image/svg+xml155 X/2/2019 INTERDISCIPLINARIA ARCHAEOLOGICA NATURAL SCIENCES IN ARCHAEOLOGY homepage: http://www.iansa.eu Thematic Review Current Development in Archaeological Remote Sensing: A Central European Experience and Evaluation Martin Gojda a,b* a Institute of Archaeology, Praha, Czech Academy of Sciences, Letenská 4, Praha 1, Czech Republic b Institute of Archaeology, University of Cardinal Stefan Wyszyński, Wóycickiego 1/3, Warszawa, Poland 1. Introduction As a consequence of the collapse of communist regimes in former Warsaw-Pact countries, the early 1990s became a period in which aerial archaeology in Central-Eastern Europe began to write its own history. This article ofers the present author’s refections on the these developments and changes within the feld of archaeological remote sensing over the last quarter of a century, along with a personal evaluation of the current situation of the subject’s methodology with an eye to the future, based on his practical involvement in systematic, long-term, aerial archaeological prospection and past landscape and settlement research.In the history of archaeological remote sensing (ARS), the last couple of decades have brought several fundamental improvements to its methodology and datasets. These are pushing the discipline of Earth’s remote sensing into the group of archaeology’s most important instruments of cognitive processes. As a consequence, the crucial role of ARS in the current research and management of ancient/historical landscapes, sites and monuments is obvious. The article describes how current trends are changing the traditional objective of aerial archaeology – prehistoric and ancient site detection and photographic recording – into a much more complex aim, namely: the integration of a variety of modern digitally-based sophisticated techniques of RS that are applicable to archaeology into the study of diachronic developments and synchronic structures of components of ancient and historical landscapes and settlements. Also included below are notes on the signifcant role of orthophoto maps recently accessible to the general public via web portals (such as globally-based Google Earth, and many national map servers/geoportals) and how to deal with this challenge in the context of sites and monuments research and management. The author presents an assessment of the role of ARS in the study of the past from a central European (mainly Czech) perspective. 2. Theoretical considerations2.1 Detecting the unknown and seeing the context. Non-destructiveness as a modern archaeology postulate To observe any kind of reality from a distance means to see it both as a whole and in context with its surroundings. This Volume X ● Issue 2/2019 ● Pages 155–164 *Corresponding author. E-mail: gojda@arup.cas.cz ARTICLE INFO Article history: Received: 5 th May 2019 Accepted: 7 th November 2019DOI: http://dx.doi.org/ 10.24916/iansa.2019.2.5 Key words: aerial archaeologyarchaeological remote sensingcentral Europeinternet map (geo)portalslandscape archaeologysatellite dataUAV ABSTRACT This article ofers thoughts on how current trends are changing the traditional objective of aerial prospection – prehistoric and ancient sites detection and the photographic record – into a more complex aim, namely, the integration of a variety of modern digitally-based, remote-sensing techniques applicable to archaeology into a process that focuses on the study of diachronic developments and synchronic patterns of past settlements. The author presents an evaluation of the current position of remote sensing in the study of the past, mainly from a central European (Czech) perspective, based on his long-term involvement in air survey and landscape archaeology in the Czech Republic.
image/svg+xmlIANSA 2019 ● X/2 ● 155–164 Martin Gojda: Current Development in Archaeological Remote Sensing: A Central European Experience and Evaluation 156 generally allows us to refect on its complexity. This is true at least when looking at such an intricate component of the world like the Earth’s surface. Its infnitely long evolution has been continually infuenced by natural (geologic, climatic, biological) processes, and which human impact has then transformed from what used to be entirely natural into a cultural landscape. These processes have shaped the surface of the Earth and continuously transformed its seemingly stable and unchanging character.The role of archaeology in contemporary Europe has shifted from the more traditional stress on investigation through the excavation of individual sites potentially rich in artefacts/structures/features towards the identifcation, documentation, mapping and protection of archaeological landscapes for both research objectives and public interest. This orientation corresponds well to the “landscape stream”, one of the most fascinating phenomena, that has attracted recent populations, at least on a European scale. Several works summarising the academic approaches to landscape, and defning the principles of landscape archaeology, have been published since the beginning of this century ( e.g. , Doneus, 2013, pp.29–38; Fairclough, Møller, eds., 2008; Gojda, 2007; Darvill, Gojda, eds., 2001). This archaeological practice has been more common in Western European countries, but thanks to the increasing number of pan-European projects operating in EU schemes, and due to a certain number of large-scale, state-funded, national research projects in some post-communist countries, it has recently been spreading over this part of Europe as well. Consequently it is non-invasive methods of archaeological research which, since the turn of the 21 st century, have taken over the main role in theoretically-motivated (research) projects based on data collected from sites that are not endangered by development. This was explicitly proclaimed as a postulate in the early 1990s when the priority of non-invasive methods was stressed as a point of archaeological ethics at the Valetta Convention for the Protection of the Archaeological Heritage of Europe. Nevertheless, despite the global trends indicating a dominance of non-invasive prospection and feld techniques, it is excavation that has maintained its position as the most frequently-applied archaeological method in the heart of Europe, primarily as a legally-supported response to permanent construction activities that have been continuously threatening archaeological heritage since 1990 on a vast scale.Concerning non-invasive methods, ARS, from a historical perspective, is probably the most important. It ranks among the limited number of techniques that have made a contribution to the study and understanding of ancient and historical (medieval, post-medieval, industrial, early modern) periods of the human past. The importance of ARS integration into the study of settlement processes has been compared, for instance, to the invention of the telescope for the study of outer space. Among the methods for gathering/processing/interpreting archaeological data, RS is of high signifcance and is equal to radiocarbon dating, digital databases, DNA analysis and GIS. At the end of the 1960s and the early 1970s, Leo Deuel, writing about aerial archaeology in his famous book Flights into Yesterday , claimed that “…no other technical advance in archaeology has come so close to fulflling the goal of recovering intricate cultural contexts, of glimpsing whole prehistoric landscapes, and of capturing a fabric of human existence through the fux of time” (Deuel, 1973, p.26). 2.2 The 1990s – 2000s turnaround: from aerial archaeology to archaeological remote sensing Recent technological development has infuenced several archaeological branches, and it is clear that ARS has profted greatly from modern technology: the innovative instruments, devices and techniques invented and produced during the last three decades. It was precisely in this period that the author established aerial archaeology in Bohemia and pushed for the inclusion of this discipline in Czech archaeology. Starting from 1992/3, the position was set in the traditional Crawfordian way of aerial prospection as developed in the 1920s and as such was recently termed “observer-based/directed reconnaissance/aerial surveying” (Verhoeven, Sevara, 2016), “interpretive” (Šmejda, 2017) and “active-interpretive” (Gojda, 2017). It was based on a visual survey of the Earth’s surface from a small aircraft fying at an elevation of c. 300 metres, taking photographs with three analogue, steady cameras and one video camera, navigating visually with the aid of a set of 1:50,000 paper maps, and then, fnally, waiting a week or so to fnd out how successful the mission was after the set of flms were developed and images enlarged in a commercial laboratory.A couple of years later, an innovative process was launched that gradually changed aerial archaeology (also referred to as aerial archaeological prospection/reconnaissance/survey) into archaeological remote sensing – a group of techniques/methods that produced a variety of remotely-sensed data and helped to process and analyse them by sophisticated (digital) procedures: 1. 1993–1995 – the arrival of GNSS/GPS for civilian use and the declassifcation of the USA’s CORONA satellite imagery;2. Second half of the 1990s – digital photography introduced to the global market; concerning aerial prospection it greatly simplifed the photography process both on board the aircraft (only one camera needed) and after fights (immediate image processing and large-scale digital applicability);3. 1999 – the launch of the frst satellite system (IKONOS) producing images of very high (sub-metre) spatial resolution (in panchro), extremely important for the central European region with a prevalence of small features (pits and small sunken huts at buried, prehistoric and early medieval, settlements);4. Around 2005 – free access via Google Earth to continuous (seamless) global orthophoto coverage (in the Czech Republic, the frst national map server was launched at the same time, with currently accessible imagery taken in fve years between 2003–2017; more details follow in the next section);
image/svg+xmlIANSA 2019 ● X/2 ● 155–164 Martin Gojda: Current Development in Archaeological Remote Sensing: A Central European Experience and Evaluation 157 5. 2005–2010 – the beginning of the massive application of airborne laser scanning (ALS) in European archaeology, perhaps the most revolutionary post-Second World War impact on the efective (fast, precise, 3D, digital,….) detection and mapping of our archaeological landscape heritage (this is absolutely true for at least central Europe where ancient, medieval and post-medieval ruined features are preserved as earthworks almost entirely in woodlands). 6. Late 2000s onward – intensifed application of image spectrometry using air- and spaceborne, hyperspectral data and experimentation with automated (computer-supervised) object ( i.e. features of archaeological origin) detection from remotely sensed imagery.There is no doubt that these innovations fundamentally changed the traditional image of aerial archaeology, which before this turnaround was – together with the rare application of early satellite imagery and aerial infrared photography (practiced before the 1990s mostly by American scholars, including in their European projects; Madry, 1987) – the exclusive method connected with the study of the (pre)historic landscape from above. The process relegated (traditional) aerial archaeology to the position of just one of several methods integrated into the archaeological remote-sensing “package”. Nevertheless, it is obvious that the integration of modern (digitally-based) sophisticated techniques of ARS with additional feld techniques, historical, cartographic and scientifc methods/data has a chance to produce more reliable results in the cognitive process focused on the study of diachronic developments and synchronic structures of the components of past settlements and landscapes. 2.3 The potential of remote sensing for central European/Czech archaeology in the 21 st century The cognitive process, which in science/research strives to integrate a discipline’s general level with contemporaneous technological achievements and theoretical concepts (paradigms), is never a linear one or one easy to coordinate. The current position of ARS is somewhat strange in that this was formerly a purely detection method predominantly dependent on the observational, physical and interpretative abilities of trained individuals (commonly termed aerial archaeologists), while during the last few years a fundamental change in the ARS agenda (platform) has occurred – primarily as a consequence of the rapid technological development. Today, the dependence of scholars (such as archaeologists, historical geographers, historical environmentalists/ecologists, etc. ) on the aerial reconnaissance specialists’ yearly cropmark “harvest” is decreasing. The ability to work with sophisticated software and digital-image data processing, particularly by the younger generation, makes it possible to incorporate air/ spaceborne data into everyday practice – both in the feld and during desktop data processing. Vast collections of aerial and satellite images, both recent and archival, taken continuously over the Earth in digital format, are available in open-accessed map portals and geoportals. It is this phenomenon of free accessibility to worldwide air/spaceborne imagery that has radically shifted and, in a sense, democratised the