Technology can unearth mysteries of Henry Tang's 'underground palace'
Technology used in archaeological digs can provide answers on when the former chief secretary built an illegal 2,250 sq ft basement at his home
Will Henry Tang Ying-yen go to jail? The former chief secretary recently resurfaced to talk about the issue that torpedoed his bid to become Hong Kong's chief executive and could land him or his wife in prison: the illegally constructed 2,250 sq ft basement discovered at their home in February last year. The construction of the basement is now under investigation by the Buildings Department. Since then, of course, the uproar over illegal structures has grown deafening with the discovery of six in Chief Executive Leung Chun-ying's house on The Peak.
While Leung's illegal additions are fairly straightforward cases of unauthorised building, the Tangs' "underground palace" involves more elaborate detective work to determine to what extent they broke the law.
If the basement was built after the certificate of occupancy was issued in 2007, they would only be liable for the civil offence of illegal construction, the same offence as Leung's. But if the basement was built at the same time as the house prior to the issuance of the certificate of occupancy in 2007, and the existence of the basement was not revealed in their building plan for the house, they could be charged with the criminal offence of falsifying information.
The technology exists to dig out, so to speak, the evidence.
Indeed, searching for subterranean structures is a time-honoured pursuit - by tomb robbers raiding the burial chambers of pharaohs in Egypt and emperors in China, intelligence agencies trying to detect secret nuclear facilities in Iran and the archaeologists looking for the ruins of ancient cities. The techniques have evolved from long poles and pickaxes to state-of-the-art equipment that detects deeply hidden structures, even from outer space.
The lost city of Ubar in southern Oman, buried under desert sands between AD100 and AD400, was found by imaging radar on the space shuttle Endeavour in 1994. Archaeologists using remote imaging techniques discovered under a modern town in the northern Nile delta the ruins of Avaris, the capital of the Hyksos, who formed Egypt's 15th dynasty 3,500 years ago. Low-flying surveillance satellites have identified the location and other details of underground bunkers housing Iran's nuclear programme.
If subterranean structures can be detected and their composition examined from such distances, why not Tang's basement?
The two technologies now available essentially analyse signals emitted from any subsurface structure. Ground-penetrating radar uses electromagnetic radiation in the microwave band (UHF/VHF frequencies) of the radio spectrum to detect signals reflected from the structure.
A radar signal - an electromagnetic pulse - is directed into the ground. The structure underground will cause reflections that are picked up by a receiver. Ground-penetrating radar can locate a subsurface structure without damaging it, and can also detect changes in its materials, voids, cracks and other characteristics.
The second method is infrared energy pattern analysis (IR-EPA). This uses specialised cameras, similar to camcorders, to capture the infrared radiation emitted by a structure, or its "thermal condition", to produce live digital images. IR-EPA shows up the specific, signature energy patterns created by underground anomalies. Changes in the material in a structure and the geometry of the material influence the propagation of the heat flow, which is detected by an infrared camera.
How can these two technologies show whether the Tang basement was part of the original structure of the house or was added after the house was occupied?
The key is to compare the characteristics of the basement and the main house, and to examine the interface between the two parts of the building. If the two parts were built at the same time using the same materials, they would generate similar signals as measured by the ground-penetrating radar (the reflected radar signals) and the IR-EPA. There also would be no sudden change in the signals at the interface between the main house and the basement.
On the other hand, if the basement was added after the main house was built, even if the same materials were used, there will be different signatures in the reflected radar signals as well as the infrared radiation emissions. Moreover, the discontinuity in the materials and geometry between the basement and the main house will show up in changes in the signals emitted from the interface where the two parts of the building meet.
Of course, while the science is clear-cut, differences in the structures and their environments could produce ambiguous results.
Doubtless the Buildings Department is doing the obvious: physical inspection and forensic analysis of the basement to determine its age, materials and relationship with the main house. But is the department applying available technologies to come up with a comprehensive body of evidence? Is it preserving the integrity of the structure and being given the unfettered access that is essential for forensic and technical analysis?
Almost a year later, the simple but critical question remains unanswered: what did the Tangs do and when did they do it? Technology can help with the answer and put the Tangs out of their misery - or behind bars.
Tom Yam is a Hong Kong-based management consultant with a doctorate in electrical engineering and an MBA from the Wharton School, University of Pennsylvania. He has worked at AT&T, Ernst & Young and IBM