A changing approach to geodetic networks and standards

A changing approach to geodetic networks and standards MATT AMOS and DON GRANT Overview Historical - Based on method of observation

Current - Based on accuracy achieved Future NZ Geodetic Datum 1949

Limitations of NZGD1949 New technology - EDM, GPS, etc Public access to global datasets Earth Deformation

- Earthquakes Edgecumbe 1987 (M6.3) Limitations of NZGD1949 New technology - EDM, GPS, etc

Public access to global datasets Earth Deformation - 1855 Wellington earthquake magnitude 8.2 18m horizontal 2.5m vertical - Continuous deformation

5m / century between east and west of NZ Motion relative to geo-centre of Earth New Zealand Geodetic Datum 2000 GPS-based Geocentric Accommodates Earth deformation

Monitored by continuous GNSS observations NZGD2000 Zero Order Network NZGD2000 2nd 4th Order Networks

NZGD2000 5th Order Network Current network still not ideal Different and conflicting uses Different and conflicting characteristics - Density - Accuracy

- Accessibility - Mark construction - Site stability Purposes not clear What exactly do we need?

Proposed Future Geodetic Networks Networks defined by purpose (not by process) Accuracy of networks related to their purpose not how they are obtained Different mark characteristics for each network

Marks can be in multiple networks National Reference Frame Connection to the global frame One station for each tectonic plate Continuous GNSS observations

Absolute gravity connection Datum Monitoring Network Maintain accuracy of geodetic datum Monitor earth deformation Re-establish cadastre following major

deformation events Density related to deformation rate Stability of marks important Cadastral Control Network Geodetic marks to support cadastral surveys

Enable connection to the geodetic datum Enable orientation to the geodetic datum Provided where cadastral surveys are being done Intervisibility important Geospatial Network Alignment of geospatial datasets

Datum connection in areas of little cadastral activity - Wilderness areas & National Parks - Offshore Islands - Ross Dependency Marks visible to aerial applications

Next steps Standard being drafted by LINZ Regulatory Group Review by expert committee early 2008 Two month public consultation period Consideration of consultation feedback by committee Publication of standard late 2008 Networks implemented by LINZ Customer Services

Summary Existing geodetic networks based on observation technique rather than function New geodetic networks based on purpose Different networks for different purposes Draft standard for consultation in early 2008

Standard publication late 2008 End