minnaert {landsat} | R Documentation |
Whole-image and pixel-based Minnaert topographic correction of remote sensing data.
Description
Adds several modified Minnaert corrections to the capabilities of topocorr().
Usage
minnaert(x, slope, aspect, sunelev, sunazimuth, na.value = NA, GRASS.aspect=FALSE,
IL.epsilon=0.000001, slopeclass = c(1, 5, 10, 15, 20, 25, 30, 45), coverclass)
Arguments
x |
Image to be corrected, in matrix, data frame, or SpatialGridDataFrame format. |
slope |
Slope image of same size and resolution as x. |
aspect |
Aspect image of same size and resolution as x. |
sunelev |
Sun elevation in degrees. |
sunazimuth |
Sun azimuth in degrees. |
na.value |
Value to use for missing data. |
GRASS.aspect |
Whether aspect is measured according to GRASS defaults (counterclockwise from east) or is measured clockwise from north. If GRASS.aspect=TRUE, aspect is converted to clockwise from north before analysis. |
IL.epsilon |
If IL == 0 (Illumination), some methods will give a topographically-corrected value of Inf due to division by zero. If desired, adding a small increment to zero values eliminates this. |
slopeclass |
The classes into which the slope will be divided before calculating k separately for each class. |
coverclass |
If present, TRUE/FALSE vector indicating which pixels to use when calculating k. This allows k to be determined separately for different cover classes. |
Details
Calculates the Minnaert k coefficients for the whole image and for the individual slope classes.
Value
allcoef |
The Minnaert k for the entire image. This is the value used in topocorr() (though the latter may have been truncated). |
classcoef |
A data frame containing the slope class midpoints, number of pixels per class, and k for that class (for the desired cover class, if specified). |
xout |
A topographically-corrected image in the same format as x. |
xout |
A topographically-corrected image in the same format as x. |
Author(s)
Sarah Goslee
References
Lu, D., Ge, H., He, S., Xu, A., Zhou, G., and Du, H. 2008. Pixel-based Minnaert correction method for reducing topographic effects on a Landsat 7 ETM+ image. Photogrammetric Engineering and Remote Sensing 74:1343-1350.
See Also
Examples
# require slope and aspect for topographic correction
data(dem)
dem.slopeasp <- slopeasp(dem)
# use cosine method of topographic correction
data(july4)
july4.minpix <- minnaert(july4, dem.slopeasp$slope, dem.slopeasp$aspect,
sunelev=61.4, sunazimuth=125.8, slopeclass=c(1, 5, 10, 15, 50))
july4.minpix$classcoef # all coefficients