Copyright © 2009, Open Geospatial Consortium, Inc. Modelling Meteorological Observations and Forecast Data as Discrete Coverages for exchange using WFS Meteorology DWG Debbie Wilson – Snowflake Software 30 September 2009

Helping the World to Communicate Geographically Copyright © 2009 Open Geospatial Consortium Rationale Met Office provide ~650 products and services to a wide range of customers: Government Research Business Media Public Until recently many of these products were exchanged with customers using traditional FTP push services for integration into their own information systems Met Office is moving away from data supply towards providing services and decision-support applications where users access highly detailed weather information directly

Helping the World to Communicate Geographically Copyright © 2009 Open Geospatial Consortium Rationale Met Office have developed several decision support systems to support transport sector: –OpenRoad –Open Runway –OpenRailway –SafeSee These applications provide access to highly detailed forecast and observation data relating to real-world objects they manage and operate To ensure that these can remain operational and increase efficiency

Helping the World to Communicate Geographically Copyright © 2009 Open Geospatial Consortium Example: OpenRoad

Helping the World to Communicate Geographically Copyright © 2009 Open Geospatial Consortium Example: OpenRoad

Helping the World to Communicate Geographically Copyright © 2009 Open Geospatial Consortium Example: OpenRoad

Helping the World to Communicate Geographically Copyright © 2009 Open Geospatial Consortium Example: OpenRoad

Helping the World to Communicate Geographically Copyright © 2009 Open Geospatial Consortium Design Brief To develop an efficient and compact schema for encoding forecast and observation data for exchange using WFS based upon: –ISO coverages specification –GML coverage profile Reusable across a wide range of Met Office projects – i.e. schema should be flexible to allow it to be easily integrated into project specific application schema We were not required to develop a full information model but demonstrated how the schema could be incorporated into a more comprehensive information models: –O&M (OGC) –WXXM (Aviation) –Route-Based Forecast Model (Internal) Compatible with GO Publisher’s WFS on-the-fly data translation capabilities

Helping the World to Communicate Geographically Copyright © 2009 Open Geospatial Consortium Design Issues and Constraints Need to understand the types of queries to be performed by WFS client: –Identity Queries: Select the 36 hour forecast for Heathrow Airport Select the latest observation for Telegraph Hill Weather Station –Spatio-temporal Queries: Select the latest observations within a user-defined bounding box –Parameter Queries: Select road surface temperature from the 36 hour forecast for A360 Select observed air temperature at Telegraph Hill over period: T00:00:00 – T11:00:00 To support ability to process these queries the data must be defined within an XML element

Helping the World to Communicate Geographically Copyright © 2009 Open Geospatial Consortium Modelling Met Office Data as Discrete Coverages

Helping the World to Communicate Geographically Copyright © 2009 Open Geospatial Consortium Modelling Issues faced Took a similar approach to CSML separating the spatio-temporal domain into two parts: –Feature of Interest: i.e. Road, railway, region, postcode, sporting venue, latest –Coverage Domain: i.e. Time-series (list or temporal grid) or MultiPoint, MultiCurve or MultiSurface For many Met Office use cases the most common discrete coverage type is the Time-Series coverage Unfortunately – ISO and GML only support spatial coverages Although-O&M does illustrate how ISO could be extended to incorporate temporal coverages and provided a O&M best practice schema provides a literal implementation schema time-series – as a geometry-value pair – not compact enough or defined within GML spec.

Helping the World to Communicate Geographically Copyright © 2009 Open Geospatial Consortium Modelling Parameter values For encoding parameter values within the gml:rangeSet 2 options: –ValueArray –AbstractScalarValueList Of these AbstractScalarValueList provides the most compact encoding for listing the values for each parameter type. Also provides ability to hard type the parameter type by specialising AbstractScalarValueList types within the application schema

Helping the World to Communicate Geographically Copyright © 2009 Open Geospatial Consortium Next Steps To test the schemas to see whether the compact encodings can support the various query types identified Evaluate the performance of GO Publisher to translate the data from RDBMS into discrete coverage schema on-the-fly Refine schemas where required