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Post Options Post Options   Thanks (0) Thanks(0)   Quote administrator Quote  Post ReplyReply Direct Link To This Post Posted: 11 Mar 2006 at 12:44pm

Steve, have you got Photoshop? I'm creating the images as Photoshop psd files, they contain the head markings, the original photographic image, then the scale groups, thus I can generate any combination by switching the layers on and off or changing the opacity settings for any layer. This lets me have anything from a full composite, to just the mug shot, just the markings, or just the scale groups.

 

 

 

 

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Post Options Post Options   Thanks (0) Thanks(0)   Quote Vicar Quote  Post ReplyReply Direct Link To This Post Posted: 11 Mar 2006 at 5:44pm

Here's an alternative layout:

Aim is to include detail of head scales, dorsal marking apex, 'V' and eyelines. Oh and sex, can use black markings for male, brown for female.

I prefer working with diagrams, rather than photos, as light and pose can make the same snake look somewhat different in two photos, somehow the eye compensates for this when using a diagram.  Thoughts ?

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Post Options Post Options   Thanks (0) Thanks(0)   Quote administrator Quote  Post ReplyReply Direct Link To This Post Posted: 12 Mar 2006 at 3:58am

Steve excellent , that is a much clearer layout, the first version seemed to have too much information (probably just colour information, but it was stretching my IQ a bit to look at it)

This new layout is really clear and I would imagine very 'field friendly' 

I was wondering how much of this work is a familiarity exercise? Not a bad thing if it aids field ID, just an observation.

What I'm saying is that spending the time doing diagrams or scale counts allow the observer to absorb a lot of information about the individual animals they are studying, which may well lead to instant recognition from a fleeting field encounter... very usefull indeedy, particularly on a warm day when they seem  to rely on rocket propulsion to get around

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Post Options Post Options   Thanks (0) Thanks(0)   Quote herpetologic2 Quote  Post ReplyReply Direct Link To This Post Posted: 12 Mar 2006 at 9:33am

 

Using individual scales and their colouration can help to determine matches very quickly - plus you have a system of ID which is determined in the field - head scales using binoculars - you dont have to capture the animal to do the ID once you have managed to get a good head shot etc.

Also I have a yearling here which I will try and get some photographs of the head to see if the system would work on neonates?

Jon

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Post Options Post Options   Thanks (0) Thanks(0)   Quote Vicar Quote  Post ReplyReply Direct Link To This Post Posted: 12 Mar 2006 at 10:20am

Jon,

According to the Sheldon/Bradley paper, the basic system works very well with neonates. From memory...out of 80? specimens studied (over 8 years?), only one developed an (one) extra scale in adulthood. I can check exact numbers if needed, but those are the right orders of magnitude.



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Post Options Post Options   Thanks (0) Thanks(0)   Quote Vicar Quote  Post ReplyReply Direct Link To This Post Posted: 14 Mar 2006 at 12:10pm

Here's an interesting issue...

I've been drawing up some diagrams from digital photos of a small study site, and came across these two, drawn up independently from separate pictures (taken a few days apart).

Now, I'm pretty certain these are the same snake, but my interpretation of the scale pattern, from digi photo, is slightly different in each case, which would lead to a slightly different Benson code (Group 6? in this case).

If I can muck it up sat at home in my lounge, you bet I'll make a sloppy mess of it using binoculars in the field :P

Anyhow, this has convinced me that I need diagrams in addition to codification, and am now back to looking at image processing to derive a unique ID (or a range of numbers close enough to be the same individual).

Anybody had similar issues using codes ?



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Post Options Post Options   Thanks (0) Thanks(0)   Quote herpetologic2 Quote  Post ReplyReply Direct Link To This Post Posted: 14 Mar 2006 at 1:25pm

 

I would say that photos are needed in this case - I would say that it is the same snake as several patterns do match -

I make the Benson code as follows

1. 6301012 or 6211012

2. 5301012 or 5211012 - you need to look at the photos to look at that fifth/sixth number 1 scale

It shows that diagrams may reflect the artist's skill in drawing through a computer -

JC

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Post Options Post Options   Thanks (0) Thanks(0)   Quote administrator Quote  Post ReplyReply Direct Link To This Post Posted: 17 Mar 2006 at 6:16am

I've not found slightly different numbers a problem. If I can't see from a digital image how many scales are in a goup I've coded the group as ! Ignoring very small scales helps.

In practical terms going through a set of say 30 different potential matches, it is easy enough to match 62313!2 with 6231321 as the majority of groups match up, then it is a case of spending a little time looking at other images for the animals to see if it was indeed the same one.

The Benson code is never going to give a unique ID for every individual, it doesn't really need to and it simply can't as some animals will have the same code, and sometimes the code produced from a digital image will be slightly wrong depending on the quality of the image.

In practice though it is a very useful system. You take a stored head shot, you spend a few minutes grouping the scales and you file the image in your site folder.

It is when you file the image that you think.. hmmm, that code looks a bit like the third one I did a month ago, you then compare the two head shots, your scale pattern diagrams and any other associated images from the two separate encounters and decide if they represent the same animal. A far better method than having to check all 30 records for a potential match



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