right of the castle) was only about one-and-a-half boat lengths from our stern. Yet it clearly isn't. I suppose the positive aspect of this trick of perspective is that it introduces an extra degree of prudence that actually does help keep us off the rocks.

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Postby Silkie » Tue Jun 10, 2008 11:50 pm

I'm constantly amazed by the difference a change of viewpoint can make over water.

Coming out of Dunstaffnage and turning south I never go inside the fish farm since there seems to be very little advantage and it's very close to the shore. Going north it's a mile off and I almost always go inside to save a huge detour.
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Postby stevepick » Wed Jun 11, 2008 10:04 am

You are not alone. I am constantly convinced by my own eyes that we are only a couple of boat lengths away from the rocks when we are at anchor. Reference to a chart will convince me this is not so , but I don't understand how this visual trick happens every time we anchor.
Last year in the small bay just to the sw of lowlandman's bay we anchored, the chart said it was a cable wide, yet it felt much more enclosed and it was only when we went ashore you could appreciate that our eyes were deceiving us by a huge margin, It is an odd trick.
From the boat:
Image

From the shore:
Image

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Postby Ghillie » Wed Jun 11, 2008 1:34 pm

Yes, estimating the distance and doubling it is usually still short....but beware when it is dusk/dark when the opposite is true as I have found to my cost (and continue to do so). Things then are much closer than they look! It may explain why anchoring in a crowd is appears easier in the dark and why you end up dragging towards all the other boats. :?

There are some simple sonic (?) devices for measuring rooms etc, I wonder what their range is. They might be useful. (unless you have radar, obviously)

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Postby ash » Wed Jun 11, 2008 7:36 pm

Ghillie wrote:There are some simple sonic (?) devices for measuring rooms etc, I wonder what their range is. They might be useful. (unless you have radar, obviously)


£37 will give you 15 metres.

£300 will give you 100 metres ( or 200 if you send SWMBO ashore with a target board ).

I'm glad to hear that others have the same problem of judging the distance to the shore line.

SWMBO and I often have a disagreement during the anchoring procedure, the perspective from the bow and the cockpit always seems to be different. I think that the height difference of the eye may be the cause. I'm at the bow, supposedly in command, but she with the tiller and throttle is in ultimate control.

For our favorite anchorages, I have taken the GPS ashore and plotted waypoints for some prominent positions and drawn large scale sketches for future reference. Once everything has settled down, it's reassuring to be able to measure the distance to the shore, even it's only accurate to +/- 10 metres or so.

Widening the discussion slightly, do you find the same difficulty in judging swinging room between other boats already at anchor?

Recently we intended to anchor next to Aquaplane. I hope the 'discussion' wasn't too loud. I wanted to ensure plenty of swinging room whilst SWMBO insisted that it would be rude to anchor too far away.

I worry about the situation when there is no wind ( or tide ) and everyone is lying at different points of the compass although then hopefully some are lying on a shorter scope to a loop in the chain.

I once read an article about a home made 'distance off meter' but I can't remember the principle.

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cpedw
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Postby cpedw » Thu Jun 12, 2008 10:37 am

ash wrote:SWMBO and I often have a disagreement during the anchoring procedure


I couldn't possibly comment and I have Jane's permission to say so.

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Postby Ghillie » Thu Jun 12, 2008 12:34 pm

Thanks for the information on the sonic measuring devices.

For measuring distances-off abeam to shore, I have simply taken hand- held bearings of a common feature from the bow and then, quickly, the stern, and have then plotted the angles. You could use a sextant horizontally of course, for finer angles if the distance required is not abeam, (provided the boat keeps still); but who has a sextant on board these days?

(on reflection, I am not sure why I am posting this....you will all know this stuff)

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Postby claymore » Thu Jun 12, 2008 1:00 pm

Ever thought of a range finder - Golfers use them to quite good effect
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ash
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Postby ash » Thu Jun 12, 2008 1:29 pm

claymore wrote:Ever thought of a range finder - Golfers use them to quite good effect


How do they work?

This One uses the height of the pin.

This One doesn't say.

BlueMoment Announcement

"Would all members please fit a golf pin sized pole, with BM Burgee, on their vessels. Further would all members carry spare poles and burgees which should be set up on the shoreline of BlueMoment Boltholes for the future benefit of BM members"

Ash :)
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Postby aitchw » Thu Jun 12, 2008 5:09 pm


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Re: Thine eyes deceiveth thee.....

Postby Windfinder » Mon Jun 16, 2008 7:55 pm

Shard wrote:I suppose the positive aspect of this trick of perspective is that it introduces an extra degree of prudence that actually does help keep us off the rocks.


Pretty hard to gauge scale over water and rock when there's nothing to gauge scale from.

I've lost count of the times that small nearby rocks turn out to be very large rocks a long way away.

Amazing photo BTW. Sickening. We've passed there so many times and never thought to over night there. It looks idylic but I guess it may get busy?

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Postby Arghiro » Tue Jun 17, 2008 8:07 pm

Sometimes, the rocks really are that near tho'!

Image

Pic taken at Mermaids cove, Llandwynn Island SE corner of Anglesey. Just about the shuggest anchorage I know. I am close to that rock astern because there is an even bigger one just off the bow. But it's OK at high water, that one dissappears & the shoreline recedes by about 100mtrs. Not much current, but tidal range is 7mtrs or so.

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Postby sahona » Tue Jun 17, 2008 9:39 pm

Looks like I'll have to start carrying my Barr & Stroud 80cm rangefinder as well as all the other paraphernalia then. Just didn't think it would be useful aboard as the previous owners seem to have stripped off all the ordnance...
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