Integration of digital and traditional methods for documenting timber heritage: Museu da Bacia do ParanáAbstract
This article evaluates the technical and operational feasibility of a hybrid protocol combining traditional manual survey and Unmanned Aerial Vehicle (UAV) based digital photogrammetry as a progressive transition strategy from conventional to digital documentation for historic timber buildings in resource-constrained regional contexts. The protocol was applied to the headquarters building of the Museu da Bacia do Paraná (MBP), Maringá, Brazil, through three phases: manual survey, UAV photogrammetry (DJI Mini 4 Pro / Agisoft Metashape), and comparative data integration within an HBIM environment. Results indicate that the hybrid approach corrected geometric inconsistencies undetected by manual methods, particularly in the roof structure, while reducing field data collection time from approximately two months to 22 minutes. The study suggests that hybrid workflows are viable even with operators in the learning phase and limited equipment, supporting the gradual adoption of digital documentation in regional heritage practice.
Keywords
Digital photogrammetry; Timber heritage; Unmanned Aerial Vehicle; Heritage preservation; Heritage Building Information Modelling
Resumo
Este artigo avalia a viabilidade técnica e operacional de um protocolo híbrido integrando levantamento manual tradicional e fotogrametria digital com Veículo Aéreo Não Tripulado como estratégia de transição progressiva do levantamento convencional para a documentação digital de edificações históricas em madeira em contextos regionais com restrições de recursos. O protocolo foi aplicado ao edifício-sede do Museu da Bacia do Paraná (MBP), em Maringá, Brasil, em três fases: levantamento manual, fotogrametria com UAV (DJI Mini 4 Pro / Agisoft Metashape) e integração comparativa dos dados em ambiente HBIM. Os resultados indicam que a abordagem híbrida corrigiu inconsistências geométricas não identificadas pelo levantamento manual, especialmente na cobertura, reduzindo o tempo de coleta de dados em campo de aproximadamente dois meses para 22 minutos. O estudo sugere que workflows híbridos são viáveis mesmo com operadores em fase de aprendizado e equipamentos de baixo custo, apoiando a adoção gradual da documentação digital na prática patrimonial regional.
Palavras-chave
Fotogrametria digital; Patrimônio em madeira; Veículo Aéreo Não Tripulado; Preservação patrimonial; Modelagem da Informação da Construção para Patrimônio Histórico
1 Introduction
Vernacular timber architecture constitutes a significant portion of the built heritage of Paraná, particularly in the northern and northwestern regions, shaped by an intense colonization process between the 1930s and 1970s (Zani, 2013). These constructions, predominantly built with peroba-rosa (Aspidosperma polyneuron) using techniques such as board-and-batten (mata-junta) cladding, reflect the adaptation of pioneers to local resources and define regional cultural identity (Hoffmann, 2015; Marques; Azuma; Soares, 2010). Timber's dual nature, at once resilient due to its inherent flexibility and vulnerable to biological agents such as fungi and xylophagous insects, moisture, and deformation, renders these structures susceptible to accelerated degradation (Santini; Borghese; Baggio, 2023), reinforcing the urgency of preservation strategies grounded in international principles of minimal intervention and reversibility (ICOMOS, 1964; ICOMOS AUSTRALIA, 2013).
Architectural documentation plays a central role in heritage preservation, providing the basis for precise diagnostics and well-grounded conservation interventions (Letellier, 2007). Non-destructive methods allow pathologies such as decay and termite infestation to be diagnosed through visual inspections and probing, integrating historical and social context in a holistic manner (Ericsson et al., 2018; Palaia et al., 2008). Traditional manual surveys, using tape measures, clipboards, and levels, offer on-site validation and contextual understanding, but are labor-intensive, susceptible to human error, and insufficient to capture the three-dimensionality and deformations characteristic of historic timber buildings (De Fino et al., 2023). The resulting 2D drawings, while fundamental, frequently oversimplify geometric nuances, motivating the adoption of digital alternatives.
Digital photogrammetry, integrated with Unmanned Aerial Vehicle (UAV) aerial imagery, enables the rapid and secure generation of detailed 3D models (Colomina; Molina, 2014). This process relies on two sequential and distinct stages: Structure from Motion (SfM) algorithms perform automated image orientation through feature detection, tie-point matching, and bundle adjustment, yielding a sparse point cloud as an intermediate output (Colomina; Molina, 2014; Marčiš; Fraštia; Terao Vošková, 2024); Dense Stereo Matching (DSM) then densifies this sparse reconstruction by correlating homologous pixels across image sets, producing a detailed point cloud or triangulated mesh (Cogima et al., 2020; Tolentino; Groetelaars, 2018). Comparative studies using terrestrial laser scanning (TLS) as a geometric reference have established operational accuracy thresholds for heritage documentation: point clouds derived from low-cost UAVs have been shown to fall within 10 mm of TLS references, constituting sufficient accuracy for architectural objects (Marčiš; Fraštia; Terao Vošková, 2024), with Brazilian applications recording 78% of UAV-derived points within 8 mm of TLS in a heritage church survey (Cogima et al., 2020).
In this study, a hybrid protocol is understood as a structured and sequential workflow in which manual survey and digital photogrammetry operate in complementarity rather than in isolation: the former provides on-site contextual validation and geometric grounding, while the latter extends spatial coverage to inaccessible areas, with outputs integrated into an HBIM environment. This conception differs from parallel or comparative approaches, in which each method is evaluated independently (De Fino et al., 2023; Marčiš; Fraštia; Terao Vošková, 2024).
In Brazil, digital photogrammetry has been applied to a range of heritage typologies and construction systems. Tolentino and Groetelaars (2018) applied terrestrial DSM photogrammetry to the masonry facade of a colonial church in Salvador (BA), demonstrating that integrating DSM with conventional photogrammetry improves geometric precision while reducing survey time and cost. Cogima et al. (2020) developed a Scan-to-HBIM workflow combining low-cost UAV and TLS for the modernist Church of São Francisco de Assis at Pampulha (BH). Gonçalves et al. (2021) applied SfM-based methods to baroque and eclectic heritage in the historic city of Goiás (GO), noting advantages for ornate facades and elevated measurements. However, applications specifically addressing vernacular timber structures in Brazil remain scarce in the literature, underscoring the methodological gap that the present study seeks to address.
Geometric accuracy provides the foundation for Heritage Building Information Modeling (HBIM), which enriches 3D models with semantic data (materials, historical records, pathologies, and costs) facilitating intervention simulations and lifecycle management (Murphy; Mcgovern; Pavia, 2013; Santini; Borghese; Baggio, 2023). In timber structures, HBIM models can incorporate non-geometric information parameters, such as damage conditions and material degradation, as component attributes (Chen et al., 2025), while geometric modeling has been shown to provide the quantitative basis for structural analysis and conservation decision-making (Santini; Borghese; Baggio, 2023). The effective implementation of HBIM requires the definition of a Level of Information Need (LOIN), which establishes the type and depth of geometric and semantic data to be modeled according to each element's intended use (Lovell; Davis; Hunt, 2023).
The comparative evaluation of survey methodologies requires terminological clarity among three related concepts. Accuracy refers to the degree of geometric correspondence between measured data and the true physical dimensions of the object (De Fino et al., 2023). Efficiency denotes the optimization of time, equipment, and personnel required to achieve a given documentation quality (Colomina; Molina, 2014). Efficacy refers to the capacity of a method to fulfill its intended purpose, encompassing geometric fidelity, surface completeness, and interpretive value of the data produced (Letellier, 2007). These distinctions are particularly relevant in resource-constrained contexts, where trade-offs among the three criteria are inherent to methodological decision-making.
In this study, resource-constrained context refers to scenarios characterized by the unavailability of survey-grade equipment (e.g., total stations, geodetic GPS, or TLS), reduced team size, limited budgets, and operators in the early stages of technical training, conditions typical of regional heritage practice in Brazil (Tolentino; Groetelaars, 2018). Low-cost is operationalized as the use of off-the-shelf consumer UAVs costing under USD 1,000 and commercially available photogrammetric software, as defined in comparable studies (Colomina; Molina, 2014; Marčiš; Fraštia; Terao Vošková, 2024).
Despite these advances, consolidated and accessible protocols specifically tailored to vernacular timber architecture remain scarce. Existing approaches have predominantly been developed for large-scale monuments or masonry structures, often requiring high-cost equipment and specialized expertise that limits applicability in smaller, resource-constrained contexts (De Fino et al., 2023). In Brazil specifically, despite the availability of sophisticated photogrammetric methods, traditional surveying techniques continue to predominate in heritage practice (Tolentino; Groetelaars, 2018), and few studies address the operational dimension of documentation, including operator learning curves and workflow adaptability in workshop-based environments.
The present study addresses this gap by evaluating the technical and operational feasibility of a hybrid protocol, defined as the structured integration of manual survey and UAV-based photogrammetry in a complementary, sequential workflow as a progressive transition strategy from conventional to digital documentation for vernacular timber heritage buildings in resource-constrained regional contexts, applied to the headquarters of the Museu da Bacia do Paraná (MBP), Maringá, Paraná, Brazil. Rather than introducing a novel photogrammetric or HBIM technique, the contribution of this study is centered on the applied context, providing an accessible workflow for vernacular timber heritage documentation under resource constraints.
2 Methodological procedures
This research is characterized as a qualitative case study focused on the architectural documentation of a historic timber building through the integration of traditional manual measured surveys and UAV photogrammetry. This approach is well-suited for investigating methodological procedures, technical limitations, and the potential for complementarity between different data acquisition methods applied to built heritage.
The methodology adopted in this study was structured into three main phases, designed to integrate traditional and digital methods for the survey and diagnosis of the MBP headquarters. This hybrid approach was conceived to maximize the accuracy of the collected data, the comprehensiveness of the documentation, and the efficacy of diagnostic processes, overcoming the inherent limitations of each method when used independently. The sequence of phases was planned to ensure the collection of complementary data and the cross-validation of information, culminating in the creation of a robust and informative HBIM model.
Figure 1 illustrates the structure of the three main phases:
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traditional manual measured surveys;
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digital survey via UAV photogrammetry; and
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comparative analysis and data integration.
From a methodological standpoint, the first two phases comprise the data collection stage, while the third represents the analytical stage.
2.1 Case study: the headquarters building of the Museu da Bacia do Paraná
The headquarters building of the MBP, located on the campus of the State University of Maringá (UEM), represents a significant example of vernacular timber architecture in northern Paraná and constitutes the primary case study for testing the proposed hybrid protocol. Its history and building characteristics render it a particularly relevant object of study for understanding the challenges and potential involved in the preservation of timber heritage. The building, originally a residence with a floor area of 193.23 m², belonged to Mr. Alfredo Werner Nyffeler, manager of the Companhia Melhoramentos do Norte do Paraná (CMNP), and was constructed between 1946 and 1947, a period of intense colonization and development in the northern region of Paraná, driven primarily by coffee cultivation (Silva; Azuma; Gonçalves, 2025). In this context, timber was the predominant construction material, given the abundance of native forests and the relative ease of handling compared to other materials.
The structural framework of the MBP headquarters building is predominantly composed of peroba-rosa (Aspidosperma polyneuron), a high-density, durable timber species widely used at the time for its excellent mechanical properties and resistance to weathering and insect attack. The construction technique employed is the mata-junta system, characterized by overlapping vertical boards and battens that form a robust and aesthetically distinctive cladding system. This technique, common in the vernacular architecture of the region, reflects the adaptation of builders to local conditions and available resources, producing buildings that, while modest in conception, demonstrate technical ingenuity and functionality. The original house featured characteristics typical of rural and urban dwellings of the period, with a floor plan designed to meet the needs of a growing family and everyday activities.
The transfer of the building to the UEM campus took place in 1984, marking a turning point in its history (Figure 2). The change of location and function, from residence to museum, brought new challenges and the need for adaptations. Although the transfer ensured the physical preservation of the structure, it also exposed the building to a new set of environmental and usage conditions, which may have contributed to the emergence or exacerbation of pathologies. The adaptation for museum use entailed internal and external modifications which, while necessary, may have altered some of the original vernacular features of the construction. The absence of detailed records concerning these interventions and the state of conservation of the building before and after the transfer, dismantling, and reassembly constitutes one of the primary documentary gaps that this study seeks to mitigate (Maringá Histórica, 1982).
The architectural analysis of the MBP reveals the presence of vernacular irregularities that are intrinsic to this type of construction. Unlike buildings designed by architects in accordance with strict standards and norms, vernacular architecture is frequently the product of an empirical construction process, transmitted orally and adapted to local conditions. This manifests in minor variations in alignment, squareness, and level, which, although they may be perceived as “imperfections” from a modern perspective, are in fact integral to the authenticity and character of the building. These irregularities, common in timber construction due to the natural movement of the material, hinder accurate surveying using traditional methods and require high-resolution three-dimensional data capture, which digital technologies can provide.
The vulnerabilities of the MBP are diverse and multifaceted. Structurally, the building exhibits signs of timber degradation, including checks, warping, board separation, and, at certain points, evidence of decay and attack by xylophagous organisms, such as insects and fungi. Continuous exposure to moisture and temperature fluctuations, the lack of adequate preventive maintenance over the years, and the absence of an efficient drainage system contribute to the exacerbation of these pathologies. Furthermore, the lack of detailed historical and technical records concerning the original construction, past interventions, and the current state of conservation prevents a comprehensive understanding of the building's evolution and hinders the planning of effective conservation measures. This documentary gap is a common problem among many examples of vernacular heritage, which were often not considered worthy of formal documentation at the time of their construction.
The relevance of the MBP to the application of HBIM and the development of a replicable protocol is undeniable. As a timber structure with vernacular features, visible pathologies, and documentary gaps, the museum's headquarters building offers an ideal scenario for testing the effectiveness of a hybrid approach.
2.2 Phase 1: traditional survey
The traditional survey began with an architectural reconnaissance structured around a characteristic of vernacular timber construction: components follow typological patterns (boards and battens, posts, rails, beams, windows, doors, flooring, and roof elements) but deviate individually due to the natural movement and empirical fabrication of the material. The survey therefore operated on two levels: cataloguing recurring elements by their average dimensions to define a preliminary BIM library, while simultaneously documenting exceptions such as doorway adaptations, dimensional deviations in openings, and discontinuities in the board-and-batten pattern, which reflect timber's intrinsic material behavior.
This phase was carried out by two Architecture and Urbanism students and involved direct measurement using conventional instruments, including tape measures, clipboards, and paper. The team measured interior spaces, openings, wall heights, and cross-sections of accessible construction elements, producing field sketches of floor plans, sections, and elevations with all dimensions annotated on-site. Photographic records supplemented the documentation, enabling the capture of construction details and visible pathologies such as decay, warping, and other surface damage.
Although it provided a solid basis for architectural modeling, the manual survey presented limitations in the collection of roof data due to difficulties in physical access and safety conditions. Nevertheless, the data obtained allowed for the development of an initial three-dimensional model with a sufficient geometric detail for facades and interior spaces, created in Graphisoft Archicad (Figure 3). This preliminary model served as the foundation for subsequent phases of integration with data derived from digital photogrammetry.
2.3 Phase 2: digital survey by photogrammetry and UAV
The second phase involved the application of aerial and terrestrial photogrammetry techniques for the acquisition of high-resolution imagery of the MBP headquarters building. For the aerial survey, a UAV equipped with a high-resolution camera was employed. The digital survey was conducted in the context of a workshop held in January 2025, organized within the scope of a research group dedicated to the documentation and preservation of vernacular timber architecture in northern Paraná. The workshop pursued the dual objectives of documenting the MBP headquarters and introducing UAV photogrammetry as an accessible tool for researchers engaged in the systematic documentation of this regional timber heritage. Unlike photogrammetric surveys structured around rigid planning protocols, this phase adopted an exploratory and applied character, with no prior formal definition of parameters such as a flight plan, standardized stand-off distance from the building, or systematic calculation of image overlap. Nevertheless, minimum conditions for three-dimensional reconstruction were empirically ensured: although no automated overlap calculation was performed prior to the survey, an estimated overlap of 60% to 80% was adopted as a guiding reference, consistent with standard photogrammetric guidelines for UAV surveys (Colomina; Molina, 2014).
The equipment used was a DJI Mini 4 Pro UAV, equipped with an integrated camera (model FC8482), which captured images in JPG format at a resolution of 4032 × 2268 pixels and a 24-bit color depth. Images were recorded under natural daylight conditions, characterized by sunny weather, high temperatures, and light to moderate winds, which did not compromise the quality of the captured images. This equipment represents an accessible entry point for heritage documentation, with an approximate acquisition cost of USD 760, in contrast to terrestrial laser scanning systems, which typically exceed USD 40,000.
Camera settings were not manually pre-configured prior to the survey; instead, the device operated under automatic exposure mode, with white balance set to automatic. The values of ISO 130 and shutter speed of 1/500 s reported in Table 1 reflect the parameters recorded in a representative image; as the camera operated in fully automatic mode, these values varied throughout the session in response to lighting conditions. Image capture was performed manually, frame by frame, without automated flight planning or intervalometer functions, a procedure consistent with the exploratory and educational character of the survey.
Imagery acquisition followed two complementary capture strategies, summarized in Table 2, defined according to site-specific conditions and the immediate objectives of the survey and workshop. Each strategy addressed distinct operational constraints identified on-site, as described below. In the first session, the interval between consecutive captures ranged from approximately 8 to 43 seconds, reflecting the time required for the operator to assess image acquisition, reposition the UAV, and trigger the next frame. In the second session, in which the device was operated exclusively as a handheld camera without flight control, the average interval between captures was approximately 8 seconds.
The first strategy consisted of a manual UAV flight along a spiral trajectory around the building's roof, beginning at 11:14 AM and concluding at 11:27 AM, yielding a total of 49 photographs. This stage focused primarily on documenting the roof geometry, addressing a data gap identified by the manual survey team, which required a more detailed understanding of this portion of the building to refine the BIM model.
The second capture strategy involved using the UAV strictly as a handheld camera, without activating its flight functions. This approach was adopted due to site constraints, specifically the dense vegetation and physical obstacles in the immediate surroundings of the MBP headquarters, which prevented safe aerial navigation (Figure 4). Between 11:31 AM and 11:40 AM, the device was manually operated around the building, resulting in 68 additional photographs with framing parallel to the facade planes.
During this phase, a stand-off distance of approximately 3 to 5 meters from the facades was maintained, at an average height of approximately 1.5 m above ground level, ensuring both comprehensive coverage of vertical elements and sufficient ground sampling distance (GSD) to resolve the constructive details of the mata-junta system, including board widths, batten profiles, and dimensional variations resulting from the natural movement of the timber.
Although no automated overlap control was implemented, an empirical visual criterion was adopted in the field: the UAV controller screen was used as a spatial reference, with each grid cell estimated to represent approximately 33% of the frame width. Lateral displacement between consecutive captures was limited to approximately one-sixth of the screen width, targeting an overlap of 60% to 80% along the horizontal axis, consistent with standard photogrammetric guidelines. Vertical overlap control was less precise due to the simultaneous demands of UAV piloting.
The adoption of this hybrid strategy, combining flight and manual capture, was also justified by operational factors, such as optimizing battery life under moderate wind conditions, which increase UAV stabilization demands during flight. Furthermore, given the educational context and the varying experience levels of participants, manual capture enhanced on-site data collection.
Following the imagery acquisition phase, photogrammetric processing was conducted in Agisoft Metashape (version 2.1.1). The workflow included image alignment with sparse point cloud generation, dense point cloud construction, 3D mesh generation, texture mapping, and model export in E57 format, as detailed in Table 3. Orthomosaic generation was not performed, as the research focused on three-dimensional reconstruction and integration with the BIM model.
Image alignment (Align Photos), based on the automatic identification of tie points between overlapping photographs, resulted in the alignment of 105 of the 117 captured images (Figure 5a), generating an initial sparse cloud of 95,456 tie points. The 12 unaligned images were not subjected to additional procedures to force their inclusion in the model. These images predominantly featured vegetation cover, as illustrated in Figure 5b, which may hinder pixel matching and compromise the photogrammetric reconstruction process.
Unaligned images in the photogrammetric processing: (a) Metashape Workspace panel listing the 12 unaligned images, identified by the "NA" (not aligned) suffix; (b) representative example of an unaligned image, with predominant vegetation cover.
The alignment parameters resulted in a root mean square (RMS) reprojection error of 0.19 pixels. This value indicates good internal consistency within the bundle adjustment. For the generation of the dense point cloud and 3D mesh, comparative trials were conducted using the 'High' and 'Ultra High' quality settings. This comparison was motivated by the known sensitivity of dense matching algorithms to homogeneous low-texture surfaces, which are prevalent in weathered timber structures, with quantitative results presented in Section 3.
No Ground Control Points (GCPs) were employed in this survey, as geodetic GPS and total station equipment were unavailable in the workshop context. This decision was deliberate: the study aims to evaluate the feasibility of a hybrid protocol accessible to practitioners with limited technical and financial resources, for whom formal georeferencing infrastructure is not readily available. Consequently, the RMS reprojection error of 0.19 pixels reflects internal consistency within the bundle adjustment and should not be interpreted as absolute geometric accuracy in a real-world coordinate system.
2.4 Phase 3: HBIM modeling and comparative analysis
In Phase 3, the development of the parametric HBIM model initiated in Phase 1 was further advanced by integrating the point cloud and the 3D model generated in Phase 2, both imported into Archicad in E57 format as a geometric reference layer. Parametric BIM elements were modeled by tracing over the point cloud, with each element adjusted to conform to the as-built geometry. Standardized timber components identified in Phase 1 were reused as parametric objects, with cross-sections and heights guided by the point cloud and complemented by manual measurements where the cloud presented gaps or insufficient density. The direct superimposition of the model onto the point cloud facilitated a geometric comparison of the structures, as illustrated in Figure 6, in which the parametric BIM model is shown in red and the dense point cloud in greyscale.
The geometric comparison between the preliminary BIM model and the as-built conditions captured in the digital data enabled the adjustment of building elements to reflect the real configuration of the structure, with discrepancies and adjustments discussed in Section 3.
Based on these discrepancies, the BIM elements representing the roof geometry were adjusted to reflect the as-built configuration captured by the photogrammetric model. Where the point cloud presented localized gaps, particularly in areas of lower image overlap or significant vegetation occlusion, the manual survey data from Phase 1 was used to interpolate and complete the geometric representation. This iterative cross-referencing between datasets ensured that the final model integrated the complementary strengths of both acquisition methods. This phase concluded with an HBIM model incorporating both the parametric elements from Phase 1 and the geometric corrections informed by the photogrammetric data from Phase 2, establishing the basis for the results and discussion presented in the following section.
3 Results and discussion
The results are presented in two stages: the outputs of photogrammetric processing (Phase 2) and the HBIM integration (Phase 3), providing the empirical basis for evaluating the hybrid protocol against the criteria of accuracy, efficiency, and efficacy defined in Section 1. The comparative processing trials were conducted to establish the most appropriate quality setting for the specific conditions of this survey, particularly the prevalence of homogeneous timber surfaces and the absence of formal ground control points. Both levels were applied to the same image dataset using identical alignment parameters, with the sole variable being the reconstruction quality setting in the Dense Point Cloud and 3D Mesh generation stages. The selection criterion prioritized geometric completeness over point density, given the documentary nature of the study and the operational constraints of the survey context.
The visual analysis of the models, illustrated in Figure 7, highlights morphological disparities between the two processing levels. It is observed that, although Ultra High processing (Figs. 7b, 7d, and 7f) yields superior definition at edges and board joints, it results in a point cloud with a higher prevalence of voids on the flat surfaces of the wall enclosures, where the texture is more homogeneous. In contrast, the High level (Figs. 7a, 7c, and 7e) presents a more continuous and complete surface, albeit with greater visual noise and planarity deviations. This behavior suggests that, at the Ultra High level, the matching algorithm demands greater rigor in point filtering, resulting in higher precision at edges while sacrificing continuity on surfaces with more homogeneous texture. Conversely, at the High level, the reduced demand for fine detail favors cloud continuity in homogeneous areas, yielding a more complete mesh, though with visually rougher and more deformed surfaces.
Processing comparison between High (left) and Ultra High (right) quality levels - (a and b) Dense point cloud; (c and d) 3D model; (e and f) Detail of texture and geometry
The observed behavior reflects a fundamental limitation of feature-based dense matching algorithms: SfM pipelines rely on the detection of distinctive keypoints across overlapping images to establish point correspondences. On surfaces with low radiometric variation, such as the weathered and uniformly painted timber boards of the MBP, the density of detectable features is insufficient to support reliable correspondence, resulting in voids in the dense point cloud precisely where geometric continuity is most expected. This limitation is compounded in vernacular timber construction by the repetitive patterning of elements such as the mata-junta boards, which introduce visual ambiguity that can cause false matches or matching failures. The problem is well documented in the photogrammetric literature: De Fino et al. (2023) identify low-texture surfaces as a primary source of reconstruction gaps in heritage photogrammetry and recommend the use of artificial coded targets to increase feature density in homogeneous areas. Said et al. (2023) similarly note that surface uniformity in heritage materials demands supplementary acquisition strategies beyond standard flight planning. The absence of such targets in the present survey was a deliberate operational simplification, justified by the exploratory nature of the protocol, but it constitutes a methodological gap to be addressed in future applications, particularly for timber surfaces where weathering progressively reduces textural differentiation. These qualitative observations are corroborated by the quantitative data presented in Table 4, which compares point density, processing time, and memory usage across both quality levels.
Accordingly, the High quality setting was selected for the final processing, and the resulting point cloud and 3D mesh were exported in E57 format for integration in Phase 3. Following post-processing steps to remove the surrounding vegetation, the model provided sufficient geometric data for roof slope characterization and volumetric documentation, as illustrated in Figure 8, although localized limitations persist in areas of lower image overlap and shaded regions.
The integration of the photogrammetric model with the HBIM model developed in Phase 1 addressed a critical data gap that the manual survey was unable to fill: the roof structure, inaccessible during Phase 1 due to safety constraints (Figure 3), was fully documented through UAV photogrammetry and incorporated into the parametric model. The resulting HBIM model reflects the complete as-built geometry of the building, including roof configuration and slopes previously absent from the documentation (Figure 9).
The photogrammetric survey revealed a roof configuration comprising approximately ten distinct slopes, a complexity that had remained entirely undocumented prior to the UAV acquisition due to physical access constraints, as evidenced by the incomplete HBIM model produced in Phase 1 (Figure 3). This geometric information was previously absent from the model and was incorporated in its entirety following Phase 2, representing a complete addition of roof geometry rather than a correction of pre-existing data.
The superimposition of the Phase 1 model (traditional survey) onto the Phase 2 - point cloud (digital photogrammetry) specifically facilitated:
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the completion of roof geometry data absent from the manual survey due to access constraints;
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the validation of photogrammetric efficiency for elements with restricted physical access; and
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a superior visual-geometric assessment of building components.
The available quantitative evidence of geometric consistency between the manual survey and the photogrammetric model derives from a facade length comparison conducted during the data integration phase: the manually measured dimension differed from the photogrammetrically derived value by less than 2% (Oliveira; Azuma; Silva, 2025). While this figure reflects point-to-point coherence in a single accessible element, it does not constitute a systematic geometric validation of the complete model. No cloud-to-mesh deviation analysis was performed, and therefore no global discrepancy metric, such as mean distance or standard deviation between the HBIM model surfaces and the dense point cloud, is available for this study.
This absence reflects a more fundamental constraint than the lack of GCPs alone. Since the roof geometry was entirely absent from the Phase 1 manual survey, HBIM roof elements were modeled directly from the photogrammetric point cloud; a cloud-to-mesh (C2M) comparison under these conditions would measure parametric modeling fidelity to its own source data, not accuracy relative to an independent baseline. Furthermore, without GCPs, any computed deviation would reflect internal model consistency rather than real-world accuracy. This contrasts with the facade, where manual measurements and photogrammetric values constituted independent datasets, yielding a deviation under 2%. Future applications should incorporate a simplified georeferencing workflow as a prerequisite for quantitative geometric validation. The HBIM model developed in this study was calibrated to a LOIN consistent with the objectives of architectural documentation and conservation planning. Parametric elements were assigned geometric properties derived from both manual measurements and photogrammetric data, complemented by semantic attributes including nominal cross-sections, material type, and observed conservation conditions. Irregular features inherent to vernacular timber construction were represented where they were dimensionally significant, while minor surface variations were deliberately simplified to maintain model usability. This calibration reflects a methodological decision that the level of information must be sufficient for its intended purpose, without introducing unnecessary complexity that would compromise the practical applicability of the model in resource-constrained contexts.
Among the challenges identified during post-processing, the most prominent were the requirement for technical proficiency in point cloud editing and the removal of unwanted artifacts, such as surrounding vegetation, alongside the absence of established protocols for UAV use on small-scale structures, which imparted an exploratory nature to this phase. The lack of formal georeferencing, through Ground Control Points (GCPs) obtained via total station or geodetic GPS, represents the primary technical limitation of this survey; the internal consistency of the photogrammetric network, reflected in a reprojection error of 0.19 pixels, remained within the operational parameters reported in comparable low-cost UAV surveys of heritage buildings (Marčiš; Fraštia; Terao Vošková, 2024; Cogima et al., 2020). Rather than invalidating the process, these limitations highlight critical areas for future development: the creation of simplified georeferencing workflows for small-scale buildings and the definition of specific guidelines for UAV applications in vernacular timber architecture.
Table 5 compares the documentation outputs achievable from Phase 1 alone against those produced by the complete hybrid protocol, illustrating the incremental contribution of photogrammetric integration and HBIM modeling to a baseline established by manual survey.
Incremental Documentation Outputs of the Hybrid Protocol Applied to the MBP: from Phase 1 Baseline to Full Integration
The hybrid protocol explored at the MBP shares structural similarities with approaches reported in the international and national literature, while presenting operational distinctions that reflect the specific constraints of vernacular timber documentation in regional Brazilian contexts. Cogima et al. (2020) developed a Scan-to-HBIM workflow combining low-cost UAV and TLS for the modernist Church of São Francisco de Assis at Pampulha, achieving 78% of UAV-derived points within 8 mm of TLS reference and demonstrating the viability of hybrid acquisition for heritage documentation in Brazil. Marčiš, Fraštia and Terao Vošková (2024) applied low-cost UAV photogrammetry to hard-to-access interior spaces, reporting deviations within 10 mm of TLS references. Chen et al. (2025) integrated UAV oblique photography and TLS into an HBIM workflow for a historic timber pavilion in China, producing 83 parametric family components and enabling downstream structural analysis via IFC export. In comparison, the present study operated without TLS or GCPs, relying instead on manual survey as the geometric reference baseline, which limited absolute accuracy assessment but preserved the protocol's accessibility for resource-constrained practitioners. This positioning confirms that the hybrid approach at the MBP is methodologically consistent with established international practice while addressing a documentation gap specific to vernacular timber architecture in northern Paraná, a typology largely absent from the existing literature.
Comparative Overview of Hybrid UAV Photogrammetry and HBIM Protocols in Heritage Documentation
The replicability of the hybrid protocol rests on its structural flexibility rather than on fixed equipment or expertise requirements, as evidenced by its execution under explicitly constrained conditions: operators in the learning phase, no GCPs, no formal flight plan, and equipment costing approximately USD 760, yet achieving facade deviation under 2% and full roof documentation in 22 minutes of capture. Unlike approaches dependent on TLS or geodetic GCPs, the workflow demonstrated at the MBP can be adjusted according to available resources, time constraints, and required documentation depth without compromising its core logic of progressive data integration. This characteristic is particularly significant in the context of small and medium-sized vernacular heritage sites in regional Brazil, where financial and technical limitations frequently preclude the adoption of more instrumented survey technologies. The identified limitations of this study, particularly the absence of formal georeferencing and the learning curve associated with photogrammetric post-processing, do not undermine replicability; rather, they define the conditions under which simplified georeferencing workflows and targeted operator training represent the next development step for the protocol.
The HBIM model produced for the MBP now constitutes the first systematic geometric and semantic record of a building that, prior to this study, had no formal architectural documentation beyond 2D sketches. Its parametric structure allows future campaigns to track the progression of identified pathologies, including board separation, biological attack, and structural deformation, directly within the model, supporting evidence-based conservation decisions for a typology at persistent risk of disappearance in northern Paraná.
4 Conclusions
This research proposed and preliminarily tested a hybrid protocol for the documentation of architectural timber heritage, using the MBP as a case study, which had no formal architectural documentation prior to this study. The integration of traditional surveying methods with advanced digital technologies, such as UAV-based photogrammetry and HBIM modeling, proved to be an effective approach for the precise documentation and detailed diagnosis of historic buildings in resource-constrained regional contexts, as demonstrated by facade deviation under 2%, complete roof documentation in 22 minutes of capture, and equipment costing approximately USD 760.
The scientific contribution of this study lies in demonstrating that a hybrid UAV-SfM and HBIM protocol is viable without TLS, GCPs, or specialist operators, unlike comparable published workflows that depend on such resources. Rather than proposing a methodological innovation in photogrammetry or HBIM, this contribution lies in the applied context: an accessible workflow tested for vernacular timber heritage in resource-constrained regional settings. The practical limits of this threshold are equally defined: the absence of GCPs precludes absolute geometric accuracy assessment, restricting the protocol's applicability to conservation planning and pathology monitoring rather than structural engineering specifications. For regional heritage practice in Brazil, where instrumented workflows remain largely inaccessible, this boundary is not a constraint but a point of entry. The resulting HBIM model, integrating a 21-million-point dense cloud with semantic attributes, constitutes the first systematic geometric and semantic record of the building.
Although significant technical limitations were identified, such as inaccuracies stemming from the absence of survey-grade georeferencing and challenges in data post-processing, the results confirmed the viability of the proposed methodology. These limitations highlight important areas for future development: the creation of simplified georeferencing protocols for small-scale structures, the establishment of specific guidelines for UAV applications on timber buildings, and the systematic replication of the protocol across comparable timber buildings in northern Paraná, building a regional documentation corpus that current literature almost entirely lacks.
Acknowledgements
To CNPq – Conselho Nacional de Desenvolvimento Científico e Tecnológico (National Council for Scientific and Technological Development) for financial support through process no. 409649/2023-6.
To F.A. - Fundação Araucária for the award of a scholarship through covenant no. 015/2024.
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SOUZA, B. A. S.; OLIVEIRA, J. G. T.; AZUMA, M. H.; SILVA, R. D. Integration of digital and traditional methods for documenting timber heritage: Museu da Bacia do Paraná. Ambiente Construído, Porto Alegre, v. 26, e155222, jan./dez. 2026. ISSN 1678-8621 Associação Nacional de Tecnologia do Ambiente Construído. http://dx.doi.org/10.1590/s1678-86212026000101015
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Declaration of Generative AI and AI-Assisted Technologies in the Writing Process
During the preparation of this work, the authors used ChatGPT and Claude to check for grammatical issues and improve readability. Following the use of these tools and services, the authors reviewed and edited the content as necessary and assume full responsibility for the content of the publication. The final manuscript was manually reviewed and refined to ensure alignment with the initial concepts and evaluations.
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Financial Support
This study was financed by CNPq – National Council for Scientific and Technological Development (process no. 409649/2023-6) and by Fundação Araucária (scholarship award, covenant no. 015/2024).
Data Availability Statement
The data supporting the findings of this study are available from the corresponding author upon reasonable request.
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Editor-in-chief:
Enedir Ghisi
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Guest editor:
Rosaria Ono
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