Quake alert among many uses for improved GPS

The Straits Times, Science

27 September 2008

BY MEASURING tiny building movements following earthquake aftershocks, a locally-developed system can warn its occupants when they are in danger.

The Singapore Land Authority (SLA) is hoping its new positioning system will be a better gauge of when an evacuation is necessary.

It is working with the Nanyang Technological University (NTU) and a commercial building to test an enhanced version of the global positioning system (GPS), which the SLA calls the Singapore Satellite Positioning Reference Network (SIReNT).

The two-year-old system is able to pick up building movements as tiny as 1mm to 2mm and this information can be sent to the building owner in real time, said Dr Victor Khoo, who helped to develop the system.

 SiReNT is a more refined version of the satellite navigation system GPS, which drivers have in their cars to help them get from one place to another.

While helpful in navigation, GPS is not always accurate or reliable and has a margin of error of about 6m to 11m, say experts.

SiReNT narrows the margin of error by making use of five signal receivers in fixed locations around the island.

The coordinates of these locations are known, so when GPS signals from satellites in the sky hit these receivers, calculations are done to get more precise coordinates of a user's position, to the nearest 50cm, said Dr Khoo, who is with SLA's survey services team.

This, in turn, allows even tiny building movements to be tracked.

In Singapore, the national water agency PUB, the Land Transport Authority and SP PowerGrid already subscribe to the system.

One use is to pinpoint underground pipes and cables more accurately. Said Dr Khoo :  "Time and money can then be saved as the workers don't have to keep digging larger and more holes in search of the pipes, in order to repair or check them."

Tracking unhealthy trees or lamp posts which need repair can also be done in the same manner, he added.

Monitoring climate change is another use of the more refined GPS.

The SLA is working with the National University of Singapore's Tropical Marine Science Institute to use SiReNT to map out coordinates of coastlines, to check for coastal erosion along the East Coast.

Research fellow Durai Raju, 42, said that with this system, a permanent station could be set up to log data continuously. "Previously, we had to go down personally to survey the coastline. If it rained, we couldn't do any work at all," he said.

Dr Khoo said that data from SiReNT will even be used by the United States' National Aeronautics and Space Administration (NASA), which is collecting data from various regions in the world to calibrate satellite images more accurately for scientific use.