GIS Web Services

1
GIS Web Services

• NDFD Technical Workshop
• November 2, 2006
• John Schattel - John.Schattel_at_noaa.gov

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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
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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

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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/
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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

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WFS

• Uses Client/Server architecture

• Supports HTTP Get and/or Post method

GET http//host/wfs.cgi?serviceWFS
requestGetCapabiliti
es POST lt?xml version1.0 ?gt
ltgetCapabilities serviceWFS /gt
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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)

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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

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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?
SERVICEWFS REQUESTGetCapabilities VERSION1.1
.0
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GetCapabilities Sections
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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?
SERVICEWFS REQUESTDescribeFeatureType VERSION
1.1.0 TYPENAMEgmlObsType,gmlSimpleFeatureType
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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?
SERVICEWFSREQUESTGetFeatureVERSION1.1.0 TYP
ENAMEgmlSimpleFeatureType LATLONLIST38.99-77.9
9 TIME2006-10-25T00-00-00 ELEMENTSmaxt
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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

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dwGML Forecast_GmlsfPoint
ltappForecast_GmlsfPointgt ltgmlpositiongt
ltgmlPoint srsName"NDFD_CRS_Dictionary.xml"gt
ltgmlposgt38.99 -77.99lt/gmlposgt
lt/gmlPointgt lt/gmlpositiongt
ltappvalidTimegt2006-10-11T000000lt/appvalidTimegt
ltappmaximumTemperature uom"Fahrenheit"gt88.0
lt/appmaximumTemperaturegt lt/appForecast_GmlsfP
ointgt
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Forecast_GmlsfPoint Data
Forecast_GmlsfPoint encoded NDFD Maximum
Temperature data decoded and displayed.
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dwGML Forecast_GmlObs
ltappForecast_GmlObsgt ltgmlvalidTimegt
ltgmlTimeInstantgt ltgmltimePositiongt2006-
10-11T000000lt/gmltimePositiongt
lt/gmlTimeInstantgt lt/gmlvalidTimegt
ltgmltargetgt ltgmlPoint srsName"NDFD_CRS_Di
ctionary.xml"gt ltgmlposgt38.99
-77.99lt/gmlposgt lt/gmlPointgt
lt/gmltargetgt ltgmlresultOfgt
ltappForecastValuegt ltappmaximumTemperatu
re uom"Fahrenheit"gt88.0
lt/appmaximumTemperaturegt
lt/appForecastValuegt lt/gmlresultOfgt lt/appFore
cast_GmlObsgt
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dwGML NdfdTimeSeriesCoverage
ltappNdfdTimeSeriesCoveragegt
ltgmlrectifiedGridDomaingt
ltgmlRectifiedGrid dimension"1"
srsName"NDFD_CRS.xml"gt ltgmllimitsgt
ltgmlGridEnvelopegt
ltgmllowgt322412lt/gmllowgt
ltgmlhighgt322556lt/gmlhighgt
lt/gmlGridEnvelopegt lt/gmllimitsgt
ltgmlaxisNamegttlt/gmlaxisNamegt
ltgmlorigingt ltgmlPoint
gmlid"timePoint1"gt
ltgmlposgt322412lt/gmlposgt
lt/gmlPointgt lt/gmlorigingt
ltgmloffsetVectorgt24lt/gmloffsetVectorgt
lt/gmlRectifiedGridgt lt/gmlrectifiedGridDomaingt
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dwGML NdfdTimeSeriesCoverage
ltgmlrangeSetgt ltgmlDataBlockgt
ltgmlrangeParametersgt
ltgmlCompositeValuegt
ltgmlvalueComponentgt
ltappMaximumTemperature uom"F"gttemplate
lt/appMaximumTemperaturegt
lt/gmlvalueComponentgt
lt/gmlCompositeValuegt lt/gmlrangeParamete
rsgt ltgmltupleListgt57 48 57 56 63 64
67lt/gmltupleListgt lt/gmlDataBlockgt
lt/gmlrangeSetgt lt/appNdfdTimeSeriesCoveragegt
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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

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QUESTIONS / SUGGESTIONS John.Schattel_at_noaa.gov