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IWXXM-2-tutorial-va-sigmet-EGXX-YYYY-MM-25T16Z





VA SIGMET FOR SHANWICK OCEANIC FLIGHT INFORMATION REGION,
16:00Z 25-MONTH-YEAR





This VA SIGMET is intended as
an example and does not represent actual conditions.


The year and month of the issue of this VA SIGMET
are unknown; these have been substituted with YYYY and MM respectively.


This tutorial is intended as a follow-on from the simple METAR tutorial.
Please work through the METAR example first as this VA SIGMET tutorial assumes
that many of the key points will already be understood.


The full XML for this example can be found here.



TAC-encoding



This example is based on the
following VA SIGMET:



 


EGGX
SIGMET 4 VALID 251600/252200 EGRR –



EGGX
SHANWICK OCEANIC FIR VA ERUPTION MT HEKLA PSN N6359 W01940 VA CLD OBS AT 1600Z
SFC/FL550 N6000 W01150 - N5900 W01300 - N6000 W01600 - N6000 W01150 MOV S 60KT
NC FCST 2200Z SFC/FL550 N6000 W01200 - N5800 W01400 - N6000 W01535 - N6000
W01200=



XML Namespaces





The following namespaces are used either directly or indirectly in this
example:



Description

XML Namespace

Default namespace prefix

XML Schema

http://www.w3.org/2001/XMLSchema

xsd

XML Linking Language

http://www.w3.org/1999/xlink

xlink

OGC GML 3.2.1

http://www.opengis.net/gml/3.2

gml

ISO/TS 19139:2007 metadata XML schema implementation

http://www.isotc211.org/2005/gmd

gmd

OGC OMXML Observations and Measurements

http://www.opengis.net/om/2.0

om

OGC OMXML Sampling Features

http://www.opengis.net/sampling/2.0

sf

OGC OMXML Spatial Sampling Features

http://www.opengis.net/samplingSpatial/2.0

sams

WMO Observable Property Model(1.2)

http://def.wmo.int/opm/2013

opm

WMO METCE (1.2)

http://def.wmo.int/metce/2013

metce

ICAO Meteorological Information Exchange Model (2.1)

http://icao.int/iwxxm/2.1

iwxxm




Note that the XML Namespace is distinct from the schema locations. For
reference, these are provided here.



Overview: the VA
SIGMET report





The XML encoded VA SIGMET has a root element <iwxxm:VolcanicAshSIGMET> within which the XML Namespace
information is declared.


The VA SIGMET report is comprised of:



  • report metadata (e.g. status,
    issuing centre, originating
    meteorological watch office
    etc.);


  • one analysis
    providing one up to two observed or forecast position and motion of the
    volcanic ash cloud; and


  • one forecast
    providing one up to two predicted positions of the volcanic ash cloud.


  • if there are more than one
    observed and/or predicted positions of volcanic ash clouds, it is expected
    that the first predicted position corresponds to the first observed
    position and so forth.




The code fragment below illustrates the report structure:



 
 1 . <?xml version="1.0" encoding="UTF-8"?>
 2 .     <iwxxm:VolcanicAshSIGMET xmlns:iwxxm="http://icao.int/iwxxm/2.1"   
 3 .                              xmlns:aixm="http://www.aixm.aero/schema/5.1.1"   
 4 .                              xmlns:metce="http://def.wmo.int/metce/2013"    
 5 .                              xmlns:om="http://www.opengis.net/om/2.0"   
 6 .                              xmlns:sam="http://www.opengis.net/sampling/2.0"   
 7 .                              xmlns:sams="http://www.opengis.net/samplingSpatial/2.0"   
 8 .                              xmlns:gml="http://www.opengis.net/gml/3.2"    
 9 .                              xmlns:xlink="http://www.w3.org/1999/xlink"  
10 .                              xmlns:xsd="http://www.w3.org/2001/XMLSchema"  
11 .                              xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"   
12 .                              xsi:schemaLocation="http://icao.int/iwxxm/2.1 http://schemas.wmo.int/iwxxm/2.1/iwxxm.xsd  
13 .                                                  http://def.wmo.int/metce/2013 http://schemas.wmo.int/metce/1.2/metce.xsd"  
14 .                              gml:id="va-sigmet-EGXX-YYYYMM25T160000Z"  
15 .                              permissibleUsage="OPERATIONAL"
16 .                              status="NORMAL">  
17 .         <iwxxm:issuingAirTrafficServicesUnit>...</iwxxm:issuingAirTrafficServicesUnit>  
18 .         <iwxxm:originatingMeteorologicalWatchOffice>...</iwxxm:originatingMeteorologicalWatchOffice>  
19 .         <iwxxm:sequenceNumber>4</iwxxm:sequenceNumber
20 .         <iwxxm:validPeriod>...</iwxxm:validPeriod
21 .         <iwxxm:phenomenon xlink:href="http://codes.wmo.int/49-2/SigWxPhenomena/VA" xlink:title="Volcanic Ash"/>  
22 .         <iwxxm:analysis>...</iwxxm:analysis
23 .         <iwxxm:forecastPositionAnalysis>...</iwxxm:forecastPositionAnalysis>  
24 .         <iwxxm:eruptingVolcano>...</iwxxm:eruptingVolcano
25 .     </iwxxm:VolcanicAshSIGMET> 





The VA SIGMET report comprises:



  • (Line 14) a unique
    identifier for the report (e.g.
    "va-sigmet-EGXX-YYYYMM25T160000Z"); each VA SIGMET report should
    have a unique identifier of the form: va-sigmet-{issuing Air Traffic Service
    Unit}-{issue date-time}.


  • (Line 15) permissible
    usage; in this case operational


  • (Line 16) report status;
    in this case normal


  • (Line 17) information
    about the issuing Air Traffic Services Unit (elaborated below)


  • (Line 18) information
    about the originating Meteorological Watch Office (elaborated below)


  • (Line 19) report
    sequence number - following the standard ICAO Annex 3 (WMO No. 49 Vol 2)
    rules for report assigning sequence numbers


  • (Line 20) definition of
    the validity period for this report (elaborated below)


  • (Line 21) definition of
    the significant weather phenomenon that the report describes; in this case
    Volcanic Ash. Terms are referenced using xlink:href from the WMO Codes Register http://codes.wmo.int/49-2/SigWxPhenomena.
    xlink:title is provided
    to supplement human readability. 


  • (line
    22) the analysis provides one up to two observed or forecast positions and
    motions of the volcanic ash clouds. This is encoded as an instance of <om:OM_Observation>
    (elaborated below).


  • (Line 23) the forecast
    provides one up to two predicted positions of the volcanic ash clouds.
    This is encoded as an instance of <om:OM_Observation> (elaborated below).


  • (Line 24) provides
    information about the source of the volcanic ash; the name and position of
    the erupting volcano (elaborated below).


 



Issuing Air Traffic
Services Unit and Originating Meteorological Watch Office



  



...
    <iwxxm:issuingAirTrafficServicesUnit>
        <aixm:Unit gml:id="fic-EGGX">
            <aixm:timeSlice>
                <aixm:UnitTimeSlice gml:id="fic-EGGX-ts">
                    <gml:validTime/>
                    <aixm:interpretation>SNAPSHOT</aixm:interpretation>
                    <aixm:name>SHANWICK OCEANIC AREA CONTROL CENTRE</aixm:name>
                    <aixm:type>ATCC</aixm:type>
                    <aixm:designator>EGGX</aixm:designator>
                </aixm:UnitTimeSlice>
            </aixm:timeSlice>
        </aixm:Unit>
    </iwxxm:issuingAirTrafficServicesUnit>
    <iwxxm:originatingMeteorologicalWatchOffice>
        <aixm:Unit gml:id="wmo-EGRR">
            <aixm:timeSlice>
                <aixm:UnitTimeSlice gml:id="mwo-EGRR-ts">
                    <gml:validTime/>
                    <aixm:interpretation>SNAPSHOT</aixm:interpretation>
                    <aixm:name>UK METEOROLOGICAL OFFICE - EXETER</aixm:name>
                    <aixm:type>MWO</aixm:type>
                    <aixm:designator>EGRR</aixm:designator>
                </aixm:UnitTimeSlice>
            </aixm:timeSlice>
        </aixm:Unit>
    </iwxxm:originatingMeteorologicalWatchOffice>
...


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  • Information about both Issuing
    Air Traffic Services Unit
    (ATSU) and Originating
    Meteorological Watch Office
    (MWO) is included in the SIGMET
    report. Both of these entities conform to the Unit data
    model defined in the Aeronautical Information eXchange
    Model (AIXM). This is intended to align with the broader ICAO Aeronautical
    Information Reference Model (AIRM); albeit only a subset of the
    information required for meteorological products is required.


  • The gml:ids shown here are fictitious.  A core feature enabling consistency and
    alignment within the AIRM, is the use of UUIDs (RFC 4122) for identifying
    and referencing information about aeronautical features. The use of UUIDs
    is adopted from AIXM 5, conjointly developed by EuroControl
    and US FAA. A managed set of information describing an aeronautical
    feature is allocated a UUID by the data publisher. The UUID is an opaque
    identifier and may be automatically generated (e.g. using an online UUID-generator
    or other mechanism). Once assigned by a data publisher, the UUID may be
    used as a unique reference to the given set of information, thus enabling
    distributed systems to assert that they are, indeed, using consistent
    information.


  • Additional information
    provided about the ATSU and MWO includes:

    • name; this must be
      provided in BLOCK CAPITALS


    • type; one of the
      following options - ARO (Aerodrome Reporting Office/ATS Reporting
      Office), ATCC (Air Traffic Control Centre), ATSU (Air Traffic Services
      Unit), FIC (Flight Information Centre) or MWO (Meteorological Watch
      Office)


    • designator; the coded designator
      associated with the Unit - this may be the ICAO 4-letter Location
      Indicator as specified in ICAO Doc 7910.



 



Valid period



 



 
...
    <iwxxm:validPeriod>
        <gml:TimePeriod gml:id="tp-25T16Z-25T22Z">
            <gml:beginPosition>YYYY-MM-25T16:00:00Z</gml:beginPosition>
            <gml:endPosition>YYYY-MM-25T22:00:00Z</gml:endPosition>
        </gml:TimePeriod>
    </iwxxm:validPeriod>
...


 



  • <iwxxm:validPeriod>
    defines the period during which this SIGMET is valid;
    noting the use of YYYY and MM in place of year and month - normally these
    would be populated (e.g. 2013-05-08T15:58:00Z)


  • The <om:OM_Observation>
    instances for the analysis and forecast both include the
    element <om:validTime> which has identical
    semantics to <iwxxm:validPeriod>.


  • Even though information
    is logically repeated, <iwxxm:validPeriod>
    has been retained to make it easier to map the XML encoding onto the ICAO
    Annex 3 regulation.


 



SIGMET Analysis





The analysis provides one up to two observed or forecast positions and motions
of the volcanic ash clouds. This is encoded as an instance of <om:OM_Observation>.


The code fragment below illustrates the outline structure of the <om:OM_Observation> instance:



 
  1 . ...
  2 .     <iwxxm:analysis>
  3 .         <om:OM_Observation gml:id="va-position-and-motion-EGXX-YYYYMM25T16Z">
  4 .             <om:type xlink:href="http://codes.wmo.int/49-2/observation-type/IWXXM/2.1/SIGMETEvolvingConditionAnalysis"/>
  5 .             <om:phenomenonTime>
  6 .                 <gml:TimeInstant gml:id="ti-25T16Z">
  7 .                     <gml:timePosition>YYYY-MM-25T16:00:00Z</gml:timePosition>
  8 .                 </gml:TimeInstant>
  9 .             </om:phenomenonTime>
 10 .             <om:resultTime xlink:href="#ti-25T16Z"/>
 11 .             <om:validTime xlink:href="#tp-25T16Z-25T22Z"/>
 12 .             <om:procedure>...</om:procedure>
 13 .             <om:observedProperty
 14 .                 xlink:href="http://codes.wmo.int/49-2/SigWxPhenomena/VA"
 15 .                 xlink:title="Volcanic ash"/>
 16 .             <om:featureOfInterest>...</om:featureOfInterest>
 17 .             <om:result>...</om:result>
 18 .         </om:OM_Observation>
 19 .     </iwxxm:analysis>
 20 . ...





The analysis <om:OM_Observation>
follows the standard OM_Observation pattern:



  • (Line 3) the <om:OM_Observation>
    instance is allocated a unique identifier within the
    scope of the XML document (e.g. "va-position-and-motion-EGXX-YYYYMM25T16Z");
    there are no special rules applied here with regards to the structure of
    the identifier. The only requirements are that it is unique within the
    document.


  • (Line 4) as outlined in
    the METAR tutorial, the observation
    type
    is specified via reference to a definition published within
    the WMO Codes Registry. For SIGMET "analysis" this is SIGMETEvolvingConditionAnalysis


  • (Lines 5-9) the phenomenon
    time
    indicates the time-instant associated with the given position
    and motion of the volcanic ash cloud described in the result
    below. In this example, the observed position and motion of the ash cloud
    is provided, thus the phenomenonTime
    is commensurate with the beginning of the SIGMET report validity period.
    The phenomenon time is expressed in ISO 8601 format;
    "YYYY-MM-25T16:00:00Z" (noting that YYYY and MM would normally
    specify year and month respectively).


  • (Line 10) the result
    time
    indicates the time-instance at which the information about
    the position and motion of the volcanic ash cloud was made available. This
    always commensurate with the beginning of the SIGMET report validity
    period. In this case, this is the same time-instant that was used to
    describe the phenomenon time thus xlink:href is used to refer to the earlier
    definition.


  • (Line 11) the valid
    time
    indicates the time-period for which the information about
    the position and motion of the volcanic ash cloud is valid - in this case
    according to international regulation. This is identical to the valid
    period
    defined in the body of the SIGMET report, thus xlink:href is used to refer
    to the earlier definition.


  • (Line 12) the procedure
    by which the position and motion of the volcanic ash cloud was observed
    (elaborated below).


  • (Lines 13-15) the observed
    property
    identifies the physical phenomenon being observed.
    Following consideration, it seems appropriate to reference "volcanic
    ash" as the observed property, rather than an aggregate of
    "position and motion" about some undefined significant weather
    phenomena! The observed property is used a key when
    searching for content within a service conforming to the Open Geospatial
    Consortium's Sensor Observation Service (SOS) specification; it seems
    likely that consumers of the data product will search based on the type of
    significant weather phenomena rather than the characteristics of that
    phenomenon. Given that observed property must be a
    reference (e.g. specified using xlink:href),
    we reference a term from the WMO Codes Registry (e.g. http://codes.wmo.int/49-2/SigWxPhenomena/VA).
    xlink:title provides a
    supplemental human-readable description.


  • (Line 16) the feature
    of interest
    provides information about the real world feature
    that the observation pertains to - in this case a Flight Information
    Region (elaborated below).


  • (Line 17) the result
    provides the information about the observed characteristics of the
    volcanic ash cloud (elaborated below).


 





SIGMET Analysis:
Procedure



 



 
  1 . ...
  2 .             <om:procedure>
  3 .                 <metce:Process gml:id="p-49-2-va-sigmet">
  4 .                     <gml:description>WMO No. 49 Volume 2 Meteorological Service for International Air Navigation 
  5 .                                      C.3.1.7 SIGMET AND AIRMET INFORMATION, AERODROME WARNINGS AND WIND SHEAR 
  6 .                                      WARNINGS AND ALERTS
  7 .                     </gml:description>
  8 .                 </metce:Process>
  9 .             </om:procedure>
 10 . ...





As outlined in the METAR example, the procedure
is constrained such that is must be an instance of METCE Process. As described
therein, <gml:description>
is used to cite a well-known reference - in this case the appropriate clause
from the ICAO Annex 3 (WMO No. 49 Vol 2) technical regulations.



SIGMET Analysis:
Feature of interest



 



 
  1 . ...
  2 .             <om:featureOfInterest>
  3 .                 <sams:SF_SpatialSamplingFeature gml:id="ss-SHANWICK_OCA">
  4 .                     <sam:type xlink:href="http://www.opengis.net/def/samplingFeatureType/OGC-OM/2.0/SF_SamplingSurface"/>
  5 .                     <sam:sampledFeature>
  6 .                         <aixm:Airspace gml:id="fir-EGGX">
  7 .                             <aixm:timeSlice>
  8 .                                 <aixm:AirspaceTimeSlice gml:id="fir-EGGX-ts">
  9 .                                     <gml:validtime/>
 10 .                                     <aixm:interpretation>SNAPSHOT</aixm:interpretation>
 11 .                                     <aixm:type>FIR</aixm:type>
 12 .                                     <aixm:designator>EGXX</aixm:designator>
 13 .                                     <aixm:name>SHANWICK OCEANIC FIR</aixm:name>
 14 .                                 </aixm:AirspaceTimeSlice>
 15 .                             </aixm:timeSlice>
 16 .                         </aixm:Airspace>
 17 .                     </sam:sampledFeature>
 18 .                     <! FIR boundary - not typically reported >
 19 .                     <sams:shape nilReason="withheld"/>
 20 .                 </sams:SF_SpatialSamplingFeature>
 21 .             </om:featureOfInterest>
 22 . ...


 



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The feature of interest for the SIGMET analysis is intended to
describe the Flight Information Region associated with the SIGMET report. As
such, the feature of interest is constrained such that it must
be an instance of SF_SamplingSurface and thus follows
the standard pattern for all SF_SpatialSamplingFeatures:



  • (Line 3) the <sams:SF_SpatialSamplingFeature>
    instance is allocated a unique identifier within the scope of the XML
    document (e.g. "ss-SHANWICK_OCA");
    there are no special rules applied here with regards to the structure of
    the identifier. The only requirements are that it is unique within the
    document.


  • (Line 4) the type
    of the <sams:SF_SpatialSamplingFeature>
    instance; in this case a SF_SamplingSurface.


  • (Lines 5-17) the sampled
    feature
    describes the real world feature to which the observation
    pertains; in this case the Shanwick Oceanic
    Flight Information Region.

    • (Lines 6-16) in lieu of
      an authoritative web-accessible register of information about Flight
      Information Regions, the information about Shanwick
      Oceanic FIR must be embedded within the SIGMET report. The data model used
      to describe the FIR is Airspace from the Aeronautical
      Information eXchange Model (AIXM). This is
      intended to align with the broader ICAO Aeronautical Information
      Reference Model (AIRM); albeit only a subset of the information required
      for meteorological products is required. While the gml:id shown here is fictitious, a core feature
      enabling consistency and alignment within the AIRM, is the use of UUIDs (RFC 4122) as outlined
      above (ATSU and MWO) - see line 6. Additional information provided about
      the Airspace includes:

      • (Line 11) type;
        one of FIR (Flight Information Region), UIR (Upper flight Information
        Region) or CTA (Control Area)


      • (Line 12) designator;
        a coded designator associated with the Airspace - in this case the ICAO
        location indicator "EGXX"


      • (Line 13) name;
        the textual name allocated to the Airspace by the responsible authority
        - this must be provided in BLOCK CAPITALS




  • (Line 18) The
    FIR bounding is not typically reported.


 



SIGMET Analysis:
Result



  



 



  1 . ...
  2 .             <om:result>
  3 .                 <iwxxm:SIGMETEvolvingConditionCollection gml:id="emc-va-obs-EGXX-YYYYMM25T16Z" timeIndicator="OBSERVATION">
  4 .                     <iwxxm:member>
  5 .                         <iwxxm:SIGMETEvolvingCondition gml:id="sec1" intensityChange="NO_CHANGE">
  6 .                             <iwxxm:directionOfMotion uom="deg">180</iwxxm:directionOfMotion>
  7 .                             <iwxxm:geometry>
  8 .                                 <aixm:AirspaceVolume gml:id="av-va-obs-position-EGGX-YYYYMM25T16Z">
  9 .                                     <! omitted lower-limit implies that the volcanic ash cloud extends to ground/sea surface >
 10 .                                     <aixm:upperLimit uom="FL">550</aixm:upperLimit>
 11 .                                     <aixm:upperLimitReference>STD</aixm:upperLimitReference>
 12 .                                     <aixm:horizontalProjection>
 13 .                                         <aixm:Surface gml:id="polygon-va-obs-position-EGGX-YYYYMM25T16Z" 
 14 .                                                       uomLabels="deg deg" 
 15 .                                                       axisLabels="Lat Lon" 
 16 .                                                       srsDimension="2" 
 17 .                                                       srsName="http://www.opengis.net/def/crs/EPSG/0/4326">
 18 .                                             <gml:polygonPatches>
 19 .                                                 <gml:PolygonPatch>
 20 .                                                     <gml:exterior>
 21 .                                                         <gml:LinearRing>
 22 .                                                             <! bounding polygon clipped to edge of FIR @ 60N >
 23 .                                                             <gml:posList>
 24 .                                                                 60.0 -11.5
 25 .                                                                 59.0 -13.0
 26 .                                                                 60.0 -16.0
 27 .                                                                 60.0 -11.5
 28 .                                                             </gml:posList>
 29 .                                                         </gml:LinearRing>
 30 .                                                     </gml:exterior>
 31 .                                                 </gml:PolygonPatch>
 32 .                                             </gml:polygonPatches>
 33 .                                         </aixm:Surface>
 34 .                                     </aixm:horizontalProjection>
 35 .                                 </aixm:AirspaceVolume>
 36 .                             </iwxxm:geometry>
 37 .                             <iwxxm:speedOfMotion uom="[kn_i]">60</iwxxm:speedOfMotion>
 38 .                         </iwxxm:SIGMETEvolvingCondition>
 39 .                     </iwxxm:member>
 40 .                 </iwxxm:SIGMETEvolvingConditionCollection>
 41 .             </om:result>
 42 . ...


 



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The analysis result provides one up to two observed position
and motion characteristics of the volcanic ash clouds. In
order to align with timings for Volcanic Ash Advisory (VAA) products, the
SIGMET analysis may describe the characteristics of the volcanic ash clouds at
some point in the near future (e.g. up to 2-hours hence); e.g. a forecast of
the volcanic ash clouds characteristics.


The result is constrained such that it must be an instance of SIGMETEvolvingConditionCollection. This class has been
specifically designed to meet the requirements published in ICAO Annex 3 (WMO
No. 49 Vol 2) regulation and allows one to specify a collection of
meteorological features (e.g. the volcanic ash cloud or other significant
weather phenomena) described by one or more members each of which contain an
instance of SIGMETEvolvingCondition.


The code fragment above illustrates the encoding of <iwxxm:SIGMETEvolvingConditionCollection> and <iwxxm:SIGMETEvolvingCondition>:



  • (Line 3) an XML
    attribute timeIndicator in <iwxxm:SIGMETEvolvingConditionCollection> identifies
    whether this section refers to an "OBSERVATION" or
    "FORECAST"


  • (Line 4) the instance of
    <iwxxm:SIGMETEvolvingConditionCollection>
    contains <iwxxm:member> each of which has
    an instance of <iwxxm:SIGMETEvolvingCondition>


  • (Line 5) the instance of
    <iwxxm:SIGMETEvolvingCondition>
    is uniquely identified within the scope of the XML document. Additionally,
    we see the intensity change specified as an XML
    attribute. In this case the value is "NO_CHANGE". The permitted
    set of options also includes "WEAKEN" and "INTENSIFY"
    as per the ICAO Annex 3 (WMO No. 49 Vol 2) technical regulation.


  • (Line 6) specifies the direction of motion of the
    volcanic ash cloud specified in degrees from true-north; in this case the
    value is 180 degrees (e.g. due south).


  • (Lines 7-36) specifies a
    2.5-dimensional representation of the observed geometry
    of the volcanic ash cloud using an instance of <iwxxm:AirspaceVolume>. In this case, the horizontal
    projection
    is given (lines 12-34) along with the upper
    limit
    at FL550 (line 10); the omitted lower limit implies that
    the AirspaceVolume extends to the ground/sea
    surface. Note that the upper-limit height is specified as measured in the
    ICAO standard atmosphere "STD" thus allowing for assessment of
    altitude as a linear distance when reading converting from barometric
    pressure (line 11). The horizontal projection is provided as an instance
    of <aixm:Surface>
    uniquely identified as
    "polygon-va-obs-position-EGXX-YYYYMM25T16Z" (lines 13-33). Note
    that, as per the GML specification, the first and last points defining the
    polygon are coincident. Following advice from ICAO secretariat, the
    horizontal projection of the significant meteorological feature must
    always be defined as a closed polygon.


  • (Line 37) specifies the speed of motion of the volcanic
    ash cloud; in this case a velocity of 60 knots.


 



 



SIGMET Forecast:
Result



 



 
  1 . ...
  2 .             <om:result>
  3 .                 <iwxxm:SIGMETPositionCollection gml:id="mpc-EGGX-YYYYMM25T16Z">
  4 .                     <iwxxm:member>
  5 .                         <iwxxm:SIGMETPosition gml:id="mp-va-fcst-EGGX-YYYYMM25T16Z">
  6 .                             <iwxxm:geometry>
  7 .                                 <aixm:AirspaceVolume gml:id="av-va-fcst-position-EGGX-YYYYMM25T22Z">
  8 .                                     <aixm:horizontalProjection>
  9 .                                         <aixm:Surface gml:id="polygon-va-fcst-position-EGGX-YYYYMM25T22Z"
 10 .                                                       uomLabels="deg deg" 
 11 .                                                       axisLabels="Lat Lon" 
 12 .                                                       srsDimension="2" 
 13 .                                                       srsName="http://www.opengis.net/def/crs/EPSG/0/4326">
 14 .                                             <gml:polygonPatches>
 15 .                                                 <gml:PolygonPatch>
 16 .                                                     <gml:exterior>
 17 .                                                         <gml:LinearRing>
 18 .                                                             <! bounding polygon clipped to edge of FIR @ 60N >
 19 .                                                             <gml:posList>
 20 .                                                                 60.0 -12.0
 21 .                                                                 58.0 -14.0
 22 .                                                                 60.0 -15.35
 23 .                                                                 60.0 -12.0
 24 .                                                             </gml:posList>
 25 .                                                         </gml:LinearRing>
 26 .                                                     </gml:exterior>
 27 .                                                 </gml:PolygonPatch>
 28 .                                             </gml:polygonPatches>
 29 .                                         </aixm:Surface>
 30 .                                     </aixm:horizontalProjection>
 31 .                                 </aixm:AirspaceVolume>
 32 .                             </iwxxm:geometry>
 33 .                         </iwxxm:SIGMETPosition>
 34 .                     </iwxxm:member>
 35 .                 </iwxxm:SIGMETPositionCollection>
 36 .             </om:result>
 37 . ...





The forecast result provides one up to two predicted positions
of the volcanic ash clouds.


The result is constrained such that it must be an instance of SIGMETPositionCollection (from IWXXM). This class comprises
one or more members, each of which must be of type SIGMETPosition
(from IWXXM). Once again, these classes have been specifically designed to meet
the requirements published in ICAO Annex 3 / WMO No. 49 Volume 2 regulation.


The code fragment above illustrates the encoding of <iwxxm:MeteorologicalPositionCollection>:



  • (Lines 3-35) define the collection
    - on this occasion with just a single member (e.g. only one position is
    predicted for the volcanic ash cloud at T+6hrs).

    • (Lines 5-33) define the
      position of the volcanic ash cloud at 22:00Z. The SIGMET
      "forecast" only requires the geometry of the
      volcanic ash cloud to be provided - once more via an instance of <aixm:AirspaceVolume> (lines 7-31).



Erupting volcano



 



 
  1 . ...
  2 .     <iwxxm:eruptingVolcano>
  3 .         <metce:Volcano gml:id="v-MT-HEKLA">
  4 .             <metce:name>MT HEKLA</metce:name>
  5 .             <metce:position>
  6 .                 <gml:Point gml:id="ref-point-MT-HEKLA"
  7 .                            uomLabels="deg deg"
  8 .                            axisLabels="Lat Lon" 
  9 .                            srsDimension="2"
 10 .                            srsName="http://www.opengis.net/def/crs/EPSG/0/4326">
 11 .                     <gml:pos>63.59 -19.40</gml:pos>
 12 .                 </gml:Point>
 13 .             </metce:position>
 14 .         </metce:Volcano>
 15 .     </iwxxm:eruptingVolcano>
 16 . ...





The final element of the VA SIGMET report is provision of information about the
source of the volcanic ash; the name and position of the erupting volcano. The
code fragment above illustrates:



  • (Line 3) erupting
    volcano
    ; a uniquely identified instance of <metce:Volcano>. METCE also
    provides a EruptingVolcano
    class which the provision for stating the date of the volcanic eruption if
    known. However, there is no requirement to provide this information within
    the VA SIGMET.


  • (Line 4) volcano
    name
    . Note that the "Global Volcanism Program" provides
    an online, searchable catalogue
    of volcanoes
    which may assist in identifying the authoritative name
    for a given volcano feature.


  • (Lines 5-13) position
    specifies the geographic location of the volcano using an instance of <gml:Point>.





Page last modified on Saturday 14 of October, 2017 11:56:34 CEST