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Compute astronomical twilight from positions and dates

Source: R/path2twilight.R
path2twilight.Rd

This function compute the theoretical twilight (i.e., datetime of sunrise and sunset) at given locations and for specific date.

We use the suntools package for this.

By default (solar_dep=0), the computation return sunrise and sunset. But, it is also possible to compute different twilights by setting depression angle value greater than 0 (6° for civil, 12° for nautical and 18° for astronomical).

Usage

path2twilight(path, date = NULL, solar_dep = 0, return_long = TRUE)

Arguments

path

a GeoPressureR path or pressurepath data.frame

date

a vector of POSIXt datetime for which sunrise and sunset are computed. Be default, uses the range of path$date provided.

solar_dep

a numerical value representing the solar depression angle used to compute sunrise and sunset.

return_long

logical defining the format of the data.frame returned. If TRUE, returns the long format identical to twilight_create(). If FALSE, return the sunrise and sunset as different column, making the data.frame the same size as date.

Value

if return_long == TRUE, a twilight data.frame (same as twilight_create()) with columns:

  • date same as input date

  • twilight date-time of twilight

  • rise logical indicating sunrise (TRUE) or sunset (FALSE).

  • stap_id same as path$stap_id

  • lat same as path$lat

  • lon same as path$lon

if return_long == FALSE, a data.frame with the same size of date with columns:

  • date same as input date

  • sunrise date-time of sunrise

  • sunset date-time of sunset

  • stap_id same as path$stap_id

  • lat same as path$lat

  • lon same as path$lon

See also

GeoPressureManual , suntools

Examples

path <- data.frame(
  stap_id = c(1, 2, 3, 4, 5),
  j = c(1L, 1L, 1L, 1L, 1L),
  ind = c(1652L, 1603L, 1505L, 1609L, 1463L),
  lat = c(48.9, 47.5, 45.5, 41.5, 37.5),
  lon = c(17.05, 16.5, 14.5, 16.5, 13.5),
  start = as.POSIXct(
    c(1501113450, 1501888650, 1501987950, 1502075550, 1502151150),
    tzone = "UTC"
  ),
  end = as.POSIXct(c(1501876050, 1501961250, 1502046750, 1502133150, 1502323050), tzone = "UTC"),
  include = c(TRUE, TRUE, TRUE, TRUE, TRUE),
  known = c(TRUE, FALSE, FALSE, FALSE, FALSE),
  interp = c(FALSE, FALSE, FALSE, FALSE, FALSE)
)

twl <- path2twilight(path)