|
|
|
June 2004 |
Documentation of Sisupalgarh fortress
Column structures are common in early historic India. But rarer are those at Sisupalgarh which have medallions on four sides at the middle. Such columns are special, but do exist in major monuments at Bharhut and Sanchi, as well as in the Buddhist caves at Khandagiri and Udayagiri in Bhubaneshwar. At the top of the list of questions stands the question: What was the function of the column structure in Sisupalgarh?
The team was also curious to know as to how much of the monument had survived from antiquity or from the first published photo of 1949. In any case, given the importance of the monument, it was imperative to record it and provide the responsible authorities with the documentation.
This long-neglected monument is difficult to record properly for the purposes of a researcher and a cultural resource manager. It is simple to make single photos, but these contain no real spatial information. One would like to know if Area D's preservation is stable and what exactly the site looks like.
It seemed best to record and evaluate by means of a laser scanner. This solution is superior to any other recording technique. Accurate hand drawings are very time consuming and can only be produced when scaffoldings or platforms are available. Stereophotogrammetric images could have been obtained easily, but the usual results in the form of CAD data would make it necessary to reduce the spatial structures to line drawings which are not adequate in this case since the structures do not show any defined sharp edges.
The scanning of the monument was undertaken very quickly in early December of 2003. First, the site was cleared of bush. Given the late and heavy rains, there was more vegetation than expected. A Leica HDS 2500 (also known as Cyrax 2500), owned by the University of Applied Sciences in Mainz, Germany, was used.
Tests at Mainz had proven an accuracy of about 2 mm for the 3D points recorded by this instrument (Boehler et. al. 2004). 20 different single scans were necessary to get a complete coverage of the columns.
The surrounding topography could be recorded together with the columns in the same scans. Since the scanning window is limited to 40° by 40°, the scanner was set up relatively far from the scene. Luckily, the relatively open site allowed this setup. The HDS 2500 can be used for ranges of 50 m and more without much loss of accuracy. Therefore, distances up to 63 m were used.
Fig 2 Sisupalgarh, Area D. Shaded digital elevation model from laser scanner data showing column locations
Fig 3 Sisupalgarh, Area D. Perspective view generated from laser scanner data
Fig 4 Sisupalgarh, detail of Area D. Perspective view generated from laser scanner data
|
|
|
|
|
|
|
