metar

package
v0.1.1 Latest Latest
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 Go to latest Published: Feb 6, 2020 License: MIT Imports: 8 Imported by: 0

Documentation

Overview

Package metar fetches METAR observations from the Aviation Weather Center's Text Data Server (TDS).

Note that the TDS stores only the past 3 days of data.

Index

Constants

View Source 
const (
	// MostRecentConstraint requests the most recent observation for each METAR
	// station in the fastest fashion. Not appropriate for historical data
	// retrieval.
	MostRecentConstraint = "constraint"

	// MostRecentPostFilter requests the most recent observation for each METAR
	// station by filtering results after applying all other constraints.
	//
	// This is the older, slower filtering method.
	MostRecentPostFilter = "postfilter"
)

Variables

This section is empty.

Functions

func Fields 

func Fields(ss ...string) func(*Request)

Fields specifies a subset of METAR fields to be collected.

func FlightPath 

func FlightPath(maxDist float64, waypoints ...string) func(*Request)

FlightPath obtains all METARs for the specified flight path, up to a maximum distance.

Waypoints may take the form of "lon,lat" or ICAO station IDs, and may be mixed interchangably. The ordering of waypoints is significant, always start with the origin and end with the destination.

Note: Flight path results are sorted by distance along the flight path from origin to destination. The flight path constraint does not support flight paths that cross the poles or flight paths that cross the international date line.

func HoursBeforeNow 

func HoursBeforeNow(h float64) func(*Request)

HoursBeforeNow requests METARs observed during the previous h hours.

func LonLatRect 

func LonLatRect(minLat, minLon, maxLat, maxLon float64) func(*Request)

LonLatRect specifies a rectangular bounding box of geographic coordinates in which to fetch METARs.

Does not support bounding boxes that encompass a pole.

func MinDegreeDistance 

func MinDegreeDistance(d float64) func(*Request)

MinDegreeDistance can be used to fetch fewer results by specifying a minimum degree distance (based on longitude and latitude) between stations.

A large MinDegreeDistance will yield less dense results. Duplicate stations are filtered and the most recent of duplicate stations is reported.

func MostRecent 

func MostRecent(mr bool) func(*Request)

MostRecent sets whether only the most recent METAR should be fetched. When requesting multiple stations, this means that only the METAR from one of them will be returned.

Use MostRecentForEachStation to apply a most-recent constraint to multiple stations.

func MostRecentForEachStation 

func MostRecentForEachStation(s string) func(*Request)

MostRecentForEachStation sets whether to fetch only the most recent METAR for each requested station. The provided string should be either MostRecentConstraint or MostRecentPostFilter.

func RadialDistance 

func RadialDistance(r, lat, lon float64) func(*Request)

RadialDistance specifies a radius around a point in which to fetch METARs.

Described area may not cross the international date line or either pole.

func StationString 

func StationString(s string) func(*Request)

StationString sets which station(s) METARs are fetched from. A Station String can contain one or more complete or partial ICAO IDs separated by whitespace and/or commas, US states or Canadian provinces prefixed with '@', or two-letter country abbrevations prefixed with '~'.

Examples:

  • "KDEN KSEA, PHNL" obtains all available METARs for KDEN, KSEA, and PHNL
  • "KSEA KDE" obtains all available METARs for KSEA and all ICAO IDs beginning with KDE (i.e. KDEN, KDEH, KDEW, etc)
  • "KSEA KDE*" is equivalent to "KSEA KDE"
  • "@WA" obtains METARs for all ICAO IDs from Washington state
  • "@BC" obtains METARs for all ICAO IDs from British Columbia, Canada
  • "~au" obtains METARs for all ICAO IDs from Australia

func TimeRange 

func TimeRange(from, to time.Time) func(*Request)

TimeRange requests METARs observed between the from and to times.

Types

type Client 

type Client struct {
	// contains filtered or unexported fields
}

A Client can fetch METARs from the TDS.

func (*Client) GetMETARs 

func (c *Client) GetMETARs(ctx context.Context, req *Request) (*Response, error)

GetMETARs fetches METARs from the TDS based on the constraints specified by the Request and returns the Response and an error.

Note that an error is only returned if there is a failure at the HTTP layer or the response could not be interpreted. The response may additionally contain error messages if the request was unable to be processed.

type METAR 

type METAR struct {
	// The raw METAR
	RawText string `xml:"raw_text"`

	// Station identifier, always a four character alphanumeric
	StationID string `xml:"station_id"`

	// Time this METAR was observed (ISO 8601 date/time format)
	ObservationTime string `xml:"observation_time"`

	// The latitude of the station that reported this METAR (decimal degrees)
	Latitude float32 `xml:"latitude"`

	// The longitude of the station that reported this METAR (decimal degrees)
	Longitude float32 `xml:"longitude"`

	// Air temperature (C)
	TempC float32 `xml:"temp_c"`

	// Dewpoint temperature (C)
	DewpointC float32 `xml:"dewpoint_c"`

	// Direction from which the wind is blowing (degrees)
	WindDirDegrees int `xml:"wind_dir_degress"`

	// Wind speed, 0 degree direction and 0 speed = calm winds (kts)
	WindSpeedKt int `xml:"wind_speed_kt"`

	// Wind gust (kts)
	WindGustKt int `xml:"wind_gust_kt"`

	// Horizontal visibility (statute miles)
	VisibilityStatuteMi float32 `xml:"visibility_statute_mi"`

	// Altimeter (inches of Hg)
	AltimInHg float32 `xml:"altim_in_hg"`

	// Sea-level pressure (mb)
	SeaLevelPressureMb float32 `xml:"sea_level_pressure_mb"`

	// Quality control flags
	QualityControlFlags QCFlags `xml:"quality_control_flags"`

	// Present weather string
	WxString string `xml:"wx_string"`

	// Up to four levels of sky cover and base can be reported
	SkyConditions []SkyCondition `xml:"sky_condition"`

	// Flight category of this METAR: VFR, MVFR, IFR, or LIFR
	FlightCategory string `xml:"flight_category"`

	// Pressure change in the past 3 hours
	ThreeHrPressureTendencyMb float32 `xml:"three_hr_pressure_tendency_mb"`

	// Maximum air temperature from the past 6 hours
	MaxTC float32 `xml:"maxT_c"`

	// Minimum air temperature from the past 6 hours
	MinTC float32 `xml:"minT_c"`

	// Maximum air temperature from the past 24 hours
	MaxT24HrC float32 `xml:"maxT24hr_c"`

	// Minimum air temperature from the past 24 hours
	MinT24HrC float32 `xml:"minT24hr_c"`

	// Liquid precipitation since the last regular METAR
	PrecipIn float32 `xml:"precip_in"`

	// Liquid precipitation from the past 3 hours. 0.0005 in = trace precipitation.
	Pcp3HrIn float32 `xml:"pcp3hr_in"`

	// Liquid precipitation from the past 6 hours. 0.0005 in = trace precipitation.
	Pcp6HrIn float32 `xml:"pcp6hr_in"`

	// Liquid precipitation from the past 24 hours. 0.0005 in = trace precipitation.
	Pcp24HrIn float32 `xml:"pcp24hr_in"`

	// Snow depth on the ground (in)
	SnowIn float32 `xml:"snow_in"`

	// Vertical visibility (ft)
	VertVisFt int `xml:"vert_vis_ft"`

	// METAR or SPECI
	METARType string `xml:"metar_type"`

	// The elevation of the station that reported this METAR
	ElevationM float32 `xml:"elevation_m"`
}

A METAR holds the raw observation data from a station included in a Response.

type QCFlags 

type QCFlags struct {
	// Corrected
	Corrected string `xml:"corrected"`

	// Fully automated
	Auto string `xml:"auto"`

	// Indicates that the automated station type is one of the following: A01,
	// A01A, A02, A02A, AOA, AWOS.
	//
	// Note: The type of station is not returned. This simply indicates that
	// this station is one of the six stations enumerated above.
	AutoStation string `xml:"auto_station"`

	// Maintenance check indicator - maintenance is needed
	MaintenanceIndicatorOn string `xml:"maintenance_indicator_on"`

	// No signal
	NoSignal string `xml:"no_signal"`

	// The lightning detection sensor is not operating - thunderstorm
	// information is not available.
	LightningSensorOff string `xml:"lightning_sensor_off"`

	// The freezing rain sensor is not operating
	FreezingRainSensorOff string `xml:"freezing_rain_sensor_off"`

	// The present weather sensor is not operating
	PresentWeatherSensorOff string `xml:"present_weather_sensor_off"`
}

A QCFlags holds quality control flags indicating the status of the station and information about the METAR.

type Request 

type Request struct {
	// contains filtered or unexported fields
}

A Request holds options for a METAR request such as a station, area, or flight path to get METARs for, the time range for which to request observations, etc.

func NewRequest 

func NewRequest(args ...func(*Request)) *Request

NewRequest builds a Request with the provided arguments. Supported Arguments include StationString, TimeRange, HoursBeforeNow, MostRecent, MostRecentForEachStation, LatLongRect, RadialDistance, FlightPath, MinDegreeDistance, and Fields.

type Response 

type Response struct {
	RequestIndex int `xml:"request_index"`
	DataSource   struct {
		Name string `xml:"name,attr"`
	} `xml:"data_source"`
	Request struct {
		Type string `xml:"type,attr"`
	} `xml:"request"`
	Errors      []string `xml:"errors>error"`
	Warnings    []string `xml:"warnings>warning"`
	TimeTakenMs int      `xml:"time_taken_ms"`
	Data        struct {
		NumResults int     `xml:"num_results,attr"`
		METARs     []METAR `xml:"METAR"`
	} `xml:"data"`
}

Response is the top-level XML document returned from the TDS. It contains some metadata about the request handling, as well as zero or more METARs (individual station observations).

type SkyCondition 

type SkyCondition struct {
	// SKC, CLR, CAVOK, FEW, SCT, BKN, OVC, OVX
	SkyCover string `xml:"sky_cover,attr"`

	// Height of cloud base in feet AGL. A value exists when SkyCover is FEW,
	// SCT, BKN, or OVC.
	CloudBaseFtAGL int `xml:"cloud_base_ft_agl,attr"`
}

A SkyCondition describes the condition of the sky at a particular altitude.

Source Files

  • metar.go

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