This article is from the May 2002 The Mexico File
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High Tech Meets Low Tech in the Pyramids
by Robert B. Simmonds
Archaeologist Jürg Leckebusch of the Zurich cantonal archaeology office specializes in using and interpreting ground penetrating radar (GPR). He hopes to shed light on the Maya civilization of Mexico using computer modeling techniques he has successfully used at the Roman city of Augusta Raurica near Basel, Switzerland. He will take part in a project at Chichen Itza, a UNESCO World Heritage Site, in the Yucatan.
Chichen Itza contains some of the most impressive ruins of the Maya civilization. Most experts agree that it was settled for the first time between 550 and 900 AD. Leckebusch will investigate an area near the Castillo pyramid, which is also known as the pyramid of Kukulcan.
In the central part of Chichen Itza, the natives created a large flat plaza for ritual purposes and processions. They covered the bedrock with four meters of fill and then paved it over with a sort of plaster concrete. Archaeologists have already discovered what seems to be the foundations of buildings within the fill – as well as an unexplained trench about ten or fifteen meters from the west side of the pyramid. This trench, which runs in a north-south direction, is at least 100 meters long and five meters wide. In places it goes down into the bedrock, and it was dug after the plaza was completed and then refilled.
The trench is a mystery. One notion about its origins is that it may have been used as access to a chamber under the pyramid – perhaps a burial chamber or a chamber used for ritual purposes. Or perhaps the trench was used only once when they buried a later king of Chichen Itza. It is hoped that Leckebusch’s GPR will generate a 3-D model to shed some light on the use of the trench. If needed, an excavation could then follow.
Leckebusch’s method involves a contraption that he designed himself, and which is much like a drivable lawnmower on which he has installed his electronic equipment. With this device, he can survey up to a hectare per day, while excavating an area the size of a hectare would take at least ten years. In contrast, obtaining a 3-D computer-modeled image of the subsurface area takes only a few weeks. GPR can reveal pillars, water channels, entrances and other large objects. It does not capture smaller objects like ceramics. So it has its limitations. Excavations can answer questions involving exact dates or the exact relationship between structures.
It is particularly important at a World Heritage Site to avoid digging when it is not necessary, not to mention the funding involved in a major excavation. GPR will help archaeologists determine where to dig if they need to – and what to leave intact.