Extended Reality on Chachapoya Cliffside Necropolises: From Digital Documentation to Public Engagement

1.1 Archaeological Context

The Chachapoya archaeological culture, also referred to as the Chachapoya tradition, emerged in the northeastern Andes of Peru, also known as the Amazonian Andes. Despite being relatively understudied within Andean archaeology, its historical significance is undeniable. The term “Chachapuyu” (also written as “Chachas” in chronicles by Garcilaso de la Vega) appears in 16th- and 17th-century ethnohistorical texts to describe a province of the Inca Empire (Garcilaso De La Vega 1976 [1609]). Traditionally perceived as a homogeneous political and cultural entity, recent archaeological research suggests a decentralized political structure (Koschmieder 2017). This model comprises independent administrative units led by regional leaders (i.e., curacas), demonstrating notable cultural diversity across different aspects, from funerary practices (Toyne and Anzellini 2017) to domestic architecture (Guengerich 2017).

The Chachapoya inhabited an extensive region between the Marañón and Huallaga rivers, a transitional zone bridging the Andes and the Amazon (Figure 2). This strategic location facilitated cultural and economic exchanges. According to Church and von Hagen (2008), “the evidence shows that, far from being isolated, the Chachapoya thrived at a cultural crossroads that connected distant Andean and Amazonian societies” (p. 933). Today, their historical territory spans the modern departments of Amazonas, La Libertad, and San Martín.

Figure 2:

Map of chachapoya territory, with the archaeological sites included in our work.

The culture’s existence dates back to approximately the 5th century CE and lasted until the late 15th and early 16th centuries, when the region was first conquered by the Inca Empire and shortly thereafter by the Spanish. These conquests triggered demographic collapse and a rapid decline in the Chachapoya economy, sociopolitical structures, and cultural identity.

The rugged landscape of the Chachapoya region, characterized by steep mountains and deep river valleys, dictated the spatial distribution of settlements. These were often built on high plateaus and fortified using terraced construction techniques to adapt to the environment (Koschmieder 2012). Despite access difficulties, archaeological research in the region has increased in recent decades, leading to the documentation of numerous sites.

However, many aspects of this culture remain poorly understood, making the Chachapoya a compelling subject for further study, including projects like Chacha XR.

The Chachapoya’s geographical setting profoundly influenced their funerary practices (Figures 3 and 4). Tombs were frequently located on cliffs or within caves, underscoring the culture’s adaptation to the environment and their emphasis on ancestor veneration. Distinct funerary patterns have been identified, varying significantly between the northern and southern regions. In the north, anthropomorphic sarcophagi (purumachos) predominate, whereas in the south, collective mausoleums are more common (Nystrom et al. 2010) (Table 1).

Figure 3:

Aerial view of the Utcubamba river valley from tingorbamba.

Figure 4:

Cloud forest in Diablo Wasi.

Many sites feature a combination of these practices. Additionally, funerary structures often exhibit intricate iconography, painted decorations, or friezes with geometric motifs. The choice of inaccessible locations and the significant effort required to construct these sacred sites further emphasize the cultural and spiritual importance attributed to the deceased and their close relationship with the landscape (Toyne and Anzellini 2017).

1.2 Sites and Previous Works

1.2.1 Kuélap

The fortified community of Kuélap, located at coordinates −6.41724666, −77.92376454 (all coordinates provided in this article follow the WGS84 reference system) in the Tingo district, Utcubamba Province, is the most prominent elite settlement of the Chachapoya civilization in the northeastern Peruvian Andes. Its massive defensive walls and intricate internal architecture underscore its function as a highly organized complex, encompassing administrative, religious, ceremonial, and residential spaces (Figure 5). Construction began during the early centuries CE, with continuous occupation until the mid-16th century (Narváez 2011).

Figure 5:

Main entrance of Kuélap.

Kuélap was digitally documented between 2010 and 2012 as part of the Kuélap Virtual project (Ribera-Torró (2016, 2021)), a collaboration between the Universitat Politècnica de València (UPV), the Spanish Agency for International Development Cooperation (AECID), and the Proyecto Especial Kuélap (PEK). The initiative included a 3D reconstruction and an immersive virtual tour based on 360° panoramic photography. However, due to a lack of maintenance and the obsolescence of the Flash-based platform, the project was discontinued.

Our current work has recovered and re-edited archival materials from Kuélap Virtual, integrating them into the interactive experience of Chacha XR (Ribera-Torró 2024). Furthermore, in 2023, a new photogrammetric documentation campaign was conducted, focusing on the site’s petroglyphs.

1.2.2 Karajía

Located at coordinates −6.15651947, −78.01940543 in the town of San Miguel de Cruzpata, Trita district, Luya Province, Karajía is home to a collection of anthropomorphic, polychrome sarcophagi locally known as purumachos (Figure 6). The most remarkable feature of this site is a group of six (originally eight) well-preserved sarcophagi, positioned 24 m high on a cliff along the western slope of the Aishpachaca ravine.

Figure 6:

Karajía sarcophagi, locally known as “purumachos”.

The digital documentation of Karajía was carried out in 2021 as part of the Chacha XR project. The site was entirely documented using drone-based surveys, resulting in high-resolution 3D models, 360° panoramas, and gigapixel imagery as extended reality (XR) assets.

1.2.3 Revash

Revash is located at coordinates −77.8564556, −6.5407174 in the town of San Bartolo, Santo Tomás district, Luya Province. This site comprises 13 mausoleums, which served as collective burial structures for mummified and wrapped bodies. These rectangular buildings, with gabled roofs, were constructed using masonry walls coated in clay and are adorned with red-painted zoomorphic and geometric motifs on a white background (Figure 7).

Figure 7:

Revash mausoleums.

Most of the digital documentation of Revash integrated into Chacha XR was originally conducted in 2011, producing a virtual tour based on 360° panoramas. In 2021, this documentation was expanded by generating a photogrammetric 3D model of the main sector. Notably, the dataset was reconstructed from a freely available drone video found on YouTube of Trans-Americas Journey (2018), demonstrating the potential of open-access media for cultural heritage documentation.

1.2.4 Tingorbamba

Also known as “Pueblo de los Muertos” (Village of the Dead), Tingorbamba is located at coordinates −6.10752034, −77.90385249 in the district of Lámud, Luya Province. The site contains 50 structures, including circular enclosures and individual sarcophagi mortuary structures (Figure 8). Rock paintings can also be observed around the site. The mausoleums exhibit U-shaped layouts with walls reaching up to three meters in height, while the sarcophagi display anthropomorphic traits.

Figure 8:

Tingorbamba sarcophagi.

Tingorbamba was digitally documented in 2021 as part of the Chacha XR project. The data acquisition was performed exclusively using drone-based surveys, generating high-resolution 3D models, 360° panoramas, and gigapixel imagery.

1.2.5 Laguna de los Cóndores

Located at coordinates −6.85367928, −77.69180727, Laguna de los Cóndores belongs to the Leymebamba district, Chachapoyas Province, in the Amazonas region, although it lies within the geographical limits of the San Martín region. Overlooking the lagoon from a rocky cliff at approximately 2,914 m above sea level, seven mausoleums stand, five of which remain well-preserved (Figure 9). These structures, aligned side by side, are constructed with stone walls coated in plastered white clay and decorated with geometric motifs.

Figure 9:

Laguna de los condores mausoleums.

The site gained international recognition in 1997 after the recovery of an extraordinary funerary assemblage, including approximately 200 funerary bundles (quipus and other significant archaeological artifacts). This discovery followed an attempted looting of the site. As a result, the Museo Leymebamba was established, where the recovered mummies and funerary bundles are now curated.

In 2011, one of the contributors to the project independently documented the site using 360° panoramic photography. This archival material has since been re-edited and integrated into the interactive experience.

1.2.6 La Petaca

Located at coordinates −6.8310547, −77.80836759, on the eastern slope of the San Miguel ravine near the border of the Leymebamba and Chuquibamba districts in Chachapoyas Province, La Petaca is a vertical necropolis (Figure 10). The Chachapoya built tombs into these sheer cliffs between the 10th and 16th centuries CE, creating a funerary complex that was used collectively and repeatedly. Spanning over 12,000 square meters, it is the largest and longest-occupied funerary site documented in the Amazonas region.

Figure 10:

La Petaca. Funerary structure n°18 with iconographic anthropomorphic rock art.

Alongside Diablo Wasi, La Petaca is one of the most extensively documented sites in Chacha XR, as the project serves as an extension of the Proyecto Arqueológico Las Peñas (PALP), directed by Dr. J. Marla Toyne. This research has focused on both sites, and a significant portion of Chacha XR’s digital content originates from data collected through PALP.

The PALP project applies a specialized methodology for these inaccessible funerary sites, integrating vertical progression techniques to facilitate documentation in cliffside contexts – a practice referred to as vertical archaeology (Toyne et al. 2018). The project has expanded topographic, audiovisual, and photogrammetric surveys, as well as the classification and analysis of excavated materials. It has also incorporated demographic reconstructions, health and pathology studies, and radiocarbon dating (C14) to enhance the understanding of Chachapoya mortuary practices.

Since 2013, four archaeological field campaigns have taken place at La Petaca and Diablo Wasi: in 2013, 2016, 2021, and 2023, with digital survey methods applied in the last three campaigns. The 2021 campaign, conducted under La Petaca Project, focused entirely on non-invasive spatial documentation, significantly expanding the site’s digital record. This multidisciplinary initiative, led by Panograma Labs in collaboration with the University of Central Florida and supported by the Ministry of Culture of Peru, produced new 3D models, 360° panoramas, and 360° video recordings.

1.2.7 Diablo Wasi

Diablo Wasi is located at coordinates −77.81538262, −6.84754943, on the eastern slope of the San Miguel ravine, near the boundary between the Leymebamba and Chuquibamba districts in Chachapoyas Province. This necropolis consists of several contiguous cliffs, which have also become a nesting ground for birds of prey (Figure 11). The name Diablo Wasi, a combination of Spanish and Quechua, translates to “The Devil’s House.” Smaller in scale than La Petaca, this site features funerary structures built into pre-existing caves, natural ledges, and constructed platforms on narrow ledges.

Figure 11:

Diablo Wasi burial chambers.

Initially, the Proyecto Arqueológico Las Peñas (PALP) focused its research on La Petaca, but in 2016, the project shifted its attention to Diablo Wasi, recognizing its unique funerary characteristics and research potential. During the 2021 field campaign, conducted under the framework of La Petaca Project, a comprehensive digital documentation of the site was carried out. This survey aimed to integrate Diablo Wasi into what would eventually become the Chacha XR interactive platform while also serving as a preliminary study for the 2023 excavation campaign, which focused on the archaeological investigation and detailed 3D reconstructions of key funerary contexts (Figure 13).

1.3 Research Motivations

Understanding the motivations behind this project is essential, as they represent key factors that have enabled its development despite the challenges and limitations encountered along the way. The study and dissemination of Chachapoya culture, combined with the application of emerging technologies for heritage documentation, have been the driving forces behind this initiative.

This project is the result of over a decade of research and fieldwork focused on the Chachapoya region, beginning in 2010 with an initial study on Kuélap. What was originally intended as a short-term engagement evolved into a long-term research commitment, including extended residence in the region, ongoing professional collaborations, and participation in multiple archaeological expeditions. These efforts have contributed to a growing body of research and digital documentation, reinforcing the need for contemporary methodologies in the study and preservation of Chachapoya heritage.

The Chachapoya culture is often characterized as enigmatic, largely due to the scarcity of comprehensive studies and the inherent challenges posed by the region’s geography. The remoteness and inaccessibility of many archaeological sites, coupled with dense vegetation, persistent humidity, and seasonal climatic conditions, have historically limited research efforts. These factors highlight the need for advanced documentation strategies that can overcome logistical constraints while ensuring accurate, non-invasive recording of funerary and architectural contexts.

Beyond its academic significance, this project is also driven by a commitment to cultural preservation. The increasing risks posed by looting, environmental degradation, and natural disasters underscore the urgency of systematic survey. While many archaeological sites are at risk of irreversible loss, digital technologies offer a means to record, analyze, and share these cultural landscapes with a broader audience.

Ultimately, this research seeks to bridge the gap between accessibility and preservation by employing digital tools to safeguard Chachapoya cultural heritage while making it available for future study and public engagement.

2.1 Non-Invasive Archaeological Documentation

The documentation strategy employed a variety of acquisition modalities, including terrestrial, aerial, and vertical progression techniques. This approach ensures that the documentation process does not disturb or alter archaeological contexts, thereby maintaining their integrity. Primary data formats include photography and video, which, after processing and editing, were converted into XR multimedia assets. The software used for this phase includes Agisoft Metashape, Blender, PTGui, Lightroom, Premiere, and Photoshop, among others (Table 3).

2.2 Multimedia Development

From the digital elements obtained through spatial documentation, we developed a web portal and a multi-platform application, forming a hypermedia system where these isolated elements are interactively interrelated within a structured narrative framework.

For evaluation, design, and production purposes, we adopted the analytical model proposed by A. Gifreu for interactive documentaries (Gifreu Castells 2013). In the software development process, we used tools such as Pano2VR, PTGui, Flutter, and WordPress (Table 3).

To methodologically structure and describe the project, we followed the Aristotelian rhetorical framework as applied to interactive construction (Table 2), based on the proposal by A. Gifreu in his dissertation (Gifreu Castells 2013). This approach is structured around the classical categories of inventio, dispositio, elocutio, memoria, and actio. As Gifreu explains:

“We can affirm that developing a web application involves carrying out a rhetorical production process related to the organization of the significant object intended to be constructed: through inventio, content is obtained and prepared; with dispositio, it is structured; and with elocutio, it is expressed using all the selected media. Finally, with memoria, its permanence in space and time is ensured, and with actio, it is built, communicated, and shared” (Gifreu Castells 2013, p. 473).

It is worth emphasizing the interdependent relationship between these categories, which, rather than representing sequential stages of a process, should be understood as interconnected levels within an iterative process as cited in Gifreu Castells (2013, p. 49), “the division into levels should not obscure the unity of the interactive as a complete product. The three fundamental layers or stages of classical rhetoric – inventio, dispositio, and elocutio – are strongly interconnected, and it is impossible to design one without redesigning the others.”

2.3 Inventio: Content, Information Units

2.4 SfM/IM Photogrammetry Datasets

Aerial photogrammetry enables the production of 3D models at varying scales, ranging from broad terrain models and entire vertical sectors to detailed reconstructions of specific structures or artifacts. For this purpose, we utilized a drone equipped with an integrated camera. While drones provide invaluable perspectives of otherwise inaccessible locations, their documentation must be complemented by close-range photogrammetry performed in situ during vertical progression. This technique offers greater detail and allows for the documentation of areas beyond the reach of drones, such as the interiors of structures.

In the specific case of on-rope photogrammetry, we developed a tailored methodology that, to our knowledge, has not been referenced elsewhere in archaeological contexts. This approach is based on the omnidirectional optical system described by Castanheiro et al. (2020), adapting their methodology for challenging vertical archaeological environments and narrow and dark spaces. Vertical progression photogrammetry presents unique challenges compared to traditional photogrammetry. First, it must be performed while suspended on a rope at considerable heights, necessitating restricted movement and stringent safety measures (Figure 12). Additionally, it requires strategies to adequately document dark and narrow spaces without altering the archaeological context.

Figure 12:

Speleologist on vertical progression in Diablo Wasi site.

Figure 13:

3D model of Diablo Wasi–sector 1 – funerary context 01.

To address these challenges, we implemented a telescopic pole system with a mounted camera and lighting unit (Figures 14 and 15). Two distinct setups were employed:

1. System 1: Compact 360° Camera + Omnidirectional Light. Primarily used for interior structures and confined, dark spaces, this system utilizes a compact 360° camera with dual fisheye lenses (e.g., GoPro Fusion). Each shot captures two simultaneous 180° images. The wide field of view provided by fisheye lenses (180° + 180° per pair of images) significantly facilitates data acquisition by reducing the number of required captures, minimizing the risk of incomplete coverage – one of the primary challenges in photogrammetric series. Additionally, an omnidirectional lighting unit is positioned as close as possible to the optical axis to ensure uniform illumination without casting disruptive shadows.

2. System 2: DSLR/Mirrorless Camera. This system also employs a telescopic pole but is equipped with a DSLR or mirrorless camera (e.g., Sony A7III, full-frame) with lighting configured similarly to the previous system. While this setup is heavier and requires greater effort to handle the pole, it provides a significant tradeoff: a full-frame sensor with high dynamic range enables the capture of exceptionally detailed images, resulting in higher-resolution models and improved photogrammetric processing.

Figure 14:

SfM/IM surveying difficult-to-acces, narrow and dark burials with a 360° cámera + omnidirectional light + telescopic pole.

Figure 15:

Interior view of a funerary chamber, during the on-rope SfM/IM surveying.

Terrestrial photogrammetry was conducted at ground level using a tripod-mounted camera. Artificial illumination was generally unnecessary, except in specific low-light conditions.

2.5 360° Panoramic Datasets

Three distinct systems were used for capturing spherical images, depending on the acquisition modality (terrestrial, vertical progression, or aerial):

1. Terrestrial 360° Photography: At ground level, a DSLR or mirrorless camera with a fisheye lens was mounted on a tripod with a panoramic head. The process involved capturing the entire surrounding environment by rotating the camera around its nodal point. The panoramic head was calibrated in advance to ensure distortion-free stitching.

2. On-Rope 360° Photography: When using a tripod was impractical – particularly during vertical progression or inside structures – a compact 360° camera mounted on a mini-tripod or telescopic pole was employed. This system captures the entire spherical environment in a single shot with two simultaneous 180° images.

3. Aerial 360° Photography: These images were captured in multiple segments and later stitched together. Using the drone’s flight software (e.g., DJI GO), the spherical panorama function was used to automate the 360° capture process. However, this method does not capture the zenith, which must be addressed during post-processing.

2.6 Gigapixel Datasets

Gigapixel photography enables the capture of ultra-high-resolution images, allowing for detailed documentation of iconographic elements, inscriptions, and architectural features. Unlike 360° panoramas, gigapixel imaging focuses on specific areas at extreme levels of magnification, providing a valuable resource for research and heritage documentation.

This technique ideally requires robotic panoramic heads and telephoto or super-telephoto lenses (240–500 mm or >500 mm) to ensure precision. However, due to logistical and financial constraints, the project relied on a conventional panoramic head and rotator, which still enabled high-quality results.

Acquisition Process

1. Equipment: Telephoto lenses were used instead of fisheye lenses, providing a narrower but highly detailed field of view.

2. Capture Strategy: A grid-based capture approach was employed, where multiple images were taken in overlapping sequences to cover the full target area.

3. Environmental Considerations: Exposure settings were adjusted dynamically to compensate for lighting variations and weather conditions, ensuring consistency across images.

2.7 360° Video Records

360° video recording extends the immersive documentation capabilities of the project by capturing dynamic, interactive perspectives of archaeological sites. Unlike static imagery, 360° video allows users to experience continuous movement through a site, enhancing spatial awareness and engagement.

2.7.1 Acquisition Modalities

1. Aerial: Mounted on a drone using a custom 3D-printed adapter, the 360° camera recorded sweeping landscape views from an elevated perspective.

2. Vertical Progression: A helmet-mounted 360° camera captured subjective perspectives during climbing and rope-access maneuvers.

3. Terrestrial: A stabilized tripod-mounted system was used for capturing static and moving 360° video at ground level.

The combination of these approaches enabled a comprehensive, first-person reconstruction of the spatial and environmental conditions of each site (Figure 16).

Figure 16:

Survey mode – equipment setup relationships: chord diagram.

2.8 Processing 360° Panoramas

Once the documentary archive was organized and categorized, we proceeded with the editing and processing phase. The workflow varied depending on factors such as camera type, tripod usage, and HDR requirements. Whenever possible, batch processing was implemented to enhance efficiency.

Workflow Steps (Figures 29 and 30).

1. RAW Development. Convert RAW image files into 16 bit TIFFs to preserve original light and color data.

2. Apply basic global adjustments (white balance, clarity, noise reduction) using predefined presets in Adobe Lightroom.

3. Exposure Fusion (HDR Processing). For high dynamic range (HDR) scenes, images were bracketed at different exposures. The LR/Enfuse plugin in Lightroom was used to merge exposures into a single balanced image.

4. Stitching. Panoramas were stitched in PTGui, aligning overlapping images automatically. Manual control points were applied to ensure seamless stitching.

5. Editing and Export. Final color grading and corrections were applied in Luminar Neo.

The final images were exported as high-quality 8 bit JPEGs, optimized for virtual tour software such as Pano2VR.

2.9 Photogrammetric Processing

Photogrammetric processing was conducted using Agisoft Metashape, a software platform offering manual precision control and batch automation for optimized workflow efficiency.

The input data consisted of photogrammetric series captured using various acquisition modalities (terrestrial, aerial, and vertical progression), employing different devices (Mavic II Zoom, Sony A7III, GoPro Fusion). Given this diversity, customized workflows were required for each case.

Workflow Steps (Figures 31 and 32).

1. Camera Calibration. Fisheye cameras (e.g., GoPro Fusion) required custom lens calibration to standardize input data accuracy.

2. Camera Alignment. Images were imported into Metashape, and sparse point clouds were generated. Low-quality images were removed, and masking techniques were applied to eliminate irrelevant background data.

3. Dense Point Cloud Generation. Dense clouds were generated to increase model accuracy, especially for architectural details.

4. Mesh Creation and Texturing. Meshes were generated using depth maps, ensuring efficient model generation.

5. High-resolution textures were applied to create photo-realistic 3D models (Figures 13 and 17).

6. Export and Publication.

Figure 17:

Funerary bundle rescued in the 2023 archaeological campaign. Orthofotos from 3D model.

The final 3D models were uploaded to Sketchfab, enabling interactive public and academic access.

2.10 Processing 360° Video

The post-production workflow for 360° video required multiple rendering stages, extensive storage capacity, and computational power.

Workflow Steps (Figure 33).

1. Stitching. Dual fisheye-lens footage was stitched into an equirectangular format using GoPro Fusion Studio.

2. Stabilization. Motion artifacts were corrected using Mocha Pro in Adobe After Effects.

3. Editing. Color grading, voiceovers, and subtitles were integrated using Adobe Premiere Pro.

4. Export and Publication. Videos were uploaded to YouTube’s 360° platform, enabling VR playback.

2.11 Processing Gigapixel Images

Gigapixel image processing focused on stitching, enhancement, and interactive publication to facilitate detailed analysis and high-resolution exploration.

Workflow Steps (Figure 34).

1. Stitching. Images were aligned and stitched together in PTGui, ensuring a seamless composite (Figure 18).

2. Editing and Enhancement. AI-based noise reduction and sharpening were performed using Topaz Denoise AI and Topaz Sharpen AI.

3. Export and Interactive Publication. The final gigapixel images were uploaded to Gigapan, enabling zoomable, interactive exploration.

Figure 18:

Gigapixel image of Diablo Wasi. (a) Stitching process of a gigapixel image of Diablo Wasi from hundreds of single photos. (b) Detail of the gigapixel image showing the high resolution achieved.

2.12 Dispositio: Semantic and Structural Links

The primary objective of this phase was to construct a hypermedia system that seamlessly integrates various digital elements – 360° panoramas, 3D models, gigapixel images, 360° videos, and textual content – into a unified, immersive, and interactive user experience. This process can be likened to assembling a puzzle: as writer Georges Perec (1978/2025) famously noted, an individual puzzle piece holds no intrinsic meaning, nor do two connected pieces; only when all the pieces are correctly arranged does the full image emerge.

Initially, we considered developing a video game-style experience with navigable 3D environments. However, practical constraints – including time limitations, resource availability, and the steep learning curve associated with game engines – led us to opt for an interactive navigation system structured around 360° panoramas. Several key factors influenced this decision:

1. Existing Data: The vast majority of our documentation consisted of 360° panoramas, which are naturally suited for immersive digital experiences.

2. Feasibility: Although engines like Unity or Unreal Engine offered compelling possibilities, their implementation required a level of technical expertise and development time that was impractical within our project’s scope.

As a result, these panoramas became the backbone of an interactive virtual tour, enriched with 3D models, gigapixel images, 360° videos, textual descriptions, and audio elements. The resulting hypermedia system is immersive, non-linear, and deployable across multiple platforms, including web, mobile, and VR.

The main node, or home screen of the application, consists of a 360° panorama that functions as a central menu, allowing users to select among seven different archaeological sites (Figure 20). To illustrate the structural relationships between nodes and links within the system, we developed a node diagram that visually represents the interconnected components (Figure 19).

Figure 19:

Node diagram of the virtual tour, showing 360° pano nodes connection.

Figure 20:

Main node of the app, with interactive hotspots to the archaeological sites.

Initially, we linked panoramas based on visual relationships. However, we soon realized that the high number of nodes created an overly complex and labyrinthine navigation structure, leading to user disorientation. To address this, we transitioned from a network-based structure to a hierarchical tree structure, significantly improving navigation clarity and user orientation.

2.12.1 Hypermedia System of the Application

The hypermedia system was developed using Pano2VR, a software platform chosen for its flexibility, compatibility with various media types (e.g., 360° videos, immersive audio), and our prior expertise with the tool. Additionally, Pano2VR features a skin editor module that allows for customized graphical and functional interface design through visual programming or direct coding. The output of this process is a web-based architecture comprising HTML, JavaScript, XML, CSS, and multimedia assets. Once uploaded to a server, this structure enables the virtual tour to be accessed and navigated online.

However, a web-based format alone was insufficient for our interactive experience, as our objective was to distribute it as an installable application across various operating systems and make it available through official app stores. To achieve this, we developed a multi-platform application using Flutter, an open-source framework specifically designed for cross-platform development, allowing a single codebase to be deployed across Android, iOS, Windows, and macOS (Figure 21).

Figure 21:

Software used and output versions of the app.

Within Flutter, we utilized a WebView component, which loads web content as an embedded layer within the app’s architecture. This approach ensured that all mobile and desktop versions remained synchronized with a single source – the web content hosted on the server. This method streamlined updates and modifications across all platforms, as changes could be implemented by simply updating the web files, eliminating the need to manually update each executable version on different platforms.

For the VR version of the application, we employed TourViewer, a software platform that allows for the implementation of virtual tours generated in Pano2VR on various VR devices, including Oculus Quest, Pico VR, and Samsung Gear VR. This software supports both locally stored and web-hosted virtual tours, significantly enhancing loading speeds and improving the user experience.

However, TourViewer’s licensing model is restricted, as each license is tied to a single device, and it does not support the development of an independent VR application. For this reason, we are currently utilizing TourViewer while exploring the possibility of developing a proprietary VR application using Unity. This transition would grant us full control over the application and allow us to publish it as an independent, installable VR app for a broader audience.

The complete application architecture, including navigation flows, content organization, and interface design, has been systematically documented through a series of technical diagrams. These include the application flow diagram (Figures 36 and 37), which maps all possible user pathways and interactions; the content tree structure (Figure 41), which hierarchically organizes all archaeological sites, nodes, and media assets; and the interface sketches (Figures 38 and 40), which detail the visual layout and functional components of each screen. This comprehensive documentation ensures reproducibility and facilitates future development iterations.

2.13 Elocutio: Presentation

2.13.1 User Experience and Interface Design (UX/UI)

The user experience (UX) and interface design (UI) of the Chacha XR application were developed with a strong emphasis on usability and user orientation. Navigation within the app’s content is structured through the following elements:

1. Hotspots: 360° panoramas are interconnected via hotspots, serving as the primary navigation method while maintaining a rough spatial correspondence with real-world sites.

2. Node Galleries: Separate galleries display XR elements, including 3D models, gigapixel images, and 360° videos. Users can switch between content types within the same site.

3. Maps:

   1. A satellite map (Google-based orthophoto) provides an overview and allows users to jump to specific nodes.

   2. A vertical map (gigapixel image) offers top-down views of cliffs, tombs, or vertical structures that are not visible in standard orthophotos.

4. Graphical User Interface (GUI) Buttons: Standard “home,” “forward,” “back,” and “jump” buttons ensure consistent and intuitive navigation.

Users are able to track their current position using the Horizontal Map (HMap) and Vertical Map (VMap), both of which indicate orientation, field of view, and potential adjacent nodes. Nodes that have already been visited change color (from white to yellow), and a numbered label (4–1) helps users keep track of their recent navigation history.

To enhance visual orientation, a symbolic hierarchy was established to distinguish different vantage points (Table 5). Each type of panoramic node is represented by an animal icon corresponding to its perspective level (Figure 22). In addition, each archaeological site has a distinctive icon inspired by emblematic motifs (Figure 23).

Table 5:

Symbolic categories of hotspots.

Symbol	Type of panorama
Condor	Aerial long range
Eagle	Aerial medium range
Owl	Aerial close range
Jaguar	Terrestrial
Monkey	On Rope
Gueko	Inside tombs
Snake	Inside underground spaces

Figure 22:

Panoramic node icons.

Figure 23:

Chacha XR site icons, inspired by emblematic motifs of each site, such as paintings, petroglyphs, or frieze patterns. (a) Kuélap, (b) Karajía, (c) Laguna de los Cóndores, (d) Revash, (e) Tingorbamba, (f) La Petaca, (g) Diablo Wasi.

2.14 Memoria: Public Storage

2.15 Actio: Distribution and Promotion

The dissemination strategy for Chacha XR was carefully designed to engage multiple audience segments, ensuring broad visibility and impact. The primary target groups include:

1. Digital Cultural Content Consumers: XR media assets have been hosted on public repositories to attract a global audience interested in cultural heritage and immersive experiences.

2. Academic and Scientific Communities: Findings and methodologies have been presented at international conferences, including Stereopsia and CHNT29, with peer-reviewed articles contributing to scholarly discourse.

3. Educational Institutions: In collaboration with the Universidad Nacional Toribio Rodríguez de Mendoza de Amazonas (UNTRM), the project is being integrated into educational frameworks, targeting students and educators during the 2023 research campaign of the Proyecto Arqueológico Las Peñas (PALP).

4. Tourism Sector: The Chacha XR official website, chachapoya.org, serves as a reliable resource for cultural tourism, providing rigorously curated information that highlights the region’s archaeological and cultural assets.

5. Local Communities: Public presentations have been conducted in Leymebamba’s central square and in Chachapoyas, hosted at the Ministry of Culture of Peru. These events were complemented by social media campaigns that further extended the project’s reach.

Through this multi-faceted dissemination approach, Chacha XR aims to bridge the gap between academic research, public engagement, and cultural heritage tourism, fostering a dynamic and interactive relationship with the past.

To ensure the long-term sustainability of the project, several strategic initiatives have been considered:

1. Institutional Partnerships: Strengthening collaborations with universities, research centers, and heritage organizations to secure funding and academic validation.

2. Public-Private Funding Models: Exploring hybrid financial models, including institutional grants, cultural sponsorships, and crowdfunding campaigns, to support continued development and expansion.

3. Open-Access Research Contributions: Encouraging the inclusion of Chacha XR within broader open-access initiatives to ensure continued availability of data and resources for both researchers and the general public.

4. Technological Upgrades: Periodic updates to maintain software compatibility with emerging XR technologies and evolving digital platforms.

5. Community Engagement: Expanding local outreach programs and participatory heritage initiatives to involve community members in content creation and documentation efforts.

By implementing these sustainability strategies, Chacha XR seeks to establish itself as a long-term resource for archaeological research, digital preservation, and cultural dissemination.

3.1 Current Achievements

The project has resulted in the comprehensive digital documentation of seven Chachapoya archaeological sites: Kuélap, La Petaca, Diablo Wasi, Karajía, Laguna de los Cóndores, Tingorbamba, and Revash. This dataset includes 91 panoramic 360° images, 37 3D models, 9 gigapixel images, and 6 360° videos, created by combining newly acquired fieldwork data from 2021 with republished materials from previous projects (Figure 24). The distribution of XR assets varies significantly across sites, with Diablo Wasi and La Petaca representing the most extensively documented locations due to their role as primary research sites within the Proyecto Arqueológico Las Peñas (PALP), while sites like Kuélap and Revash incorporate primarily archival materials from earlier documentation campaigns.

Figure 24:

General XR assets by archaeological site and type of multimedia element.

The temporal evolution of spatial documentation efforts (Figure 25) reveals a progression from initial exploratory surveys between 2010 and 2012 (primarily at Kuélap and Laguna de los Cóndores) to systematic, multi-site campaigns in 2021 and 2023. This timeline reflects both technological advancement – with early projects relying primarily on 360° panoramic photography evolving toward comprehensive multi-modal documentation incorporating photogrammetry, gigapixel imaging, and 360° video – and the consolidation of archaeological research priorities at cliffside necropolis sites.

Figure 25:

Temporal evolution of spatial documentation according to archaeological site and type of media.

These XR assets have been published individually or as curated collections on Gigapan (Ribera-Torró 2023d), Sketchfab (Ribera-Torró 2023a), YouTube, and Google Maps–Street View, depending on their format and intended use.

Leveraging the XR assets, we have developed an interactive first-person application featuring a non-linear narrative, allowing users to explore the seven documented sites (Figure 26). The Chacha XR application (Ribera-Torró 2023c) is available on major distribution platforms, including Google Play Store (Android), Mac App Store (macOS and iOS), and Microsoft Store (Windows). For mobile platforms, VR support has been integrated, enabling users to experience immersive content using affordable Cardboard VR devices. Additionally, a VR-dedicated version has been released for Meta Quest and other widely used VR headsets, utilizing the third-party VR Tourviewer software.

Figure 26:

Chacha XR initial screen on android mobile device.

Complementing the immersive application, we have developed a web portal with an encyclopedic approach (Ribera-Torró 2023b), accessible at https://chachapoya.org. This platform serves as the central hub for the Chacha XR project, providing detailed site descriptions, direct access to digital reconstructions, and an integrated search engine for academic articles related to Chachapoya culture. By consolidating relevant scientific research and multimedia resources, the portal enhances accessibility and engagement with this unique archaeological heritage.

The established system facilitates seamless updates; by modifying the web content hosted on the server, changes are automatically reflected across all app versions, ensuring a consistent user experience across platforms.

The published results meet commercial app quality standards, delivering an immersive user experience with robust interactive features. However, further improvements and developments are envisioned to enhance usability, expand content, and ensure long-term impact.

A comprehensive spatial documentation catalog organized by archaeological site, sector, and individual funerary context is provided in Figures 27 and 28. This hierarchical organization demonstrates the systematic approach employed throughout the project, enabling precise reference to specific structures and facilitating future research by clearly identifying the location and coverage of each documented element. The catalog encompasses all seven sites and includes detailed breakdowns of sectors (e.g., Diablo Wasi Sectors 1–4) and individual funerary structures (e.g., La Petaca EF01-EF18), providing a complete inventory of the digital archive.

3.2 Future Directions

1. Usability Enhancements. User feedback will be pivotal in identifying usability improvements, refining navigation, and addressing any detected shortcomings. A primary goal is to incorporate an interactive tutorial or guide to assist less experienced users in adapting to the app’s interface, ensuring accessibility for diverse audiences.

2. Audio Improvements. Spatial audio integration, particularly for VR formats, is a high-priority enhancement. During the latest research campaign at Diablo Wasi (August 2023), ambient sound was recorded in Ambisonic format, enabling the capture of 360° soundscapes. These recordings will be processed and implemented using Pano2VR’s tools to create dynamic, immersive audio experiences. Additionally, the overall sound design, including background music and narrations, will be improved to enhance emotional resonance. Pre-recorded voiceovers will eventually replace synthetic text-to-speech narrations, especially in Spanish, where current results lack naturalness.

3. Quality Optimization. Balancing high-resolution multimedia content with efficient loading speeds remains a central challenge. Offline playback, though currently unfeasible due to storage requirements, could be explored through segmented app versions dedicated to individual archaeological sites. This approach would distribute data demands while allowing localized content optimization.

4. Enhanced stabilization for 360° videos is another priority, aiming to reduce visual artifacts and motion-related discomfort, particularly in VR applications.

5. Content Expansion. The app’s content repository will be enriched with additional XR resources, including new archaeological sites, expert interviews with researchers and local residents and 360° ambient soundscapes. This expansion will provide users with more diverse and comprehensive experiences, further reinforcing the project’s role as a digital heritage platform.

6. Platform Extensions. While the app currently supports mobile VR via cardboard devices, efforts will be made to develop a dedicated VR application for platforms like Meta Store, utilizing Unity to overcome technical constraints. Additionally, TourViewer, currently used in its demo version, offers an interim solution for VR device integration.

7. Dissemination and Marketing. Greater emphasis will be placed on outreach and marketing efforts to raise public awareness of the app’s capabilities and cultural significance. A structured dissemination strategy is under development to systematically increase visibility among both general and specialized audiences.

8. Transmedia Publications. Exploring connections between digital and physical media, the project envisions linking immersive XR content with printed materials through QR codes or augmented reality markers. This hybrid approach would bridge interactive experiences with traditional formats, further broadening accessibility and engagement.

9. Interactive Modes. Expanding user interactivity is another priority. A proposed feature is a guestbook, allowing users to leave comments or share experiences, fostering a sense of community and engagement. This could be complemented by additional participatory features.

10. Museographic Applications. Beyond digital accessibility, the project aspires to develop immersive installations for physical museum spaces. Adapting the app for a CAVE (Cave Automatic Virtual Environment) setup would deliver a profoundly impactful user experience, ideal for educational and exhibition purposes.

11. Gamification. To heighten engagement, a gamified mode is proposed, where users take on the role of heritage researchers. This interactive experience would involve overcoming challenges, unlocking inaccessible areas, and progressing through levels, blending educational objectives with entertainment.

Figure 27:

Spatial documentation by site, sector and funerary context (1/2).

Figure 28:

Spatial documentation by site, sector and funerary context (2/2).

Figure 29:

Workflow 360° panoramas (1/2).

Figure 30:

Workflow 360° panoramas (2/2).

Figure 31:

Workflow SfM/IM photogrammetry (1/2).

Figure 32:

Workflow SfM/IM photogrammetry (2/2).

Figure 33:

Workflow 360° videos.

Figure 34:

Workflow gigapixel images.

Figure 35:

Icons used in the app GUI.

Figure 36:

APP flow diagram (1/2).

Figure 37:

APP flow diagram (2/2).

Figure 38:

APP sketch (1/3).

Figure 39:

APP sketch (2/3).

Figure 40:

APP sketch (3/3).

Figure 41:

APP content tree.

Figure 42:

Web flow diagram.