Digital applications for preserving archaeological sites and tourism management

Cultural heritage is an important part of our life, a resource for the identity and the cohesion of communities. The paper aims to identify possible solutions for cultural heritage management of the archaeological sites and monuments from Dobrogea. The authors documented and researched above-ground archaeological structures, analysing their characteristics and suggesting solutions for conservation and promoting of archaeological heritage. The rapid development of digital technologies like augmented reality can help us finding cost-effective solutions for archaeology and cultural heritage tourism.


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Introduction Digital technologies have advanced faster than any other form of innovation in history, playing an important role in the development of science and technology.The use of computers for tedious tasks evolved and now it helps us in creating new forms of realities like virtual or augmented reality which can have multiple uses, including in the field of archaeology and cultural heritage.The digital reconstruction of artifacts or archaeological sites can be an important tool for understanding and appreciating the cultural values.At the same time, the use of this type of technology, derived from video games, can play a special role in the education of young generations, relying on the affinity that young people show for the digital world.
Augmented reality can be used as tool for scientific study, design, industrial production, training, learning or recreation.Using it in cultural tourism can improve the sensorial experience of a visitor when seeing an archaeological site [1] adding new information like images of a building, peoples or sounds.The article presents the main types of archaeological sites in Dobrogea, studying how they are conserved at the present time and how their significance is shown to the public, then reviews the traditional restoration methods used.We introduce the technologies that allowed the development of the concept of virtual heritage and the way in which augmented reality can enhance the Dobrogean sites and contribute to the development of cultural tourism, bringing as an argument similar solution used in Europe.

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Touristic sites in Dobrogea Dobrogea is an area with an important touristic potential, its geographical position and proximity to the Black Sea being an advantage.Tourists come here primarily for recreation and rest, but the multitude of archaeological sites dating back to the last 2500 years can create the premises for the development of cultural tourism.
The Greek civilization founded the first cities on the shores of the Black Sea, a place that facilitated commercial relations with the indigenous population.The expansion of the Roman Empire led to a more pronounced development of the area and to an increase in the number of settlements, many of them being fortified.The need to defend the borders of the empire against barbarian attacks led to the creation of a fortified line represented in Dobrogea by the Danube limes, formed by earth walls, defence towers and forts.
One type of archaeological site is the urban site like those found in Constanta (the ancient city of Tomis) and Mangalia (the ancient city of Callatis).Tomis and Callatis are among the first cities founded IOP Publishing doi:10.1088/1757-899X/1304/1/012017 2 by Greek colonists in the 6 th -7 th centuries BC and they have been continuously inhabited throughout time, a fact that has advantages but also disadvantages.The advantage is that they are easily accessible, but many of the original buildings have been lost over time, the stones from their masonry were used for other buildings, the foundations remained hidden under ground or were swallowed by the Black Sea, the southern part of the of the Romanian seashore being subjected to a continuous erosion.
Archaeology, as a science, has its beginnings in the 18 th century, and only at the end of the 19 th century, the industrial revolution and the demographic growth made more people interested in it but this science was in its beginnings in Romania and not popular enough to impact people's life and way of thinking.
When these cities began their expansion at the end of the 19 th century, they used all the available space and did not pay too much attention to the historical vestiges.The streets and houses were placed according to their usefulness at the time of construction without carefully avoiding the ruins encountered.This way of thinking is changed now, recent urban planning being made in order to protect and value the archaeological remains, but part of the walls of the fortresses and houses still remain under the foundations of the new buildings, unable to be accessed by the public.In the post-war period, the two cities experienced an important development, and it is worth mentioning the protection of some of the historical remains that can be visited, like the Greek wall of the Callatis fortress, which can be visited within the premises of a hotel.There are also vestiges hidden, at least for now, from the public, such as a Roman amphitheatre in Tomis, which was protected in the basement of a hotel.
In these two cities there are other vestiges presented to the public, some of them are currently valued, others are not.In the Archaeological Park of Constanta you can admire the entrance gate of the old Tomis, (figure 1) and in Mangalia, near the archaeology museum, the ruins of the northwest corner of the Callatis fortress (figure 2) that were recently highlighted.Other sites, where archaeological excavations are advanced, such as Ulmetum, Tropaeum Traiani, Dinogetia, Halmyris, Argamum, are more difficult to access and do not offer tourists information to facilitate understanding of the site and its component elements.Some of the sites, part of the fortified frontier of the Roman Empire, some are completely unexplored: Sucidava, Beroe, Cius, Salsovia, others are impossible to visit, Axiopolis, or partially destroyed by the stone mining in the area: Arrubium, Capidava.

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Restauration and valorisation methods used From the very beginning of the archaeological excavations, the fragility of the uncovered ruins was noted by archaeologists who, with the help of local craftsmen, took the first primary conservation measures.And now the archaeologists are dealing with the primary conservation of the ruins, operations that consist mainly of restoring the joints with mortar and anchoring the insufficiently supported masonry elements.Compared to the beginning of the 20 th century, a mineralogical analysis of the mortar can be done now with the aim of using materials similar to the original ones.
The restoration of the remains was done in many fortresses, using, in general, the materials found on the site or when the walls were dismantled many centuries ago, they were reconstructed with similar materials, so that the visitor can more easily imagine the greatness of the original walls.This type of restoration was applied to the walls of fortresses such as those of Tropaeum Traiani or Dinogetia.
Recently, several projects have been proposed to restore and enhance some fortresses such as Noviodunum, Histria, Carsium, Halmyris, so the expected number of tourist attractions is growing.

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Use of digital technologies in virtual heritage and cultural tourism Virtual heritage starts from existing cultural heritage and proposes the application of new digital technologies to save or reconstruct the image of a building or an object as it was originally.The first attempt to use the technology for the purpose described above was made in 1994 by reconstructing the 3d image of Dudley Castle in England in its form from 1550.
Concerns to integrate new digital technologies have materialized since 2000 in the regulations of the Krakow and London Charters, the Ename Charter and the Seville Principles that define terms such as virtual restoration, virtual reconstruction or virtual anastylosis.All these documents standardize the most suitable practices for virtual reconstructions and have entered into the common use of archaeologists and other specialists involved in the restoration process, be it physical or virtual.
There is also a concern in Romania for the digitization, mainly, of treasure objects from museum collections, objects too fragile to be exposed to the public for a longer period of time.Regarding heritage buildings, as consolidation works are carried out, 3D scanning is used more and more, and these images are used by specialists in order to identify the optimal intervention measures.
In detail digital reproduction of the surrounding world was made possible by a series of inventions and innovations which appeared in the 20 th century.
Computer tomography, also known as CT, is an imaging technique that has exceeded the boundaries of medicine, being successfully applied in all fields.It consists in measuring the absorption of X-rays by materials and through computerized processing of the measurements, the model is digitally reconstructed in three-dimensions.Although the theoretical possibility of creating such devices has been known since the beginning of the 20 th century, their emergence was in the early 1970s when the first thermal imaging cameras and computers powerful enough to quickly perform calculations necessary for image reconstruction appeared.
The invention of photography and laser technology allowed the development of 3D scanning and photogrammetry which together can give a realistic three-dimensional model of an object.The development of computing power has facilitated the appearance of augmented, virtual and mixed reality and the possibility to see objects in detail and even interact virtually with them.
The first steps in the digitization of tourism were achieved by creating virtual tours of museums.With the help of a PC or tablet device, the user can virtually walk through the museum, being able to follow a circuit through which they can view the exhibits.To do this, the proposed path is photographed and the images obtained are digitally combined to create an overall view with a three-dimensional appearance.

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There are many possibilities offered by augmented reality or other types of mixed realities [2].With the help of a phone equipped with a GPS and an application it is possible to visit a historical site and at the same time see on the screen a reconstructed image of the original site.The whole perception of the site will be enriched with a new dimension and the experience will be totally different.
This technology is already used in several places in Europe [3], a good example being the Kameiros site in Rhodes, Greece where virtual three-dimensional constructions are superimposed over the ruins of the old city.This experience can be accessed through the "Kameiros 3D" mobile application developed by MOPTIL.
The application's main screen presents the existing overview and a reconstruction of the site.Arriving in front of a building, a comparison can be made between the image seen on the spot (figure 5 and figure 7) and the one proposed for reconstruction (figure 6 and figure 8).This type of technology could be successfully applied to archaeological sites in the Dobrogea area.In the reconstruction, it will be possible to introduce elements from different periods and give the visitor an image both of how the fortress looked when it was full of life, during the growth periods of the empire, and how it looked later after the barbarian raids had subsided in intensity and people started to build huts in the former granaries.1304 (2024) 012017 IOP Publishing doi:10.1088/1757-899X/1304/1/0120175

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Using classical methods versus a digital approach The image of the site presented as it was at a certain moment in time can be done through digitalization, the costs required for reconstruction are greatly reduced, the only procedures that needs to be done being those of conservation and protection.
Another advantage of this method is the fact that it can easily integrate any other discoveries subsequent to the decision to reconstruct.From this point of view, the monuments and future researchers have a lot to gain, the authenticity of the ruins being ensured and their research and reinterpretation being possible at any time in the future.
A disadvantage of these techniques is the perception of the visitor, because the image obtained with the help of augmented reality is not identical to the one given by a reconstructed building.The fact that the virtual experience is more attractive compared to observing the ruins of some foundations cannot be neglected, but this technology has its drawbacks.

Conclusion
This article introduces the idea of using the augmented reality as a mean to increase the public interest for the Dobrogean archaeological sites and contribute to their conservation and valorisation.The first section highlighted the main characteristics of the sites and analysed the way in which there are presented to the public at the present moment.An overview of the main technologies related to the concept of virtual heritage was introduced, pointing out the benefits of augmented reality technologies.An example of similar approaches was then described making suggestions about the possibilities offered by augmented reality to simulate lost cities and forts.
The ideas presented in the article could represent a way to satisfy the public curiosity about the way of life of people in the past, about what a house of the ancient Romans looked like or to see how high were the walls of their fortresses.All of this can be seen standing in front of their ruins and watching what remained from the different layers of construction and what significant destructive effect the passage of time had, offering a new perspective of their importance.The idea is quite simple and can be easily put into practice using the new digital technologies, making possible the development of cultural tourism in Dobrogea with a relatively small investment.

Figure 1 .
Figure 1.The gate of the old Tomis

Figure 2 .
Figure 2. The northwest corner of the Callatis fortress wall Another type of Dobrogea's sites, from cultural tourism point of view is represented by sits ready to welcome tourists, such as the Greco-Roman fortress of Histria or the Roman fort from Capidava.The archaeological excavations started in the first part of the 20 th century and were continued, with small interruptions, until today.The sites also have nearby museums where the most important discoveries are exhibited.