On Wed, May 14, 2014 at 03:23:35PM +0200, [email protected] wrote: > I have 2.4 nm islands on a flat substrate. I would like to count them as > precise as possible with Gwyddion. > > The procedure I'm following is to mark by threshold the islands and then > in statistics check the number of grains. > > Unfortunately this number is not so precise, by hand i get 134 islands > while with Gwyddion I get 294. The difference is too big. Moreover, if I > change just a bit the threshold that number changes a lot. > > Instead, if I divide the projected area by pi times the square of the mean > grain size (as if the grains were circles) I get a more reasonable number. > > Which method do you suggest?
First, you can try other marking algorithms, such as Mark by Watershed and Mark by Edge Detection. I'm also working on another method, but it is not finished yet. I don't know if you get too many grains due to oversegmentation or marking of areas that should not be marked as grains (e.g. small few-pixel ‘grains’ caused by noise). But the currently available methods are more prone to the latter. If this is the case, you can use grain filtering to get rid of the extra grains. However, the area method may be still more robust. You can get good threshold also from the height distribution or a Minkowski functional and, if there is no serious under- or oversegmentation, divide the total projected area by the median grain area. Median will likely to be better than mean but you need to export the values for all grains using Grains → Distribution, sort them and take the middle value. Regards, Yeti ------------------------------------------------------------------------------ "Accelerate Dev Cycles with Automated Cross-Browser Testing - For FREE Instantly run your Selenium tests across 300+ browser/OS combos. Get unparalleled scalability from the best Selenium testing platform available Simple to use. Nothing to install. Get started now for free." http://p.sf.net/sfu/SauceLabs _______________________________________________ Gwyddion-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/gwyddion-users
