Air mass: Difference between revisions

------------------------------------

0 1.00000000 1.00000000

5 1.00380963 1.00380965

10 1.01538466 1.01538475

15 1.03517744 1.03517765

20 1.06399053 1.06399093

25 1.10305937 1.10306005

30 1.15418974 1.15419083

35 1.21998076 1.21998246

40 1.30418931 1.30419190

45 1.41234169 1.41234567

50 1.55280404 1.55281025

55 1.73875921 1.73876915

60 1.99212000 1.99213665

65 2.35199740 2.35202722

70 2.89531368 2.89537287

75 3.79582352 3.79596149

80 5.53885809 5.53928113

85 10.07896219 10.08115981

90 34.32981136 34.36666557

</pre>

=={{header|Julia}}==

{{trans|FreeBASIC}}

<lang julia>using Printf

const DEG = 0.017453292519943295769236907684886127134 # degrees to radians

const RE = 6371000 # Earth radius in meters

const dd = 0.001 # integrate in this fraction of the distance already covered

const FIN = 10000000 # integrate only to a height of 10000km, effectively infinity

""" the density of air as a function of height above sea level """

rho(a::Float64)::Float64 = exp(-a/8500.0)

""" a = altitude of observer

z = zenith angle (in degrees)

d = distance along line of sight """

height(a, z, d) = sqrt((RE + a)^2 + d^2 - 2 * d * (RE + a) * cosd(180 - z)) - RE

""" integrates density along the line of sight """

function column_density(a, z)

dsum, d = 0.0, 0.0

while d < FIN

delta = max(dd, (dd)*d) # adaptive step size to avoid it taking forever:

dsum += rho(height(a, z, d + 0.5 * delta)) * delta

d += delta

end

return dsum

end

airmass(a, z) = column_density(a, z) / column_density(a, 0)

println("Angle 0 m 13700 m\n", "-"^36)

for z in 0:5:90

@printf("%2d %11.8f %11.8f\n", z, airmass(0, z), airmass(13700, z))

end

</lang>{{out}}

<pre>

Angle 0 m 13700 m