In August 2017 the Singapore Land Authority (SLA) released a standard and specifications for the procedure and practice of utility surveying in Singapore. The standard specifies the data that should be captured for new underground utilities including telecommunication, sewerage, water supply, electric power, gas, and drainage. It specifies that after installing utilities and prior to filling the trenches an as-built survey should be performed by a registered surveyor to capture the location of the utilities with horizontal accuracy of ±100mm and vertical accuracy of ±100mm. It specifies that the survey equipment to be used should be a total station, GNSS Real Time Kinematic (RTK), or 3D Laser Scanning.
This standard is not mandated by the Singapore Government but is intended to provide a baseline to be incorporated in construction contracts. Since 85% of land is owned by the Singapore government, if a major government agency such as the Urban Redevelopment Authority (URA) routinely incorporated this standard in its contracts as part of standard procurement practice, it would effectively become a de facto mandate.
In addition to location, the standard also defines the attribute information to be captured. For example, for an electric power cable, the standard specifies that x,y,z should be surveyed at 20 meter intervals for a straight line cable and more frequently for a curving cable. In addition, height, width, number of columns, number of rows, number of ducts, number of cables and quality level should also be captured. The quality standard used in Singapore is; 1) ±100mm, 2) ±300mm, 3) ±500mm, 4) Unknown accuracy and 5) Trenchless method. In Singapore most underground utility work is open trench, although there is some trenchless which requires gyro surveying.
The standard does not specify format or what is to be done with the as-built information. Currently in Singapore there is nothing in place to require sharing of information about the underground like Netherland's BRO or the British National Underground Asset Registry (NUAR) project. But there is a Digital Underground project underway to create an ecosystem for a digital twin of the underground as part of the Mapping Singapore in 3D project. The digital underground project was initiated by the Singapore Land Authority with the the support of the Urban Redevelopment Authority. The standard for underground utility surveying would create a basic data model for sharing information about underground utilities.
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