processing – Grassroots Mapping http://grassrootsmapping.org Stories of community based mapping projects Sun, 01 Apr 2018 14:24:10 +0000 en-US hourly 1 https://wordpress.org/?v=4.9.5 Quantify wetland from aerial UV photo http://grassrootsmapping.org/2011/02/quantify-wetland-from-aerial-uv-photo/ http://grassrootsmapping.org/2011/02/quantify-wetland-from-aerial-uv-photo/#respond Thu, 24 Feb 2011 09:25:19 +0000 http://grassrootsmapping.org/?p=773 test_cesar_adam>>Question : How can you extract the % of wetland from an UV aerial picture using photoshop? Video tutorial by Cesar Harada and Adam Griffith: _ Instructions : 1. isolate the part that you are interested in using the menu/ image/ adjustment/ replace color. There you want to have a quite fuzzy selection and darken […]]]> >>Question : How can you extract the % of wetland from an UV aerial picture using photoshop?

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Video tutorial by Cesar Harada and Adam Griffith:

_ Instructions :
1. isolate the part that you are interested in using the menu/ image/ adjustment/ replace color. There you want to have a quite fuzzy selection and darken the desired part.
2. after isolating the part you are interested in -black area- apply menu/ image/ adjustment/ threshold
3. use magic wand /untick “contiguous” pixel to select all the black pixels available. Open menu/ window/ histogram/ expanded view. Here you will see how many black pixels are selected. Now you know how many black pixels there is on this image – corresponding the area of wetland from the original UV picture. You can convert the number of pixels into a % (proportions of wetland) or in surface area for quantifying. It is possible to optimize this workflow by creating a script or recording the chain of actions.
Same thread on Public Laboratory

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