Purpose
This repository provides Ruby code for calculating values defined in the following documents:
-
International Standard Atmosphere (ISA) from ISO 2533:1975
-
ICAO Standard Atmosphere (ICAO Doc 7488/3, 1994)
Which are technically identical documents but different in presentation and
units (the ICAO document includes ft
in addition to m
).
Usage
Formulas and calculations
> require 'atmospheric'
> instance = Atmospheric::Isa.method_name
> # method_name is one of the following
The available methods are:
-
geometric_altitude_from_geopotential(geopotential_altitude)
-
geopotential_altitude_from_geometric(geometric_altitude)
-
temperature_at_layer_from_geopotential(geopotential_altitude)
-
temperature_at_layer_celcius(geopotential_altitude)
-
pressure_from_geopotential_mbar(geopotential_altitude)
-
pressure_from_geopotential_mmhg(geopotential_altitude)
-
density_from_geopotential(geopotential_altitude)
-
gravity_at_geopotential(geopotential_altitude)
-
p_p_n_from_geopotential(geopotential_altitude)
-
rho_rho_n_from_geopotential(geopotential_altitude)
-
root_rho_rho_n_from_geopotential(geopotential_altitude)
-
speed_of_sound_from_geopotential(geopotential_altitude)
-
dynamic_viscosity_from_geopotential(geopotential_altitude)
-
kinematic_viscosity_from_geopotential(geopotential_altitude)
-
thermal_conductivity_from_geopotential(geopotential_altitude)
-
pressure_scale_height_from_geopotential(geopotential_altitude)
-
specific_weight_from_geopotential(geopotential_altitude)
-
air_number_density_from_geopotential(geopotential_altitude)
-
mean_air_particle_speed_from_geopotential(geopotential_altitude)
-
air_particle_collision_frequency_from_geopotential(geopotential_altitude)
-
mean_free_path_of_air_particles_from_geopotential(geopotential_altitude)
Generating ISO 2533 tables
ISO 2533:1975
All tables in the 1975 edition are arranged in these steps in meters:
(-2000..31999).step(50) +
(32000..50999).step(100) +
(51000..80000).step(200)
Tables 5 to 7 all have height information of the following keys in the hash:
-
geopotential-altitude-m
-
geopotential-altitude-ft
-
geometrical-altitude-m
-
geometrical-altitude-ft
Table 5
Title: "Temperature (T and t), Pressure (p), Density (p) and Acceleration of free fall (g) in terms of geometrical altitude (h) and geopotential altitude (H)"
Provides the following values in addition to geopotential and geometric height:
-
temperature-K
-
temperature-C
-
pressure-mbar
-
pressure-mmHg
-
density
-
acceleration
Atmospheric::Export::Iso25331975.table_5 #=> Hash
Atmospheric::Export::Iso25331975.table_5_yaml #=> YAML
Table 6
Title: "Relations of p’pn, p/pn and bar(p/pn), Speed of sound (a), Dynamic viscosity (p), Kinematic viscosity (v) and Thermal conductivity (lambda) in terms of geometrical altitude (h), and geopotential altitude (H)"
Provides the following values in addition to geopotential and geometric height:
-
ppn
-
rhorhon
-
sqrt-rhorhon
-
speed-of-sound
-
dynamic-viscosity
-
kinematic-viscosity
-
thermal-conductivity
Atmospheric::Export::Iso25331975.table_6 #=> Hash
Atmospheric::Export::Iso25331975.table_6_yaml #=> YAML
Table 7
Title: "Pressure scale height (H_p) Specific weight (gamma), Air number density (n), Mean air-particle speed (v), Air-particle collision frequency (omega) and Mean free path of air particles (l) in terms of geometrical altitude (h) and geopotential altitude (H)"
-
pressure-scale-height
-
specific-weight
-
air-number-density
-
mean-speed
-
frequency
-
mean-free-path
Atmospheric::Export::Iso25331975.table_7 #=> Hash
Atmospheric::Export::Iso25331975.table_7_yaml #=> YAML
ISO 2533 ADD 1:1985
Addendum 1 adds "Hypsometrical tables".
Table 1 (hPa)
Title: "Geopotential altitude as a function of barometric pressure for 5 ⇐ p < 20 hPa at intervals of 0.01 hPa"
For the range of (5.0..19.99).step(0.01)
in hPa.
Provides:
-
pressure-mbar
-
geopotential-altitude
Atmospheric::Export::HypsometricalTables.table_1 #=> Hash
Atmospheric::Export::HypsometricalTables.table_1_yaml #=> YAML
Table 2 (hPa)
Title: "Geopotential altitude as a function of barometric pressure for 20 ⇐ p < 1200 hPa at intervals of 0.1 hPa"
Same as Table 1 but for the range of (20.0..1199.9).step(0.1)
in hPa.
Atmospheric::Export::HypsometricalTables.table_2 #=> Hash
Atmospheric::Export::HypsometricalTables.table_2_yaml #=> YAML
Table 3 (mmHg)
Title: "Geopotential altitude as a function of barometric pressure for 4 ⇐ p < 10 mmHg at intervals of 0.01 mmHg"
Same as Table 1 but for the range of (4.0..9.99).step(0.01)
and results in mmhg.
Provides:
-
pressure-mmhg
-
geopotential-altitude
Atmospheric::Export::HypsometricalTables.table_3 #=> Hash
Atmospheric::Export::HypsometricalTables.table_3_yaml #=> YAML
Table 4 (mmHg)
Title: "Geopotential altitude as a function of barometric pressure for 10 ⇐ p < 900 mmHg at intervals of 0.1 mmHg"
Same as Table 3 but for the range of (10.0..899.9).step(0.1)
and results in mmhg.
Atmospheric::Export::HypsometricalTables.table_4 #=> Hash
Atmospheric::Export::HypsometricalTables.table_4_yaml #=> YAML
Table 5 (hPa) and Table 6 (mmHg)
The difference is Table 5 is in hPa while Table 6 is in mmHg.
Title: "Barometric pressure, in hectopascals, as a function of geopotential altitude for -1000 ⇐ H < +4600 m at intervals of 1m"
Provides:
-
geopotential-altitude
-
pressure-mbar
-
pressure-mmhg
Range of (-1000..4599).step(1)
.
Atmospheric::Export::HypsometricalTables.table_56 #=> Hash
Atmospheric::Export::HypsometricalTables.table_56_yaml #=> YAML
ISO 2533 ADD 2:1997
Addendum 2 is exactly like ISO 2533:1975 with the tables but extended the tables:
-
1975’s range is -2km to 80km. 1997 provides -5km to 2km (yes -2km to 2km overlaps…)
-
1975 tables only provide H and h in meters. 1997 adds a lookup table of H and h in feet.
(-5000..2000).step(50)
(-16500..-13999).step(250) +
(-14000..104999).step(200) +
(105000..262500).step(500)
Table 1 (-5km to 2km)
Title: "Temperature (T and t), pressure (p), density (p) and acceleration of free fall (g) in terms of geometrical altitude (h) and geopotential altitude (H) — Altitudes in metres"
Exactly same as ISO 2533:1975 Table 5, but with a different height range.
In addition, pressure at mmHg is no longer produced, but the implementation still provides it for completeness.
Atmospheric::Export::Iso25331997.table_1 #=> Hash
Atmospheric::Export::Iso25331997.table_1_yaml #=> YAML
Table 2 (-5km to 2km)
Title: "Relations of p’pn, p/pn and bar(p/pn), Speed of sound (a), Dynamic viscosity (p), Kinematic viscosity (v) and Thermal conductivity (lambda) in terms of geometrical altitude (h), and geopotential altitude (H) — Altitudes in metres"
Exactly same as ISO 2533:1975 Table 6, but with a different height range.
Atmospheric::Export::Iso25331997.table_2 #=> Hash
Atmospheric::Export::Iso25331997.table_2_yaml #=> YAML
Table 3 (-5km to 2km)
Title: "Pressure scale height (H_p) Specific weight (gamma), Air number density (n), Mean air-particle speed (v), Air-particle collision frequency (omega) and Mean free path of air particles (l) in terms of geometrical altitude (h) and geopotential altitude (H) — Altitudes in metres"
Exactly same as ISO 2533:1975 Table 7, but with a different height range.
Atmospheric::Export::Iso25331997.table_3 #=> Hash
Atmospheric::Export::Iso25331997.table_3_yaml #=> YAML
Table 4 (-16.5kft to 262.5kft)
Title: "Temperature (T and t), pressure (p), density (p) and acceleration of free fall (g) in terms of geometrical altitude (h) and geopotential altitude (H) — Altitudes in feet"
Exactly same as ISO 2533:1975 Table 5, but in feet and different range.
Pressure at mmHg is not produced, but the implementation still provides it for completeness.
Atmospheric::Export::Iso25331997.table_4 #=> Hash
Atmospheric::Export::Iso25331997.table_4_yaml #=> YAML
Table 5 (-16.5kft to 262.5kft)
Title: "Relations of p’pn, p/pn and bar(p/pn), Speed of sound (a), Dynamic viscosity (p), Kinematic viscosity (v) and Thermal conductivity (lambda) in terms of geometrical altitude (h), and geopotential altitude (H) — Altitudes in feet"
Exactly same as ISO 2533:1975 Table 6, but in feet and different range.
Atmospheric::Export::Iso25331997.table_5 #=> Hash
Atmospheric::Export::Iso25331997.table_5_yaml #=> YAML
Table 6 (-16.5kft to 262.5kft)
Title: "Pressure scale height (H_p) Specific weight (gamma), Air number density (n), Mean air-particle speed (v), Air-particle collision frequency (omega) and Mean free path of air particles (l) in terms of geometrical altitude (h) and geopotential altitude (H) — Altitudes in feet"
Exactly same as ISO 2533:1975 Table 7, but in feet and different range.
Atmospheric::Export::Iso25331997.table_6 #=> Hash
Atmospheric::Export::Iso25331997.table_6_yaml #=> YAML
Testing
$ rspec
Tests are encoded in spec/fixtures/tests.yml
in the following format:
- H: -2000.0
h: -1999.0
TK: 301.15
TC: 28.0
p_mbar: 1277.74
p_mmhg: 958.382
rho: 1.47808
g: 9.8128
p_p_n: 1.26103
rho_rho_n: 1.20659
root_rho_rho_n: 1.09845
a: 347.886
mu: 1.8514e-05
v: 1.2526e-05
lambda: 0.026359
H_p: 8809.5
gamma: 14.504
n: 3.0734e+25
v_bar: 469.18
omega: 8535100000.0
l: 549710000.0
Each of these values are associated with a cell in the tables of the source documents.
The only defining value in a tests is H
(geopotential altitude).
It is used to generate all the other values.
License
Copyright Ribose.
TODO
-
expose this as a plugin to LutaML / Metanorma YAML2text