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i.oif - Calculates Optimum-Index-Factor table for spectral bands


imagery, multispectral, statistics


i.oif --help
i.oif [-gs] input=name[,name,...] [output=name] [--overwrite] [--help] [--verbose]
[--quiet] [--ui]

Print in shell script style

Process bands serially (default: run in parallel)

Allow output files to overwrite existing files

Print usage summary

Verbose module output

Quiet module output

Force launching GUI dialog

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

Name for output file (if omitted or "-" output to stdout)


i.oif calculates the Optimum Index Factor for multi-spectral satellite imagery.

The Optimum Index Factor (OIF) determines the three-band combination that maximizes the
variability (information) in a multi-spectral scene. The index is a ratio of the total
variance (standard deviation) within and the correlation between all possible band
combinations. The bands that comprise the highest scoring combination from i.oif are used
as the three color channels required for d.rgb or r.composite.

The analysis is saved to a file in the current directory called "i.oif.result".


Landsat 1-7 TM: Colour Composites in BGR order as important Landsat TM band combinations
(example: 234 in BGR order means: B=2, G=3, R=4):

· 123: near natural ("true") colour; however, because of correlation of the 3 bands
in visible spectrum, this combination contains not much more info than is
contained in single band.

· 234: sensitive to green vegetation (portrayed as red), coniferous as distinctly
darker red than deciduous forests. Roads and water bodies are clear.

· 243: green vegetation is green but coniferous forests aren’t as clear as the 234

· 247: one of the best for info pertaining to forestry. Good for operation scale
mapping of recent harvest areas and road construction.

· 345: contains one band from each of the main reflective units (vis, nir, shortwave
infra). Green vegetation is green and the shortwave band shows vegetational stress
and mortality. Roads are less evident as band 3 is blue.

· 347: similar to 345 but depicts burned areas better.

· 354: appears more like a colour infrared photo.

· 374: similar to 354.

· 457: shows soil texture classes (clay, loam, sandy).

By default the module will calculate standard deviations for all bands in parallel. To run
serially use the -s flag. If the WORKERS environment variable is set, the number of
concurrent processes will be limited to that number of jobs.


North Carolina sample dataset:
g.region raster=lsat7_2002_10 -p
i.oif input=lsat7_2002_10,lsat7_2002_20,lsat7_2002_30,lsat7_2002_40,lsat7_2002_50,lsat7_2002_70


Jensen, 1996. Introductory digital image processing. Prentice Hall, p.98. ISBN

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