Modelling Australian geodetic data and metadata Roger Fraser & Nick Brown eGeodesy Working Group, Permanent Committee on Geodesy

Overview eGeodesy Working Group, Permanent Committee on Geodesy History Design goals Methodology Scope Implementation Current status Next steps for GGOS

History GNSS CORS and datum maintenance – a distributed responsibility No standardised approach for geodetic data management High level of variability in: Standards Procedures Systems Data translation a common burden and prone to error No comprehensive way for discovering / sharing / exchanging information eGeodesy Working Group, Permanent Committee on Geodesy

Design goals Develop comprehensive data model for geodetic data and metadata Standardise and document national geodetic processes Facilitate automated, distributed (m-to-m) processing Enable ubiquitous discoverability eGeodesy Working Group, Permanent Committee on Geodesy

Methodology A twofold process: 1.Identify what data is managed 2.Identify how data is used, modified or generated Document using international standards eGeodesy Working Group, Permanent Committee on Geodesy

Scope eGeodesy Working Group, Permanent Committee on Geodesy Time dependent reference frames, datums and coordinate systems Observing system (including site / station metadata) Measurements (GNSS and terrestrial) Positions and time series Lineage (or traceability) Transformations Grid/coverages Adjustment Projects and roles Quality and standards Physical marks and monuments

Implementation A logical model is realised in at least three ways: Database (physical model) Software (object model) XML Schema (data model) eGeodesy Working Group, Permanent Committee on Geodesy Database Software XML Schema Logical model Behaviour Structure Object oriented classes Tables, fields, views, triggers Semantics, structure, rules GeodesyML

Implementation: Database (physical model) eGeodesy Working Group, Permanent Committee on Geodesy Database schema (table structure and fields) Automated tools for generating DB schemas from XML schema Manual DB schema creation Existing DB schemas can be ‘mapped’ to XML schemas

Implementation: XML Schema (data model) eGeodesy Working Group, Permanent Committee on Geodesy Fundamental imperative: adopt an international standard GML Application Schema design offers multiple options

Implementation: Software (object model) Technical implementation achieved by Automated ‘XML schema binding’ tools Manual ‘binding’ (i.e. hand-written code) Permits loading of data in XML files into memory Providing open source encourages and expedites vendor adoption eGeodesy Working Group, Permanent Committee on Geodesy using namespace std; class ClusteredAdjustedMeasurement : public ::xml_schema::complex_content { public: // Parser callbacks. virtual void pre (); // Overridden in implementation class virtual void AprioriErrorScalar1(); virtual void AprioriErrorScalar2(); virtual void AprioriErrorScalar3(); virtual void SingleAdjustedMeasurement(); virtual void ClusteredMeasurement();... using namespace std; class ClusteredAdjustedMeasurement : public ::xml_schema::complex_content { public: // Parser callbacks. virtual void pre (); // Overridden in implementation class virtual void AprioriErrorScalar1(); virtual void AprioriErrorScalar2(); virtual void AprioriErrorScalar3(); virtual void SingleAdjustedMeasurement(); virtual void ClusteredMeasurement();... XML schema (.xsd) Source code

Current Status eGeodesy Working Group, Permanent Committee on Geodesy GeodesyML 0.1 accessible via SMES GeodesyML current draft: version 0.2 Supports SOPAC Site Log XML Schema Presently finalising documentation and software for I/O

Example: WFS response and rendering in Open Layers eGeodesy Working Group, Permanent Committee on Geodesy From this

Example: WFS response and rendering in Open Layers eGeodesy Working Group, Permanent Committee on Geodesy To this

Next steps for GGOS eGeodesy Working Group, Permanent Committee on Geodesy Architect the ‘system’, its components, actors and their relationships Adopt and build upon an existing data model Extend the model to include other GGOS elements: 1.Identify what GGOS data is to be modelled (structural) 2.Identify how GGOS data is handled (behavioural) 3.Collaborate to extend GeodesyML Documentation Logical model

Geodetic data exchange: An Australian perspective Roger Fraser & Nick Brown eGeodesy Working Group, Permanent Committee on Geodesy