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**GRASS** **GIS** **7.4.0** **Reference** **Manual**

GeographicResourcesAnalysisSupportSystem, commonly referred to as GRASS, is a Geographic Information System (GIS) used for geospatial data management and analysis, image processing, graphics/maps production, spatial modeling, and visualization. GRASS is currently used in academic and commercial settings around the world, as well as by many governmental agencies and environmental consulting companies. This reference manual details the use of modules distributed with Geographic Resources Analysis Support System (GRASS), an open source (GNU GPLed), image processing and geographic information system (GIS). Go to imagery introduction | topics Go back to help overviewImagerycommands:i.albedo Computes broad band albedo from surface reflectance. i.aster.toar Calculates Top of Atmosphere Radiance/Reflectance/Brightness Temperature from ASTER DN. i.atcorr Performs atmospheric correction using the 6S algorithm. i.biomass Computes biomass growth, precursor of crop yield calculation. i.cca Canonical components analysis (CCA) program for image processing. i.cluster Generates spectral signatures for land cover types in an image using a clustering algorithm. i.colors.enhance Performs auto-balancing of colors for RGB images. i.eb.eta Actual evapotranspiration for diurnal period (Bastiaanssen, 1995). i.eb.evapfr Computes evaporative fraction and root zone soil moisture. i.eb.hsebal01 Computes sensible heat flux iteration SEBAL 01. i.eb.netrad Net radiation approximation (Bastiaanssen, 1995). i.eb.soilheatflux Soil heat flux approximation (Bastiaanssen, 1995). i.emissivity Computes emissivity from NDVI, generic method for sparse land. i.evapo.mh Computes evapotranspiration calculation modified or original Hargreaves formulation, 2001. i.evapo.pm Computes potential evapotranspiration calculation with hourly Penman-Monteith. i.evapo.pt Computes evapotranspiration calculation Priestley and Taylor formulation, 1972. i.evapo.time Computes temporal integration of satellite ET actual (ETa) following the daily ET reference (ETo) from meteorological station(s). i.fft Fast Fourier Transform (FFT) for image processing. i.gensig Generates statistics for i.maxlik from raster map. i.gensigset Generates statistics for i.smap from raster map. i.group Creates, edits, and lists groups of imagery data. i.his.rgb Transforms raster maps from HIS (Hue-Intensity-Saturation) color space to RGB (Red-Green-Blue) color space. i.ifft Inverse Fast Fourier Transform (IFFT) for image processing. i.image.mosaic Mosaics several images and extends colormap. i.in.spotvgt Imports SPOT VGT NDVI data into a raster map. i.landsat.acca Performs Landsat TM/ETM+ Automatic Cloud Cover Assessment (ACCA). i.landsat.toar Calculates top-of-atmosphere radiance or reflectance and temperature for Landsat MSS/TM/ETM+/OLI i.maxlik Classifies the cell spectral reflectances in imagery data. i.modis.qc Extracts quality control parameters from MODIS QC layers. i.oif Calculates Optimum-Index-Factor table for spectral bands i.ortho.camera Select and modify the imagery group camera reference file. i.ortho.elev Select or modify the target elevation model. i.ortho.init Interactively creates or modifies entries in a camera initial exposure station file for imagery group referenced by a sub-block. i.ortho.photo Menu driver for the photo imagery programs. i.ortho.rectify Orthorectifies an image by using the image to photo coordinate transformation matrix. i.ortho.target Select or modify the imagery group target. i.ortho.transform Computes a coordinate transformation based on the control points. i.pansharpen Image fusion algorithms to sharpen multispectral with high-res panchromatic channels i.pca Principal components analysis (PCA) for image processing. i.rectify Rectifies an image by computing a coordinate transformation for each pixel in the image based on the control points. i.rgb.his Transforms raster maps from RGB (Red-Green-Blue) color space to HIS (Hue-Intensity-Saturation) color space. i.segment Identifies segments (objects) from imagery data. i.smap Performs contextual image classification using sequential maximum a posteriori (SMAP) estimation. i.spectral Displays spectral response at user specified locations in group or images. i.target Targets an imagery group to a GRASS location and mapset. i.tasscap Performs Tasseled Cap (Kauth Thomas) transformation. i.topo.corr Computes topographic correction of reflectance. i.vi Calculates different types of vegetation indices. i.zc Zero-crossing "edge detection" raster function for image processing. Main index | Topics index | Keywords index | Graphical index | Full index © 2003-2018 GRASS Development Team, GRASS GIS 7.4.0 Reference Manual