# Detecting Change at Archaeological Sites in North Africa Using Open-Source Satellite Imagery
## 1 Introduction  
This paper presents a remote sensing workflow for identifying landscape changes that threaten archaeological sites. The workflow has been developed as part of the work of the Endangered Archaeology of the Middle East and North Africa (EAMENA) project. We identify, document, and monitor archaeological sites across the MENA region, using a combination of remote sensing and fieldwork methodologies. EAMENA also works to support local heritage agencies and professionals in the region to develop strategies for heritage protection [1, 2]. We use a standardised approach to recording and make data available in an open-access database using the Arches platform [3, 4, 5]. We are particularly concerned with promoting the use of open-source satellite data and technologies to make this methodology as accessible as possible, rather than higher-resolution data which is prohibitive in terms of cost and political sanctions. In this paper, we demonstrate the results of applying a bespoke change detection workflow using Google Earth Engine to two case studies (Figure 1); the Aswan and Kom-Ombo area in Egypt (collaborating with the Aswan-Kom Ombo Archaeological Project, AKAP, directed by [PERSON] andAntonio [PERSON]), and the Jufra oases in Libya (collaborating with the Trans-SAHARA project, directed by [PERSON]). These case studies were selected because they comprise a range of types and dates of sites in comparable arid/oasis environments, but also offer a diversity of context in terms of heritage management processes. The workflow can detect vegetation and settlement growth and also bulldozing, extraction and infrastructure projects. Given that it allows rapid recording via a bird's eye perspective, remote sensing has been an important part of archaeology in North Africa for several decades, although modern high-resolution imagery is underutilised [6]. [PERSON] and [PERSON] recent review paper [7] (p. 11 Figure 1) describes this trajectory in detail and maps the geographical range of these studies. [PERSON] and [PERSON]'s review shows the recent expansion of scientific literature discussing satellite imagery for looting detection [8]. This activity has its roots in historical aerial photographs, which enabled early remote identification of sites, including the work along the Nile by [PERSON] [9] (1953). In the 1950s and 1960s, colonial regimes instigated national mapping programs using aerial photography that covered most of the inhabited regions of North Africa. This wealth of imagery has continued to be used by archaeologists up to the present day (see the work in Fazzan in Libya [10; 11]). In the twenty-first century, commercial high-resolution imagery has allowed detailed recording (spatial resolution of 0.3-0.5), but it is very expensive. Some archaeological projects have used it for recording damage, whether by image interpretation [12] or automation [13]. Due to EU and US embargos, licenses for this kind of imagery often cannot be obtained for use in the Middle East and North Africa [14]. Given these political restrictions, as well as the high cost, it does not represent a good solution for widespread change detection. Due to these problems many archaeologists take advantage of the high-resolution imagery available in a limited form for free via Google Earth, Google imagery imported into QGIS etc. ; however, this is provided stripped of its original radiometric information. Google Earth has been used extensively by EAMENA, AKAP and Trans-SAHARA for image interpretation [2; 15] as well by as other projects working in the region [16]. Moreover, the high-resolution imagery does not offer the same repeat-viewing perspective of other free satellite data of lower resolution, such as Sentinel and Landsat. Archaeologists have used Landsat since its early days as a source of overview information about landscapes in North Africa [17]. Despite its lower resolution, several recent projects have used this kind of imagery to successfully assess changes at archaeological sites [18; 19].