TopoAltfromAppAlt: Determine Topocentric altitude from Apparent 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 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 an Apparent altitude of -3.5deg, the Topocentric altitude is made equal.

1	TopoAltfromAppAlt(AppAlt, TempE = TempDefault, PresE = PressureDefault)

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

TopoAlt thee Topocentric 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

TopoAltfromAppAlt(0,15,1013.25)
#-0.5598886443

TopoAltfromAppAlt(c(-4,-0.5,0,2,20))
#-4.0000000000 -1.1817229649 -0.5598886443  1.7010159897 19.9561578991