Up to Kotlin 2.1.20 use

Since Kotlin 2.2.0 use

METARs typically come from airports or permanent weather observation stations. Reports are generated once an hour or half-hour at most stations, but if conditions change significantly at a staffed location, a report known as a special (SPECI) may be issued. There are stations that make regular reports more often.(Such as KPLU which reports 3 per hour.) Some METARs are encoded by automated airport weather stations located at airports, military bases, and other sites. Some locations still use augmented observations, which are recorded by digital sensors, encoded via software, and then reviewed by certified weather observers or forecasters prior to being transmitted. Observations may also be taken by trained observers or forecasters who manually observe and encode their observations prior to transmission.

A typical METAR contains data for the temperature, dew point, wind direction and speed, precipitation, cloud cover and heights, visibility, and barometric pressure. A METAR may also contain information on precipitation amounts, lightning, and other information that would be of interest to pilots or meteorologists such as a pilot report or PIREP, colour states and runway visual range (RVR). Read more.

This is an example for Ulyanovsk Central Airport METAR:

UWLL 251200Z 16008MPS 8000 -SN BLSN OVC013 M09/M13 Q1008 R20/820242 NOSIG RMK QFE746/0994

<dependency>
  <groupId>io.github.alexmaryin.metarkt</groupId>
  <artifactId>parser</artifactId>
  <version>1.0.1</version>
</dependency>

implementation 'io.github.alexmaryin.metarkt:parser:1.0.1'

implementation("io.github.alexmaryin.metarkt:parser:1.0.1")

<dependency>
  <groupId>io.github.alexmaryin.metarkt</groupId>
  <artifactId>metarkt</artifactId>
  <version>1.1.2</version>
</dependency>

implementation 'io.github.alexmaryin.metarkt:metarkt:1.1.2'

implementation("io.github.alexmaryin.parser:metarkt:1.1.2")

The main interface implemented in library is MetarParser. It's including companion object with constructor of standard implementation: MetarParser.current().

Returning data type of Metar is composed of following values:

    val station: String?,
    val reportTime: LocalDateTime?,
    val wind: Wind?,
    val visibility: Visibility?,
    val phenomenons: Phenomenons?,
    val clouds: List<CloudLayer>,
    val temperature: Temperature?,
    val pressureQNH: PressureQNH?,
    val pressureQFE: PressureQFE?,
    val ceilingAndVisibilityOK: Boolean,
    val raw: String

Primitive properties:

• station is parsed ICAO code of Airport or Weather observation station, i.e. UWLL
• reportTime report time in LocalDataTime format from kotlinx-datatime library.
• ceilingAndVisibilityOK return true for CAVOK status
• raw original METAR string

• direction value in degrees from which wind is blowing
• variable is true if the direction is undefined
• speed average speed of the wind in original units
• speedUnits units of the speed from enum WindUnit (KT, MPS, KPH)
• gusts max speed of the gusts
• isCalm return true if the wind is calm
• speedKt, gustsKt - speed in Knots
• speedMps, gustsMps - speed in Meters per second

• distAll either visibility in defined units for the airfield or null if the visibility defined by individual direction or runway
• distUnits units of visibility distance from enum VisibilityUnit (METERS, SM)
• byDirections list of VisibilityByDir objects which contains:
  • dist visibility in defined units
  • direction direction of this visibility distance from enum VisibilityDirection (NORTH, NORTH_EAST, EAST, SOUTH_EAST, SOUTH, SOUTH_WEST, WEST, NORTH_WEST)
• byRunways list of VisibilityByRunway objects which contains:
  • dist visibility in defined units
  • runway name of the runway

• phenomemons is the list of WeatherPhenomenon objects which contains:
  • group set of Phenomenons enum items (DRIZZLE, RAIN, SNOW, SNOW_GRAINS, ICE_PELLETS, SMALL_HAIL, HAIL, SHOWER, FREEZE, THUNDERSTORM, DUST_STORM, SANDSTORM, FOG, IN_VICINITY, SHALLOW, PARTIAL, PATCHES, MIST, HAZE, SMOKE, DUST, BLOWING, SQUALL, ICE_CRYSTALS, VOLCANIC_ASH, DRIFTING, SAND)
  • intensity flag of the intensity from enum PhenomenonIntensity (NONE, HIGH, LIGHT) for this group

• clouds is the list of CloudLayer objects which contains:
  • type of the cloud layer from enum CloudsType (CLEAR, NIL_SIGNIFICANT, FEW, SCATTERED, BROKEN, OVERCAST)
  • lowMarginFt low margin of the cloud layer in Feet
  • cumulusType null if the clouds are not generating precipitation or one of the enum CumulusType type (CUMULONIMBUS, TOWERING_CUMULUS)

• air temperature of the air in Celsius
• dewPoint temperature of the dew point

• hPa sea level pressure in Hectopascals
• inHg sea level pressure in the Inch of mercury

Helper constructors:

PressureQNH.fromHpa(hPa: Int) - automatically adds converted inHg

PressureQNH.fromInHg(inHg: Float) - automatically adds converted hPa

PressureQNH.standard() - returns QNH (1013 hPa = 29.92 inHg)

• mmHg ground level pressure in millimeters of mercury
• 'hPa ground level pressure in Hectopascals

Helper constructors:

PressureQFE(mmHg: Int) - automatically adds converted hPa

PressureQDE.standard() - returns QNE (760 mmHg = 1013 hPa)

    val wind = Wind(direction = 225, speed = 10, speedUnits = WindUnit.KT)
    val runway = 180    // true course not magnetic!
    val component = wind.componentForRunwayTrue(runway)

Extension componentForRunwayTrue returns WindComponent object which contains:

data class WindComponent(
    val headwind: Double,   // positive = headwind, negative = tailwind
    val crosswind: Double,  // always positive magnitude
    val fromLeft: Boolean   // true if crosswind comes from the left
)

Convert QFE to QNH for ISA (Standard Atmosphere) as it using for METAR or ATIS reports:

    val qfe = PressureQFE(mmHg = 750)
    val elevation = 100 // meters
    val actualQnh = qfe.toIsaQnh(elevation) // return 1011

Convert QFE to QNH for actual atmosphere concerning temperature:

    val qfe = PressureQFE(mmHg = 750)
    val elevation = 100 // meters
    val temperature = 25 // celsius
    val actualQnh = qfe.toCorrectedQnh(elevation, temperature) // return 1011

Copyright 2021-2025 ALex Maryin

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