radiocorr | R Documentation |
Implements several different methods for absolute radiometric correction of satellite data.
radiocorr(x, gain, offset, Grescale, Brescale, sunelev, satzenith = 0, edist,
Esun, Lhaze, method = "apparentreflectance")
x |
Image to be corrected, in matrix, data frame, or SpatialGridDataFrame format. |
gain |
Band-specific sensor gain. Require either gain and offset or Grescale and Brescale to convert DN to radiance. |
offset |
Band-specific sensor offset. Require either gain and offset or Grescale and Brescale to convert DN to radiance. |
Grescale |
Band-specific sensor Grescale (gain). Require either gain and offset or Grescale and Brescale to convert DN to radiance. |
Brescale |
Band-specific sensor Brescale (bias). Require either gain and offset or Grescale and Brescale to convert DN to radiance. |
sunelev |
Sun elevation in degrees |
satzenith |
Satellite sensor zenith angle (0 for Landsat) |
edist |
Earth-Sun distance in AU. |
Esun |
Exo-atmospheric solar irradiance, as given by Chandler et al. 2009 or others. |
Lhaze |
Haze value, such as SHV from DOS() function. Not needed for apparent reflectance. |
method |
Radiometric correction method to be used. There are currently four methods available: "apparentreflectance", "DOS" (Chavez 1989), "COSTZ" (Chavez 1996), "DOS4" (SWS+2001). |
Uses one of four image-based radiometric correction methods to adjust a satellite image to compensate for atmospheric conditions.
Returns a radiometrically-corrected image in the same format as x.
Sarah Goslee
Chavez, Jr., P. S. 1989. Radiometric calibration of Landsat Thematic Mapper multispectral images. Photogrammetric Engineering and Remote Sensing 55:1285-1294.
Chavez, Jr., P. S. 1996. Image-based atmospheric corrections revisited and improved. Photogrammetric Engineering and Remote Sensing 62:1025-1036.
Song, C.; Woodcock, C. E.; Seto, K. C.; Lenney, M. P. & Macomber, S. A. 2001. Classification and change detection using Landsat TM data: when and how to correct atmospheric effects? Remote Sensing of Environment 75:230-244.
DOS
data(july1)
data(july3)
# One approach to choosing a Starting Haze Value is to take the lowest DN value
# with a frequency greater than some predetermined threshold, in this case 1000 pixels.
SHV <- table(july1@data[,1])
SHV <- min(as.numeric(names(SHV)[SHV > 1000]))
# this is used as Lhaze in the radiocorr function
# Grescale, Brescale, sun elevation comes from metadata for the SHV band
july.DOS <- DOS(sat=7, SHV=SHV, SHV.band=1, Grescale=0.77569, Brescale=-6.20000,
sunelev=61.4, edist=ESdist("2002-07-20"))$DNfinal.mean
# DOS() returns results for the complete set of scattering coefficients
# need to choose the appropriate one based on general atmospheric conditions
### -4.0: Very Clear SHV <= 55
### -2.0: Clear SHV 56-75
### -1.0: Moderate SHV 76-95
### -0.7: Hazy SHV 96-115
### -0.5: Very Hazy SHV >115
# for july, SHV == 70, so use -2.0: Clear
july.DOS <- july.DOS[ , 2]
# Use DOS value as Lhaze in radiocorr() for DOS correction to reflectance
july3.DOSrefl <- radiocorr(july3, Grescale=0.77569, Brescale=-6.20000,
sunelev=61.4, edist=ESdist("2002-07-20"), Esun=1533,
Lhaze=july.DOS[3], method="DOS")
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