Mersa/Wadi Gawasis, Mission 2007-2008 - Kathryn A. Bard and Rodolfo Fattovich et alii

Mapping - A. D'Andrea, G. Iannone and S. Tillia

Mapping
S. Tilia

During the 2007-08 field season at Mersa/Wadi Gawasis, a number of tasks were planned concerning both the further definition of the area's topography and the documentation of the caves. In order to carry out the latter, it was decided to acquire surface data through the use of a new generation laser scanner. The topographer's duty in this case, was to geo-reference the laser scan point clouds and to offer reference points where the lack of point cloud overlap created difficulties in their joining (e.g., narrow passages between caves and at entrances). This was accomplished through the acquisition of point cloud registration markers using a total station. The coordinates assigned in this way to the markers were coherent with the site's chosen reference system (WGS84 UTM).
Along with the collaboration with the laser scanning team, assistance was also given to the field archaeologists in order to position every excavation trench created during the fieldwork. In particular, the surveying of a number of points enabled a better documentation of the features which were brought to light in WG 55-56.
Another task was the positioning of a series of test pits excavated along a number of transects crossing the wadi bed. The goal of these pits was to determine the ancient coast lines running deeper into the wadi and thus closer to the archaeological area. In fact, a series of trenches excavated just southeast of the main terrace had brought to light evidence of a possible beach environment. In this case it was important to assess the altimetry of this particular area also in relation to the test pit's geological stratigraphy. The positioning of these pits was carried out by taking their elevation (relative to sea level) into account.
The final phase of the topographical fieldwork was the acquisition of elevation points in the coastal area where there were tumuli/shrines along the northern side of Mersa Gawasis. These measurements will enable further advancement of the general topographic map of the area. In order to complete this elevation map, the northern coastline of Mersa Gawasis still needs to be surveyed. In addition, it would be advisable to complete the topography by surveying the southern bank of Mersa Gawasis where at least one more tumulus has been located.


Laserscanning Technology Application
A. D'Andrea and G. Iannone

Introduction
In the 2007-08 field season laserscanning technology was applied with the support of the Centro Interdipartimentale di Servizi di Archaeologia (CISA), UNO, Naples, to generate a detailed 3-D model of the western terrace wall, where Caves 2-5 were located, and the inside of Caves 2 and 3, in order to provide a proper reconstruction and plan of these caves, as well as a more precise assessment of the preservation and stability of these features for a future consolidation project.[2] An Imager 5005 3D scanner manufactured by Zoller & Frolich was used (Figure 10). The software JRC 3D Reconstructor was used to generate 3D reconstruction of the images.

Procedure
The procedure required four days of fieldwork and four weeks of analysis and elaboration of the scanned images. Targets were applied to the outside and inside walls of the caves, paying much attention to place the targets in intermediate locations between the different surfaces in order to obtain one geometric reconstruction of all shots. On the whole, 15 shots were made (5 for the outside coral wall, 4 in Cave 2, and 6 in Cave 3). Each target was also mapped with TLS to georeference the whole reconstruction. Finally, digital photos of the surfaces were used to calibrate the images produced with the scanner.
The last phase of the data elaboration was a 3D model in movement in order to show the plan and profiles of the structures from different perspectives (Figures 11, 12, 13).

Results
A relevant result is the elaboration of simulated horizontal and vertical cross plans, which can provide useful information for future work in the caves.

Pleases find attached .pdf files with the full report and the related figures