NDVI Identification and Survey of a Roman Road in the Northern Spanish Province of Álava

Juan Fuldain González,Félix Varón Hernández

doi:10.3390/rs11060725

Juan Fuldain González, Félix Varón Hernández

Open Access

https://doi.org/10.3390/rs11060725

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Abstract

The Iter 34 (Antonine Itinerary XXXIV) is the name of the Roman road that crosses the province of Álava from west to east. Since no specific path was officially recognized before our study, the remains of the road did not benefit from heritage protection. In 2017, we made a project to determine the course of the road through rural Álava. In addition to traditional archaeological excavation and prospecting techniques, we used UAVs (unmanned aerial vehicle) to produce NDVI (normalized difference vegetation index) orthomosaic plans of ten cultivated areas through which the road is conjectured to pass. NDVI orthomosaics let us see crop marks better than with conventional photography, allowing us to detect the crop marks during times of the year and in places where conventional photography would fail to show them. Thanks to the NDVI orthomosaics, remains of the road were identified not only in places where we knew it existed, but also in previously unknown locations. Furthermore, other archaeological features were identified close to the roadway. This technique heralds a great advance in non-invasive methods of archaeological surveying. By using precision farming techniques we have identified the course of the Roman road Iter 34 in several locations in a short period of time and with few resources.

Highlights

During the past two decades, satellite images have been used for archaeological surveying, laying the foundations of remote sensing for archaeology
Low aerial photographs taken from UAVs have a much higher spatial resolution, such us the photographs used in this study case which are around 3.2 cm per pixel
The resulting orthomosaics were not automatically analyzed; we looked at the NDVI orthomosaics and compared them with historical photographs and maps to try to find traces of the Roman road

Summary

Introduction

During the past two decades, satellite images have been used for archaeological surveying, laying the foundations of remote sensing for archaeology. The development of photogrammetry softwares, which are able to process pictures taken with general purpose cameras, has brought about a revolution in archaeological recording, which in conjunction with the appearance of UAVs (which can accurately follow pre-programed missions), has allowed archaeologists to produce accurate surveys and 3D models and quickly [11,12,13]. Precision agriculture techniques are creating software and workflows that use remote sensing principles to asses crops health. All these elements are drastically changing the panorama of aerial archaeology, whereby aerial images obtained from UAVs are widely used for survey, recording and publication [19,20,21,22,23,24,25,26]

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