Public Lab Research note


Quantify wetland from aerial UV photo

by cesarharada | February 24, 2011 09:13 | 115 views | 1 comments | #102 | 115 views | 1 comments | #102 24 Feb 09:13

Read more: i.publiclab.org/n/102


You want to watch the video tutorial : https://www.youtube.com/watch?v=xKy1EZ_TbNs

Question : How can you extract the % of wetland from an UV aerial picture using photoshop?

_ 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.

  1. after isolating the part you are interested in -black area- apply menu/ image/ adjustment/ threshold

  2. 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.

Files Size Uploaded
test_cesar_adam.JPG 251 KB 2011-02-24 09:12:17 +0000
test_cesar_adam4.jpg 497 KB 2011-02-24 09:12:29 +0000

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Adam Griffith reported back that:

Beaufort County, SC contracted with Fugro Earth Data for the image acquisition. This is a very expensive technique, at least they charge a TON for it. Maybe even 100 K minimum. "Fugro EarthData operates multiple Leica ADS40 airborne digital sensors outfitted with the second-generation SH-52 sensor heads for digital aerial imagery acquisition at pixel resolutions ranging from 5 cm to 2 m." - http://www.fugroearthdata.com/servicessubcat.php?subcat=digital-photogrammetry

This is one of the more interesting PDFs: http://www.fugroearthdata.com/pdfs/FCT_COL-ADS40.pdf

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