Crate itu_rs 

Selected ITU-R P-series atmospheric propagation models.

This crate is a Rust port of the subset of python-itu-r needed for Earth-space atmospheric attenuation on a slant path. It currently focuses on atmospheric_attenuation_slant_path and the recommendation data needed to compute gas, cloud, rain, scintillation, and total attenuation contributions.

Data files

Model grids are loaded lazily on first use. In a repository checkout, the crate looks for data under data/ next to Cargo.toml.

Automatic Data Download

For published package use, enable features = ["data"]. No runtime configuration is required: the build uses local data/ files when present, otherwise downloads and embeds the verified data archive.

The raw ITU-R grids are too large to include directly because crates.io limits .crate archive size.

Manual Data Directory

If automatic data embedding is not suitable, set ITU_RS_DATA_DIR to a directory containing the python-itu-r itur/data layout. On Unix shells:

export ITU_RS_DATA_DIR=/path/to/ITU-Rpy/itur/data

On Windows PowerShell:

$env:ITU_RS_DATA_DIR = "C:\path\to\ITU-Rpy\itur\data"

The examples that depend on recommendation grids check whether data is available before calling the model. That keeps doctests useful in this repository, with features = ["data"], and in downstream builds that set ITU_RS_DATA_DIR.

Conventions

Public APIs use plain f64 values and encode units in argument and return names:

• _deg: degrees. lat_deg is geodetic latitude and must be in [-90, 90]. lon_deg is geodetic longitude; any finite degree value is accepted and map lookups wrap it internally.
• _ghz: carrier frequency in gigahertz.
• _km and _m: kilometres and metres. Site heights are above mean sea level unless the function says otherwise.
• _hpa: pressure in hectopascals.
• _gm3: density in grams per cubic metre.
• _kgm2: columnar mass in kilograms per square metre.
• _mmh: rainfall rate in millimetres per hour.
• _db and _db_per_km: attenuation in decibels and specific attenuation in decibels per kilometre.
• _k and _c: temperature in kelvin and degrees Celsius.

The p argument is a percentage of time exceeded, not a probability fraction. For example, 0.1 means 0.1% of an average year. Elevation angles are above the local horizon and must be in the open interval (0, 90).

Example

use itu_rs::{atmospheric_attenuation_slant_path, SlantPathOptions};

let attenuation = atmospheric_attenuation_slant_path(
    45.4215,   // latitude, degrees
    -75.6972,  // longitude, degrees
    12.0,      // frequency, GHz
    30.0,      // elevation, degrees
    0.1,       // time percentage exceeded
    1.2,       // antenna diameter, m
    SlantPathOptions::default(),
)?;

assert!(attenuation.total_db.is_finite());

Structs

ItuError

Error returned by ITU-R model loading, validation, and calculation routines.

SlantPathContributions

Atmospheric attenuation contribution breakdown in dB.

SlantPathOptions

Optional environmental and model inputs for slant-path attenuation.

Enums

GasPathMode

Calculation mode for P.676 gaseous path attenuation.

HydrometeorType

Hydrometeor phase used by P.453 saturation vapour-pressure formulas.

Functions

atmospheric_attenuation_slant_path

Computes total atmospheric attenuation for one Earth-space slant path.

atmospheric_attenuation_slant_path_many

Computes atmospheric attenuation for multiple elevation angles.

bicubic_2d_interpolate

Interpolates a regular P.1144 grid with bicubic interpolation.

bilinear_2d_interpolate

Interpolates a regular P.1144 grid with bilinear interpolation.

cloud_attenuation_db

Computes cloud attenuation from ITU-R P.840.

cloud_attenuation_lognormal_db

Computes cloud attenuation with the P.840 lognormal approximation.

cloud_liquid_mass_absorption_coefficient

Computes the P.840 cloud liquid-water mass absorption coefficient.

cloud_reduced_liquid_kgm2

Looks up reduced cloud liquid water content from ITU-R P.840.

cloud_specific_attenuation_coefficient

Computes the P.840 cloud specific attenuation coefficient.

dn1

Looks up the P.453 refractivity gradient exceeded over the lowest 1 km.

dn65

Looks up the P.453 refractivity gradient exceeded in the lowest 65 m.

dry_term_radio_refractivity

Computes dry-term radio refractivity from ITU-R P.453.

fit_rain_attenuation_to_lognormal

Fits P.618 rain attenuation statistics to a lognormal model.

gamma0_approx_db_per_km

Computes the P.676 dry-air approximate compatibility attenuation in dB/km.

gamma0_exact_db_per_km

Computes dry-air specific attenuation from ITU-R P.676 in dB/km.

gamma_exact_db_per_km

Computes total specific gaseous attenuation from ITU-R P.676 in dB/km.

gammaw_approx_db_per_km

Computes the P.676 water-vapour approximate specific attenuation in dB/km.

gammaw_exact_db_per_km

Computes water-vapour specific attenuation from ITU-R P.676 in dB/km.

gas_attenuation_default

Computes gas-only atmospheric attenuation for one elevation angle.

gas_attenuation_default_many

Computes gas-only atmospheric attenuation for multiple elevation angles.

gas_attenuation_default_many_checked

Computes gas-only atmospheric attenuation for multiple elevation angles.

gaseous_attenuation_inclined_path_db

Computes gaseous attenuation on an inclined path from ITU-R P.676.

gaseous_attenuation_slant_path_db

Computes gaseous attenuation on an Earth-space slant path from ITU-R P.676.

gaseous_attenuation_terrestrial_path_db

Computes gaseous attenuation on a terrestrial path from ITU-R P.676.

inter_annual_variability

Computes inter-annual variability from ITU-R P.678.

is_regular_grid

Tests whether latitude and longitude matrices describe a regular P.1144 grid.

lognormal_approximation_coefficients

Looks up P.840 lognormal cloud liquid-water distribution coefficients.

map_wet_term_radio_refractivity

Looks up wet-term radio refractivity maps from ITU-R P.453.

nearest_2d_interpolate

Interpolates a regular P.1144 grid with nearest-neighbour interpolation.

radio_refractive_index

Computes radio refractive index from ITU-R P.453.

rain_attenuation_db

Computes rain attenuation from ITU-R P.618.

rain_attenuation_probability_percent

Computes rain-attenuation occurrence probability from ITU-R P.618.

rain_cross_polarization_discrimination_db

Computes rain cross-polarization discrimination from ITU-R P.618.

rain_height_km

Looks up rain height from ITU-R P.839.

rain_specific_attenuation_coefficients

Computes ITU-R P.838 rain specific attenuation coefficients.

rain_specific_attenuation_db_per_km

Computes ITU-R P.838 rain specific attenuation in dB/km.

rainfall_probability_percent

Computes annual rain probability from ITU-R P.837.

rainfall_rate_mmh

Computes rainfall rate exceeded for a requested time percentage from ITU-R P.837.

rainfall_rate_r001_mmh

Looks up rainfall rate exceeded for 0.01% of an average year from ITU-R P.837.

risk_of_exceedance

Computes exceedance risk from ITU-R P.678.

saturation_vapour_pressure_hpa

Computes saturation vapour pressure from ITU-R P.453.

scintillation_attenuation_db

Computes scintillation attenuation from ITU-R P.618.

scintillation_sigma_db

Computes the P.618 scintillation standard deviation in dB.

site_diversity_rain_outage_probability_percent

Computes P.618 site-diversity rain outage probability.

slant_inclined_path_equivalent_height_km

Computes P.676 equivalent heights for dry air and water vapour.

standard_pressure_hpa

Computes standard-atmosphere pressure from ITU-R P.835.

standard_temperature_k

Computes standard-atmosphere temperature from ITU-R P.835.

standard_water_vapour_density_gm3

Computes standard water-vapour density from ITU-R P.835.

surface_mean_temperature_k

Looks up annual mean surface temperature from ITU-R P.1510.

surface_month_mean_temperature_k

Looks up monthly mean surface temperature from ITU-R P.1510.

surface_water_vapour_density_gm3

Looks up surface water-vapour density from ITU-R P.836.

topographic_altitude_km

Looks up topographic altitude above mean sea level from ITU-R P.1511.

total_water_vapour_content_kgm2

Looks up total columnar water-vapour content from ITU-R P.836.

unavailability_from_rainfall_rate_percent

Inverts ITU-R P.837 rainfall-rate statistics.

water_vapour_pressure_hpa

Computes water-vapour pressure from ITU-R P.453.

wet_term_radio_refractivity

Computes wet-term radio refractivity from ITU-R P.453.

zenith_water_vapour_attenuation_db

Computes P.676 zenith water-vapour attenuation.

zero_isotherm_height_km

Looks up zero-degree isotherm height from ITU-R P.839.