AppAltfromTopoAlt: Determine Apparent altitude from Topocentric altitude
In vreijs/ARCHAEOCOSMO: In-Line Documentation for ARCHAEOCOSMO

Description Usage Arguments Value Author(s) References See Also Examples

The astronomical refraction is determined using the inverse of Sinclair's formula. This formula is based on the International Standard Atmosphere (ISA: which by the way does not mean the 'average' atmosphere;-). Due to the uncertainties aorund the atmsopheric condition of the Boundary Layers, the calcuated refractions will not be very accurate (say with 0.5deg). Below a Topocentric altitude of -3.5deg, the Apparent altitude is made equal.

1 2	AppAltfromTopoAlt(TopoAlt, TempE = TempDefault, PresE = PressureDefault)

`TopoAlt`	the Topocentric altitude (deg), double
`TempE`	Temperature at height eyes (C, default=15C), double
`PresE`	Airpressure at height eyes (mbar, default=1013.25mbar), double

AppAlt de Apparent altitude (deg), double

Victor Reijs, lists@archaeocosmology.org

Bennett, G.G. 1982. 'The calculation of astronomical refraction in marine navigation', Journal of Inst. navigation, Vol 35: pp. 255-59.

http://www.archaeocosmology.org/eng/refract.htm

AppAltfromTopoAlt(0,15,1013.25)
#0.4721438916

AppAltfromTopoAlt(c(-4,-0.5,0,2,20))
#-4.00000000000  0.04956607457  0.47214389159  2.27870879488 20.04373829337