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From the eyes in space
Photos: Courtesy National Remote Sensing Agency, Hyderabad
Technological help: CARTOSAT-1 image shows Emperor Qin’s Mausoleum (left) and the Terracotta Museum (right); Figure 2 from CARTOSAT-2 shows Emperor Qin’s Mausoleum (the innermost square).
With this kind of scattered treasure, one can think of using tools that will allow us to look at and survey swaths of several kilometres at once. This can be achieved with the help of “eyes” in space.
Space-based remote sensing has made this possible by producing imagery of multi spatial and spectral resolution. Figure 1 is an image taken by India’s high resolution remote sensing satellite CARTOSAT-1 with a spatial resolution of 2.5m on March 27, 2007, which gives an overall view of the whole area showing the mausoleum and the Terracotta Museum.
The square pyramid of the mausoleum can be easily identified on the image because of its shape and the uniform vegetative cover over the pyramid. Identifying such uniform coloured geometric shapes could be used as keys to find more. The protective outer wall, which surrounds the pyramid in a rectangular shape with length around 2km, width around 1km and the inner wall, can be identified as linear features in 1m spatial resolution CARTOSAT-2 imagery (See Fig. 3 and 4).
CARTOSAT-2 is the latest member of the ISRO’s remote sensing constellation. These features are preserved on the ground as field boundaries or footpaths and roads, an example for a historical setting altering the landscape. NRSA Hyderabad programmed the acquisition of CARTOSAT-2 image on September 20, 2007 specifically for this study.
The presence of artefacts and construction underground would apply a stress on the vegetation that grows over it. This would affect the spectral reflectance of the area and in turn would result in that area becoming easily identifiable in contrast with its surrounding.
At a future date using stereo images and generating Digital Elevation Models (DEM), pyramid-like three dimensional shapes would stand out as anomalies in between the natural terrain undulations. Further more, active remote sensors such as radar will be able to penetrate the land surface and vegetation. A radar scan of this whole area would throw light on the hidden treasures of the Qin dynasty. The enigmatic ancients are calling out for modern technology and asking for them to be rediscovered and better understood.
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