Geodesy and Unit Conversion

Two small packages of plain functions, standard library only and on every platform. Latitudes and longitudes are decimal degrees, headings degrees true unless named magnetic.

pkg/calc

Function	Gives
`HaversineMeters`, `HaversineNM`, `HaversineKM(lat1, lon1, lat2, lon2)`	Great-circle distance (mean Earth radius 6,371,000 m)
`BearingDegrees(lat1, lon1, lat2, lon2)`	Initial great-circle bearing, [0, 360)
`BearingFromOffsets(xEast, zNorth)`	Bearing to a point in a local frame (X east, Z north, as SimConnect’s airport frame); 0 at the origin
`CrossTrackMeters(latA, lonA, latB, lonB, latD, lonD)`	Distance of D from the great circle A → B: positive right of track, negative left
`AlongTrackMeters(latA, lonA, latB, lonB, latD, lonD)`	Distance from A to the point of A → B nearest D: negative behind A
`DisplaceByHeading(lat, lon, hdgDeg, distanceMeters)`	The point `distanceMeters` along `hdgDeg` (negative: backwards); sub-metre to about 50 km
`IntermediatePoint(lat1, lon1, lat2, lon2, f)`	The point a fraction `f` (0–1) along the great circle
`Dubins(lat1, lon1, heading1, lat2, lon2, heading2, r, step, first)`	Shortest path with turn radius `r` m between two positions and headings, as `[lat, lon]` points every `step` m; `first` +1 right, -1 left, 0 either; `nil` when none
`TrueToMagnetic(trueHeading, magVar)`, `MagneticToTrue(magneticHeading, magVar)`	Heading conversion, [0, 360); `magVar` positive east
`WindCorrectionAngle(windDir, windSpeed, tas, course)`	WCA in degrees: fly course + WCA; 0 when `tas` is about 0
`HeadwindCrosswind(windDir, windSpeed, runwayHeading)`	Headwind (negative: tailwind) and crosswind (positive: from the right); also `HeadwindComponent`, `CrosswindComponent`

d := calc.HaversineNM(50.1008, 14.26, 48.1103, 16.5697) // LKPR → LOWW
brg := calc.BearingDegrees(50.1008, 14.26, 48.1103, 16.5697)
head, cross := calc.HeadwindCrosswind(240, 15, 243)    // wind 240/15, runway 24

pkg/convert

Group	Functions
Altitude, vertical speed	`FeetToMeters`, `MetersToFeet`, `FeetPerMinuteToFeetPerSecond`, `FeetPerSecondToFeetPerMinute`
Distance	`NMToMeters`, `MetersToNM`, `NMToKilometers`, `KilometersToNM`, `KilometersToMeters`, `MetersToKilometers`, `NMToStatuteMiles`, `StatuteMilesToNM`, `KilometersToStatuteMiles`, `StatuteMilesToKilometers`, `StatuteMilesToMeters`, `MetersToStatuteMiles`
Speed	`KnotsToKilometersPerHour`, `KilometersPerHourToKnots`, `KnotsToMetersPerSecond`, `MetersPerSecondToKnots`, `KnotsToFeetPerSecond`, `FeetPerSecondToKnots`, `FeetPerMinuteToMetersPerSecond`, `MetersPerSecondToFeetPerMinute`; Mach at sea-level ISA (661.4788 kt): `KnotsToMach`, `MachToKnots`, `KilometersPerHourToMach`, `MachToKilometersPerHour`
Pressure	`InHgToMillibar`, `MillibarToInHg`, `InHgToHectopascal`, `HectopascalToInHg`, `InHgToPascal`, `PascalToInHg`
Temperature	`CelsiusToFahrenheit`, `FahrenheitToCelsius`, `CelsiusToKelvin`, `KelvinToCelsius`, `FahrenheitToKelvin`, `KelvinToFahrenheit`
Weight, volume	`PoundsToKilograms`, `KilogramsToPounds`, `USGallonsToLiters`, `LitersToUSGallons`
Angles	`DegreesToRadians`, `RadiansToDegrees`, `NormalizeHeading` ([0, 360)), `NormalizeAngle` ((-180, 180]), `AngleDifference(from, to)` (signed, positive clockwise)
Local offsets	`OffsetToLatLon(latRef, lonRef, xEast, zNorth)` and `LatLonToOffset(latRef, lonRef, lat, lon)`: metres east/north of a reference point (WGS84), round-trip
ICAO codes	`IsICAOCode(code)` (a known prefix, not a registry check), `ICAORegion(code)` (by the first letter), `ICAOCountry(code)` (by the first two letters)

x, z := convert.LatLonToOffset(refLat, refLon, lat, lon) // metres east, north of the reference
lat2, lon2 := convert.OffsetToLatLon(refLat, refLon, x+50, z)
qnh := convert.InHgToHectopascal(29.92)
country := convert.ICAOCountry("LKPR")