Combined 5th Trans Tasman Survey Conference & 2nd Queensland Spatial Industry Conference 2006 – Cairns, 18-23 September 2006 SunPOZ : Enabling Centimetre Accuracy GNSS Applications in Queensland

SUNPOZ : ENABLING CENTIMETRE ACCURACY GNSS APPLICATIONS IN QUEENSLAND G.J. Cislowski SunPOZ Manager Department of Natural Resources Mines & Water Level 2 Landcentre Cnr Main & Vulture Streets Woolloongabba 4102 Tel: 07 3896 3030 Fax: 07 3891 5168 Email: [email protected] M. B. Higgins Principal Survey Advisor Department of Natural Resources Mines & Water Level 2 Landcentre Cnr Main & Vulture Streets Woolloongabba 4102 Tel: 07 3896 3754 Fax: 07 3891 5168 Email: [email protected] Presenter Garry Cislowski ABSTRACT In South-East Queensland Natural Resources Mines & Water (NRMW) has established a network of Continuously Operating Reference Stations (CORS) using the Trimble Virtual Reference (VRS) technology. SunPOZ offers both real-time and post-processed products. The real-time service has delivered field productivity increases of between 30% to 50% depending on the application. The VRS technology uses CORS and mobile phones to deliver real-time centimetre positions. The accuracy of these positions does not degrade relative to the distance from a reference station. Because SunPOZ operates within a network of reference stations an interruption to a reference station does not automatically result in an interruption to the survey. SunPOZ has been used in applications as diverse as setting out rowing courses, photogrammetry and road construction. A number of case studies will look at the performance of the SunPOZ service as well as productivity. While the current applications for SunPOZ are in the surveying arena there are expanding applications in the areas of machine guidance for mining and construction as will as precision agriculture and asset management. The robustness of GNSS has benefited by the resurgence of the GLONASS satellite positing system. Together with the pending Galileo system these additional satellites will contribute significantly to the reliability of GNSS in difficult applications like open cut mines. KEYWORDS: SunPOZ, VRS, GPS Network, RTK,

INTRODUCTION The Department of Natural Resources Mines and Water (NRMW) has a diverse portfolio that includes: management of land, water, vegetation mineral and petroleum resources and the preservation of our cultural heritage. The management of our natural resources today will directly affect the liveability and future prosperity of Queensland. The Department of Natural Resources, Mines and Water works together with industry, community, landholders and government to ensure that the management of our natural resources is innovative, responsible and balanced. Page 1 of 9

Combined 5th Trans Tasman Survey Conference & 2nd Queensland Spatial Industry Conference 2006 – Cairns, 18-23 September 2006 SunPOZ : Enabling Centimetre Accuracy GNSS Applications in Queensland

Land Information (LI) is the agency within NRMW that is responsible for providing ready access to natural resource related information including maps, geographical data and products, and survey infrastructure services that define the location and extent of property interests and land features. Land Information’s products and services support sustainable natural resource management within government, industry and the wider community by providing foundation land information. This foundation data is the core business of Land Information and is essential infrastructure required by Queensland for the sound management of the State’s economic, social and environmental well-being. Rapid population growth in South-East Queensland provides significant challenges in delivering a sustainable future for its residents. Meeting that challenge requires innovative and flexible approaches to management and infrastructure development. NRMW recognises that precision positioning services are a key enabling technology to support development in this growth area. In 2001 the department established a pilot network to test the application of networked RTK technology in the Southern Hemisphere. A network of Continuously Operating References Stations (CORS) was established in the corridor between Brisbane and the Gold Coast. The network corrections were derived using the VRS technology. Following this successful trial the department has established an operational network between the Gold Coast in the south to Caboolture (44Km North of Brisbane). Work is currently under way to significantly expand the network coverage to encompass the sites of two recently proposed dams as well as the rich agricultural area of the Darling Downs. The positioning service delivered using this network is called SunPOZ. SunPOZ delivers both real-time and post-processing services supporting Government and private users as well as the academic and scientific communities. Improved efficiency in the traditional high accuracy areas of surveying is only one driver to the expansion of the network. Improved efficiency and accuracy in non-traditional areas such as “control track” framing, bulk earthworks for civil construction using machine-guidance as well as the increasingly important area of asset management are much more compelling reasons for expansion of the network. UNDERSTANDING THE TECHNOLOGY The department’s approach to the delivery of accurate real-time positions over wide area is based on the Trimble VRS technology and before examining the performance of this approach it is useful to explain briefly how the technology works. The Virtual Reference Station Concept The VRS concept from Trimble is an extension of the real time kinematic (RTK) technique developed for GPS surveying and other forms of high precision positioning. With RTK, one can establish a base (or reference) station at a known point and broadcast the data from the reference station to one or more roving receivers. The computer processor at the roving receivers combines the reference station data with the rover data. With modern equipment, only a minute or two of data are typically required to fix the ambiguities associated with the GPS phase data observable and compute a GPS baseline; the difference in latitude, longitude and height between the reference and rover positions. RTK enables the roving receivers to be positioned with accuracy better than a few centimetres relative to the reference station. Before RTK, GPS baselines had to be post-processed in the office. The ability of RTK to process and display results in real time is further revolutionising the productivity achievable with GPS. VRS takes the productivity increase a step further by overcoming three main limitations of the current RTK technique. Firstly, operators no longer need to establish and run a GPS receiver and radio at their own reference station every time they want to work. Secondly, the use of mobile phone technology overcomes the limitation of the range of radio communications. Thirdly, multiple reference stations increase the redundancy and thus the confidence in the resulting rover positions. The VRS concept involves permanently running Global Navigation Satellite System (GNSS) reference stations, at spacings up to 70km. They feed their data to a central processing computer via a computer network. The central processing computer can use the reference station data to model spatial errors that limit GNSS accuracy and generate appropriate corrections. From the user’s perspective, a roving receiver makes a mobile phone call into the central processing facility, supplies its approximate position (based on its GNSS single point position) and then Page 2 of 9

Combined 5th Trans Tasman Survey Conference & 2nd Queensland Spatial Industry Conference 2006 – Cairns, 18-23 September 2006 SunPOZ : Enabling Centimetre Accuracy GNSS Applications in Queensland

requests corrections. The central processing computer then generates corrections as though there was a physical reference station at the coordinates of the rover’s approximate position and the rover is positioned relative to this virtual reference station. The relatively short GPS baselines between the virtual reference station and the rover receiver ensure that the position is not degraded by being too far from a reference station. Even when the rover is 30 or 40 Km from the nearest reference station the rover’s positional accuracy retains an accuracy of ± 2 cm (horizontal). This performance is because of the short baseline between the rover and the virtual reference station and the fact that the corrections from virtual reference station are interpolated from the surrounding physical reference stations. In practical terms RTK algorithms cannot reliably resolve the GPS phase ambiguities over distances greater than 30Km and the abilities of portable radio transmitters reach their limits well short of this mark. This gives the VRS approach a significant advantage over traditional RTK techniques. The VRS approach greatly improves the reliability of RTK operations because the network is “self-healing”. Interruption of data from a reference station does not result in loss of data at the rover. The VRS algorithms quickly recompute the atmospheric and orbital models to account for the new network configuration and typically recover within one minute of the data interruption. For more information on the technical background to VRS see Vollath et al (2000a), Vollath et al (2000b) and Trimble (2000). The SunPOZ CORS Network The Department of Natural Resources Mines & Water is a decentralised organisation with more than 30 offices located across the state. This offers significant benefits in the establishment of a CORS network that is suitable for VRS operations. Before implementing a full operational CORS network the Department in conjunction with the local Trimble agent, Ultimate Positioning, conducted a technical trial to explore the technical issues involved in the establishment and operation of such a network. (see Higgins, 2001 and Higgins and Talbot, 2001) The features of the SunPOZ CORS Network are: • The majority of reference stations are located at NRMW offices, that are linked by high-speed Wide Area Network (WAN) with each building also having a Local Area Network (LAN) enabling all sites to be linked by frame relay. • The installations at Caboolture, Ipswich, Beenleigh and Gold Coast are NRMW District Offices. • The Brisbane station is the Landcentre building, which houses Survey Infrastructure Services (the section within NRMW responsible for the service) and also hosts the Network Control Centre. • The Landcentre is also the host for the department’s IGS installation, which is also managed by the GPSNet software that is the heart of the VRS technology. While this reference station does not contribute to the VRS correction algorithms it demonstrates the flexibility of the software to manage diverse CORS networks. • The network is made up from a mixture of new and existing equipment. Existing equipment has the advantage of lowering the cost of establishment. However, modern CORS designed equipment balances this advantage with vast improvements in remote management of the receiver, lowering the operational management costs. The network uses a mixture of Trimble 4700, R7 and NetRS receivers as well as Leica GXR 1200 Pro receivers. The Trimble NetRS and Leica GXR 1200 Pro receivers are specifically designed for operation in CORS networks offering features like integrated network (TCP/IP) capability, full remote management through a browser interface local data logging and the ability to transfer data “missed” due to communication outages. • Antenna installations utilise rigid brackets firmly fixed to structural building roof elements mounted with geodetic class antennae forced centred and fixed directly to the bracket. • Data from all reference stations are recorded at one second epochs and archived. The data is available for post-processed users on demand. By utilising NRMW office sites issues such as access to and security of equipment are covered by existing arrangements as well as giving access to on-site staff with the ability to troubleshoot problems when they do occur. Page 3 of 9

Combined 5th Trans Tasman Survey Conference & 2nd Queensland Spatial Industry Conference 2006 – Cairns, 18-23 September 2006 SunPOZ : Enabling Centimetre Accuracy GNSS Applications in Queensland

However, experience from the technical trial and subsequent operation has demonstrated GNSS receivers operated in these environments are very stable and reliable. In the seven years that the department has operated IGS and VRS CORS installations only one GNSS equipment related failure has occurred. Advantages of the SunPOZ CORS Network The key drivers for the department in establishing an RTK CORS network are meeting its legislative requirement for establishment, maintenance and proliferation of the State Survey Control Network, improved efficiency of internal operations in undertaking these tasks, improving efficiency for other government agencies requiring accurate positioning and improved efficiency for the wider community involved in positioning applications. Advantages of the SunPOZ CORS network for field users are: • Reduced costs of RTK equipment by eliminating the need for a base GNSS receiver, radio transmitter and associated radio licence (the cost of annual radio transmitters in major metropolitan areas are in the order of $3,000); • Reduced setup time, only need to setup the rover; • Lower staff requirements since there are no security issues of a base station to be considered; • Reduction in sources of error in rover observations by eliminating the possibility of entering incorrect coordinates in the base receiver; • Improved communication stability by replacing the radio link to the base receiver with mobile phone data communications; • Redundancy, loss of data from a reference station does not cause a significant loss of productivity for the rover. The technology typically recovers from such a situation in around one minute; • Greater access to real-time positioning for non-technical users by removing much of the complexity in setup and operation; • Expansion of real-time positioning into areas such as: o Machine guidance and control for mining and construction; o “Control Track” farming; and, o Other integrated solutions that require position as a component. • The combination of these factors means greater reliability and productivity. Advantages of the SunPOZ CORS network for the Department: • Consistency of reference frame delivered from high accuracy control through to the field user, eliminating the issue of different datasets using differing coordinate systems. That ensures that datasets are capable of easy aggregation for future applications; • Significant cost reduction in the maintenance of ground marked control within the coverage area; • Greater responsiveness to client needs by eliminating the need to provide new control networks in previously undeveloped areas; • Creating a dataset that contributes to national and international projects, which in turn improve the satellite orbit data and contribute to the maintenance of the reference frame. The dataset also contributes to scientific research such as improving ionospheric modelling. Performance of SunPOZ CORS Network The department individually and in conjunction with local universities has undertaken a range of testing programs to investigate: • Rover initialisation time in absolute terms; • Rover initialisation time relative to traditional RTK; • Absolute accuracy and repeatability; • Effect of network configuration on initialisation and accuracy. Initialisation Testing Testing of “absolute” was done using controlled conditions of a reference station acting as a roving receiver. The “rover”, using diagnostic software initialised and recorded five seconds of data before reinitialising and the test was Page 4 of 9

Combined 5th Trans Tasman Survey Conference & 2nd Queensland Spatial Industry Conference 2006 – Cairns, 18-23 September 2006 SunPOZ : Enabling Centimetre Accuracy GNSS Applications in Queensland

conducted over a 15 hour period (see Higgins and Talbot, 2001). In more than 500 initialisations for a satellite constellation with 5 or more satellites the average time for initialisation was 1.7 minutes, in over 400 cases where 7 or more satellites were visible this reduced to 1.3 minutes. Having investigated initialisation under optimum conditions further testing was conducted by the University of Southern Queensland (see Ong, 2003) to test the performance of VRS in field applications. The test included accuracy as well as initialisation performance. The testing called for three receivers of the same type and firmware version, in this case Trimble 5700, using a single antenna via an antenna splitter. The receivers were configured for VRS, RTK and fast static observations. The results of Ong’s testing demonstrated superior performance of VRS over RTK in all situations even for short base lines (from the RTK base stations) where it was anticipated that RTK would out perform VRS in accuracy and initialisation. The test also showed that at a number of sites RTK did not work either through loss of the communication link or failure to initialise even though base had clear line of site to the base receiver. Importantly, at those sites VRS performed as expected, highlighting its greater reliability compared to the often unpredictable nature of single station RTK. The results of Ong’s accuracy tests showed that VRS compared to static solutions agreed within 9-15mm horizontally and 15-25mm vertically (at 99% confidence). Case Studies RoadTek The Queensland Main Roads Department oversees Queensland’s 34,000km of state-controlled road network. This task involves planning, designing, building and maintaining the associated infrastructure (such as bridges built) on these roads. This network carries 60-70% of Queensland’s traffic. The South East Queensland region covers 18,887 sq km and services Queensland’s most highly populated service and manufacturing area (See Figure 1 South East Queensland Transport Region). It has an estimated population of 2.65 million, growing at an average rate of nearly 3% annually. This rapid growth continues to place heavy demands on the region’s transport system. The South East Queensland region has responsibility for approximately 2,868km of state-controlled roads, including 427km of Auslink national network roads. In 2005, the Australian Government changed its approach to funding national land transport infrastructure. The new approach bases Australian Government investment around an AusLink National Transport Network involving land transport corridors of national importance. Key transport corridors in SEQ of interest to AusLink are the: • Brisbane Urban Corridor; • Bruce Highway; • Cunningham Highway; • Gateway Motorway and Bridge; • Ipswich Motorway; • Logan Motorway; • north coast rail line; • Pacific Motorway/Pacific Highway; • Port of Brisbane Motorway; • proposed inland rail freight corridor (incorporating Gowrie-Grandchester); • Sydney to Brisbane Railway; and • Warrego Highway.

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Combined 5th Trans Tasman Survey Conference & 2nd Queensland Spatial Industry Conference 2006 – Cairns, 18-23 September 2006 SunPOZ : Enabling Centimetre Accuracy GNSS Applications in Queensland

Figure 1 South East Queensland Transport Region

RoadTek Consulting provides Main Roads with an extensive portfolio of integrated services. The agency acts as “commercial” entity being a single provider for complete, coordinated and integrated solutions for civil engineering . Their integrated services include: • • • • • • • • •

Preconstruction; Traffic and transportation; Public utility plant; Environmental; Community consultation; Material and geotechnical; Construction monitoring; Contract management; Asset management;

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• •

Project management; Geospatial.

Combined 5th Trans Tasman Survey Conference & 2nd Queensland Spatial Industry Conference 2006 – Cairns, 18-23 September 2006 SunPOZ : Enabling Centimetre Accuracy GNSS Applications in Queensland

Given the diversity of road infrastructure in the South East Queensland region RoadTek needed a solution that delivered centimetre level accuracy over a wide geographical area that was both simple to use and time efficient. A significant proportion of RoadTek’s work involves controlling traffic to allow work to proceed, making time efficiency an important component of their work. Working over the long distances involved in new road projects often required the base station to be relocated during the day to maintain the communications link. The SunPOZ real-time services have been a boon to RoadTek’s operations in south east Queensland. Setup for survey operations have been slashed from 40-60 minutes to less than five minutes, the time that it takes to unpack and assemble the rover to gaining initialisation. Similarly the time required to relocate from one part of the project has been significantly reduced without compromising accuracy. RoadTek’s use of SunPOZ has not been limited to real-time applications. The post process data service has helped RoadTek significantly reduce field observation times for fast static surveys. The VRS technology allows users to create Virtual Reference Station RINEX data for specified locations. The technology uses the raw data along with the observed residuals and atmospheric models to re-create a RINEX data file for locations remote from the physical reference stations. Results from limited testing indicate that the method is comparable to fast static using actual observations from a reference station close to the project site. This has enabled RoadTek to reduce observation times from 45 minutes to 8 minutes for their local control surveys without the need to run additional reference receivers. RoadTek estimates that the net benefit has been productivity increases of 30% to 50% depending on individual project requirements. Additionally the ability to use what was previously a base/rover combination as two rovers has effectively doubled the survey capacity of RoadTek without the need to purchase new equipment. QASCO Busway Project Qasco was originally formed in 1962 in Brisbane. Today Qasco also has offices in Sydney, Melbourne, Darwin and Perth, and is a respected leader in aerial surveying and mapping throughout Australia, South East Asia and the Pacific Islands. Qasco is a pioneer in the use of Global Positioning Systems (GPS) in the surveying field, undertaking the first production GPS project in Queensland. This technology and expertise is now an integral part of the surveying and mapping process being used for both ground and airborne survey control. Qasco was contracted to provide surveying control for Brisbane’s inner city Busway project. Qasco is experienced in GPS RTK surveying and is well equipped for this activity. The length of the project made it suitable for GPS surveying (see Figure 2 Inner Northern Busway). However, being located so close to the city centre the logistics of finding a base station location that was accessible, secure and capable of servicing all or most of the project area with reliable communications proved to be too problematic to solve within the project timeframe. The SunPOZ CORS network effectively solved all of the problems immediately and had the added advantage of freeing up staff who would have otherwise been employed to ensure security of the RTK base station. The project used the SunPOZ real-time service to produce pre-planned photogrammetric control as well as construction control for the “cut and cover” tunnels called for in the project plan. In addition to the real-time service the project also used the post-processed service to process the construction control stations. In this case the RINEX data used was from the SunPOZ reference station located at the Landcentre, Woolloongabba, because of its proximity to the project site no significant advantage would have been gained from using a Virtual Reference Station for post-processing. Following good survey practice Qasco also used the real-time service as an independent check for the post-processing of the construction control. As a result of this checking process a difference of over one metre was detected between a fast static observation and the real-time observation. Further investigation revealed that in the processing of the fast static observation the phase ambiguities were not correctly resolved and the real-time position was the correct solution. Qasco employed the independent check using the real-time service because of the low marginal cost in doing so and the importance of accuracy to the success of the project. Qasco estimates that the overall benefit was a productivity increase of 30% plus solving the base station issues and isolating and checking post-processing errors.

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Combined 5th Trans Tasman Survey Conference & 2nd Queensland Spatial Industry Conference 2006 – Cairns, 18-23 September 2006 SunPOZ : Enabling Centimetre Accuracy GNSS Applications in Queensland

Figure 2 Inner Northern Busway

CONCLUSIONS Real-time positioning systems using networked RTK technologies deliver significant productivities to field users as well as increased flexibility to respond to increasing demand in a rapidly developing area. While the SunPOZ Page 8 of 9

Combined 5th Trans Tasman Survey Conference & 2nd Queensland Spatial Industry Conference 2006 – Cairns, 18-23 September 2006 SunPOZ : Enabling Centimetre Accuracy GNSS Applications in Queensland

system has already delivered significant advantages for high accuracy surveying applications its potential in nontraditional areas is yet to be fully realised. However, this is set to change with the Brisbane City Council (BCC) recently issuing tenders for the supply of GNSS equipment to act as rovers under the SunPOZ network. Those rovers will be utilised in the capture of asset data. More interestingly the intended users of the equipment are not surveyors but construction team leaders. The BCC has adopted SunPOZ as the key supplier of the accurate positioning service because of its potential for the development of turn-key services for non-technical users. The BCC local government area encompasses some 774 sq. km. housing a population of 970,000 and with an annual budget of some $1.4b, it is one of the most significant local governments in Australia. The pace of development within South East Queensland will provide significant challenges for infrastructure development and management and services such as the SunPOZ CORS network will play an integral role in that development. ACKNOWLEDGEMENTS The author wishes to acknowledge the support of the Garry Burton from the Queensland Department of Main Roads and Nevil Jansen of RoadTek and Kelvin Dawson of Qasco. Their experiences in the practical application of the SunPOZ CORS positioning service has provided information that has been invaluable to the content of this paper. REFERENCES Higgins, M.B., 2001, An Australian Pilot Project for A Real Time Kinematic GPS Network Using the Virtual Reference Station Concept, FIG Working Week 2001, International Federation of Surveyors (FIG), Seoul, Korea 6 – 11 May 2001. Higgins, M.B. and N. Talbot, 2001, Centimetres for Everyone: Initial Results from an Australian Virtual Reference Station Network Pilot Project, SatNav 2001, The 5th International Symposium on Satellite Navigation Technology and Applications, Canberra, Australia, 24 – 27 July 2001. Ong Kim Sun, G, 2003, Reliability assessment of the Virtual Reference Station (VRS) system of GPS base stations, Thesis (B. Surv.) University of Southern Queensland. Trimble, 2000, GPS Reference Station Networks, Product Brochure, Spectra Precision Terrasat GmbH, Trimble Navigation Limited, September 2000. (available on-line at http://www.terrasat.de/applications/refvirtual.htm) Vollath U., A. Buerchl, H. Landau, C. Pagels and B. Wagner, 2000a, Multi-Base RTK Positioning Using Virtual Reference Stations, Proceedings of ION GPS 2000, 13th International Technical Meeting of the Satellite Division of the Institute of Navigation, September 2000, Salt Lake City, Utah. Vollath U., A. Buerchl, H. Landau, C. Pagels and B. Wagner, 2000b, Long-Range RTK Positioning Using Virtual Reference Stations, Proceedings of ION GPS 2000, 13th International Technical Meeting of the Satellite Division of the Institute of Navigation, September 2000, Salt Lake City, Utah.

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