The Joining Land and Sea project is helping bring together data on Aotearoa New Zealand’s coastline, so changes in sea levels, flooding, and tsunami inundation can be effectively modelled, supporting greater resilience to natural hazards.

Bringing data together to support New Zealand

New Zealand’s marine and land elevation data are currently captured in many different datums. A datum is a reference system for describing positions on the curved surface of the Earth. Historically, it has been hard to merge and align multiple datums, so the Joining Land and Sea (JLAS) project will provide the tools for users to bring these datasets together, supporting seamless mapping and modelling across our entire coastline.

We’ve identified the best approach for undertaking this work in New Zealand based on evaluating global solutions for similar projects.

How we’re doing it

We are working with experts from NIWA to produce a new national tidal model for New Zealand. The tidal model is being developed using contemporary technologies and will incorporate a richer tidal and bathymetric dataset. With it we will generate tidal surfaces including Lowest Astronomical Tide, Mean High Water Springs, and more.

We are also establishing ‘coastal link’ sites which we will use to join the model across the land/sea boundary. We will install temporary tide gauges to collect sea level data, establish permanent geodetic survey marks and calibrate existing tide gauges.

When will the new tidal model and data be available?

The tidal surfaces will be used to update the online coordinate converter so users can convert their datasets between vertical datums. Tidal surfaces will also be available from the LINZ Data Service. This is planned for late 2023.

More information

Find out more about the project in our factsheet:

To contact the project team, email us at

Contact Kōrero whakapā

For general enquiries: