i.zero2null - GRASS GIS manual

Note: This addon document is for an older version of GRASS GIS that will be discontinued soon. You should upgrade your GRASS GIS installation, and read the current addon manual page.

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

Figure: Sentinel-2 red band after correction with i.zero2null

AUTHOR

Markus Metz, mundialis

SOURCE CODE

Available at: i.zero2null source code (history)

Latest change: Mon Jun 28 07:54:09 2021 in commit: 1cfc0af029a35a5d6c7dae5ca7204d0eb85dbc55