i.zero2null - GRASS GIS manual

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NAME

i.zero2null - Replaces zero values with null at edges, otherwise replaces zero values with appropriate neighboring values.

KEYWORDS

imagery, satellite

SYNOPSIS

i.zero2null

i.zero2null --help

i.zero2null map=name[,name,...] [--help] [--verbose] [--quiet] [--ui]

Flags:

--help: Print usage summary
--verbose: Verbose module output
--quiet: Quiet module output
--ui: Force launching GUI dialog

Parameters:

map=name[,name,...] [required]: Name of raster map(s)

DESCRIPTION
EXAMPLE
SEE ALSO
AUTHOR

DESCRIPTION

i.zero2null replaces zero cells with NULL cells at the edges of imagery, e.g. Sentinel-2 scenes.

Sentinel-2 scenes can also have small patches of zero cells, typically in water bodies. These patches are removed and filled with neighboring cells.

EXAMPLE

The Sentinel-2 scene S2B_MSIL2A_20190724T103029_N0213_R108_T32ULA_20190724T130550, uuid: 0a7cb5ee-80d4-4d15-be19-0b3fdf40791f shows unexpected no-data pixels in lakes.

# download S2 scene affected by no.data pixels within the scene
i.sentinel.download settings=credentials.txt \
  uuid=0a7cb5ee-80d4-4d15-be19-0b3fdf40791f output=test_s2_scene

# show lst of granules in scene
i.sentinel.import -p input=test_s2_scene

# import selected bands of scene
i.sentinel.import input=test_s2_scene pattern='B0(2|3|4|8)_10m'
g.list raster
g.region raster=T32ULA_20190724T103029_B04_10m -p

Figure: Sentinel-2 red band with undesired 0-value pixels

# zoom to scene subset with undesired 0-value pixels
g.region n=5516940 s=5516840 w=334410 e=334550 res=10
# visualize pixel values, e.g. in red band
d.rast T32ULA_20190724T103029_B04_10m
d.rast.num T32ULA_20190724T103029_B04_10m text_color=blue

# fix 0-value pixels
i.zero2null map=T32ULA_20190724T103029_B02_10m,T32ULA_20190724T103029_B03_10m,T32ULA_20190724T103029_B04_10m,T32ULA_20190724T103029_B08_10m
# visualize updated pixel values (0 values now replaced), e.g. in red band
d.rast T32ULA_20190724T103029_B04_10m
d.rast.num T32ULA_20190724T103029_B04_10m text_color=blue