ASM
Inside SiReNT
The Singapore Land Authority’s SiReNT
GPS reference system is operational, according to Victor Khoo, the manager of survey services at SLA.
The uptake by the nation’s cadastral surveyors may be somewhat disappointing, Khoo says, but eventually, that may not matter much. Plans to make SiReNT an integral part of the island nation’s traffic management system will provide all the justification, and revenue, that is required.
Singapore has been dabbling in GPS augmentation since 1999. At that time a team from the Nanyang Technical University and the University of New South Wales developed a nationwide correction system based on multiple reference stations.
Eventually, this system was abandoned, but the experience gained by both teams led to the establishment of the Sydnet system in Sydney, and SiReNT in Singapore.
SiReNT works in three modes: differential correction to any one of its five base stations, Real Time Kinematic – which enables sub-metre positioning on the move – and post processing, requiring an internet connection.
Post processing is the most accurate. Khoo says that with one hour’s occupancy, the position is sufficiently accurate to conform to Singapore’s requirements for legal traceability of position.
However, less than half of local land surveyors have taken up the system. Khoo says the price – $1200 per annum or 50c/min – may be to blame, rather than the innate conservatism of surveyors.
The most interesting part of the SiReNT project is that it uses GPRS to communicate its RTK corrections. GPRS gives internet connectivity over a standard GSM telephone connection.
This is already in demand for machine guidance applications, says Julia Tan, the operations and marketing manager at GPS Lands, the local Trimble distributor. She says it may also provide a communications channel for information from traffic management authorities.
Authorities in Singapore are considering the idea of moving to a pay-per-kilometre charging system to replace an annual usage fee. GNSS would track the movement of vehicles and fees would be based on the distance travelled.
Such a system could also be tied to traffic management systems, enabling drivers to track congestion, so they can delay travel, or use alternative routes.
