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Daniela_06

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About Daniela_06

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  1. I am using University software and cant download this module. I have ENVI 4.8 but the Rig. Ortho. module is not enabled or need a license. Any other procedure?
  2. Hello everyone, I am going crazy with this orthorectification procedure. This is what i have. I have several satellite images TM and ETM+ from different years that i need to classify and the perform change detection techniques. This images are 30m resolution. UTM Zone 30N WGS1984. I also have gather 2 DEM 1 arc sec (approx 30m ) UTM WGS1984. I need to do a mosaic of this two DEM because together cover the area of each satellite images. But not exactly. This to DEMS together are only a portion of the area of each satellite image, but it covers the area that i need. (NOT ALL THE SATELLITE IMAGE IS NEEDED). 1. Do I have to reproject the mosaic DEM to UTM ZONE 30N WGS1984 first? 2. I am using ENVI 4.2 and I am doing an Automated Image to image registration. This generates automatic GCP in the DEM and relates this GCP to the Satellite image (Band 1 for example) 3. The table of GCP shows a error of 25.50m is this to much of an error? because the images are 30m. 4. I have done the registration with this values and obtain a quite similar image than the original. Can anyone tell me if my procedure is correct? If its not, can someone explain me step by step how to do an orthorectification. I have seen tutorials, but ENVI 4.2 does not have USGS images or Landsat satellites listed to do orthorectification as all the tutorial shows. I need a more step by step (orthorectification for dummies) Thank you very much, I am really losing my mind here.
  3. Let me be more clear. I did a ¨extract by mask¨ using ARCMAP to mask the area that i needed from the whole satellite image. And then saved this new image as .tif to open in ENVI. The new image in envi shows the are that I want and a black background and when classifying using unsupervised classification in also classifies the background. How can i fix this so that the background of the image is not part of any classification.
  4. Hello, I am doing an unsupervised classification using ENVI. I have an ETM+ 1992 image already orthorectified and I have mask the study are of interest (administration boundary). Anyway when I perform an unsup classification the background is being classified. How to eliminate the black background of all the imageS?
  5. Hello everyone. I am doing a classification for 2 different dates 2002 and 2012. For the year 2002 I have a shapefile with polygons that show the classes (16) in total, using ERDAS and ENVI I was able to turn those polygons into training sites a do a proper classification. For the year 2012 I have no shapefile nor ground thruthing information and I am going to do a visual analysis of the 2002 classification map to create signatures for the 2012. Now. I need to asses the deforestation of the area and my classification covers other classes that may be not necessary how ever I want to do use this classes for one classification and maybe do another classification of only vegetation. I am using the color compsite 4,3,2, RGB false colour to appreciate vegetation. I would like to know how NDVI or vegetation indexes are used and how can use it to create the " only vegetation¨ classification I want to do. Do NDVI is applied to the stacked images with the 3 layers or only to one band of the ETM satellite image? Once i have tge NDVI image how do I use it? does it substitues a layer in the RGB composite? Which one? what other indices can I use or band combinations to have a more acurrate vegetation classification? Please help me, thank you for your time.
  6. Hello, I figured out my classification procedure and is GREAT! I was able to work with the shape file i had for the 2002 year and basically by visual analysis I will have to do the classification of the years that i dont have apriori information whatsoever. I have another question: I am collecting the signatures, or training samples myself, by comparing by visual analysis (looking at the map) of the 2002 classification I have. However, can you explain me the procedure i need to follow to assess the accuracy of my samples and the accuracy of my classification?.. vs what am I comparing or creating a matrix if I dont have ground control points? Accuracy in base according to what and what do I need to report? I am using ENVI or ERDAS software with TM, ETM+ and ASTER IMAGES. THANKS!
  7. Thank you very much. So? Orthorectification can be done using ANY year DEM over ANY year image? I dont think my images need Orthorectification, but no harm can be done if i do it anyway. right? Regarding the classification, im going to follow your advice and see what happens.
  8. 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!
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