Airborne Laser Bathymetry – detecting and recording submerged archaeological sites from the air (original) (raw)
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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,
MULTI-WAVELENGTH AIRBORNE LASER SCANNING FOR ARCHAEOLOGICAL PROSPECTION
In: Pierre Grussenmeyer (Hg.): XXIV International CIPA Symposium 02–06 September 2013, Strasbourg, France. Göttingen: Copernicus Publications (ISPRS Archives, Volume XL-5/W2), S. 119–124.
Airborne laser scanning (ALS) is a widely used technique for the sampling of the earth’s surface. Next to the widely used geometric information current systems provide additional information about the signal strength of each echo. In order to utilize this information, radiometric calibration is essential. As a result physical observables that characterise the backscatter characteristic of the sensed surface are available. Due to the active illumination of the surfaces these values are independent of shadows caused by sunlight and due to the simultaneously recorded 3D information a single-channel true orthophoto can be directly estimated from the ALS data. By the combination of ALS data utilizing different laser wavelengths a multi-wavelength orthophoto of the scene can be generated. This contribution presents, next to the practical calibration workflow, the radiometric calibration results of the archaeological study site Carnuntum (Austria). The area has been surveyed at three different ALS wavelengths within a very short period of time. After the radiometric calibration of each single ALS wavelength (532nm, 1064nm and 1550nm) a multi-channel ALS orthophoto is derived. Subsequently, the radiometric calibration results of the single- and multi-wavelength ALS data are studied in respect to present archaeological features. Finally, these results are compared to the radiometric calibration results of an older ALS data acquisition campaign and to results of a systematic air photo interpretation.
The Application of Airborne Laser Scanning Systems in Archaeology: Moving beyond pretty pictures
The last decade, Airborne Laser Scanning (ALS) has proven to be a valuable tool for large-scale archaeological survey and mapping. It has especially revolutionized survey of densely forested areas, thanks to its ability to penetrate vegetation canopies. In recent years, research interest has moved beyond producing pretty pictures and has focused more on technological issues, e.g. the influence of point density and the benefits of full-waveform systems. Despite its potential, ALS also has limitations and the use of ALS data encounters challenges such as data filtering, classification and issues of interpretation. This review presents an overview of ALS technology for archaeological purposes, taking into account its benefits and limitations.
Towards an improved archaeological record through the use of airborne laser scanning
Space, Time and Place. 3rd International Conference on Remote Sensing in Archaeology (eds. M. Forte, S. Campana & C. Liuzza), 2010
The archaeological survey situation in Norway is rather uneven because it is largely settled farmland areas that have been the object of systematic survey campaigns. The archaeological records for forests and other outfield areas are very flawed, which makes proper cultural heritage management of these areas difficult. This paper outlines how airborne laser scanning (ALS) can contribute to an improvement in the situation. The advantages and challenges of using ALS are discussed and analysis of statistics from two completed ALS projects shows how large a percentage of the cultural remains it is possible to detect, to what degree we have succeeded with interpretation of the digital elevation models and the accuracy of remote sensing based documentation of the remains. The conclusion is that ALS can successfully be used to conduct remote sensing based surveys and documentation of cultural monuments and remains with competitive accuracy in all kinds of landscape. Forest and outfield areas which so far have been given little attention can now be surveyed efficiently and improve research and cultural heritage management.
Flights into the past: full-waveform airborne laser scanning data for archaeological investigation
Journal of Archaeological Science, 2011
Airborne Light Detection and Ranging (LiDAR) is a quite recent (mid-1990s) remote sensing technique used to measure terrain elevation. Recent studies have examined the possibility of using LiDAR in archaeological investigations to map and characterize earthworks, to capture features that may be indistinguishable on the ground and to aid the planning of archaeological excavation campaigns.Despite the great potential of LiDAR
In 2011 the ISCR (Rome), in the frame of the Project Restoring Underwater directed by Barbara Davidde Petriaggi, started to test Naumacos Laser Scann 1, designed by Gabriele Gomez de Ayala, in order to document the restoration of a room paved with opus sectile probably part of the Bath of Punta Epitaffio (Underwater Park of Baiae – Marine Protected Area, Naples). The experimentation conducted in Baiae by ISCR has shown the effectiveness of the Laser Scanner; this method also allowed to considerably reduce times and costs of underwater surveying. Moreover, the 3D relief obtained, has the characteristic of being geometrically (accuracy is sub-millimetric) and chromatically faithful to the reconstructed structure, as well as being exportable in various forms and usable in several contexts. From 2011 to 2013 the evolution of the instrument Naumacos Laser Scanner 3 was developed and tested in the restoration work of the Villa con ingresso a protiro, where three structures were documented in 3D (a paved with black and white mosaic decorated with hexagons and peltae, a very fragmentary black and white mosaic and a stone artefact. This paper shows the results of this documentation campaign and it underlines the prominent role in documentation and in museum display of Underwater Cultural Heritage played by the three-dimensional laser scanning survey. This technique also contributes to the increase of the value of scientific dissemination.
State of the art and applications in archaeological underwater 3D recording and mapping
Journal of Cultural Heritage, 2018
Since remote times, mankind has been bound to water bodies and evidence of human life from the very beginning hides under the water level, off the coasts, under shallow seas or deep oceans, but also inland water bodies of countries all around the world. Recording, documenting and, ultimately, protecting underwater cultural heritage is an obligation of mankind and dictated by international treaties like the Convention on the Protection of the Underwater Cultural Heritage that fosters and encourages the use of "non-destructive techniques and survey methods in preference over the recovery of objects". 3D digital surveying and mapping techniques represent an invaluable set of effective tools for reconnaissance, documentation, monitoring, but also public diffusion and awareness of underwater cultural heritage (UCH) assets. This paper presents an extensive review over the sensors and the methodologies used in archaeological underwater 3D recording and mapping together with relevant highlights of well renowned projects in 3D recording underwater.