Variation/combination of ship-to-shore method used for gold counting in electron micrographs of spread mammalian cells and of annulus macros used to measure intensity variation at equal distances from a perimeter.  The benefit over the older methods is that this method is fast and simple even where the particles cannot be segmented by thresholding and must be chosen by manual clicking.  Instructions for use in comments at top of macros:  puddle-edge-v102.txt

In this example, powdered ice was plated on gridded concrete using natural pre-vernal cryo precipitation methods.  Calcium chloride crystals were applied to the ventral surface and incubated for two weeks at environmentally normal temperatures with periodic 5 to 6 hours per day exposure to electromagnetic radiation ranging from the low UV up through high IR as well as fluctuation of approximately 20 degrees C in the ambient atmosphere at sea level.  The repeated thaw and freeze cycles resulted in the formation of discrete pools referred to in the vernacular as "puddles".  We sought to quantify the calcium chloride aggregates as a function of distance from the (retracting) perimeter of the puddles.


Lamella of the organism.

Green channel extracted as bw image for use in automated analysis.  Traced by the human operator.

Results of software calculating minimum distance from each chloride precipitate to the retracting edge.
Results from multiple pools may be pooled.

Admittedly the quick thresholding in this example was not particularly robust at selecting only pure particles of interest (but the clumping near the perimeter is really groups of individual particles squished together when the image was shrunk to fit on this web page; they were discrete in the original data measured).  This would be cleaned up in real world applications.