Hello Everyone! Hope you all are safe.
I need a bit of help. I have a Landsat ETM (metadata says ETM instead of ETM+) image that I need to classify using the Support Vector Machine classifier in ENVI. I FLAASH corrected the full scene and then created a subset of the study area using shapefile. In the subset image, there was a black background which I converted to 'No Data' using the 'Edit ENVI Header' tool. The image then had a clear background and the cursor value showed 'No Data' (see attached image). Then I created ROI's and classified the image using SVM but the final output showed background as one of the classes (right side image in the attached picture). I tried all the ways given here: https://www.l3harrisgeospatial.com/Support/Forums/aft/4920 and others as well but to no avail.
Also, the classified image has no spatial reference. If I tried to add it manually using 'Edit ENVI header' then it firstly said 'Missing Parameter' and then showed this error "Attempt to call undefined method IDLCFPROJECTION::ISRPC". I tried converting it to TIFF and opening it in ArcGIS but could not project it. I tried adding it manually using ArcCatalog, still, shapefile of the study area did not fit over the classified image. Probably there is some hidden error there. I could not find its solution on the internet. Please help.
File -> Edit ENVI Header -> Edit Attributes -> Data Ignore Value
https://www.l3harrisgeospatial.com/docs/editclassificationimages.html
https://gis.stackexchange.com/questions/189989/removing-black-background-in-envi
Ashwani Kumar Aggarwal Sir I tried this but didn't work out. The "No Data' being shown in the screenshot that I shared is after doing this step only. All the 0.000 values started showing a "No Data".
Ashwani Kumar Aggarwal Sir, the other image has the outside value (yellow area outside my study area) same as my class value i.e. 3. If I apply DIV on it, the class within the study area also gets affected.
I have found the solution to both problems now.
Firstly, the RGB image somehow did not have sensor information in its metadata, although it had accurate spatial reference and other parameters. I don't know why it happened though I imported the data using the built-in ENVI module which read and processed the data automatically from the .MTL file.
This error lead to my classified image not having any spatial reference. So when I manually added the sensor information to the RGB image and again classified it, the spatial reference was there.
I then exported the classified image to ArcGIS and using the Clip function, I removed the background. One important thing that I noticed was that the value of "No data" in the Clip dialogue box should be changed to "0" instead of the default "255/256" otherwise the background does not go away.
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