Re: Vegetative cover estimates- grid overlay possible?

Posted by Glen MacDonald-2 on Feb 23, 2011; 5:26pm
URL: http://imagej.273.s1.nabble.com/Vegetative-cover-estimates-grid-overlay-possible-tp3685534p3685541.html

Dear Sarah,
I'm sending you an ImageJ macro that I've been recycling for different stereology applications.  Note that the scaling on this version is only a 'placeholder'  for scanned EM negatives and has not yet been calibrated - hoping to get the calibration images this week.  But you can either comment out that part of the macro or reset the scaling in Image>Properties after running the setup command.  I'm not sending here because the scaling is not yet verified.  

Alternatively, you can edit the Grids plugin within ImageJ to change the the appearance of the grid.  

Regards,
Glen

Glen MacDonald
Core for Communication Research
Virginia Merrill Bloedel Hearing Research Center
Box 357923
University of Washington
Seattle, WA 98195-7923  USA
[phone]
[hidden email]








On Feb 23, 2011, at 1:26 AM, sarah Al-beidh wrote:

> Hi all,
>
> A few months ago I emailed the list to ask how I could calculate the proportion of vegetation on hundreds of 3mx3m plot photographs.  Your suggestions were to adjust the color threshold and then threshold each image and finally to use a macro to calculate the proportion of white pixels on each thresholded photo.  This worked a treat but it has ended up meaning that by standardising the protocol (ie. hue=32 etc.) I end up underestimating vegetative cover on many of the plots (where vegetation is either pure white or dark brown).
>
> Consequently, we have come up with an alternative idea that would involve overlaying a grid over each photograph and counting the number of filled squares to gain a separate estimate of vegetative cover per plot.  Is there any way of overlaying a grid of a set size on each photo using Image J?
>
> Many thanks,
> Sarah
>
> Dr. Sarah Al-Beidh
> RHS Wisley