Mapping Mediterranean origins in 3D

Before the Greeks

From the latin, medius ‘middle’ and terra ‘land’, the Mediterranean Sea, as in the original sense, is the "sea in the middle of the earth.” Intersecting at the pass between the East to the West, the 850-metre long Mediterranean island of Motya holds the key to many ancient history secrets of the region. This Sicilian island is, therefore, a strategic point to study the history, exchange, trade and cultural mixing that converged in this area, the bottle-neck of the “Middle Sea.”

More than 3,000 years ago, Phoenicians spread west in the Mediterranean reaching Sicily and settled in the island of Motya. Recent archaeological investigations, carried out by the Sapienza University, discovered the earliest Phoenician landing berth in Motya dates back to the 8^th century BC. Phoenicians lived all around Sicily and gathered in Motya after the Greeks arrived in vast number.

Led by Prof. Lorenzo Nigro, experts from Sapienza University have studied for years, together with the Superintendence of Trapani and with the support of Whitaker Foundation, Palermo, this unique archaeological site to make accurate assumptions on the people, cultures and civilisations that intersected in the island. Based on the ruins and remains that have been unveiled, producing maps and 3D models of what meets and escapes the eye is helping the team to better understand and share the past of this region.

Blending technologies to document cultural heritage

The Motya 3D Model Pilot Project created 3D models of the archaeological findings and the excavation sites to support the archaeological research, both in the field and in the office. The specific goals of this survey campaign were to create the first complete 3D model of the entire island of Motya and the 3D models of six relevant archaeological areas.

Most survey operations are time-limited; in archaeology, this is no exception. To generate accurate 3D models and capture the survey data quickly to not interrupt the archaeological excavations and the tourist visits, Prof. Mattia Crespi and Dr. Roberta Ravanelli from the Geodesy and Geomatics Division of the Sapienza University of Rome joined the team. To do the survey, the team relied on Leica Geosystems’ Geographic Information System (GIS) collectors, Unmanned Aerial Vehicle (UAV) systems, GIS application software and HxGN SmartNet satellite positioning service.

“We had the support of a Leica Geosystems team in the field, which was directly involved with the data collection. We are very pleased with the products and the support of the personnel. The data acquired in the field allowed us to produce high quality 3D models, with an accuracy ranging from a few millimetres to a few centimetres, of the six archaeological areas, including some details within them and the entire island,” said Crespi.

Images and GPS coordinates were collected to reconstruct the 3D model of the Motya island. The aerial imagery provided by the HxGN Content Program was used as a basemap for the GNSS measurements. The Leica Zeno 20 GIS data collector was used together with Leica Zeno GG04 plus Smart Antenna to collect the positions of the ground control points. With the coordinates of the control points, the team in the field could save further info, such as pictures, notes and IDs using the Leica Zeno Mobile data collection software. The measured control points were then exported as ASCII files to be used for the photogrammetric processing of the images captured by the UAV.

Despite the fierce winds, the two UAVs perfectly captured the images needed for the photogrammetric processing. Special attention was paid to the six relevant archaeological areas and the coastline, needed to compute the sea-level projections. HxGN SmartNet was finally used to get the required RTK corrections.

All raw spatial data, including the digital images acquired from the UAVs and on the ground, the GNSS data and the surveying measurements were collected and processed through Agisoft software, to create the 3D model of the entire mythic island and of single excavation sites and relevant archaeological finds.

Last but not least, the 3D model of the entire island will also enable, for the first time and in detail, the study of the effects of the eustatism (sea level rise) on the whole archaeological area by experts of the Istituto Nazionale di Geofisica e Vulcanologia, Rome, Italy.

Merging archaeology with geomatics

Collecting, analysing and interpreting georeferenced data is an area where experts from multiple disciplines converge. Referenced bases, maps and 3D models are key for all professionals in the archaeological realm. Cultural heritage sites can be documented with a variety of technologies:

• Mobile mapping
• Asset collection and management
• 3D laser scanning
• Photogrammetry
• Remote sensing
• Airborne sensors and UAVs
• GNSS
• Utility detection
• Measurement software
• Cloud-based dynamic maps.

“The new needs asked by the archaeological research and the new methodological and technological solutions offered by geomatics remarkably boosted the interaction between two disciplines belonging to different and apparently distant areas during the last decade,” concluded Nigro.