APPENDIX
Appendix A:  BASIC subroutine to determine the Equations of Time (EqT) in minutes of time
This is used in the calculation of longitude to correct for the elliptical nature of the earth's orbit, and the tilt of the earth's axis, in the following manner:

East Longitude = 360 - (time of midnight (hours)) ( 15 - (eqT (minutes)) ( 4

  Dim MidnnightGMT as Date, correctedyear as Integer, T as Double
  Dim correctedmonth as integer, G as Double, C as Double
  Dim l as Double, alpha as Double

  If Month(MidnightGMT) > 2 Then
    correctedYear = Year(MidnightGMT)
    correctedMonth = Month(MidnightGMT) - 3
  Else
    correctedYear = Year(MidnightGMT) - 1
    correctedMonth = Month(MidnightGMT) + 9
  End If
  
  T = (MidnightGMT - Int(MidnightGMT) + Day(MidnightGMT)
  T = T + Int(30.6 * correctedMonth + 0.5)
  T = T + Int(365.25 * (correctedYear - 1976)) - 8707.5) / 36525

  G = (357.528 + 35999.05 * T)
  C = 1.915 * Sin(DTR * (G)) + 0.02 * Sin(DTR * (G * 2))
  l = (280.46 + C + 36000.77 * T)
  alpha = 2.466 * Sin(DTR * (2 * l)) - 0.053 * Sin(DTR * (4 * l))
  EqT = (alpha - C) * 4


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Hill and Braun


Geolocation by Light Level
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