This project aimed to assess the accuracy and precision of SBAS and PPP technologies across different farming tasks on farming properties using a range of GNSS positioning systems. In addition, this project conducted an economic survey of mixed farming enterprises throughout WA to collect data on the impact, benefits, and potential uptake of SBAS technology in small-medium mixed farming enterprises.

Currently, growers with commercial off-the-shelf (COTS) non-RTK, non-subscription autosteer equipment obtain accuracies of ~0.1m. Our original expectations were that this level of accuracy could not be reliably achieved with any of the tested signals. The level of accuracy initially anticipated from the SBAS signals was 0.5 – 1.0m @95%, significantly worse than available from growers COTS systems. These expectations of the SBAS signal were largely confirmed by the testing completed as part of this project. We believe that the testing results and survey feedback clearly demonstrate that the SBAS signals should not be attempting to compete with or replace COTS systems at the <10cm level.

However, whist the COTS systems are widespread and grower’s accuracy expectations are driven by COTS system performance, they are aimed at high value tasks (harvesting, sowing, spreading) and as a result are expensive and lack flexibility. Based on the testing conducted and survey feedback from growers, we believe that growers will need accuracies of <=20cm for less critical high value tasks (such as spreading ameliorants and spraying chemicals) and >20cm for general tasks. It is these areas that we believe SBAS signals will offer the greatest benefit, primarily in terms of cost, reliability, and flexibility.  

Our thoughts with regards to grower’s accuracy requirements changed over the course of the year. In particular we recognised different levels of accuracy are needed for different tasks (although this is not necessarily recognised by the growers). With increasing adoption of cm-level NRTK technology by growers (particularly in WA) future SBAS signals need to deliver as close as possible to cm-level accuracies. If reliable performance at accuracies of<20cm can be achieved, the reduced costs associated with SBAS may encourage some farmers to compromise on accuracy for high value tasks.

This project aimed to assess the accuracy and precision of SBAS and PPP technologies across different farming tasks on farming properties using a range of GNSS positioning systems. In addition, this project conducted an economic survey of mixed farming enterprises throughout WA to collect data on the impact, benefits, and potential uptake of SBAS technology in small-medium mixed farming enterprises.

The project performed tests at 10 farms throughout the Corrigin region in Western Australia between May to September 2018 using a variety of SBAS and PPP receivers. Each test involved the mounting multiple SBAS and PPP capable GNSS receivers on the grower’s machinery as well as one GNSS receiver operating in RTK mode and one survey prism monitored by a Robotic Total Station to both provide a source of ground truth. Measurements were to be taken whilst the grower was performing routine activities (e.g. seeding, spreading). This report outlines the methodology and data analysis in greater detail.

This project has delivered accuracy testing results of 0.5m @95% to 1.0m @95% across the range of technologies. However, we note that a number of the individual test results did deliver precisions at the 10-20cm level using various SBAS signals and we are optimistic that further system developments may deliver such results with greater consistency and reliability.

Based on the testing conducted and survey feedback from growers, over 80% of producers surveyed indicated that will need accuracies of <=10cm for high value tasks like harvesting and seeding but <=20cm for less critical high value tasks (such as spreading ameliorants and spraying chemicals) and >20cm for general tasks. Therefore, the observed accuracies do not satisfy producers needs for high value tasks and producers would be unlikely to utilise the SBAS signal until the accuracy improved or it demonstrated value-add to their existing systems (e.g. through improved reliability).

However, the survey results indicate that if free SBAS signals were available at 0.5-1.0m @95% accuracy then this would significantly benefit producers who want to do general tasks (e.g. point positing, soil sampling, livestock management, etc.).  It is these areas that we believe SBAS signals will offer the greatest benefit, primarily in terms of cost, reliability, and flexibility. Further research and development (including testing) to improve kinematic precisions from future SBAS signals to <20cm @95%.

An unexpected benefit from the survey was evidence of the real value of SBAS signals for livestock businesses. It is the authors opinion that the use of SBAS signals would greatly benefit the livestock industry through enhanced livestock tracking and virtual fencing.

In addition, we experienced no difficulties (with any receiver) with connecting the SBAS Satellite and/or with receiving the correction from the SBAS Satellite. There are clearly still issues in rural areas with GNSS correction reliability. If the SBAS signals can objectively demonstrate improved GNSS correction delivery reliability, then it will certainly have something to offer to producers. Further investigation into the reliability of SBAS signals compared to NRTK corrections is required.

The project has contributed new knowledge as to the suitability of an SBAS model for agriculture, not only as a tool for advanced growers but as a means of engaging the broader farming population to consider some form of spatially-enabled agriculture. Improved and cheaper access to SBAS technologies will lead to increased efficiencies and production outcomes for Australian growers.