Monday, 19 September 2011

The Latest Nessie Sonar Contact

They just keep coming thick and fast these Nessie stories. On the back of two intriguing photographs these past four months and a head-neck sighting, a sonar contact has entered the fray.

This story appeared in the Scottish edition of the Daily Mail for Thursday 15th September 2011. It looks like it did not make the UK website of the Mail, so it is reproduced here for those outside of Scotland.

But first the basics on sonar. I do not claim to be an expert but it is an important tool in the hunt for the Loch Ness Monster. However, like normal photographs and pictures, there are degrees of interpretation, misidentification and, yes, hoaxes.

A sonar contact is a picture made from sound waves instead of light waves. The sonar device sends pulses of sound at various frequencies depending on how deep one wants to go. The reflected echo is processed to form a snapshot of the area within the sound beam.

However, being a continuous series of pulses, the sonar picture is more like a film than photograph and each successive echo builds a trail of images as the targets in the beam move. In fact, one could argue it is more like a picture taken with a very long time exposure.

So if an object is moving it will describe a trail of some shape and thickness. This thickness is not the girth or height of the whole object but whatever returns the strongest echo. This depends not on the size of the animal (for example) but the difference in density between the water and the object. In the case of the fish, the greatest density difference is between the swimbladder and the water since it contain much less dense air (or some other gases). The rest of the fish is closer to the density of water than the swimbladder. In the case of mammals and reptiles, one main area of interest would be the lungs.

The Daily Mail story now follows.




THERE is no sign of the trademark elongated neck, or the signature green humps. But the experts believe this almost unfathomable sonar image could be a breakthrough in the hint for Nessie that began in earnest in 1934.

Surrounded by fish, the ‘blip’ has a girth of about 5ft, though there is no way of estimating its length as it was moving. The image was captured by the quick thinking skipper of a pleasure boat who took a picture of the reading while waiting for his customers at Urquhart Castle, in Inverness-shire. Marcus Atkinson, 42, knows Loch Ness like the back of his hand and spends every day on its waters — but said he had never seen anything like this before.


He added: It's very weird. It was obvious it wasn‘t a shoal of fish and it just kept getting bigger and bigger. This thing is completely different from anything I've seen before.’ Mr Atkinson, of Fort Augustus, Inverness-shire, was idling in the bay when he saw the unusual sonar image. He said: ‘it's one of those moments where you just think, “What on earth is that?" I grabbed my mobile phone and took a picture before it disappeared of the screen. it's all very bizarre.‘ Mr Atkinson's picture shows a cross-section of the loch, with the boat itself at the top right of the picture.


The bright green area on the bottom right of the sonar screen is the bottom of the loch, which rises as the boat gets closer to shore. The small green flashes scattered across the monitor are deepwater fish. But the part of the picture that is exciting interest is the long, thin streak - that looks a little bit like a propeller - between the 20 and 25 metre depth markers. The measurements show it is about 5ft thick - but there is no way of telling how long it is as, if the object was following the boat, it would show up on every ‘blip’ of the sonar.



Expert Nessie hunter Steve Feltham said: ‘This is a sonar contact that defies all explanation — it's a huge object. ‘it’s fascinating, because the camera hasn't an imagination — it just shows what's there.’


So ends the account and I wrap this latest sighting with some comments. The first is that the captions editor makes a howler in comparing the elongated pattern to a sleek, lithe plesiosaur. If they had read the article, they would have gone for a different picture for (as said in the intro) this is a trace built up over a succession of sonar pulses.

The other observation is that the stated 5ft girth is not necessarily the complete height of the object because if it is an animal, it will be the lungs or swimbladder being measured. But then, five feet of lung or bouyancy organs points to one big creature.

I presume the five feet measure is taken by comparing it to the 20-25 metre depth scale in the picture above. Using my trusty ruler, I get an average estimate of 2.5 feet "girth" which is still quite a measurement. I would add that if this was Nessie and we assume a true girth twice as much as my measurement (i.e. giving us five feet) and apply classic Nessie proportions based on numerous eyewitness tesimonies and analysis, then a total tail tip to head length would come out as about 30 to 35 feet - which is a typical Nessie size.

So what was it with a minimum girth of 2.5 feet that was moving at a depth of about 70 feet? No doubt some will have a rational, non-Nessie explanation for this odd signal. Was it some human artefact somehow floating at a great depth? Was it a strange effect of sonar bouncing of the underwater sides of Loch Ness? Or was it the famous and mysterious denizen of Loch Ness?

As for us, this goes into our log of claimed Nessie sightings.

ERRATA: I just remembered "girth" is the measurement around an object as opposed to its thickness. So assuming a circular type girth, a rough girth estimate given a thickness of 5ft would be Pi x 5ft which is roughly 16ft.

17 comments:

  1. Great, fascinating update.
    And thank you for your wonderfully informative and fair-minded site, what a delight and a refreshing break from dogmatism on both sides.
    Do keep up the great work :)

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  2. Two skeptical persons have said it is or looks like a log.

    I would point out that the sonar screen is recording the signal at just below 25 metres and logs do not tend to float at the depths.

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  3. Many thanks indeed for posting this. The difference between fish traces and the big one is startling. Has Shine commented?

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  4. I believe Mr. Shine is out of town but being the local expert on Loch Ness and sonar, his comments would be useful. I have tried to contact the witness as well, which I regard as equally as important to get more info.

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  5. Looks like a Beluga Sturgeon. They can grow to that size.

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  6. Interesting, but the thickness of the echo only represents strength and cannot be used to provide a measurement of any description so girth or depth of body or anything else of that nature cannot be interpreted from the contact.

    Similar contacts can be obtained by the side lobe reflecting off the loch wall or simply side echoes.

    This is why the Loch Ness Project spent several YEARS analysing causes of errors, so that individual contacts like this would not enter the public domain.

    Nevertheless they still do and will never be stopped ... and it is all good for the local tourist industry.

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  7. But surely the bigger the strength of the echo - the greater the size of the object?

    And why is the sonar's vertical readings in metres if the echo is not measuring distance?

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  8. No, that does not always apply. It could apply, but it cannot be relied upon. The distance is the distance to the contact and the maximum distance on the screen is the range the sonar is set to.

    If you look at causes of error in my book a good example is why a fish is a crescent.

    When it first appears in the beam it is at the edge of the beam which might have a 20 degree spread. Visualise it. The fish enters the beam at the edge of the beam so appears further away as the edge of the beam is the hypotenuse. As the fish moves into the centre of the beam it appears stronger and closer as it is now in the centre of the beam, then, as it moves out of the beam it is again further away (the hypotenuse) again and weaker so you end up with a crescent.

    However, if you look at the range of the sounder and then use that distance to measure the thickness of the crescent in the middle of the beam it might well show a fish 2 or 3 feet thick. In the examples I show it would mean a shoal of fish bigger than the biggest salmon ever caught.

    This is the same illusion as the ridiculous Discovery Channel documentary who had a diver swim under their boat to show what a human would look like on sonar. Well that human only recorded between 1% and 5% of the strength of the contact as the remainder was the air in the wetsuit and in the mask, the STEEL tank on the diver's back and the large stream of bubbles coming from his valve. The whole concept was wrong yet there it is, part of the history of the use of sonar in Loch Ness and other people take it as fact because it was the Discovery Channel.

    Sadly garbage in, garbage out.

    However a single contact like this is totally meaningless.

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  9. Sounds like sonar is totally useless for establishing whether there is anything unknown in Loch Ness. A large creature could pass by a beam and a variety of explanations could be forthcoming as to what it means!

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    1. Thats funny.ive seen sonar that shows images of actual featureslike sunken ships and structures almost like photos.hmmmmm.

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    2. Depends on the quality of equipment and whether the object is stationary.

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  10. wouldn't it be great if they actually brought that thing up and it looked exactly like it does on the sonar? a 3 inch green blob.

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    1. LOL, that would be an even greater mystery.

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  11. Hmmm... I would really love to know the exact date when this sonar contact was made. If I recall, I remember reading somewhere that it was taken on August 24th, 2011. However, I am not sure if that is right. Can someone please tell me when this sonar photograph was taken? Thanks! :)

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  12. Hmmm if sonar doesnt work then why bother with operation deepscsn tony. not just discovery chanel bin ridiculous eh ????

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  13. This sonar is not real if they cant prove it to anybody ... You would have to show somebody to get them to believe you and also that photo says underneath it that it is a painting by Seb Gecko

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    1. That credit refers to the plesiosaur painting they reproduced for the article and not the sonar photo. I thought that would be obvious but obviously not LOL!

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