R/arcdist.R

In fishvice/ghsllr:

#' Title
#'
#' @param lat XXX
#' @param lon XXX
#' @param lat1 XXX
#' @param lon1 XXX
#' @param scale XXX
#'
#' @export
#'
arcdist  <- function (lat, lon, lat1 = NULL, lon1 = NULL, scale = "nmi")
{
  if (is.null(lat1)) {
    lat1 <- lon$lat
    lon1 <- lon$lon
    lon <- lat$lon
    lat <- lat$lat
  }
  if (scale == "nmi")
    miles <- 1.852
  else miles <- 1
  rad <- 6367
  mult1 <- (rad/miles)
  mult2 <- pi/180
  return(mult1 * acos(sin(mult2 * lat) * sin(mult2 * lat1) +
                        cos(mult2 * lat) * cos(mult2 * lat1) * cos(mult2 * lon -
                                                                     mult2 * lon1)))
}