Detecting Neolithic Burial Mounds from LiDAR-Derived Elevation Data Using a Multi-Scale Approach and Machine Learning Techniques

Alexandre Guyot,Laurence Hubert-Moy,Thierry Lorho

doi:10.3390/rs10020225

Abstract

Airborne LiDAR technology is widely used in archaeology and over the past decade has emerged as an accurate tool to describe anthropomorphic landforms. Archaeological features are traditionally emphasised on a LiDAR-derived Digital Terrain Model (DTM) using multiple Visualisation Techniques (VTs), and occasionally aided by automated feature detection or classification techniques. Such an approach offers limited results when applied to heterogeneous structures (different sizes, morphologies), which is often the case for archaeological remains that have been altered throughout the ages. This study proposes to overcome these limitations by developing a multi-scale analysis of topographic position combined with supervised machine learning algorithms (Random Forest). Rather than highlighting individual topographic anomalies, the multi-scalar approach allows archaeological features to be examined not only as individual objects, but within their broader spatial context. This innovative and straightforward method provides two levels of results: a composite image of topographic surface structure and a probability map of the presence of archaeological structures. The method was developed to detect and characterise megalithic funeral structures in the region of Carnac, the Bay of Quiberon, and the Gulf of Morbihan (France), which is currently considered for inclusion on the UNESCO World Heritage List. As a result, known archaeological sites have successfully been geo-referenced with a greater accuracy than before (even when located under dense vegetation) and a ground-check confirmed the identification of a previously unknown Neolithic burial mound in the commune of Carnac.

Highlights

Since the early 2000s, Airborne LiDAR remote-sensing technology has become an important tool for locating and monitoring cultural heritage sites in large or hard-to-access areas
To enhance the interpretation of subtle landforms from Digital Terrain Models (DTMs), archaeologists have relied on common visualisation techniques (VTs), including hillshade, slope, or colour-casted models derived from DTMs
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Summary

Introduction

Since the early 2000s, Airborne LiDAR remote-sensing technology has become an important tool for locating and monitoring cultural heritage sites in large or hard-to-access areas. High-density and high-precision LiDAR point clouds are processed to generate terrain models that are used to detect and characterise archaeological evidence through the analysis of morphological or topographic anomalies [1,2,3]. To enhance the interpretation of subtle landforms from Digital Terrain Models (DTMs), archaeologists have relied on common visualisation techniques (VTs), including hillshade, slope, or colour-casted models derived from DTMs. More recently, advanced VTs, such as principal component analysis (PCA) of hillshades, sky-view factor, and openness models have been developed and successfully used to improve visual detection of archaeological remains. The increasing development and complexity of these VTs can make the manipulation of LiDAR-derived models confusing and their interpretation subjective by non-expert users

Methods

Results

Discussion

Conclusion