Archaeological Surveying of Subarctic and Arctic Landscapes: Comparing the Performance of Airborne Laser Scanning and Remote Sensing Image Data

Abstract

What can remote sensing contribute to archaeological surveying in subarctic and arctic landscapes? The pros and cons of remote sensing data vary as do areas of utilization and methodological approaches. We assessed the applicability of remote sensing for archaeological surveying of northern landscapes using airborne laser scanning (LiDAR) and satellite and aerial images to map archaeological features as a basis for a) assessing the pros and cons of the different approaches and b) assessing the potential detection rate of remote sensing. Interpretation of images and a LiDAR-based bare-earth digital terrain model (DTM) was based on visual analyses aided by processing and visualizing techniques. 368 features were identified in the aerial images, 437 in the satellite images and 1186 in the DTM. LiDAR yielded the better result, especially for hunting pits. Image data proved suitable for dwellings and settlement sites. Feature characteristics proved a key factor for detectability, both in LiDAR and image data. This study has shown that LiDAR and remote sensing image data are highly applicable for archaeological surveying in northern landscapes. It showed that a multi-sensor approach contributes to high detection rates. Our results have improved the inventory of archaeological sites in a non-destructive and minimally invasive manner.

Detecting Archaeological Features with Airborne Laser Scanning in the Alpine Tundra of Sápmi, Northern Finland

“…As suggested by the near doubling of the known archaeological features in the case study area in our initial exploratory analyses, the wider utilization of ALS-5p data in the upcoming years will likely produce thousands of new sites and features that need to be checked in the field, e.g., [22]. One thing that needs to be taken into account in the future is that this development can easily skew the known and protected archaeological sites towards localities with features visible in the DEMs, at the expense of, for example, prehistoric habitation sites with few or no aboveground structures.…”

“…However, this open landscape is often covered by knee-high or lower dwarf birch, willow, and heather shrub, that often effectively hides the archaeological features. Alongside the ALS analyses, we assessed the visibility of the features in the NLS natural color (red-greenblue) and color-infrared orthophotos (NIR-Red-Green) with 0.5-m resolution [20] ( [22] for northern Norway). In Figure 5, a small, remote German Second World War military outpost situated at Hirvasvuohppi on the Norwegian border (case study area 3) is illustrated as an example of the different datasets.…”

“…Visual analysis is always subjective and dependent on, for instance, the experience of the observer [22]. Therefore, we are also testing different semi-automated feature detection methods based on machine learning (ML) and deep learning (DL) approaches to computer vision with the ALS-5p data [29].…”

“…Number of archaeological features in each case study area before and after the exploratory analysis of ALS-5p data (numbers of the previously registered sites based on the Finnish Heritage Agency (FHA) and the Project Sturmbock (PS) data; "Other sites" are Stone Age and Iron Age habitation and find localities), and the percentage of total features that are visible in the orthophotos (both natural and false-color), and the percentage of how many were detected by the used U-Net detectors D1-3. Thuestad and others [22] have noted on the Norwegian side of Sápmi that multispectral images, especially including the near infrared (NIR) bands, appear promising for locating settlement sites with turf hut foundations. Even centuries-old habitation has enhanced the underlying soils which impacts the vegetation cover and composition, e.g., [38,39].…”

Revealing Archaeological Sites under Mediterranean Forest Canopy Using LiDAR: El Viandar Castle (husum) in El Hoyo (Belmez-Córdoba, Spain)

“…There is currently a multitude of research being performed in Europe that uses LiDAR. For example, in Norway, LiDAR has been implemented (in some cases even working with the use of semi-automatic detection techniques, thanks to the use of CultSearcher software) in arctic and subarctic areas with excellent results; a total of 1186 pieces of archaeological evidence has been discovered so far [20] (p. 17). In the Istrian Peninsula, both in Croatia and Slovenia, hillforts dating from the Bronze and Iron Ages have been found [21] (p. 6) [22] (pp.…”