Krista West
New Member
Posts:8  
| 11 Aug 2023 04:41 PM |
|
|
When I downloaded Landsat data and imported the MTL file to ENVI in the past, I needed to perform Spectral Math to re-scale the data per USGS information.
Meaning, if the Landsat metadata's REFLECTANCE_MULT_BAND_1 = 2.75e-05 and REFLECTANCE_ADD_BAND_1 = -0.2, I would enter the expression: "s1*.0000275 - 0.2" and then Map Variable to Input File.
Now, when I perform Spectral Math steps on Landsat Collection 2, Level-2 data, the resulting spectra do not look right. When I don't perform Spectral Math, spectra look as expected.
With ENVI 5.6.3 and IDL 8.8.3 (64-bit) (and newer), is ENVI automatically scaling (multiplying by the gain and adding the offset) for each band provided in the header? Or do I still need to perform Spectral Math for Landsat 4, 5, 7, 8, and 9?
Thank you!
|
|
|
|
MariM
Veteran Member
Posts:2396 
| 14 Aug 2023 08:25 AM |
|
|
Yes, ENVI auto-applies the reflectance scale factors on the fly. I think this was updated around ENVI 5.6.1 when there were many updates to the Landsat Collection data.
https://www.nv5geospatialsoftware.com/docs/whatsnew_envi561.html#Improved
Do your spectra look correct without applying any spectral math to the image?
|
|
|
|
Krista West
New Member
Posts:8
| 22 Aug 2023 11:24 AM |
|
|
Hi Mari,
Spectra did look as expected. However, when I went to double-check, I encountered a new issue starting a couple days ago: the Cursor Value and Spectral Profile tools/pop-ups no longer display any spectral information.
That was with ENVI 5.6.3 + IDL 8.8.3, so I installed ENVI 5.7 + IDL 8.9. I've tried restarting my computer. Still experiencing the same issue, unfortunately. I even tried the "Spectral Analyst" tool and received the error message: Problem: Input file must be of type: ENVI Spectral Library.
These are all files that definitely had spectral information associated with them and displayed last week. What am I doing wrong now?
Thank you!
|
|
|
|
MariM
Veteran Member
Posts:2396
| 28 Aug 2023 12:37 PM |
|
|
Try moving or deleting the .idl directory found in your HOME. For example, on windows, this is:
C:\users\\.idl
Then restart ENVI. This directory will be re-created 'fresh' as if a new install.
The .idl directory contains many configuration files that can sometimes become corrupted or conflicting.
Doing this can often fix some strange behaviors.
|
|
|
|
Krista West
New Member
Posts:8
| 30 Aug 2023 12:53 PM |
|
|
I followed your advice, and that did not solve the issue. Then I re-deleted the .idl directory in HOME, uninstalled ENVI, downloaded a new install file, reinstalled ENVI 5.7, and then restarted my computer. Still behaving strangely, unfortunately.
However, I did discover a possible workaround -- when I import an ROI (or XML) file to another image file, the Cursor Value and Spectral Profile tools begin working.
But now those ROIs show up in very different places then when I originally created them, almost as if the location data were lost or corrupted/adjusted.
What do you recommend I try next for a full ENVI fix? Thank you!
|
|
|
|
MariM
Veteran Member
Posts:2396
| 31 Aug 2023 10:28 AM |
|
|
You should come directly to support with this issue. I would like to reproduce it.
|
|
|
|