First/Latest observation extension

Introduction

This extension allows clients to query the first or latest observation for an offering, observableProperty and procedure or/and featureOfInterest. It is also possible to execute the first/latest observation temporal filter with another temporal filter, e.g. a TM_During.

Definition

In a GetObservation request use a TimeInstant in the eventTime parameter and define in timePosition getFirst or latest. For a combination define the TimeInstant for the first/latest in a relatedTime element of the TimeInstant/!TimePeriod. Examples for each operation can be found in the following four figures.

Get first observation

Single temporal filter

With this query you get for each procedure the first measured value for each observed property.

<eventTime>
   <ogc:TM_Equals>
      <ogc:PropertyName>om:samplingTime</ogc:PropertyName>
      <gml:TimeInstant>
         <gml:timePosition>getFirst</gml:timePosition>
      </gml:TimeInstant>
   </ogc:TM_Equals>
</eventTime>

Combined temporal filter

With this query you get for each procedure the first measured value in the defined temporal filter, here the TimePeriod, for each observed property.

<eventTime>
   <ogc:TM_During>
      <ogc:PropertyName>om:samplingTime</ogc:PropertyName>
      <gml:TimePeriod>
         <gml:relatedTime>
            <gml:TimeInstant>
               <gml:timePosition>getFirst</gml:timePosition>
            </gml:TimeInstant>
         </gml:relatedTime>
         <gml:beginPosition>2012-04-03T04:46:00+00:00</gml:beginPosition>
         <gml:endPosition>2012-04-03T06:53:00+02:00</gml:endPosition>
      </gml:TimePeriod>
   </ogc:TM_During>
</eventTime>

Get latest observation

Single temporal filter

With this query you get for each procedure the latest measured value for each observed property.

<eventTime>
   <ogc:TM_Equals>
      <ogc:PropertyName>om:samplingTime</ogc:PropertyName>
      <gml:TimeInstant>
         <gml:timePosition>latest</gml:timePosition>
      </gml:TimeInstant>
   </ogc:TM_Equals>
</eventTime>

Combined temporal filter

With this query you get for each procedure the latest measured value in the defined temporal filter, here the TimePeriod, for each observed property.

<eventTime>
   <ogc:TM_During>
      <ogc:PropertyName>om:samplingTime</ogc:PropertyName>
      <gml:TimePeriod>
         <gml:relatedTime>
            <gml:TimeInstant>
               <gml:timePosition>latest</gml:timePosition>
            </gml:TimeInstant>
         </gml:relatedTime>
         <gml:beginPosition>2012-04-03T04:46:00+00:00</gml:beginPosition>
         <gml:endPosition>2012-04-03T06:53:00+02:00</gml:endPosition>
      </gml:TimePeriod>
   </ogc:TM_During>
</eventTime>

Metadata

• Topic created by: CarstenHollmann
• Topic created on: 2012-11-26