Satellite Based Augmentation System (SBAS) Development
The National Airspace and Air Navigation Plan contains an objective for the NSS programme to 'complete further analysis of the need for Satellite Based Augmentation Systems (SBAS)'.
In 2015, NSS (Ministry of Transport / LINZ / CAA) completed a Cost Benefit Analysis of the aviation aspects of SBAS.
The initiative below takes the analysis to another level.
Australasian SBAS Test-Bed
The SBAS trial signal goes live on 01 June 2017
See NOTAM 23 May 2017 for more information.
The Australasian Satellite-Based Augmentation System (SBAS) test-bed is a collaboration between the New Zealand and Australian governments to evaluate SBAS technology over the region in 2017 and through to Jan 2019.
As part of developing the New Zealand Government's National Positioning Infrastructure (NPI) capability, LINZ on behalf of the New Zealand government, is co-operating with Geoscience Australia to deliver an Australasian SBAS test project. The New Zealand part of the project is funded through LINZ, New Zealand Transport Agency, Ministry of Business, Innovation and Employment and Ministry of Transport.
As well as testing current-generation SBAS, the two-year project will test two new satellite positioning technologies including next generation SBAS and Precise Point Positioning, which will provide positioning accuracies of several decimetres and five centimetres respectively.
In April 2017, CRC-SI on behalf of LINZ and Geoscience Australia called for organisations from across the aviation, road, rail, maritime, spatial, construction, mining, utilities and agriculture sectors to participate in the test-bed. Expressions of Interest are being evaluated.
CRC-SI is the Australia and New Zealand Cooperative Research Centre for Spatial Information. It is a collaborative research centre that partners with government, academia and industry to conduct user-driven research related to spatial information. The SBAS initiative resides within the Positioning programme of the CRC-SI.
The Technical Perspective:
The Australia New Zealand joint SBAS trial test-bed signal will be broadcast from 01/06/2017 through to the end of February 2019. New Zealand is dependent on GNSS (GPS) signals for aviation navigation and surveillance. The SBAS test-bed downlink signal is not aviation approved however provides test correction signals for the L1 signal provided by GPS, the same signal used by aviation approved Technical Standard Order (TSO) equipment. The test signal will be broadcast with bit “0” set, this should ensure aviation TSO equipment ignores the test signal test correction values.
New Zealand utilises GNSS aviation equipment for navigation that is designed to RTCA DO-229 standards and approved under Federal Aviation Authority (FAA) TSO-C145 or TSO-C146 standards (and EASA equivalents). The CAA has verified that these TSO certified navigation systems have a function that will ignore SBAS signals transmitted with bit “0” set and no aviation navigation issues are expected during the SBAS trial broadcasts.
Note that GPS receivers designed to meet the requirements of RTCA DO-208 (TSO-C129) will not be affected by the SBAS test signal as they have no SBAS functionality.
Hence, for aviation approved (TSO) GNSS IFR navigation aircraft systems no abnormal behaviour is expected. If any navigation anomalies occur, or are suspected, report the situation promptly under Part 12 as a non-standard navigation situation and mention “SBAS issue” in the description.
The SBAS trial test bed will also broadcast an L5 signal. There is no certified aviation equipment using the L5 signal (or corrections) currently in NZ.
What is the purpose of the test?
The SBAS testing is designed to achieve three main objectives:
- Test the performance of the technology directly in a number of industries.
- Test the current industry-specific requirements and how they interact with the technology.
- Test future industry-specific innovations that might be borne out by the technology.
Ultimately, the test-bed will help determine if New Zealand should pursue the development of an operational SBAS.
Will the SBAS be certified for aviation?
The SBAS test-bed will not be certified for safety-of-life use. Importantly, the test signals will not put existing GNSS services at risk, especially safety-of-life services such as aircraft navigation. Built into the SBAS test-bed message set is a specific provision for broadcasting signals that are not authorised for safety-of-life applications. Aviation certified GNSS receivers are designed to reject SBAS signals that are being broadcast in a test environment.
Any aircraft operator wishing to participate in the aforementioned trial will need to engage the relevant GPS equipment manufacturer for their aircraft type and seek a software update necessary to allow reception of the test signal. It should be noted that any such aircraft trial will, likely require the test-aircraft to be operated on an experimental type certificate.
When will the test begin, and how will the Aviation sector be kept informed?
The test signal will be broadcast from 01 June 2017.
There is a NOTAM dated 23 May 2017, and an AIP supplement is expected with the next update. We will continue to update the CAA and NSS web sites with any new information. There is also an article on the trial in the May / June 2017 issue of Vector.
As an aviation operator what will I “see” once the test signal goes live (01/06/2017)?
For aviation-approved (TSO) GNSS IFR navigation aircraft systems no abnormal behaviour is expected. Approved equipment will ignore the test signal due to the bit ‘0’ setting, so as an operator you are expected to “see” no impact or changes.
If any navigation anomalies occur, or are suspected, report the situation promptly under Part 12 as a non-standard navigation situation and mention “SBAS issue” in the description.
For non-certified GPS equipment or agricultural application GPS equipment being used for non-safety of life application (but within aviation activities) user monitoring is prudent. The test signal is still expected to be ignored (as it will be received on the bit ‘0’ setting). However the wide range of devices available and varying manufacturing standards globally mean caution is required.
Any change in the performance and/or any noticeable correction to any non-certified GPS equipment or agricultural application GPS equipment used in the aviation sector should also be reported using the Part 12 process which will allow accurate trial impacts on the aviation sector to be considered.
How would an aviation participant report an issue with the SBAS test-bed?
In the unlikely event that the SBAS trial affects (or is suspected of affecting) your GPS system, the nature of the incident should be reported to CAA per the normal Part 12 defect and incident reporting process, as a failure, malfunction or degraded performance of a Navigation System. You should continue to use your normal aviation safety incident reporting channel. Including the text ‘SBAS issue’ in the description field is important for CAA identification and response.
What will the CAA do if an issue is reported?
The CAA, after receipt of any report related to the SBAS trial, will undergo an investigation process and take action or respond as required on a case by case basis.
What are the benefits offered by SBAS if implemented in the future?
More accurate and reliable satellite-based positioning, navigation and timing technology, essential for the implementation of many intelligent transport systems.
The addition of a certified SBAS can assist in landing solutions by enabling vertical guidance from GPS (ILS like approaches).
Remember, the SBAS test-bed signal will not be available for instrument flying because the signal cannot be used for safety-of-life applications.
More information on the SBAS test-bed can be found on the LINZ site.
If you have any questions about the SBAS test-bed, please contact CAA .