What is Digital Preservation of Heritage?
Heritage preservation has been an essential phenomenon since the eighteenth century when Europe started paying attention to different national identities and cultural diversity. However, the past methods of preserving heritage have proven unreliable due to climate change effects, globalization, modernization, and rapid urbanization (Gao et al., 2018). Additionally, no well-laid-out policies protect and preserve the cultural heritage. For instance, ancient Chinese architectural designs are more prone to natural disasters such as fire and earthquakes. Most heritage cities are under threat, and there is a consensus that they need protection and safeguarding for future generations.
For the past two decades, digital preservation of heritage has been a wide area of research, although the technology has faced many challenges. In resolving these problems, scientists have innovated modern methods of preserving heritage using digital means (Singh, 2012). The main aims of digital preservations are; to enable the supply of heritage through digital outlets to large audiences, to guarantee that initial measurements and forms of natural heritage are not lost in case of natural disasters, to pick out art forgery, to develop replicas and enable the collection of particular texture and geometrical information from the natural objects (Gomes et al., 2014). Therefore, digital preservation is a revolution against the traditional method of preserving natural and cultural heritage.
In the past, 2D models were used to capture heritage. The model first used the geographic information system, which helped link a heritage with its semantics. In other instances, they connected the cultural heritage with the spatial information system, especially for single buildings (Pepe et al., 2021). However, this method was insufficient because it was only limited to 2D, and therefore there was a need for more digitalization of heritage preservations that saw the development of 3D (Evens & Hauttekeete, 2011). The 3D systems are more focused on using volumetric picture images. Although it is challenging to construct 3D images due to the nature of the environment, scientists have used complex shapes such as Non-Uniform Rational Basis-Splines (NURBS) to have a digital recording of natural heritage. The other digital method for collecting cultural heritage uses a laser scan Building Information Modelling (BIM) software (Valetutti, 2015). This type of reverse engineering uses the help of a laser to construct a map of photogrammetric data. However, this method cannot be used for ancient Chinese architecture because the lasers may damage the painting and materials used by ancient Chinese, and the architecture is structurally complicated, requiring close-range scanning.
Nowadays, more communities are adopting new digital methods of storing their cultural heritage for future generations by highlighting the values of different cultural terms. Therefore, digital heritage preservation relies heavily on 3D imaging (Peters et al., 2017). It uses computer-based systems such as NURBS and BIM to create, share, and store natural and cultural heritage information. The more the development of digital preservation methods, the more different cultures will be able to store their natural and cultural heritage and share it with a large audience of people. For instance, the internet can be used to share a cultural heritage across many people, indicating that it is a digital heritage product.
Reasons for Digital Preservations for Architectural Heritage
One of the main reasons for adopting digital preservations for architectural heritage is a detailed and comprehensive portrayal of heritage. A study conducted by Aburamadan et al. (2021) showed that more reliance on digital technologies in Jordan had been adopted to provide a more accurate and holistic representation of their culture. Digital technology can document and eliminate various barriers found in previous versions. For instance, a laser scan can record a building within one day and share it with experts situated miles away using the internet, significantly improving the previous versions of preserving natural and cultural heritage (Aburamadan et al., 2021). Some of the technologies which enable the more accurate recording include AutoCad, a 2D tool, and Laser scanning for 3D. Therefore, these tools can capture historical buildings using computerized 2D and 3D images. However, these technologies have been found to sometimes produce inconsistent results due to the effects of lasers on the historic buildings, which can lead to a detrimental impact on the value and significance of these buildings (Gao et al., 2018). Therefore, the processes are integrated with BIM to provide accurate and consistent results while preserving the heritage sites’ functional physical, and cultural components.
Digital preservations have been adopted because they help to achieve resilient conservation. Innovative technologies have been used to move design communities and buildings to resilience. One of the innovative technology is the Internet of Things (IoT) and Heritage Building Information Modeling (HBIM) (Elabd et al., 2021). Designers often use these tools to help them overcome the complexities which lead to conflicting objectives. Using 3D heritage models, researchers can rely on photogrammetry and laser scanners to tape cultural and natural heritage sites. HBIM helps map parametric objects to image survey data and cloud through reverse engineering (Khalid, 2021). Mapping historical buildings using HBIM produces complete 3D images and orthographic images, which help restore heritage. The HBIM enables collective decision-making by visualizing and enhancing system thinking by weighing up against other designs. On the other hand, IoT helps communicate information technologies that connect researchers with other designs to compare their data (Elabd et al., 2021). It provides real-time communication capability between people in different geographical locations, making digital preservations more reliable and fast. Therefore, digital preservation can achieve resilience through IoT and HBIM.
Digital preservation helps in saving the original architectural heritage. This method is mostly used for documents or other architectural heritage features available in singular forms, and their demand is high (Boamah, 2018). In some instances, some architectural heritage features can only be available in one copy, which makes them not assessable enough for all the people who want to use them. Additionally, the exposure to too many people would also destroy the original architectural heritage. Therefore, the best solution to avoid the destruction of the authentic architectural heritage, such as a manuscript, buildings, or structures, would be through digitalization, where the original copy is well kept or guarded (Boussaa, 2014). Then a replica of that is available for public viewing. Digital preservation also improves access to the architectural heritage because multiple people can use digital replicas simultaneously. For instance, if people come to a specific architectural heritage site to read a manuscript, the manuscript can be digitalized. People pay to view it online, reducing the number of visitors to the architectural heritage site, saving it from deterioration.
The use of digital preservation enhances the strengthening of policy regarding architectural heritage. The traditional methods did not have any policies or formal methods of allocating resources to the architectural heritage (Boamah, 2018). The oldest people in the society were heavily relied on for information regarding the cultural and architectural heritage, and sometimes information would be lost as it was passed down generations (Boamah, 2018). This is because the information and knowledge were delivered through word of mouth, and sometimes the death of such individuals would lead to a loss of knowledge regarding architectural and cultural heritage. Therefore, the use of digital preservation methods helped bring out good policies on effective information management for architectural heritage sites. The local societies and those with the most knowledge are significantly consulted during digitalization, making information passing seamless and accurate.
How Digital Technologies Preserve the Architectural Heritage
Digital technologies use 2D and 3D segmentation and classification techniques to preserve architectural heritage. In 3D images, they look for gradient, surface normal, and other geometric characteristics, while 2D images look for color, shape, scale, and shape patterns (Deligiorgi et al., 2021). They use both cloud and image segmentation to conduct medical analyses, detect objects, classify microorganisms, and vehicle recognition. Segmentation is used to identify point clouds, images, or meshes of a homogenous nature while factoring in the different unique properties.
One of the methods used in recording architectural heritage is edge-based segmentation. This method has two main parts: the first part detects edges, and the other combines points inside the segment to develop the final details. Edges are mainly identified through principal curvatures, gradients, and high-order derivatives, and they are recorded in places of a given threshold (Grilli & Remondino, 2019). This method is fast in segmentation, but it may sometimes produce inaccurate results because of uneven density clouds and noise. Additionally, when using this method in 3D framing, segmentation filling can be used to make identification simpler.
The other commonly used segmentation method is the model-fitting approach. This method relies on observing artificial objects, figuring out primitive shapes, such as cubes, cylinders, and spheres, and restoring them into their original state based on their mathematical representations (Grilli & Remondino, 2019). The commonly used methods to restore these shapes are Random Sample Consensus (RANSAC) and Hough Transformation (HT). This is a fast method of restoring architectural heritage; however, sometimes, it may present complex shapes that are not easy to figure out.
Surveying measures the characteristic angles and distances in a moment to identify its original position by transforming it into an orthogonal coordinate system. This method depends on a 3D orthogonal coordinate system using high complex accuracy measurement tools such as total station (El Araby & Okeil, 2004). In the digitization of monuments, the surveying method can restore architectural heritage. This method has high accuracy and reliability and is easy to identify the original monument. However, the method is so demanding that one must be physically available at the site, and it is commonly used in complex situations.
Laser scanning techniques can as well be used to restore architectural heritage. They enable the researchers to measure the topographic quantities and use the optical line, which connects the characteristic point and merges them with the reference point of the device (Pavlidis et al., 2007). They also use the triangulation principle to automatically estimate the distance and plot it in a Cartesian plane. This method is reliable, fast, accurate, and allows the collection of a large volume of data within a short period.
The last method of preserving architectural heritage is through photogrammetry. It uses topographical methods to take accurate measurements from digital photographs. Using the CAD software, photogrammetry can transform photos to get the exact coordinates measurements (Pavlidis et al., 2007). However, this method is relatively slow and must be integrated with other methods to produce accurate results. It can also be used for architectural heritages which cannot be accessed or have prohibited entry.
Examples of Worldwide Digital Preservations of Architectural Heritage
There have been various urban and architectural conservations worldwide, mostly in Arabic countries. One of the cities that have undergone digital conservations is As-Salt, a city in Jordan. The city had historic houses built of two or three stories in the local yellow stone. It was the capital city in 1922, but the town was left to decay (Trillo et al., 2020). The city’s increasing population focused more on modern houses than on restoring the older ones, and therefore the Salt Development Corporation chose to develop one iconic house called the Qaqish House. This house was restored in three phases in 1989, 1993, and 2000 and now acts as the As-Salt City Development Office (Trillo et al., 2020). The team used BIM objects to find the relevant architectural elements in the house, and using various software such as Auto-desk Revit and AutoCAD, they were able to restore it. 3D laser scanning was used to identify assets in the house. This transformation is iconic in the city, and every step was well documented for future reference.
Another example is the Hazzazi House in Old Jeddah, restored using the HBIM model and ArchiCAD software. King Abdulaziz University and volunteers did the preservation because restoration was not common in the city. Hazzazi is a house located in the Al Mazloum neighborhood and was named after the family that lived in it (Baik et al., 2021). It was a four-story building that was initially built in 1875 and was chosen by the local administration to preserve the historical significance of Jeddah. The restoration of this house was done in five phases; the first was collecting relevant information from King Abdelaziz University using the available online sources. The second step was organizing the data collected and verifying its validity (Baik et al., 2021). The third step involved laser scanning of the Hazzizi house, the fourth stage was to use the information from the laser to re-draw the plan for the house, and the final step was to come up with a redesigned house. After the completion of the house, it became a major architectural heritage in the city of Jeddah, and the UNESCO declaration was made in 2014, naming the city a major cultural and architectural heritage center.
The last example is the Al Bastakia district, formed in the early 1900s. Most of the houses in the district were created between 1890-and 1950, making it the largest historic area of architectural heritage in Dubai (Hadjri & Boussaa, 2007). The district was deserted in the 1970s due to the migration of people to modern cities that were being created in Dubai. In 1994 after the government noticed how people had deserted the district, it appointed Llewellyn Davies to develop a conservation plan to conserve the district’s heritage (Hadjri & Boussaa, 2007). The government set aside funds for conserving the area after many old buildings had been demolished. The recreation was based on rebuilding the old houses with the same old format using the locally available products. However, due to the lack of policies and legislation, there is little evidence on whether the material used to rebuild the district had the same composition as those used in those ancient times (Abdelmonem, 2017). This implies that although the district was reconstructed, UNESCO has not yet declared it a cultural or architectural heritage.
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