Units, angles, one wind sign

The station and briefing packages compute with the same units, angles, and wind sign convention. They are defined in units.ts, angles.ts, and wind.ts.

One wind sign convention

Wind values carry two complementary representations, and the sign convention between them is fixed across the platform.

Direction is meteorological. It is the compass bearing the wind blows from, in degrees clockwise from north. Components are the velocity of the air itself. uMps is the zonal component, positive eastward, and vMps is the meridional component, positive northward. Both are in m/s.

The two representations point opposite ways. The conversion owns that minus sign, so no other package ever writes it.

• windToComponents(speedMps, directionDeg) computes uMps = -speed · sin(θ) and vMps = -speed · cos(θ), where θ is the from-direction in radians.
• componentsToWind(uMps, vMps) recovers speed and from-direction. Calm air (both components exactly zero) reports direction 0.

So a 10 m/s wind from the west (direction 270°) has uMps = 10: the air moves eastward.

import { componentsToWind, windToComponents } from "@azohra/meteo.core";

// A 10 m/s wind from the west (direction 270°) moves air eastward:
const { uMps, vMps } = windToComponents(10, 270);
// uMps === 10; vMps ≈ 0 (floating point, ~2e-15)

// And back: purely eastward-moving air is a wind from the west.
const wind = componentsToWind(10, 0);
// wind.speedMps === 10; wind.directionDeg === 270

The WindComponents interface names the component pair (uMps, vMps) wherever it travels between packages.

Mean direction

meanDirectionDeg(directionsDeg) is the unit-vector circular mean of from-directions (every direction weighted equally, regardless of speed). It returns null on empty input. Averaging compass degrees arithmetically is wrong across north, where 350° and 10° average to 180°. The circular mean reports 0°.

Units

Speeds are computed in m/s, and km/h is a display conversion.

• KMH_PER_MPS: the constant 3.6.
• kmhToMps(value): divides by KMH_PER_MPS.
• msToKmh(value): multiplies by KMH_PER_MPS.
• plausibleWindMps(value, subject): returns the wind speed unchanged, or throws when it is outside the plausible 0–140 m/s range. The subject names the source in the error message, so a decoder or adapter that produces an impossible speed fails loudly with its name attached.

Angles

• DEGREES_TO_RADIANS: the constant Math.PI / 180.
• degreesToRadians(degrees) / radiansToDegrees(radians): the two conversions.
• normalizeDegrees(degrees): wraps any degree value, including negative values, into [0, 360).

Direction arcs

An arc of acceptable from-directions, such as a station’s favorable sectors or a launch’s wind window, has one shape across the platform. It is defined in arcs.ts.

• DirectionArc: { fromDeg, toDeg }, meteorological FROM bearings in degrees clockwise from north. fromDeg > toDeg wraps through north, and both boundaries are inclusive. fromDeg === toDeg reads as a single bearing rather than a full circle.
• inDirectionArcs(directionDeg, arcs): whether a bearing falls inside any arc of the list; an empty list holds nothing.
• directionArcSpanDeg(arc): the arc’s clockwise span in [0, 360).

import { inDirectionArcs } from "@azohra/meteo.core";

// A NW-through-NE window wraps through north:
const window = [{ fromDeg: 315, toDeg: 45 }];
inDirectionArcs(0, window); // true — due north sits inside the wrap
inDirectionArcs(180, window); // false

Wherever arcs gate a drawing or a verdict, they are a judgment parameter. No package supplies a default list, and a consumer that passes none gets no marks drawn.