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GIS Web Services. NDFD Technical Workshop November 2, 2006 John Schattel - [email protected] Motivation. NWS Embraces Standards and GIS NWS Migrates to digital services.

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GIS Web Services

NDFD Technical Workshop

November 2, 2006

John Schattel - [email protected]

NDFD Technical Workshop (Nov 2, 2006)


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Motivation

NWS Embraces Standards and GIS

NWS Migrates to digital services

“We will work with the weather, water, and climate enterprise to investigate, develop, and expand the use of new technologies in data management and information systems, such as new internet-based standards and Geographic Information Systems (GIS), to accelerate development and implementation of appropriate NWS and NOAA products and services and to integrate these services in ways that are meaningful to our customers.”

“… by evolving our services from a text-based paradigm to one based on making NWS and NOAA information available quickly, efficiently, and in convenient and understandable forms (e.g., National Digital Forecast Database and GIS) …”

From: Working Together to Save Lives, National Weather Service Strategic Plan for 2005 - 2010

NDFD Technical Workshop (Nov 2, 2006)


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OVERVIEW

  • Open Geospatial Consortium (OGC)

  • Web Feature Service (WFS)

  • National Digital Forecast Database WFS (ndfdWFS)

  • Geography Markup Language (GML)

  • Digital Weather GML (dwGML)

  • Development Schedule

NDFD Technical Workshop (Nov 2, 2006)


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OGC

  • Develop open interface specifications for geographic information systems (GIS)

  • 300+ members (GIS users/developers)

    • Corporations

    • Government agencies

    • Universities

  • Developed 18 consensus specifications

    • WFS and GML plus others

http://www.opengeospatial.org/

NDFD Technical Workshop (Nov 2, 2006)


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WFS

  • OGC standard for accessing feature data

    • Features are real-world objects

      • School, road, or state border

      • NDFD forecast

    • Features defined by properties

      • Geometric (point, polygon, or solid)

      • Non-geometric (color, height, or temperature)

    • Transaction versus non-transaction service

      • Non-transaction only allows feature retrieval

      • Transaction allows for insert, update, and locking

NDFD Technical Workshop (Nov 2, 2006)


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WFS

  • Uses Client/Server architecture

  • Supports HTTP Get and/or Post method

  • GET: http://host/wfs.cgi?service=WFS&

  • request=GetCapabilities&

  • POST: <?xml version=“1.0” ?>

  • <getCapabilities service=“WFS” />

NDFD Technical Workshop (Nov 2, 2006)


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WFS

  • 3 Request/Response Interfaces

    • GetCapabilities

      • Provides meta data about service

        • Service identification

        • Operations metadata

        • Feature types

    • DescribeFeatureType

      • Provides the structure of available features

      • GML application schema

    • GetFeature

      • Retrieves desired features (GML)

NDFD Technical Workshop (Nov 2, 2006)


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ndfdWFS

  • Standards-based NDFD data retrieval

  • Leverages GML-aware processors in GIS community

  • Basic WFS functionality

    • Non-transaction service

    • HTTP Get only

  • Determine best data encoding structure

    • Balance encoding efficiency and processor support

    • Assess volume of data required by GIS users

NDFD Technical Workshop (Nov 2, 2006)


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ndfdWFS Interfaces

  • GetCapabilities

    • What feature data are available

    • What operations are permitted on the features

    • How to access the feature data

  • Sample GetCapabilities request

http://weather.gov/OGC_servives/ndfdOWSserver.php?

SERVICE=WFS&

REQUEST=GetCapabilities&

VERSION=1.1.0&

NDFD Technical Workshop (Nov 2, 2006)


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GetCapabilities Sections

NDFD Technical Workshop (Nov 2, 2006)


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ndfdWFS Interfaces

  • DescribeFeatureType

    • Provides structure of the encoding data model

    • Returns an application schema

  • Sample DescribeFeatureType request

http://weather.gov/OGC_servives/ndfdOWSserver.php?

SERVICE=WFS&

REQUEST=DescribeFeatureType&

VERSION=1.1.0&

TYPENAME=gmlObsType,gmlSimpleFeatureType&

NDFD Technical Workshop (Nov 2, 2006)


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ndfdWFS Interfaces

  • GetFeature

    • Returns NDFD data encoded in dwGML

    • Data determined by user input

      • A comma delimited list of latitude and longitude points

      • Valid time of the requested data

      • A comma delimited list of NDFD weather parameters

  • Sample GetFeature request

http://weather.gov/OGC_servives/ndfdOWSserver.php?

SERVICE=WFS&REQUEST=GetFeature&VERSION=1.1.0&

TYPENAME=gmlSimpleFeatureType&

LATLONLIST=38.99^-77.99&

TIME=2006-10-25T00-00-00&

ELEMENTS=maxt&

NDFD Technical Workshop (Nov 2, 2006)


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dwGML

  • Developed to disseminate NDFD data

    • uses OGC standards (GML)

    • GIS user is target customer

  • Provides 3 data models

    • Simple Feature Profile based point

      • Forecast_GmlsfPoint

    • GML Observation

      • Forecast_GmlObs

    • Time series

      • NdfdTimeSeriesCoverage

NDFD Technical Workshop (Nov 2, 2006)


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dwGML – Forecast_GmlsfPoint

<app:Forecast_GmlsfPoint>

<gml:position>

<gml:Point srsName="NDFD_CRS_Dictionary.xml">

<gml:pos>38.99 -77.99</gml:pos>

</gml:Point>

</gml:position>

<app:validTime>2006-10-11T00:00:00</app:validTime>

<app:maximumTemperature uom="Fahrenheit">88.0

</app:maximumTemperature>

</app:Forecast_GmlsfPoint>

NDFD Technical Workshop (Nov 2, 2006)


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Forecast_GmlsfPoint Data

Forecast_GmlsfPoint encoded NDFD Maximum Temperature data decoded and displayed.

NDFD Technical Workshop (Nov 2, 2006)


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dwGML – Forecast_GmlObs

<app:Forecast_GmlObs>

<gml:validTime>

<gml:TimeInstant>

<gml:timePosition>2006-10-11T00:00:00</gml:timePosition>

</gml:TimeInstant>

</gml:validTime>

<gml:target>

<gml:Point srsName="NDFD_CRS_Dictionary.xml">

<gml:pos>38.99 -77.99</gml:pos>

</gml:Point>

</gml:target>

<gml:resultOf>

<app:ForecastValue>

<app:maximumTemperature uom="Fahrenheit">88.0

</app:maximumTemperature>

</app:ForecastValue>

</gml:resultOf>

</app:Forecast_GmlObs>

NDFD Technical Workshop (Nov 2, 2006)


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dwGML – NdfdTimeSeriesCoverage

<app:NdfdTimeSeriesCoverage>

<gml:rectifiedGridDomain>

<gml:RectifiedGrid dimension="1" srsName="NDFD_CRS.xml">

<gml:limits>

<gml:GridEnvelope>

<gml:low>322412</gml:low>

<gml:high>322556</gml:high>

</gml:GridEnvelope>

</gml:limits>

<gml:axisName>t</gml:axisName>

<gml:origin>

<gml:Point gml:id="timePoint1">

<gml:pos>322412</gml:pos>

</gml:Point>

</gml:origin>

<gml:offsetVector>24</gml:offsetVector>

</gml:RectifiedGrid>

</gml:rectifiedGridDomain>

NDFD Technical Workshop (Nov 2, 2006)


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dwGML – NdfdTimeSeriesCoverage

<gml:rangeSet>

<gml:DataBlock>

<gml:rangeParameters>

<gml:CompositeValue>

<gml:valueComponent>

<app:MaximumTemperature uom="F">template

</app:MaximumTemperature>

</gml:valueComponent>

</gml:CompositeValue>

</gml:rangeParameters>

<gml:tupleList>57 48 57 56 63 64 67</gml:tupleList>

</gml:DataBlock>

</gml:rangeSet>

</app:NdfdTimeSeriesCoverage>

NDFD Technical Workshop (Nov 2, 2006)


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Schedule

  • Prototype software (Jan07)

    • Support for 3 data structures

    • Multiple NDFD points

  • Experimental ndfdWFS (Jan07)

  • Interoperability assessment (Mar07)

    • Verify OGC-compliant clients can use service

    • Access degree to which GML-aware application can decode dwGML

NDFD Technical Workshop (Nov 2, 2006)


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QUESTIONS / SUGGESTIONS

[email protected]

NDFD Technical Workshop (Nov 2, 2006)


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