Thanks @piyushrpt
Yes indeed; the pixels of those images don’t match. Subsequently, I made the comparison for the same pixel and the variability is reduced. I don’t know if this can be useful to anyone, but I did some basic statistics of the average variability in the reflectance (for tropical dry forests and grasslands) and these are the results (bands 4 and 8):
| Band 4 | Media | Median | StDeviat | Varianz |
|---|---|---|---|---|
| Dry forest | 0,0009 | 0,001 | 0,0002 | 0,00000007 |
| Wet Forest | 0,0074 | 0,0068 | 0,0026 | 0,0000072 |
| Grasslands | 0,0001 | 0,00008 | 0,0001 | 0,000000012 |
| Medium | 0,001 | 0,00096 | 0,00139 | 0,0000019 |
| Band 8 | Media | Median | StDeviat | Varianz |
|---|---|---|---|---|
| Dry forest | 0,00085 | 0,0004 | 0,001 | 0,000001 |
| Wet Forest | 0,042 | 0,02 | 0,05 | 0,002 |
| Grasslands | 0,00088 | 0,0005 | 0,00084 | 0,0000007 |
| Medium | 0,0023 | 0,0005 | 0,0129 | 0,000168 |
Band 8 (left) and Band 4 (right)
open for discussion 