Michele Toma:
I have multiple Landsat 8 scenes taken on the same day/same path, but
they vary in brightness. I believe this to be caused by the time of day
that the image was taken as the northern image is brighter (taken
earlier in the day) and the southern image is darker (taken later in
the day). This has occurred for multiple images. Is there a way to make
the colors match between tiles?
I've attempted to use i.histo.match on my composite rgb images which
resulted in distorted colors. Should this tool only be used on
grayscale images?
You would want to perform histogram matching after the conversion to
radiance/reflectance and before composing an RGB image.
Are there other GRASS tools I am not aware of that I
should be using? Is the color distortion caused by any of the other
tools that I am using?
Below are the steps that I've taken to process my images:
1. Import all Landsat 8 bands to GRASS 7.0.4
2. Convert DN to reflectance
a. i.landsat.toar input=LC81100362016082LGN00_B
output=LC81100362016082LGN00_refl metfile=LC81100362016082LGN00_MTL.txt
3. Pansharpen using i.fusion.hpf
a. i.fusion.hpf pan=LC81100362016082LGN00_relf8
msx=LC81100362016082LGN00_refl4, LC81100362016082LGN00_relf3,
LC81100362016082LGN00_refl2 suffix=hpf
4. Histogram equalization
a. r.colors -e map=LC81100362016082LGN00_refl4.hpf color=grey
Note, this merely retouched the "color-table" and not the data itself.
Nikos
5. Color balance using i.colors.enhance
a. i.colors.enhance red=LC81100362016082LGN00_refl4.hpf
green=LC81100362016082LGN00_refl3.hpf blue=LC81100362016082LGN00_refl2.hpf
6. Set region
a. g.region raster=LC81100362016082LGN00_refl2.hpf
7. Create RGB composite
a. r.composite red=LC81100362016082LGN00_refl4.hpf
green=LC81100362016082LGN00_refl3.hpf blue=LC81100362016082LGN00_refl2.hpf
output=LC81100362016082LGN00_refl_rgb
8. Export image
a. r.out.gdal input= LC81100362016082LGN00_refl_rgb output=
LC81100362016082LGN00.tif format='GTiff'
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