British scientists are hoping to develop a portable ‘gravimeter’, which would allow councils to test for utilities under streets before major works begin.
The Times reports that the device would drop a super-cooled atom into a vacuum then monitor it’s progress with a laser to measure the minute fluctuations in the earth’s magnetic field caused by underground pipes and cables.
Birmingham University’s prof. Kai Bongs told the paper that less than 50% of urban infrastructure is noted on council maps and suggested that the gravimeter could save billions a year.
Surveyor has reported on tram schemes such as Nottingham’s Express Transit, which ran into heavy delays and extra costs due to unforeseen utilities beneath the street.
Working with the National Physical Laboratory, Prof Bongs suggested that by utilising quantum mechanical techniques the team have come close to developing something portable that could spot tiny changes in density to map beneath the ground.
Using laser cooling, scientists can control a single atom and isolate it in a vacuum. Gravity can then be measured by monitoring its effect on a single atom, helping reveal piping for instance as the ground becomes less dense.
To avoid the difficulties caused by a device this sensitive, prof. Bongs suggested a solution lies in having two different ‘clouds’ of atoms, a distance apart, and using the paired readings to cancel out non-gravitational effects.
Highlighting the limitations of other subterranean mapping methods, Prof Bongs said: ‘With radar it depends very much on ground conditions. If it is wet you can’t penetrate very far. For things that are not conducting, like plastic pipes, you also don’t get a large electromagnetic signal.’