An On-Site Presentation of Invisible Prehistoric Landscapes

The rapid development of information technology has enabled the creation of entirely new presentation frameworks and this article will attempt to explore the subject of on-site presentation of archaeological sites. The most frequently used environment currently has been in the form of a variety of virtual museums that are accessible on the Internet; in essence these keep their visitors stuck in front of a PC monitor. One option that allows leaving the monitor and stepping directly out-of-doors into a virtual open-air museum is by means of applications for mobile phones. Terms such as 'virtual' or 'augmented reality' no longer represent a million light-years away science-fiction concepts, but rather a new tool for public archaeology and for the preservation of the archaeological heritage. This article presents several projects that have been implemented by the Archaeological Institute in Prague, who, by using mobile applications, built virtual open-air museums directly in the locations of archaeological excavations.

This extended abstract is also available in hard copy in K. May (ed) 2017 Digital Archaeological Heritage, EAC Occasional Paper No.12, Archaeolingua, Budapest.

The aim of this paper is to demonstrate the possibility of presentation of prehistoric sites in locations where there is neither preserved construction, nor any relics of the original landscape. Such sites usually meet with indifference both from the public and from institutions involved in preservation of historical monuments. The possibility of creating virtual and augmented reality proved to be a potential tool to grasp the invisible and to describe the disappeared. Based on the examples of the Neolithic sites in Bylany near Kutna Hora and Prague Vinor and Bronze Age site in Zalezlice in the Czech Republic, we show a potentially powerful tool for digital heritage management. Terms such as 'virtual' or 'augmented reality' no longer represent a million light-years away science-fiction concept, but rather a new tool for public archaeology and this paper discusses its use for in situ presentation of archaeological sites. The very rapid development of information technology, the accessibility of the Internet and the overwhelming scale of the adoption of computer technology in recent years have created room for a change in presentation of archaeological features and their reconstructions. However, on-site virtual presentations have very specific requirements and possible solutions still need to take into account technical limits.

The advantage of using augmented reality (hereinafter AR) is evident for 3D reconstructions displaying non-existing archaeological or historical structures. Already established AR applications use two basic technologies to overlay digital data with real environment. The first and the most used is the marker-based method, where virtual data are extended on two-dimensional images or in some cases three-dimensional objects. The second method works without these auxiliary markers and for locating of virtual data to real environment are used in portable device functions such as GPS, digital compass, and accelerometer sensors. This mode usually contains a database for locational information and when a device using GPS location and compass orientation establishes a match, it will display the desired virtual visualization. The downside to this method, however, is the inaccuracy of the GPS localization, which on mobile devices can be out by metres. This may not matter for applications that provide data overlays of supplementary information for physical objects that are perfectly visible with the naked eye, but for placing archaeological/historical buildings in their surroundings, it has a significant impact. Another possibility is the application based on mixture / augmented reality, which works without an auxiliary marker on the basis of an algorithm that teaches the device to identify the real natural objects while, at the same time, also utilising the special method called Speeded Up Robust Features. The implementation of this method is still difficult for mobile devices because of limited computation performance, memory, network connectivity, etc. and as far as we know, it has not been used to display 3D virtual reconstructions of archaeological or historical sites.

The above-mentioned technical limits and specifics of Central European prehistoric sites that are not visible in the modern landscape forced us to find another and more simple solution for presenting them in the field. The first application encompasses nine stops located in the extended surroundings of Bylany to capture the main features and settlement components of the Neolithic landscape. The application enables visitors using the map to navigate themselves between stops while the current position of the visitor is also highlighted, and to obtain basic text and visual information about each point of interest. All the 3D reconstructions that are displayed are based on archaeological evidence from almost half a century of archaeological research that has taken place in Bylany since the 1950s. Based on the data obtained by means of aerial laser scanning, the selected landscape section was subsequently modelled, with particular features being geo-referenced and exactly positioned where the original constructions stood. Visitors have the opportunity to see displayed on their own device the different phases of the Bylany Neolithic settlement's evolution, including the nearby Neolithic circle enclosure (i.e. a rondel) and the Miskovice burial site, all incorporated with the character of the cultural landscape at that time. In order to facilitate the visitor's opportunity to better understand and experience the 3D reconstruction at the prehistoric site, the above-mentioned principle of virtual reality, combined with the gyro mode function, was used for this part of the application. It is therefore possible after implementing this feature of the application at a predefined location to 'set foot' in the middle of this Neolithic village and, by moving the device sideways, to look all around it. This results in combining the virtual world, comprising 3D reconstructions of Neolithic dwellings, with the real world, since the current form of the contemporary landscape has been incorporated in the model. Information panels set up next to the Institute of Archaeology's field base included two markers enabling an AR visualisation of a full-size Neolithic burial, and a 3D model of a vessel that was found in Miskovice.

Another virtual open-air museum was put into use in Prague Vinor, where, in 2014, a rescue excavation uncovered parts of a Neolithic settlement, including the remains of two longhouses. The excavation results, including plans and geodetic localisation, were used to produce an ideal 3D reconstruction of the village and its vicinity. The application works analogously – the attached map highlights the points in the newly built-up area where users should initiate the specific virtual views in order to preserve the spatial context. Each of these 360-degree panoramic views captures a different part of the Neolithic settlement. By clicking on the points on the displayed 3D reconstruction that are marked, information boxes will pop up and provide explanations of the different features or show images of sample artefacts that can be found locally. One of these views takes the user to a photogrammetrically recorded excavation site, enabling an explanation both of the rescue excavation process and the manner of the detection of archaeological features.

3D photogrammetry was conducted at the rescue excavation of a Late Bronze Age settlement in Zalezlice near Melnik and enabled the creation of 3D models of all the inhumation burials in settlement pits. The augmented reality application that was devised for their presentation uses the marker principle previously discussed. At present, leisure shelters with inbuilt markers and information panels are being constructed along a popular cycling route adjacent to the site.