R/eudist.r

In jdbcode/LandsatLinkr: Tools to spectrally link Landsat data

#' Earth-Sun distance by day of year
#'
#' Earth-Sun distance by day of year
#' @param doy numeric. image day-of-year
#' @export
#' @references http://landsathandbook.gsfc.nasa.gov/excel_docs/d.xls

eudist = function(doy){
  
  dau = c(
    0.98331,
    0.98330,
    0.98330,
    0.98330,
    0.98330,
    0.98332,
    0.98333,
    0.98335,
    0.98338,
    0.98341,
    0.98345,
    0.98349,
    0.98354,
    0.98359,
    0.98365,
    0.98371,
    0.98378,
    0.98385,
    0.98393,
    0.98401,
    0.98410,
    0.98419,
    0.98428,
    0.98439,
    0.98449,
    0.98460,
    0.98472,
    0.98484,
    0.98496,
    0.98509,
    0.98523,
    0.98536,
    0.98551,
    0.98565,
    0.98580,
    0.98596,
    0.98612,
    0.98628,
    0.98645,
    0.98662,
    0.98680,
    0.98698,
    0.98717,
    0.98735,
    0.98755,
    0.98774,
    0.98794,
    0.98814,
    0.98835,
    0.98856,
    0.98877,
    0.98899,
    0.98921,
    0.98944,
    0.98966,
    0.98989,
    0.99012,
    0.99036,
    0.99060,
    0.99084,
    0.99108,
    0.99133,
    0.99158,
    0.99183,
    0.99208,
    0.99234,
    0.99260,
    0.99286,
    0.99312,
    0.99339,
    0.99365,
    0.99392,
    0.99419,
    0.99446,
    0.99474,
    0.99501,
    0.99529,
    0.99556,
    0.99584,
    0.99612,
    0.99640,
    0.99669,
    0.99697,
    0.99725,
    0.99754,
    0.99782,
    0.99811,
    0.99840,
    0.99868,
    0.99897,
    0.99926,
    0.99954,
    0.99983,
    1.00012,
    1.00041,
    1.00069,
    1.00098,
    1.00127,
    1.00155,
    1.00184,
    1.00212,
    1.00240,
    1.00269,
    1.00297,
    1.00325,
    1.00353,
    1.00381,
    1.00409,
    1.00437,
    1.00464,
    1.00492,
    1.00519,
    1.00546,
    1.00573,
    1.00600,
    1.00626,
    1.00653,
    1.00679,
    1.00705,
    1.00731,
    1.00756,
    1.00781,
    1.00806,
    1.00831,
    1.00856,
    1.00880,
    1.00904,
    1.00928,
    1.00952,
    1.00975,
    1.00998,
    1.01020,
    1.01043,
    1.01065,
    1.01087,
    1.01108,
    1.01129,
    1.01150,
    1.01170,
    1.01191,
    1.01210,
    1.01230,
    1.01249,
    1.01267,
    1.01286,
    1.01304,
    1.01321,
    1.01338,
    1.01355,
    1.01371,
    1.01387,
    1.01403,
    1.01418,
    1.01433,
    1.01447,
    1.01461,
    1.01475,
    1.01488,
    1.01500,
    1.01513,
    1.01524,
    1.01536,
    1.01547,
    1.01557,
    1.01567,
    1.01577,
    1.01586,
    1.01595,
    1.01603,
    1.01610,
    1.01618,
    1.01625,
    1.01631,
    1.01637,
    1.01642,
    1.01647,
    1.01652,
    1.01656,
    1.01659,
    1.01662,
    1.01665,
    1.01667,
    1.01668,
    1.01670,
    1.01670,
    1.01670,
    1.01670,
    1.01669,
    1.01668,
    1.01666,
    1.01664,
    1.01661,
    1.01658,
    1.01655,
    1.01650,
    1.01646,
    1.01641,
    1.01635,
    1.01629,
    1.01623,
    1.01616,
    1.01609,
    1.01601,
    1.01592,
    1.01584,
    1.01575,
    1.01565,
    1.01555,
    1.01544,
    1.01533,
    1.01522,
    1.01510,
    1.01497,
    1.01485,
    1.01471,
    1.01458,
    1.01444,
    1.01429,
    1.01414,
    1.01399,
    1.01383,
    1.01367,
    1.01351,
    1.01334,
    1.01317,
    1.01299,
    1.01281,
    1.01263,
    1.01244,
    1.01225,
    1.01205,
    1.01186,
    1.01165,
    1.01145,
    1.01124,
    1.01103,
    1.01081,
    1.01060,
    1.01037,
    1.01015,
    1.00992,
    1.00969,
    1.00946,
    1.00922,
    1.00898,
    1.00874,
    1.00850,
    1.00825,
    1.00800,
    1.00775,
    1.00750,
    1.00724,
    1.00698,
    1.00672,
    1.00646,
    1.00620,
    1.00593,
    1.00566,
    1.00539,
    1.00512,
    1.00485,
    1.00457,
    1.00430,
    1.00402,
    1.00374,
    1.00346,
    1.00318,
    1.00290,
    1.00262,
    1.00234,
    1.00205,
    1.00177,
    1.00148,
    1.00119,
    1.00091,
    1.00062,
    1.00033,
    1.00005,
    0.99976,
    0.99947,
    0.99918,
    0.99890,
    0.99861,
    0.99832,
    0.99804,
    0.99775,
    0.99747,
    0.99718,
    0.99690,
    0.99662,
    0.99634,
    0.99605,
    0.99577,
    0.99550,
    0.99522,
    0.99494,
    0.99467,
    0.99440,
    0.99412,
    0.99385,
    0.99359,
    0.99332,
    0.99306,
    0.99279,
    0.99253,
    0.99228,
    0.99202,
    0.99177,
    0.99152,
    0.99127,
    0.99102,
    0.99078,
    0.99054,
    0.99030,
    0.99007,
    0.98983,
    0.98961,
    0.98938,
    0.98916,
    0.98894,
    0.98872,
    0.98851,
    0.98830,
    0.98809,
    0.98789,
    0.98769,
    0.98750,
    0.98731,
    0.98712,
    0.98694,
    0.98676,
    0.98658,
    0.98641,
    0.98624,
    0.98608,
    0.98592,
    0.98577,
    0.98562,
    0.98547,
    0.98533,
    0.98519,
    0.98506,
    0.98493,
    0.98481,
    0.98469,
    0.98457,
    0.98446,
    0.98436,
    0.98426,
    0.98416,
    0.98407,
    0.98399,
    0.98391,
    0.98383,
    0.98376,
    0.98370,
    0.98363,
    0.98358,
    0.98353,
    0.98348,
    0.98344,
    0.98340,
    0.98337,
    0.98335,
    0.98333,
    0.98331)
  return(dau[doy])
}