In Hong Kong, underground utility detection relies on two primary methods: electromagnetic detectors and ground penetrating radar (GPR).
Electromagnetic detectors function in two modes: passive and active. Passive mode detects signals emitted by metallic utilities, providing information on their alignment. Active mode, requiring a transmitter and sonda connected to the utility, reveals both the alignment and depth of metallic and non-metallic utilities. However, the depth limit for most commercially available electromagnetic detectors is around 3 meters.
Ground penetrating radar (GPR) offers a more comprehensive solution. By emitting radio waves and analyzing the reflections from buried utilities, GPR can accurately determine both the depth and alignment of both metallic and non-metallic utilities. This versatility makes it a powerful tool for underground mapping. However, the cost of GPR equipment and the complexity of data interpretation remain drawbacks.
As detailed in the LD, DSD 2000 reference, these two technologies offer distinct advantages and disadvantages, and the choice between them depends on the specific requirements of the underground utility detection project.