<?xml version="1.0" encoding="UTF-8"?>
<!-- 
EGGX SIGMET 04 VALID 251600/252200 EGRR-
EGGX SHANWICK OCEANIC FIR VA ERUPTION MT H HEKLA PSN N6359 W01940 VA CLD OBS 1600Z 
SFC/FL550 N OF N6100 W01000 – N5900 W01300 – N6100 W01900 MOV S 60KT NC VA CLD 
FCST 2200Z SFC/FL550 N OF N6100 W01100 – N5800 W01400 – N6100 W01600=
-->
<!-- note: year and month of this SIGMET unknown; YYYY and MM used in place of actual values -->
<iwxxm:VolcanicAshSIGMET xmlns:iwxxm="http://icao.int/iwxxm/1.0RC1"
    xmlns:saf="http://icao.int/saf/1.0RC1"
    xmlns:metce="http://data.wmo.int/def/metce/1.0RC1" 
    xmlns:om="http://www.opengis.net/om/2.0"
    xmlns:sam="http://www.opengis.net/sampling/2.0"
    xmlns:sams="http://www.opengis.net/samplingSpatial/2.0"
    xmlns:gml="http://www.opengis.net/gml/3.2" 
    xmlns:gmd="http://www.isotc211.org/2005/gmd"
    xmlns:gco="http://www.isotc211.org/2005/gco" 
    xmlns:xlink="http://www.w3.org/1999/xlink"
    xmlns:xsd="http://www.w3.org/2001/XMLSchema"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
    xsi:schemaLocation="http://icao.int/iwxxm/1.0RC1 http://schemas.wmo.int/iwxxm/1.0RC1/iwxxm.xsd
    http://data.wmo.int/def/metce/1.0RC1 http://schemas.wmo.int/metce/1.0RC1/metce.xsd"
    gml:id="va-sigmet-EGXX-YYYYMM25T160000Z"
    status="NORMAL">
    <iwxxm:analysis>
        <om:OM_Observation gml:id="va-position-and-motion-EGXX-YYYYMM25T16Z">
            <om:type 
                xlink:href="http://data.wmo.int/def/observationType/iwxxm/1.0RC1/SIGMETEvolvingConditionAnalysis" 
                xlink:title="SIGMETEvolvingConditionAnalysis"/>
            <om:phenomenonTime>
                <gml:TimeInstant gml:id="time-instant-25T16Z">
                    <gml:timePosition>YYYY-MM-25T16:00:00Z</gml:timePosition>
                </gml:TimeInstant>
            </om:phenomenonTime>
            <om:resultTime xlink:href="#time-instant-25T16Z"/>
            <om:validTime>
                <gml:TimePeriod gml:id="time-period-25T16Z-25T22Z">
                    <gml:beginPosition>YYYY-MM-25T16:00:00Z</gml:beginPosition>
                    <gml:endPosition>YYYY-MM-25T22:00:00Z</gml:endPosition>
                </gml:TimePeriod>
            </om:validTime>
            <om:procedure>
                <metce:Process gml:id="va-sigmet-position-and-motion-analysis">
                    <!-- authoritative documentation reference and title TBC -->
                    <metce:documentationRef
                        xlink:href="http://wis.wmo.int/procedure=Sigmet"
                        xlink:title="WMO No. 49 Volume 2 Meteorological Service for International Air Navigation [C.3.1.]7 SIGMET AND AIRMET INFORMATION, AERODROME WARNINGS AND WIND SHEAR WARNINGS AND ALERTS"/>
                </metce:Process>
            </om:procedure>
            <om:observedProperty 
                xlink:href="http://data.wmo.int/def/observableProperty/sigmet/evolvingConditionAnalysis"
                xlink:title="Observed position and motion for significant weather phenomenon"/>
            <om:featureOfInterest>
                <sams:SF_SpatialSamplingFeature gml:id="sampling-surface-SHANWICK_OCA">
                    <sam:type 
                        xlink:href="http://www.opengis.net/def/samplingFeatureType/OGC-OM/2.0/SF_SamplingSurface" 
                        xlink:title="SF_SamplingSurface"/>
                    <!-- Shanwick Oceanic Flight Information Region -->
                    <sam:sampledFeature 
                        xlink:href="http://icao.int/def/fir/SHANWICK_OCA" 
                        xlink:title="Shanwick Oceanic"/>
                    <sams:shape>
                        <gml:Polygon gml:id="boundary_geometry-SHANWICK_OCA" 
                            axisLabels="Lat Lon" 
                            srsDimension="2"
                            srsName="http://www.opengis.net/def/crs/EPSG/0/4326">
                            <gml:exterior>
                                <gml:LinearRing>
                                    <!-- SHANWICK FIR boundary (positions defined based on reference to map so possibly incorrect) -->
                                    <gml:posList>60.0 -30.0 60.0 -10.0 54.0 -10.0 53.0 -15.0 51.0 -15.0 51.0 -8.0 45.0 -8.0 45.0 -30.0</gml:posList>
                                </gml:LinearRing>
                            </gml:exterior>
                        </gml:Polygon>
                    </sams:shape>
                </sams:SF_SpatialSamplingFeature>
            </om:featureOfInterest>
            <om:result>
                <iwxxm:EvolvingMeteorologicalCondition gml:id="va-obs-EGXX-YYYYMM25T16Z" intensityChange="NO_CHANGE">
                    <!-- note: UCUM provides on 'plane angle' [deg]. Annex 3 requires use of 'degrees true'. WMO will provide an authoritative reference -->
                    <iwxxm:directionOfMotion uom="http://data.wmo.int/def/uom/degrees-true">180</iwxxm:directionOfMotion>
                    <iwxxm:geometry>
                        <!-- note: the geometry of the volcanic ash cloud is described as a 2.5-dimensional object; horizontal projection
                            plus (optional) lowerLimit and upperLimit describing the vertical extent. A missing lowerLimit indicates that
                            the phenomenon extends to the surface, whilst a missing upperLimit indicates that it extends above the range
                            of aeronautical operations -->
                        <saf:AirspaceSolid gml:id="va-geometry-EGXX-YYYYMM25T16Z">
                            <saf:horizontalProjection>
                                <gml:Polygon gml:id="volcanic-ash-cloud-polygon-EGXX-YYYYMM25T16Z" 
                                    axisLabels="Lat Lon" 
                                    srsDimension="2"
                                    srsName="http://www.opengis.net/def/crs/EPSG/0/4326">
                                    <gml:exterior>
                                        <gml:LinearRing>
                                            <!-- bounding polygon clipped to edge of FIR @ 60N -->
                                            <gml:posList>60.0 -11.5 59.0 -13.0 60.0 -16.0</gml:posList>
                                        </gml:LinearRing>
                                    </gml:exterior>
                                </gml:Polygon>
                            </saf:horizontalProjection>
                            <!-- note: lowerLimit is excluded as this feature extends down to the surface -->
                            <!-- note: unit of measure is "foot" (ft). The Unified Code for Units of Measure (UCUM @ http://unitsofmeasure.org)
                                specifies the symbol for "foot" as "[ft_i]". However, square-brackets "[" and "]" are not permitted as normal
                                characters within a URI and are thus encoded as "%5B" and "%5D" respectively.
                            -->
                            <saf:upperLimit uom="http://opengis.net/def/uom/UCUM/0/%5Bft_i%5D">55000</saf:upperLimit>
                        </saf:AirspaceSolid>
                    </iwxxm:geometry>
                    <iwxxm:speedOfMotion uom="http://opengis.net/def/uom/UCUM/0/knot">60</iwxxm:speedOfMotion>
                </iwxxm:EvolvingMeteorologicalCondition>
            </om:result>
        </om:OM_Observation>
    </iwxxm:analysis>
    <!-- EGGX Area Control Centre -->
    <iwxxm:issuingAirTrafficServicesUnit 
        xlink:href="http://icao.int/id/acc/EGGX" 
        xlink:title="Shanwick Oceanic"/>
    <!-- EGRR Meteorological Watch Office -->
    <iwxxm:originatingMeteorologicalWatchOffice 
        xlink:href="http://icao.int/id/mwo/EGRR" 
        xlink:title="UK Meteorological Office - Exeter"/>
    <!-- note: the <CodeList> class "AeronauticalSignificantWeatherPhenomenon" specifies tagged value "vocabulary" as 
        "http://data.wmo.int/def/49-2/SigWxPhenomena". This code-list contains the sub-set of terms from BUFR Code-table 
        0 08 011 "Meteorological feature" (http://data.wmo.int/def/bufr4/0-08-011) that describe meteorological phenomena
        that are considered _significant_ to aeronautical operations as defined in ICAO Annex 3.
    
    <iwxxm:phenomenon xlink:href="http://data.wmo.int/def/bufr4/codeflag/0-08-011/17" xlink:title="Volcano"/>
    -->
    <!-- note: the <CodeList> class "AeronauticalSignificantWeatherPhenomenon" specifies tagged value "vocabulary" as 
        "http://data.wmo.int/def/49-2/SigWxPhenomena". This code-list contains the set of terms listed in 
        WMO No. 49 C.3.1. sub-clause 1.1.4.
    -->
    <iwxxm:phenomenon xlink:href="http://data.wmo.int/def/49-2/SigWxPhenomena/VA" xlink:title="Volcanic Ash"/>
    <iwxxm:sequenceNumber>4</iwxxm:sequenceNumber>
    <iwxxm:validPeriod xlink:href="#time-period-25T16Z-25T22Z"/>
    <iwxxm:eruptingVolcano>
        <metce:Volcano gml:id="volcano-MT-HEKLA">
            <metce:name>MT HEKLA</metce:name>
            <metce:position>
                <gml:Point gml:id="point-MT-HEKLA" 
                    axisLabels="Lat Lon" 
                    srsDimension="2"
                    srsName="http://www.opengis.net/def/crs/EPSG/0/4326">
                    <gml:pos>63.59 -19.40</gml:pos>
                </gml:Point>
            </metce:position>
        </metce:Volcano>
    </iwxxm:eruptingVolcano>
    <iwxxm:forecastPositionAnalysis>
        <om:OM_Observation gml:id="va-position-EGXX-YYYYMM25T22Z">
             <om:type 
                 xlink:href="http://data.wmo.int/def/observationType/iwxxm/1.0RC1/SIGMETPositionAnalysis" 
                 xlink:title="SIGMETPositionAnalysis"/>
            <om:phenomenonTime>
                <gml:TimeInstant gml:id="time-instant-25T22Z">
                    <gml:timePosition>YYYY-MM-25T22:00:00Z</gml:timePosition>
                </gml:TimeInstant>
            </om:phenomenonTime>
            <om:resultTime xlink:href="#time-instant-25T16Z"/>
            <om:validTime xlink:href="#time-period-25T16Z-25T22Z"/>
            <om:procedure>
                <metce:Process gml:id="va-sigmet-position-forecast">
                    <!-- authoritative documentation reference and title TBC -->
                    <metce:documentationRef
                        xlink:href="http://wis.wmo.int/procedure=Sigmet"
                        xlink:title="WMO No. 49 Volume 2 Meteorological Service for International Air Navigation Appendix 6 TECHNICAL SPECIFICATIONS RELATED TO SIGMET AND AIRMET INFORMATION, AERODROME WARNINGS AND WIND SHEAR WARNINGS AND ALERTS"/>
                </metce:Process>
            </om:procedure>
            <om:observedProperty 
                xlink:href="http://data.wmo.int/def/observableProperty/sigmet/positionAnalysis"
                xlink:title="Observed position and motion for significant weather phenomenon"/>
            <om:featureOfInterest xlink:href="#sampling-surface-SHANWICK_OCA"/>
            <om:result>
                <iwxxm:MeteorologicalPositionCollection gml:id="collection-EGXX-YYYYMM25T16Z">
                    <iwxxm:member>
                        <iwxxm:MeteorologicalPosition gml:id="va-fcst-EGXX-YYYYMM25T16Z">
                            <iwxxm:geometry>
                                <saf:AirspaceSolid gml:id="va-geometry-EGXX-YYYYMM25T22Z">
                                    <saf:horizontalProjection>
                                        <gml:Polygon gml:id="volcanic-ash-cloud-polygon-EGXX-YYYYMM25T22Z" 
                                            axisLabels="Lat Lon" 
                                            srsDimension="2"
                                            srsName="http://www.opengis.net/def/crs/EPSG/0/4326">
                                            <gml:exterior>
                                                <gml:LinearRing>
                                                    <!-- bounding polygon clipped to edge of FIR @ 60N -->
                                                    <gml:posList>60.0 -12.0 58.0 -14.0 60.0 -15.35</gml:posList>
                                                </gml:LinearRing>
                                            </gml:exterior>
                                        </gml:Polygon>
                                    </saf:horizontalProjection>
                                    <!-- note: this is an alternative method of specifying the unit of measure "foot"; in this case
                                        the unit of measure is _assumed_ to be specified in the Unified Code for Units of Measure (UCUM) -->
                                    <saf:upperLimit uom="[ft_i]">55000</saf:upperLimit>
                                </saf:AirspaceSolid>
                            </iwxxm:geometry>
                        </iwxxm:MeteorologicalPosition>
                    </iwxxm:member>
                </iwxxm:MeteorologicalPositionCollection>
            </om:result>
        </om:OM_Observation>
    </iwxxm:forecastPositionAnalysis>
</iwxxm:VolcanicAshSIGMET>
