| 03 Dec 2015 03:19 PM |
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Hello,
I'dlike to ask you for help. I noticed a small shift of vector positon (evf)from original raster layer.
After supervised image classification I want to convert raster into vector (raster to evf to shape) to be able to make some final corrections and later on to extract pixel values but due to the shift some invalid data were also exported. I corrected this 1 pixel shift in ArcGIS and import shape in ENVI in order to use later for ROI formation. When shape was opened it perfectly match the raster area but with ROI formation from shape shift of ROI area happened again. Does anyone has explanation and solution for this?
Cheers!
Matej
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Deleted User
Basic Member
Posts:228  
| 08 Dec 2015 01:18 PM |
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Perhaps it would help if you would describe in more detail exactly which tools you used in ENVI, and the exact steps you took, including where you noticed the shift. It is not clear to me from your description which steps might have led to a shift.
- Peg
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Deleted User
New Member
Posts: 
| 09 Dec 2015 09:43 AM |
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Hi Peg,
I've recorded 100 grains and prepared ROIs for classification. After supervised classification (Mahalanobis...) , I used function "classification to vector" on my grain class. When I opened grain.evf I was able to noticed one pixel shift from my grain class area. If I used function "classic evf to shapefile" i was able to correct this shift in ArcGIS program. If I opened shape file back in ENVI showed perfect match to area of my grain class. After I used shape to prepare ROI back (to be able to extract values) I noticed slighty different shift of ROI area. Because grain area is quite small those one pixel shift means a lot to me. I hope I was clear enough. Picture would explain even more.
Regards
Matej
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Deleted User
Basic Member
Posts:228
| 20 Jan 2016 02:21 PM |
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I think that to track down exactly what is causing this problem would require testing and working with your data. Do you have access to full Technical Support for ENVI? For example, though Harris GS Tech Support or a local distributor? That would probably be a better way to proceed than trying to explain things on this forum.
My guess is that it has something to do with the algorithm being used to convert from raster to vector and back again. In ENVI, ROIs are raster entities. There is always some room for disagreement about how a vector to raster conversion should decide which pixels are in the vector and which are out of it. And vice versa (raster to vector).
I'm sorry that I don't know more specifically what might be causing the shift you are seeing.
- Peg
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