R/sunrise_sunset_times.R

In biometryhub/BiometryTools: A Suite of Functions for Conducting Post Analysis Tasks with ASReml-R V4 Models tasks with ASReml-R V4 models

# Copyright (c) 2020 University of Adelaide Biometry Hub
#
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# Code author: Russell A. Edson
# Date last modified: 13/10/2020
# Send all bug reports/questions/comments to
#     russell.edson@adelaide.edu.au
#
# Functions to compute sunrise/sunset times given a date and
# latitude/longitude coordinates. Useful for e.g. factoring a
# dataset into Day/Night phases.
#
# TODO: >90% code duplication between these two functions.
#       Maybe worth refactoring into a single function that
#       parameterises on sunrise/sunset, or perhaps use a
#       function-generating macro?

# library(sp)
# library(maptools)


#' Return the time of sunrise given the date and GPS coordinates.
#'
#' @param datetime A POSIXct object for the local date (and timezone).
#' @param latitude The decimal-degrees for the latitude (Northing).
#' @param longitude The decimal-degrees for the longitude (Easting).
#' @return A POSIXct object for the local time of sunrise.
#'
#' @export
#'
#' @examples
#' library(lubridate)
#' date <- as_datetime("2020-01-01", tz = "Australia/Adelaide")
#' sunrise_time(date, -35.69167, 136.9650)
sunrise_time <- function(datetime, latitude, longitude) {
  coordinates <- sp::SpatialPoints(
    matrix(c(longitude, latitude), ncol = 2),
    proj4string = sp::CRS("+proj=longlat +datum=WGS84")
  )

  sunrise <- maptools::sunriset(
    coordinates,
    datetime,
    direction = "sunrise",
    POSIXct.out = TRUE
  )
  sunrise[, 2]
}


#' Return the time of sunset given the date and GPS coordinates.
#'
#' @param datetime A POSIXct object for the local date (and timezone).
#' @param latitude The decimal-degrees for the latitude (Northing).
#' @param longitude The decimal-degrees for the longitude (Easting).
#' @return A POSIXct object for the local time of sunset.
#'
#' @export
#'
#' @example
#' library(lubridate)
#' date <- as_datetime("2020-01-01", tz = "Australia/Adelaide")
#' sunset_time(date, -35.69167, 136.9650)
sunset_time <- function(datetime, latitude, longitude) {
  coordinates <- sp::SpatialPoints(
    matrix(c(longitude, latitude), ncol = 2),
    proj4string = sp::CRS("+proj=longlat +datum=WGS84")
  )

  sunset <- maptools::sunriset(
    coordinates,
    datetime,
    direction = "sunset",
    POSIXct.out = TRUE
  )
  sunset[, 2]
}