[NatureNS] Sizing Cougars and Cats on Photos

From: Hans Toom <htoom@hfx.eastlink.ca>
To: naturens@chebucto.ns.ca
Date: Wed, 09 Feb 2011 17:51:22 -0400
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It is relatively easy to measure the dimensions of an animal on a photograph quite accurately  A telephoto lens has an angle of departure from the frame, even a point and shoot camera. Measure the distance from the spot the photo was taken to the place where the animal was photographed and then by using geometric calculations, for say a 35mm sized film frame, one can develop a scale on the frame of the photo fairly accurately.  The distance from the photo taker's location to the animal can be measured by tape or laser range finder.

Another technique is to place a ruler or tape at the location where the animal was originally photographed and then take another photograph from the original spot. Use the same telephoto lens focal length.  One then superimposes the image with the tape onto the image with the animal, using tree limbs or other marks to align the photos, and presto you can measure the overall length, tail length, leg length, shoulder height and anything else you want.

I use these techniques to size birds in photos; for example, I did this once to differentiate between a Cooper's Hawk and a Sharp-shinned Hawk.  The techniques work best when the animal is in a flat on profile.

Hans Toom
Portuguese Cove, Nova Scotia, Canada
http://www.hanstoom.com/

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<DIV><FONT size=2 face=Arial>It is relatively easy to measure the dimensions of 
an animal on a photograph quite accurately&nbsp; A telephoto lens has an angle 
of departure from the frame, even a point and shoot camera.&nbsp;Measure the 
distance from the&nbsp;spot the photo was taken to the place where the animal 
was photographed and then by using&nbsp;geometric calculations, for say 
a&nbsp;35mm sized film frame, one can develop a scale on the frame of the photo 
fairly accurately.&nbsp; The distance from the photo taker's location to the 
animal can be measured by tape or laser range finder.</FONT></DIV>
<DIV><FONT size=2 face=Arial></FONT>&nbsp;</DIV>
<DIV><FONT size=2 face=Arial>Another technique is to place a ruler or tape at 
the location where the animal was originally photographed and then take another 
photograph from the original spot. Use the same telephoto lens focal 
length.&nbsp; One then superimposes&nbsp;the image with the tape onto the image 
with the animal, using tree limbs or other marks to align the photos, and presto 
you can measure the overall length, tail length, leg length, shoulder height and 
anything else you want.</FONT></DIV>
<DIV><FONT size=2 face=Arial></FONT>&nbsp;</DIV>
<DIV><FONT size=2 face=Arial>I use these techniques to size birds in photos; for 
example, I did this once to differentiate between a Cooper's Hawk and a 
Sharp-shinned Hawk.&nbsp; The techniques work best when the animal is in a flat 
on profile.</FONT></DIV>
<DIV><FONT size=2 face=Arial></FONT>&nbsp;</DIV>
<DIV><FONT size=2 face=Arial>Hans Toom<BR>Portuguese Cove, Nova Scotia, 
Canada<BR><A 
href="http://www.hanstoom.com/">http://www.hanstoom.com/</A></FONT></DIV></BODY></HTML>

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