topographic_corr: Topographically correct a raster
In azvoleff/teamlucc: TEAM land use and cover change data processing toolkit

Description Usage Arguments Details Value References Examples

Performs topographic correction using code based on topocorr from the landsat package by Sarah Goslee. The code in this package has been modifed from topocorr to allow using a subsample of the image for Minnaert k calculations, and to provide the option of running the topographic correction in parallel using foreach.

1
2
3

topographic_corr(x, slopeaspect, sunelev, sunazimuth,
  method = "minnaert_full", sampleindices = NULL, scale_factor = 1,
  asinteger = FALSE, DN_min = NULL, DN_max = NULL, ...)

`x`	an image to correct
`slopeaspect`	a `RasterBrick` or `RasterStack` with two layers. The first layer should be the slope, the second layer should be the aspect. The slope and aspect are defined as in `terrain` in the `raster` package, and both should be in radians.
`sunelev`	sun elevation in degrees
`sunazimuth`	sun azimuth in degrees
`method`	the topographic correction method to use. See the help for `topocorr` for more guidance on this.
`sampleindices`	(optional) row-major indices of sample pixels to use in regression models used for some topographic correction methods (like Minnaert). Useful when handling very large images. See `gridsample` for one method of calculating these indices.
`scale_factor`	factor by which to multiply results. Useful if rounding results to integers (see `asinteger` argument).
`asinteger`	whether to round results to nearest integer. Can be used to save space by saving results as, for example, an 'INT2S' `raster`.
`DN_min`	minimum allowable pixel value after correction (values less than `DN_min` are set to NA)
`DN_max`	maximum allowable pixel value after correction (values less than `DN_max` are set to NA)
`...`	additional arguments to pass to `minnaert_samp` or `topocorr_samp`, depending on chosen topographic correction method

This function will run in parallel if a parallel backend is registered with foreach.

The topographically corrected image as a RasterLayer or RasterStack

Sarah Goslee. Analyzing Remote Sensing Data in R: The landsat Package. Journal of Statistical Software, 2011, 43:4, pg 1–25. http://www.jstatsoft.org/v43/i04/

## Not run: 
# Mosaic the two ASTER DEM tiles needed to a Landsat image
DEM_mosaic <- mosaic(ASTER_V002_EAST, ASTER_V002_WEST, fun='mean')

# Crop and extend the DEM mosaic to match the Landsat image
matched_DEM <- match_rasters(L5TSR_1986, DEM_mosaic)
slopeaspect <- terrain(matched_DEM, opt=c('slope', 'aspect')

# Apply the topographic correction
sunelev <- 90 - 44.97 # From metadata file
sunazimuth <- 124.37 # From metadata file
L5TSR_1986_topocorr <- topographic_corr(L5TSR_1986, slopeaspect, sunelev, 
                                        sunazimuth, method='minslope')

plotRGB(L5TSR_1986, stretch='lin', r=3, g=2, b=1)
plotRGB(L5TSR_1986_topocorr, stretch='lin', r=3, g=2, b=1)

## End(Not run)