Singapore: Acting as a great catalyst, Chris Rizos, Prof and Head, School of Surveying and Spatial Information Systems, University of New South Wales, Australia, steered the seminar on Satellite Based Infrastructure to make it quite interactive and discussion-oriented today.

Making the keynote presentation, Prof Rizos narrated the origin, evolution and proliferation of GNSS networks and how being a versatile positioning technology, they address many user segments. Dwelling on limitations of GNSS networks, Rizos said GNSS cannot magically solve the problems of indoor navigation, which requires augmentation for higher accuracy. To enable this, substantial ground-based infrastructures have been and are being established, he said.

After a brief intro on the GNSS networks, he talked about how GNSS CORS infrastructure is aiding science and society. He said permanent reference stations (CORS) are a significant civilian co-investment in GNSS capability. Though the precise positioning receivers are expensive, the economic benefits accrued from them are enormous.

He discussed the contribution of GNSS to geodesy and said that GNSS is now a tool so interwoven into all geodetic practices. GNSS geodesy relies on national geodetic/survey organisations to fund the establishment and support modern scientific applications.
He said a variety of real time kinematic (RTK) services and business models are possible with these networks. He predicted that these networks will soon go from post process mode to real time, will address precision positioning markets, and act as catalyst for a new beginning by increasing a variety of RTK techniques and value-added services. He concluded saying that GNSS will increasingly be important for global change studies.

The number one requirement for reliability of GNSS networks is to have a good combination of accuracy, integrity and availability, declared Rod MacLeod, Regional Manager- South East Asia and Australia, NovAtel Inc. This reliability challenge can be achieved with an integrated GNSS and INS solution, he opined.

In spite of best efforts, availability of GNSS is limited. Though surveying and basic GIS are least affected applications, real time urban navigation, autonomous vehicles, and ground mobile mapping applications are most affected. The solution lies in combining GNSS with additional independent measurements to increase availability or add integrity as one of the system checks. Other options include having more constellations, image matching or have inertial measurement. According to Rod, the most robust solution is inertial measurement.

He said while GNSS provides accurate absolute position, INS provides accurate relative position. A deeply coupled integration of these can provide a blended solution to bridge through short periods of poor or no GNSS coverage. He then described SPAN, an integrated solution from NovAtel.

TOR, Yam Khoon, Associate Professor, Nanyang Tech University, Singapore, discussed a project done to monitor static and dynamic characteristic of tall building using GPS virtual reference station and seismic sensor data. Simon CW Kwok, Chief Land Sureyor, Land Department, Hong Kong special administrative area, detailed the experience in setting up Hong Kong Satellite positioning reference station network. Though the consumer market has not fully utilised various RTK services, he said it is important to create an environment for innovation which will ultimately improve the quality of life.

Victor Khoo, Senior Manager, Survey Services, SLA, discussed the unique project of SLA – SiReNt – which will help position Singapore for the future. SiReNT system was launched in September 2006 to provide homogeneous geographic ref frame for cadastral survey. This also aims to provide nation wide infrastructure to support differential GPS technique and to provide up to centimetre level accuracy and flexible and ready for integration. He then detailed how SiReNT is enabling precision positioning on demand.

SiReNT is enabling several application projects in Singapore like building DGPS systems for GIS data collection, DGPS systems for fleet management, structural deformation monitoring, determination of integrated water management, parks management, accident site mapping, real-time landslide mapping. He concluded saying SLA is making SiReNT a buoyant and self-reliant system and is promoting it well for its sustainable function.

Ahmad Fauzi bin Nordin – Deputy Director General of Survey and Mapping, JUPEM, Malaysia briefed about the Malaysia Real-time Kinematic GNSS network, his history and evolution into an active GPS network. MyRTNET was started in 2003 and began collecting data since 2003. It is being used for various applications like cadastral and mapping surveys, navigation, engineering, geodynamic and scientific studies and listed out the services offered by the network.

Wrapping up the session, Prof Rizos took the delegates on a trip of future reference systems and discussed the importance of having regional reference systems like AP-REF, AFREF etc. Though an unclear thought so far, he said a select group of APAC CORS stations can come together. A JAXA team has come up with a preliminary concept for multi-GNSS demo campaign, he said and wished more such campaigns be taken up.

Source : By our special correspondent