LIDAR-supported archaeological prospection

Systematic detection of archaeological sites in wooldland is one of the unsolved problems in arcaheological prospetion. Even aerial archaeology and fieldwalking in woodland get to their limits. Therefore, there is - not only in Austria - a big deficit in the archaeological prospection of woodlands, which poses large problems when trying to analyse archaeological landscapes. Over the past few years, however, a method has been developed that can help to solve the problems with the recognition and measurement of above ground, preserved sites in forested areas. It has to do with LIDAR (Light Direction and Ranging), an airborne laser scanner that produces high precision terrain models even in woodland. Using these terrain models, archaeological traces can be detected and interpreted comparatively easy. The goal of the requested project is to explore the potential of LIDAR for Archaeological Prospection in a densely forested area; specifically, to evaluate an approx. 190 sq km forest area within the Leitha mountain range in an archaeological case study. The area to be examined was selected with the expectation of making an important supplemental contribution to the archaeological information that will emerge from the FWF supported landscape- archaeological project "The Celts in the Hinterland of Carnuntum". In the course of the proposed project, a systematic record of all sites in the Leitha mountain range should be created through the employment of LIDAR and Aerial Archaeology. Selected sites should be measured terrestrially and used as test surfaces for the tuning and calibration of filter parameters, as well as for evaluation of the accuracy of the LIDAR data function. Structures recognized on this basis are then to be archaeologically verified by targeted field surveys. Together with the results from the Aerial Archaeology and the field surveys, an evaluation of the LIDAR data should be conducted. By integration of the data into the existing archaeological landscapes of the adjacent areas, we expect new realizations about the overall archaeological picture, as well as to settlement and communication patterns in the Leitha mountain range. Thus, it is ensured that the study will be conducted using an innovative method of research within a logical framework and that results that can be evaluated directly will be provided for the regional archaeological research.

The goal of the requested project was to explore the potential of airborne laserscanning (ALS) for archaeological prospection in a densely forested area; specifically, to evaluate an approx. 190 sq km forest area within the Leitha mountain range in an archaeological case study. Forests can be regarded as an important archive of past cultural landscapes. Archaeological sites and traces are in many cases still visible in relief. Systematic detection of these archaeological sites is, however, one of the unsolved problems in archaeological prospection. Even aerial archaeology and field inspection in woodland get to their limits. Therefore, there is - not only in Austria - a deficit in the archaeological prospection of woodlands, which poses large problems when trying to analyse archaeological landscapes. Over the past few years, a method has been developed that can help to solve the problems with the recognition and measurement of above ground, preserved sites in forested areas: ALS. A laser scanner is usually mounted below an aeroplane or helicopter, where it emits short infrared pulses (between 30.000 and 200.000 per second) towards the earth`s surface into different directions across the flight path. Each pulse will result in one or more echoes, where the last echo is typically returned from the ground surface. The case study was designed to investigate the potential of ALS for systematic large scale archaeological prospection. The 190 sq km large forested area of the Leithagebirge south of Vienna was scanned. Using only the last echoes and after applying special filter techniques, most of the forest canopy and brushwood covering the archaeological features could be removed. The resulting digital terrain model shows a detailed map of the topography with even faint archaeological structures under the forest canopy and therefore clearly demonstrates the potential of full-waveform ALS for archaeological prospection of forested areas. Using the ALS data of the total area, a GIS-based systematic record of all sites in the Leithagebirge was created. Structures recognized on this basis were archaeologically verified by targeted field surveys. Due to its potential to penetrate vegetated areas, ALS is becoming an increased importance in the field of documentation and preservation of cultural heritage. The results of the project will hopefully help archaeologists to better understand past landscapes. In that way, it can also enhance local understanding of cultural heritage.