Ionospheric modelling for the ACS and NPI

Modelling the Earth’s upper atmosphere to support high precision positioning across Australia

The Challenge

The ionosphere is the part of Earth’s upper atmosphere, from about 50 km to 500 km altitude that is ionized by solar radiation. As Global Navigation Satellite System (GNSS) signals pass through the charged particles of the ionosphere, they get slowed down which creates timing errors. Mathematical ionospheric models can be used to account for most of this error. A new high precision ionospheric model is needed for the purposes of supporting Analysis Centre Software (ACS) functionality and enabling high precision positioning across Australia. This project will evaluate exiting models and develop two new high precision ionospheric models for the “user side” and the “network side” of the ACS.


The project partners are Geoscience Australia and the Royal Melbourne Institute of Technology (RMIT).

The Solution

This project is a sub project of the On-going Development of the Multi-GNSS Analysis Centre Software. It aimed to develop and implement two modules that allow the ACS to benefit from the ionosphere modelling process:

  1. A user side model – a regional (Australia and New Zealand) Ionosphere model aimed at producing Ionospheric corrections that can accelerate the convergence of PPP-RTK positioning solutions.
  2. A network side model – a global Ionosphere model aimed at strengthening the measurement used by the ACS and thus improving convergence time and reliability of ACS solutions.

Three work packages were used to achieve project objectives:

  1. Work Package 1 (WP1): Evaluation of current Ionospheric measurements and models. WP1 studied the ACS modules, Ionospheric modelling algorithm and PPP-RTK algorithms developed in past project and evaluated the changes necessary to implement the “user side” model and the “network side” model.
  2. Work Package 2 (WP2): Design and implementation of Ionospheric models for end user PPP-RTK processing. WP2 developed and implemented the “user side” model, aimed at delivering precise position with fast convergence to the end user.
  3. Work Package 3 (WP3): Design and implementation of Ionospheric models for network PPP processing. WP3 developed and implemented a “network side” ionosphere model aimed at strengthening the measurement model that calculates satellite orbits and clocks.

Position allows us to locate ourselves in the world and get to where we want to go. This brings increased productivity, improved community safety and boosted innovation. The reported economic benefits of positioning technologies have the potential to generate upward of $73 billion of value to Australia by 2030. This project will develop the knowledge and software tools required to allow ionospheric delay measurements generated by the ACS to be used by PPP-RTK users (user side model) and to allow the ACS to benefit from the increased measurement model strength and robustness provided by ionospheric modelling (network side model). This will accelerate convergence for end users and strengthen the measurement model of network solutions, for more accurate and reliable products.


To learn more, please contact us at or Chief Delivery Officer Kate Williams at to find out more.