Dear Colleagues,

I apologise to those who get this two, or even three times.

Is anyone apart from me interested in determining roof angles from
photographs?

I am interested in people's perception of the steepness of roofs.  In
many cases, because of alteration or destruction, or because the
building is thousands of miles away, I only know a building from a
photograph.  Since it is not possible to put a protractor on a
photograph of a building which has been taken at an angle, I have been
exploring ways of finding out what the angle really is.

A mathematically literate friend has come up with an equation which he
feels _might_ work, and before testing this, we want to determine the
precision and accuracy needed.  Based on two too small samples of
allegedly steep and allegedly nothing buildings, I think I need a
precision of 2 or 3 degrees, and an accuracy of 7 degrees.

Are we re-inventing the wheel here?  Would it be possible to digitally
distort the photograph and achieve results of the necessary accuracy?
If anyone else is interested in roof angle, and would find an equation
useful, please get in touch.

With best wishes to all,

Pat

Pat Reynolds
Research student, University of York

--
Pat Reynolds
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     "I have now got a pesitilent doctorate thesis to explore,
      when I would rather be doing something less useful ..."

                (JRR Tolkien Letter 176)