I'm trying to extract the areas with vegetation as a polygon-shape from a landsat7-image, 30m resolution, RGB, using QGis 1.8 or Bilko or (hopefully in the near future) ArcGIS. The area is in Northern Peru, dry season, so basically I want to extract all the shades of green.
I have never really worked with raster data and don't know what to do. I have found out there are "vegetation indices" which can be calculated, and have found Bilko as a software I could do this with. However, if I got it right I need more bands than RGB to do this – is this true? I'm not sure.
On this website I have also found threads on how to calculate vegetation area in QGis – using GDAL tools or SEXTANTE: Calculating area of vegetation in raster file?
However I would like to not only calculate but extract the data as a polygon.
What would be the best way to do this? I've never worked with Bilko, GDAL or SEXTANTE, of course I will go into that and try to learn, but I would like to know what will work before I spend hours and hours only to find out I can't do it…
P.S.: I will probably have ARCGis in a while, so if it is much easier with ARCGis I might wait for that…
Best Answer
There is also another possibility to solve that problem. The software "Monteverdi", which is based on the OTB Library, could handle that. It is a open-source remote sensing software, developed by CNES (French space agency) to process their Pleiades-Imagery.
I suggest Version 1.18.
http://sourceforge.net/projects/orfeo-toolbox/files/Monteverdi/Monteverdi-1.18/
There is a filtering-module included, which is called "Connected Component Segmentation". It basically does the following (more details can be found here: http://wiki.orfeo-toolbox.org/index.php/Connected_component_segmentation_module):
I used this for exactly that purpose. Not on Landsat data, but aerial imagery. A NIR channel is mandatory though.