Hello,
I need to do a land cover classification of satellite images from diff years 86,91,98,02,12 from different providers like ASTER and LANDSAT and I have several questions regarding some issues I am presenting. Hope someone can help me.
1. Do the Landsat images need to be ortho rectified, they are L1T images TM and ETM+ if so, can I use the ASTER DEM of 2011 that I have to ortho rectify all of them? no matter the year? An if the DEM is in a different resolution that the 30m how should I do this?
2. I need to do some atmospheric correction and enhancement of the bands that i need to use that will be the false colour combination to be able to distinguish vegetation. This enhancement should help me with the classification procedure right?
3.For the year of 1992 I have a shapefile with different polygons of the different classes. I been meaning to use this polygons as ROI in ENVI but I cant seem to make the classification work. (Supervised classification Maximum likelihood) . When loading the shapefile as ROI or EVF and using it as ROI's for classifications is returning a white screen. How can I fix this?
4. A 1992 is the only year I actually have some a priori info I want to (by visual analysis) try to get some signatures or ROI for the other year to do the classifications, however, in some cases land covers or pixels that represent a land cover are very similar to pixels that represent other land cover and this is producing a horrible and totally inaccurate map. What level of treshold should I set to that one region does not get ¨confused¨by another region?.
Please I hope someone can help me, right now I am trying to classify 14 classes. in the case the maps are really complicated then I may focus in reducing the classes and maybe concentrate in levels of vegetation, but I would like to give it a try.
The area of Study is a semi-arid area where all the land covers are similar. I know that the shapefile that I have is key to this and would like to make the classification work. The attribute table of this shape file is like this.
ID/CODE/POLYGONS where the code is the one showing the type of land. Please help!