Airborne LiDAR for the Detection of Archaeological Vegetation Marks Using Biomass as a Proxy

Abstract

In arable landscapes, the airborne detection of archaeological features is often reliant on using the properties of the vegetation cover as a proxy for sub-surface features in the soil. Under the right conditions, the formation of vegetation marks allows archaeologists to identify and interpret archaeological features. Using airborne Laser Scanning, based on the principles of Light Detection and Ranging (LiDAR) to detect these marks is challenging, particularly given the difficulties of resolving subtle changes in a low and homogeneous crop with these sensors. In this paper, an experimental approach is adopted to explore how these marks could be detected as variations in canopy biomass using both range and full waveform LiDAR data. Although some detection was achieved using metrics of the full waveform data, it is the novel multi-temporal method of using discrete return data to detect and characterise archaeological vegetation marks that is offered for further consideration. This method was demonstrated to be applicable over a range of capture conditions, including soils deemed as difficult (i.e., clays and other heavy soils), and should increase the certainty of detection when employed in the increasingly multi-sensor approaches to heritage prospection and management.

Engaging with the Canopy—Multi-Dimensional Vegetation Mark Visualisation Using Archived Aerial Images

“…Since one no longer has to rely solely on the colour contrasts exhibited by the photograph itself, this novel approach adds serious significance to the use of archaeological aerial imagery. Although it is the first time that aerial photographs have been employed in this way for the identification of vegetation marks, a similar approach was taken by Stott et al [30] using ALS-derived CHMs. Even though they did not use the LRM to visualise elevation contrasts, these scholars could demonstrate that in certain situations, the CHM provides better definition of archaeological features than aerial photographs acquired at the same time.…”

“…Such a canopy model-which is sometimes denoted a Crop Surface Model (CSM) when dealing with crops [24]-has since been commonly applied in forestry [25,26] and agriculture [27][28][29]. The rare investigations that rely on a vegetation canopy model for archaeological vegetation mark identification [30] indicate that, to this very day, archaeologists have still not truly realised the archaeological prospection potential of digitally encoded plant height differences.…”

A cost-effective image processing approach for analyzing the ecohydrology of river corridors

“…The NDRGI measures vegetative greenness based on difference between the reflectance values of the red ( ρ Red ) and green ( ρ Green ) spectral bands on a scale from 0 to 1 with a value of 0 corresponding to entirely green vegetation and a value of 1 corresponding to completely dormant vegetation (Yang et al ; Stott et al ). The index is highly transferable as it can be derived from any camera which produces images in RGB color space.…”

Locating and Mapping the Traces of the Covered Ancient Theater of Amphipolis (Eastern Macedonia, Greece)

“…Using a drone equipped with a modern digital 18 Mp resolution camera allows the three-dimensional (3D) mapping of an archaeological site with a spatial resolution of 1-2 cm [19]. The appearance of marks on the ground or on the vegetation are caused by the interaction of a buried monument (a "concrete construction", e.g., the boundaries of a building, or an "open construction", e.g., an ancient trench) with the ground or vegetation [20,21]. In aerial and remote sensing archaeology, significant efforts are made for automatic detection, digital visual enhancement of marks in images, and interpretation of the phenomenon of interaction between buried monuments and the ground or vegetation, using panchromatic, multispectral, and hyperspectral sensors [11][12][13]21,22].…”