R/velocity_calc.R

In USGS-R/GDopp: processing of ADV data

#'@title gets along-stream mean velocity
#'@description 
#'gets along-stream mean velocity  \cr
#'
#'@details a \code{GDopp} function for calculating along-stream mean velocity.\cr 
#'
#'@param chunk.adv a data.frame created with load.ADV, with the window.idx column
#'@return a single mean along-stream velocity value
#'@keywords v.calc
#'@examples 
#'\dontrun{
#'folder.nm <- system.file('extdata', package = 'GDopp') 
#'file.nm <- "ALQ102.dat"
#'data.adv <- load_adv(file.nm=file.nm, folder.nm =folder.nm)
#'window.adv <- window_adv(data.adv,freq=32,window.mins=10)
#'chunk.adv <- window.adv[window.adv$window.idx==7, ]
#'velocity_calc(chunk.adv)
#'}
#'@export
velocity_calc <- function(chunk.adv){
  
  if ('velocity.X' %in% names(chunk.adv)){
    veloc.cube <- chunk.adv$velocity.Y^2 + chunk.adv$velocity.X^2 + chunk.adv$velocity.Z^2
  } else {
    veloc.cube <- chunk.adv$East^2 + chunk.adv$North^2 + chunk.adv$Up^2
  }
  
  
  veloc <- veloc.cube^(1/3)
  del.t = 1 #delta time, will be divided off, so is arbitrary unless it is irregular
  dist.traveled <- veloc*del.t
  adv.veloc <- sum(dist.traveled)/length(dist.traveled)
  
  return(adv.veloc)
  
}