From pixel to mesh: accurate and straightforward 3D documentation of cultural heritage from the Cres/Lošinj archipelago

Most people like 3D visualizations. Whether it is in movies, holograms or games, 3D (literally) adds an extra dimension to conventional pictures. However, 3D data and their visualizations can also have scientic archaeological benets: they are crucial in removing relief distortions from photographs, facilitate the interpretation of an object or just support the aspiration to document archaeology as exhaustively as possible. Since archaeology is essentially a spatial discipline, the recording of the spatial data component is in most cases of the utmost importance to perform scientic archaeological research. For complex sites and precious artefacts, this can be a di€cult, time-consuming and very expensive operation. In this contribution, it is shown how a straightforward and cost-eective hard- and software combination is used to accurately document and inventory some of the cultural heritage of the Cres/Lošinj archipelago in three or four dimensions. First, standard photographs are acquired from the site or object under study. Secondly, the resulting image collection is processed with some recent advances in computer technology and so-called Structure from Motion (SfM) algorithms, which are known for their ability to reconstruct a sparse point cloud of scenes that were imaged by a series of overlapping photographs. When complemented by multi-view stereo matching algorithms, detailed 3D models can be built from such photo collections in a fully automated way. Moreover, the software packages implementing these tools are available for free or at very low-cost. Using a mixture of archaeological case studies, it will be shown that those computer vision applications produce excellent results from archaeological imagery with little eort needed. Besides serving the purpose of a pleasing 3D visualization for virtual display or publications, the 3D output additionally allows to extract accurate metric information about the archaeology under study (from single artefacts to entire landscapes)

Airborne laser bathymetry for documentation of submerged archaeological sites in shallow water

Knowledge of underwater topography is essential to the understanding of the organisation and distribution of archaeological sites along and in water bodies. Special attention has to be paid to intertidal and inshore zones where, due to sea-level rise, coastlines have changed and many former coastal sites are now submerged in shallow water. Mapping the detailed inshore topography is therefore important to reconstruct former coastlines, identify sunken archaeological structures and locate potential former harbour sites. However, until recently archaeology has lacked suitable methods to provide the required topographical data of shallow underwater bodies. Our research shows that airborne topo-bathymetric laser scanner systems are able to measure surfaces above and below the water table over large areas in high detail using very short and narrow green laser pulses, even revealing sunken archaeological structures in shallow water. Using an airborne laser scanner operating at a wavelength in the green visible spectrum (532 nm) two case study areas in different environmental settings (Kolone, Croatia, with clear sea water; Lake Keutschach, Austria, with turbid water) were scanned. In both cases, a digital model of the underwater topography with a planimetric resolution of a few decimeters was measured. While in the clear waters of Kolone penetration depth was up to 11 meters, turbid Lake Keutschach allowed only to document the upper 1.6 meters of its underwater topography. Our results demonstrate the potential of this technique to map submerged archaeological structures over large areas in high detail providing the possibility for systematic, large scale archaeological investigation of this environment

Airborne laser scanning and mediterranean environments: Croatian case studies

Coastal archaeology combines research in dierent environments: land surface, intertidal zone and sub-aquatic area. In consequence of the use of dierent archaeological methods for these dierent physical environments, there is a border between land and underwater zones. Archaeological topographic research is mainly con€ned to land surfaces and intertidal zones. is is unfortunate since knowledge of oshore underwater topography is essential to understand the organisation and distribution of sites on islands and coastal zones. Bridging the “border” between land and water in archaeological topographic research therefore requires the development of new archaeological documentation methods. e latest technique to combine terrestrial and underwater survey is Airborne Laser Bathymetry (ALB), which utilizes a green, water-penetrating laser and therefore can be applied for mapping surfaces under shallow water. Depending on the water clarity these systems can provide a detailed characterization of the underwater topography and even be used to prospect archaeological sites under shallow water. The presented paper will discuss the actual available ALB hardware and possibilities and limitations of the bathymetric sensor technique using sample data sets in Croatian case study areas in the northern Adriatic Sea. Maritime archaeological prospection is being tested in this area to provide high quality topographic mapping for later research questions regarding the rise and decline of settlements due to the changes in the shipbuilding, topography and navigational routes/natural harbours, and topography and harbour organisation

Confronting Complexity: Interpretation of a Dry Stone Walled Landscape on the Island of Cres, Croatia

Dry stone walls are a worldwide phenomenon that may shape entire regions. As a specific form of vernacular agro-pastoral practice, they are expressions of the culture and history of a region. Dry stone walls have recently received increased attention in Croatia, primarily due to research in landscape architecture and (historical) geography, though archaeological research on such remains is rare in part due to the challenges of undertaking such work in areas covered by dense evergreen maquis vegetation. In this paper, this type of landscape has been studied in detail for the first time using Airborne Laser Scanning (ALS) based digital feature models as a basis to articulate dynamic dry stone wall landscapes in a diachronic archaeological interpretation. Using a case study from the Mediterranean region of Punta Križa, Croatia, we show that what superficially appears to be a simple system of dry stone walls contains a wealth of information on a complex sequence of human activity. The systematic, detailed, and diachronic interpretation applies a transparent workflow that provides a tool for all those undertaking interpretative mappings of archaeological prospection datasets and has proved highly effective when working with ALS-derived visualizations. The capacity to develop spatio-temporal interpretation within the framework of GIS and a Harris Matrix is especially powerful and has the potential to change our image of any region. While the case study presented here deals with a small area in Croatia, the methods described have a broad application in any areas of complex landscape remains

Archaeological Ground Point Filtering of Airborne Laser Scan Derived Point-Clouds in a Difficult Mediterranean Environment

International audienc

Confronting Complexity: Interpretation of a Dry Stone Walled Landscape on the Island of Cres, Croatia

Dry stone walls are a worldwide phenomenon that may shape entire regions. As a specific form of vernacular agro-pastoral practice, they are expressions of the culture and history of a region. Dry stone walls have recently received increased attention in Croatia, primarily due to research in landscape architecture and (historical) geography, though archaeological research on such remains is rare in part due to the challenges of undertaking such work in areas covered by dense evergreen maquis vegetation. In this paper, this type of landscape has been studied in detail for the first time using Airborne Laser Scanning (ALS) based digital feature models as a basis to articulate dynamic dry stone wall landscapes in a diachronic archaeological interpretation. Using a case study from the Mediterranean region of Punta Križa, Croatia, we show that what superficially appears to be a simple system of dry stone walls contains a wealth of information on a complex sequence of human activity. The systematic, detailed, and diachronic interpretation applies a transparent workflow that provides a tool for all those undertaking interpretative mappings of archaeological prospection datasets and has proved highly effective when working with ALS-derived visualizations. The capacity to develop spatio-temporal interpretation within the framework of GIS and a Harris Matrix is especially powerful and has the potential to change our image of any region. While the case study presented here deals with a small area in Croatia, the methods described have a broad application in any areas of complex landscape remains