Air mass: Difference between revisions
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(Added Java solution) |
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fmt.Printf("%2d %11.8f %11.8f\n", z, airmass(0, fz), airmass(13700, fz)) |
fmt.Printf("%2d %11.8f %11.8f\n", z, airmass(0, fz), airmass(13700, fz)) |
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} |
} |
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}</lang> |
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{{out}} |
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<pre> |
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Angle 0 m 13700 m |
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------------------------------------ |
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0 1.00000000 1.00000000 |
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5 1.00380963 1.00380965 |
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10 1.01538466 1.01538475 |
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15 1.03517744 1.03517765 |
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20 1.06399053 1.06399093 |
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25 1.10305937 1.10306005 |
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30 1.15418974 1.15419083 |
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35 1.21998076 1.21998246 |
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40 1.30418931 1.30419190 |
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45 1.41234169 1.41234567 |
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50 1.55280404 1.55281025 |
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55 1.73875921 1.73876915 |
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60 1.99212000 1.99213665 |
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65 2.35199740 2.35202722 |
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70 2.89531368 2.89537287 |
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75 3.79582352 3.79596149 |
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80 5.53885809 5.53928113 |
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85 10.07896219 10.08115981 |
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90 34.32981136 34.36666557 |
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</pre> |
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=={{header|Java}}== |
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{{trans|FreeBASIC}} |
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<lang java>public class AirMass { |
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public static void main(String[] args) { |
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System.out.println("Angle 0 m 13700 m"); |
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System.out.println("------------------------------------"); |
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for (double z = 0; z <= 90; z+= 5) { |
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System.out.printf("%2.0f %11.8f %11.8f\n", |
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z, airmass(0.0, z), airmass(13700.0, z)); |
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} |
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} |
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private static double rho(double a) { |
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// the density of air as a function of height above sea level |
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return Math.exp(-a / 8500.0); |
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} |
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private static double height(double a, double z, double d) { |
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// a = altitude of observer |
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// z = zenith angle (in degrees) |
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// d = distance along line of sight |
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double aa = RE + a; |
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double hh = Math.sqrt(aa * aa + d * d - 2.0 * d * aa * Math.cos(Math.toRadians(180 - z))); |
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return hh - RE; |
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} |
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private static double columnDensity(double a, double z) { |
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// integrates density along the line of sight |
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double sum = 0.0, d = 0.0; |
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while (d < FIN) { |
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// adaptive step size to avoid it taking forever |
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double delta = Math.max(DD * d, DD); |
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sum += rho(height(a, z, d + 0.5 * delta)) * delta; |
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d += delta; |
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} |
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return sum; |
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} |
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private static double airmass(double a, double z) { |
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return columnDensity(a, z) / columnDensity(a, 0.0); |
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} |
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private static final double RE = 6371000.0; // Earth radius in meters |
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private static final double DD = 0.001; // integrate in this fraction of the distance already covered |
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private static final double FIN = 10000000.0; // integrate only to a height of 10000km, effectively infinity |
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}</lang> |
}</lang> |
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