R/ANIRmodis.R

In klauswiese/AngleIndexes: AngleIndexes

#Función ANIR para MODIS
ANIRmodis <- function(Red, NIR, SWIR){
  ANIRIndex <- overlay(Red, NIR, SWIR, fun=function(x,y,z){
    a <- (sqrt((0.858-0.648)^2+(y-x)^2))
    b <- (sqrt((1.240-0.858)^2+(z-y)^2))
    c <- (sqrt((1.240-0.648)^2+(z-x)^2))
    d <- (a^2+b^2-c^2)/(2*a*b)
    d2 <- ifelse(d > 1, 1, ifelse(d < -1, -1, d))
    ind <- acos(d2)
    return(ind)
  })
  return(ANIRIndex)
}