GEOCODING TREASURE-MAPS IN THE SOUTHERN TAKLAMAKAN DESERT

by Dr. Pamela Logan (October 15, 1997 Dunhuang)

Picture me, the diligent scientist, in the front seat of a jeep, my lap buried under maps, satellite photos, notebook, pencils, compass, and a Magellan GPS receiver. The jeep is barreling crazily down a bumpy dirt road; the driver, Muhammad Amin, is dodging goats, pot-holes and children while I attempt not only to keep my papers together on my lap, but also to track our progress on several different charts simultaneously. Just in time, amid a flurry of violent vehicle oscillations and fluttering papers, I manage to spot a landmark--a small swamp beside the road--and shout "STOP!"

By now Amin does not need my English translated into Uighur. He is used to my strange interest in rivers, street intersections, and bends in the highway. I am looking at the landscape not with the eyes of a geographer or archeologist; instead I imagine that I'm a microwave transceiver orbiting the earth high overhead, an advanced remote sensing device that sends outbursts of microwave radiation and then senses energy that is reflected back, assembling the signal into a two-dimensional image not unlike a photograph.

A microwave transceiver sees the earth's surface not as a collection of colors, light and dark, but as texture: vegetation that reflects cross-polarized radiation but is otherwise invisible, sand that appears translucent and reveals what's buried beneath the surface, bright white concrete, and surface water that sends back scarcely any energy at all.

Some of the papers on my lap are images captured in 1994 by SIR-C, a synthetic aperture radar system carried on board Space Shuttle Endeavor. In "the deep desert," the Taklamakan's torrid interior where few but archeologists and oil explorers dare to travel, the radar's sand-penetrating properties turn up blips on the images that are undoubtedly buried Silk Road ruins. Such ruins, archeologists have found, are repositories of murals, statuary, texts, and the implements of daily life. They are crucial clues about commerce and cultural exchange in Asia's distant past.

Thus, the radar images are virtual treasure maps -- but they have one important problem. NASA did not acquire reliable position information with the images, so the latitude and longitude of my buried treasure is uncertain. In the middle of an ocean of blowing sand there are no fixed features suitable for navigation. My job here at the desert's edge is to acquire some positional information that can be extrapolated out into the dunes. With the radar images thus geocoded, subsequent expeditions will be able to travel into the desert to uncover sand-buried cities that have been lost for a thousand years.

My journey began in Khotan, once a flourishing and important city-state of the southern Silk Road. Khotan is rich with agricultural wealth generated by channeling two large rivers that flow down from the Kunlun Mountains. Like other oasis cities of the region, in Khotan they grow wheat, rice, corn, cotton, grapes, peaches, and melons. Shepherds graze their flocks at the community's fringe. Once Khotan was wealthy from Silk Road trade that passed through the city, but that was centuries ago, and today's regional economics hinges not on trade but on the oil reserves lying under the desert sands. No major petroleum deposits have been found near Khotan, and so the city is a backwater, little changed from my visit four years ago. It's still a reservoir of pure Uighur culture where courtyards are shaded by grape arbors, people are devout Muslims, and little Mandarin is heard.

Further east, in the town of Minfeng (known as Niya to Uighurs), I see the fruits of the oil boom: streets widened and paved, and a new hotel constructed by the Italian company Agippe. Even more remarkable, there is am new highway going north, straight through the Taklamakan's arid interior. The changes confound my work, and I am constantly having to ask whether this road or that bridge is new since 1994 when the radar images were acquired. In Minfeng's shady suburbs, however, I found that the grid of long, straight avenues that define agricultural land-holdings is virtually unchanged. With water in increasingly short supply, little new land can be brought under cultivation.

At every town along the route, I bring out a radar images that I laboriously processed and enhanced using computers at NASA's Jet Propulsion Laboratory back home. The images I have brought with me are but a tiny fraction of the data acquired in the region. They are in the form of image strips that can be overlapped to form a mosaic. It is mind-bogging to think how many archeological finds might result from just a few minutes of data gathering. With such huge potential for discovery, I know I'll be returning to this area many times in the years ahead.


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