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OGC Observations and Measurements - GML Simple Features Profile Encoding

This GML application schema defines GML encoding of the the OMSF implementation model compliant with GML Simple Features Profile version 2.0 (OGC Document 10-100r3). The TimeseriesObservation type is compliant with the Simple Features Profile level SF-1 due to repeated time and value elements, all other Observation types are compliant level SF-0.

Example of a omsf:MeasureObservation encoded in GML:

<omsf:MeasureObservation gml:id="f-1">
  <gml:identifier codeSpace="fmi-fi-weatherobs">kumpula-2017-08-17_12-00_air-temp-1</gml:identifier>
  <omsf:geometry>
      <gml:Point gml:id="p-1" srsName="http://www.opengis.net/def/crs/EPSG/0/4258" srsDimension="2">
          <gml:pos>60.20307 24.96131</gml:pos>
      </gml:Point>
  </omsf:geometry>
  <omsf:phenomenonTime>2017-08-17T12:00:00Z</omsf:phenomenonTime>
  <omsf:resultTime>2017-08-17T12:01:25Z</omsf:resultTime>
  <omsf:procedureName>Meteorological surface observations</omsf:procedureName>
  <omsf:procedureReference xlink:href="http://xml.fmi.fi/process/met-surface-observations" />
  <omsf:observedProperty xlink:href="http://vocab.nerc.ac.uk/collection/P07/current/CFSN0023/" xlink:title="air_temperature" />
  <omsf:observerName>Vaisala AWS310</omsf:observerName>  
  <omsf:platformName>Helsinki Kumpula weather observation station</omsf:platformName>
  <omsf:ultimateFeatureOfInterestName>Helsinki Kumpula</omsf:ultimateFeatureOfInterestName>
  <omsf:ultimateFeatureOfInterestReference xlink:href="http://sws.geonames.org/843429/about.rdf"/>
  <omsf:result uom="Cel">12.5</omsf:result>

MeasureTimeseriesObservation example:

<omsf:MeasureTimeseriesObservation gml:id="f-1">
   <omsf:geometry>
        <gml:Point gml:id="p-1" srsName="http://www.opengis.net/def/crs/EPSG/0/4258" srsDimension="2">
            <gml:pos>60.20307 24.96131</gml:pos>
        </gml:Point>
    </omsf:geometry>
    <omsf:phenomenonTimeStart>2017-08-17T12:00:00Z</omsf:phenomenonTimeStart>
    <omsf:phenomenonTimeEnd>2017-08-17T18:00:00Z</omsf:phenomenonTimeEnd>
    <omsf:resultTime>2017-08-17T12:11:20Z</omsf:resultTime>
    <omsf:procedureName>Meteorological surface observations</omsf:procedureName>
    <omsf:procedureReference xlink:href="http://xml.fmi.fi/process/met-surface-observations" />
    <omsf:observedProperty xlink:href="http://vocab.nerc.ac.uk/collection/P07/current/CFSN0023/" xlink:title="air_temperature" />
    <omsf:observerName>Vaisala AWS310</omsf:observerName>    
    <omsf:platformName>Helsinki Kumpula weather observation station</omsf:platformName>
    <omsf:ultimateFeatureOfInterestName>Helsinki Kumpula</omsf:ultimateFeatureOfInterestName>
    <omsf:ultimateFeatureOfInterestReference xlink:href="http://sws.geonames.org/843429/about.rdf"/>
    <omsf:timeStep>2017-08-17T12:00:00Z</omsf:timeStep>
    <omsf:timeStep>2017-08-17T13:00:00Z</omsf:timeStep>
    <omsf:timeStep>2017-08-17T14:00:00Z</omsf:timeStep>
    <omsf:timeStep>2017-08-17T15:00:00Z</omsf:timeStep>
    <omsf:timeStep>2017-08-17T16:00:00Z</omsf:timeStep>
    <omsf:timeStep>2017-08-17T17:00:00Z</omsf:timeStep>
    <omsf:timeStep>2017-08-17T18:00:00Z</omsf:timeStep>
    <omsf:unitOfMeasure xlink:href="www.opengis.net/def/uom/UCUM/degC" xlink:title="Degree Celsius"/>
    <omsf:result>12.5</omsf:result>
    <omsf:result>12.0</omsf:result>
    <omsf:result>11.0</omsf:result>
    <omsf:result>13.2</omsf:result>
    <omsf:result>12.5</omsf:result>
    <omsf:result>14.1</omsf:result>
    <omsf:result>14.1</omsf:result>
</omsf:MeasureTimeseriesObservation>

The work version of the XML Schema for the OMSF is available at omsf-profile.xsd

GML encoding details

omsf:AbstractObservationType

This type is an abstract base type for all the OMSF Observation types. The phenomenonTime mapping is implemented with XML Schema choice between a single xsd:dateTime valued property phenomenonTime (when the value is a time instant) and a set of two xsd:dateTime valued properties phenomenonTimeStart and phenomenonTimeEnd (when the value is a time period). Similarly the time period of the validTime property is split into two properties validTimeStart and validTimeEnd.

Unless stated otherwise, all property names linking to externally referenced resources end with @link. The display names for those resources have otherwise identical property names but end with @name. The reason for providing the separate, optional @name properties instead of leveraging the xlink:title attributes is that referenced external resources may not be available in all cases, but it may still be useful for the data user to get the display names these resources. This would not be possible using the only the gml:ReferenceType which does not allow using xlink:title by itself as the xlink:href attribute is always required. In cases where there is no externally referenceable object to link to the @name property alone without the @link may be sufficient to convey the required information.

OMSF property name GML SF property name Multiplicity GML type Notes
geometry geometry 1 gml:GeometryPropertyType
phenomenonTime phenomenonTime 0..1 (choice with start-end pair) xsd:dateTime required only if the phenomenon time is a time instant
phenomenonTime phenomenonTimeStart 0..1 (choice with single phenomenonTime) xsd:dateTime required only if the phenomenon time is a time range
phenomenonTime phenomenonTimeEnd 0..1 (choice with single phenomenonTime) xsd:dateTime required only if the phenomenon time is a time range
resultTime resultTime 1 xsd:dateTime
stimulusTime stimulusTime 0..1 xsd:dateTime
validTime validTimeStart 0..1 xsd:dateTime
validTime validTimeEnd 0..1 xsd:dateTime
observer observerName 0..1 xsd:string
observer observerReference 0..1 gml:ReferenceType external reference
platform platformName 0..1 xsd:string
platform platformReference 0..1 gml:ReferenceType external reference
procedure procedureName 0..1 xsd:string
procedure procedureReference 0..1 gml:ReferenceType external reference
observedProperty observedProperty 1 gml:ReferenceType external reference to a code list
proximateFeatureOfInterest proximateFeatureOfInterestName 0..1 xsd:string
proximateFeatureOfInterest proximateFeatureOfInterestReference 0..1 gml:ReferenceType external reference
ultimateFeatureOfInterestName ultimateFeatureOfInterestName 0..1 xsd:string
ultimateFeatureOfInterest ultimateFeatureOfInterestReference 0..1 gml:ReferenceType external reference
metadata metadataReference 0..1 gml:ReferenceType external reference

omsf:GenericObservationType extends omsf:AbstractObservationType

In addition to the properties of omsf:AbstractObservationType, omsf:GenericObservationType has the following property:

OMSF property name GML SF property name Multiplicity Type Notes
result resultReference 1 gml:ReferenceType external reference

omsf:MeasureObservationType extends omsf:AbstractObservationType

In addition to the properties of omsf:AbstractObservationType, omsf:MeasureObservationType has the following property:

OMSF property name GML SF property name Multiplicity Type Notes
result result 1 gml:MeasureType

omsf:CategoryObservationType extends omsf:AbstractObservationType

In addition to the properties of omsf:AbstractObservationType, omsf:CategoryObservationType has the following property:

OMSF property name GML SF property name Multiplicity Type Notes
result result 1 gml:ReferenceType URI reference recommended indicating both the codelist and the value

Note that as a deviation of the generic rule of post-fixing a word Reference to the names of the externally referenced properties, the result name is not post-fixed.

omsf:TruthObservationType extends omsf:AbstractObservationType

In addition to the properties of omsf:AbstractObservationType, omsf:TruthObservationType has the following property:

OMSF property name GML SF property name Multiplicity Type Notes
result result 1 xsd:boolean

omsf:CountObservationType extends omsf:AbstractObservationType

In addition to the properties of omsf:AbstractObservationType, omsf:CountObservationType has the following property:

OMSF property name GML SF property name Multiplicity Type Notes
result result 1 xsd:integer

omsf:AbstractTimeseriesObservationType extends omsf:AbstractObservationType

This abstract feature type is a common ancestor for all time series Observation types. In addition to the properties of omsf:AbstractObservationType, omsf:AbstractTimeseriesObservationType has the following property:

OMSF property name GML SF property name Multiplicity Type Notes
timeStep timeStep 1..n xsd:dateTime one for each time series data point

omsf:MeasureTimeseriesObservationType extends omsf:AbstractTimeseriesObservationType

In addition to the properties of omsf:AbstractTimeseriesObservationType, omsf:MeasureTimeseriesObservation has the following properties:

OMSF property name GML SF property name Multiplicity Type Notes
unitOfMeasure unitOfMeasure 0..1 gml:ReferenceType external reference to a code list
result 1..n xsd:double one for each time series time step

Time series with result values for several points in time does not fit with the GML Simple Features Profile compliance level SF-0 without mild violence, since repeated elements are not allowed. Technically the time series values (and even time instances) could be encoded inside a single element using list type, but encoding and decoding would require special processing, which would at least partly defeat the gains of restricting the feature type to SF-0. Thus the MeasureTimeseriesObservation contains repeated timeStep and result properties which require using SF-1 compliance level when encoding into GML Simple Features.

Using of repeated properties allows client applications to treat both timeStep and result as arrays of simple values, which would not be possible using time-value-pair encoding.