ISADORA - ICAO 1983 Compliant International Standard Atmosphere (ISA)

Isadora is a lightweight, precise, and Pythonic implementation of the International Standard Atmosphere (ISA) model. It provides atmospheric properties (temperature, pressure, density, dynamic and kinematic viscosity, speed of sound) at any geopotential altitude.

The package is fully unit-aware, supporting SI, USCS, and Imperial units, and validated against ICAO 1983 reference tables.

Ideal for aerospace engineers, researchers, and students, Isadora simplifies atmospheric computations while ensuring accuracy and unit safety.

Features

• Compute unit-aware atmospheric properties at any geopotential height.
• Compute derived quantities: Mach number, dynamic pressure, geometric height.
• Support for multiple unit systems: SI (default), USCS, Imperial.
• Physical constants implemented using type-safe, immutable units.
• Fully ICAO 1983 compliant calculations.
• Pytest-tested for physical consistency, numerical correctness, and unit integrity.

Installation

Install via pip:

pip install isadora

Or clone the repository and install locally:

git clone https://github.com/techkaduna/isadora.git
cd isadora
pip install .

Dependencies

• Python >= 3.10
• mudu – unit and measurement library
• dataclasses (Python 3.10+ has it built-in)
• pytest – for running the test suite

Quick Start

Import the package and create an ISA atmosphere:

from isadora import ISA

# Create an ISA atmosphere at 5 km geopotential height
atm = ISA(geopotential_height=5)

print("Temperature:", atm.temperature)
print("Pressure:", atm.pressure)
print("Density:", atm.density)
print("Dynamic Viscosity:", atm.dynamic_viscosity)
print("Kinematic Viscosity:", atm.kinematic_viscosity)
print("Speed of Sound:", atm.speed_of_sound)
print("Mach Number at 20 m/s:", atm.mach_number(20))
print("Geometric Height:", atm.geometric_height)

Switching Units

Change the global unit system using UnitRegistry:

from isadora.units import UnitRegistry

# Set to USCS units
UnitRegistry.set_unit_standard("USCS")

atm_uscs = ISA(geopotential_height=10)
print("Temperature (USCS):", atm_uscs.temperature)
print("Pressure (USCS):", atm_uscs.pressure)

Derived Quantities

The ISA object provides convenient methods:

• atm.mach_number(velocity) – computes Mach number for a given velocity.
• atm.dynamic_pressure(velocity) – computes dynamic pressure at altitude.
• atm.geometric_height – converts geopotential height to geometric height.
• atm.speed_of_sound – sound speed at the specified altitude.

Testing

Run the full Pytest test suite:

pytest -v tests/

Tests cover:

• ICAO 1983 reference validation
• Physical consistency (hydrostatic equilibrium, monotonicity)
• Derived quantities (Mach, dynamic pressure, geometric height)
• Unit system correctness and conversion

References

• International Civil Aviation Organization (ICAO), 1983, Standard Atmosphere Tables
• U.S. Standard Atmosphere, 1976, NASA

License

MIT License. See LICENSE file for details.

Contributing

Contributions are welcome! Follow PEP 8 style, include tests for new features, and submit via GitHub Pull Requests.

Contact

Author: Kolawole Andrew
GitHub: https://github.com/techkaduna/isadora
Email: andrewolakola@gmail.com