How to measure an animal track dimension from a photo containing a scale displayed on a monitor.

This requires that the viewer know the size of the scale beforehand.

  • Call the value of the size of the scale S.
  • Use a ruler to measure the size (e.g., length, diameter) of the scale on the monitor screen and call that value U.
  • Use the ruler to measure the dimension of the track (e.g., length, width) on the monitor screen and call that value M.

    • The size of the dimension, D is given by D = S * M/U.

    Example: Suppose you photograph a Bobcat track and with a coin such as a quarter near the track. Also suppose that you display the photo on your computer monitor and you measure the length of the track as displayed on the monitor as being 65mm (this is M). Next, suppose that you measure the diameter of the quarter as being 28mm (this is U). Next, suppose you either measure the diameter of an actual quarter or you do a web search and determine that a quarter is 0.955" in diameter (this is S).

    The length of the track, D, is 0.955" * 65mm/28mm = 2.31".

    הועלה ב-דצמבר 26, 2018 07:03 אחה"צ על ידי ollerton ollerton

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    @ollerton nice write-up and your method is the most precise I can think of. I usually place a piece of thin paper over my screen and trace the scale object and then use that as a mobile ruler that I can shift around the screen. Not very precise.

    פורסם על-ידי jim_carretta לפני יותר מ 5 שנים

    Cool. I like that too. I have done with Jim suggested too, by using paper and them moving it on the screen. Or I open the image in Photoshop and compare it there. I can shrink or enlarge until the ruler dimensions match the tic marks in the software to see real sized image.

    פורסם על-ידי beartracker לפני יותר מ 5 שנים

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