Developing a Practice-Based Guide to Terrestrial Laser Scanning (TLS) for Heritage Documentation

Abstract

This research advances the integration of terrestrial laser scanning (TLS) in heritage documentation, targeting the development of holistic and practical guidance for practitioners to adopt the technology effectively. Acknowledging the pivotal role of TLS in capturing detailed and accurate representations of cultural heritage, the study emerges against a backdrop of technological progression and the evolving needs of heritage conservation. Through a comprehensive literature review, critical case studies of heritage sites in the U.S., expert interviews, and the development of a TLS for Heritage Documentation Best Practice Guide (the guide), the paper addresses the existing gaps in streamlined practices in the domain of TLS’s applications in heritage documentation. While recognizing and building upon foundational efforts such as international guidelines developed over the past decades, this study contributes a practice-oriented perspective grounded in field experience and case-based analysis. The developed guide seeks to equip practitioners with structured methods and practical tools to optimize the use of TLS, ultimately enhancing the quality and accessibility of heritage documentation. It also sets a foundation for integrating TLS datasets with other technologies, such as Building Information Modeling (BIM), virtual reality (VR), and augmented reality (AR) for heritage preservation, tourism, education, and interpretation, ultimately enhancing access to and engagement with cultural heritage sites. The paper also critically situates this guidance within the evolving theoretical discourse on digital heritage practices, highlighting its alignment with and divergence from existing methodologies.

1. Introduction

Built heritage serves as a tangible connection to our past, reflecting the architectural innovations, craftsmanship, and societal values of when it was constructed. It acts as a physical archive of history and bridges the gap between present generations and their cultural roots. Heritage documentation (HD) serves as a critical repository of cultural, historical, and architectural knowledge and provides invaluable data for preservation, restoration, and educational purposes. As defined by Stylianidis [1], HD is a continuous process that enables the monitoring, maintenance, and understanding needed for conservation by the supply of appropriate and timely information. Within this framework, HD records play a pivotal role in safeguarding the architectural identity of societies and provide vital clues for understanding the evolution of architectural styles, materials, and construction techniques.

Preservationists and conservationists rely heavily on HD to guide their efforts. Accurate and detailed records of built heritage are essential for making informed decisions about restoration, repair, and maintenance [2]. They provide architects and builders with the precise information required to recreate or restore intricate architectural features. Architectural historians and researchers also turn to these records as primary sources for uncovering the stories and significance behind historic structures. They delve into the drawings, photographs, and historical reports in the documentation archives to interpret the architectural language of the past. This, in turn, informs people’s understanding of cultural shifts, technological advancements, and artistic movements [2,3]. Furthermore, educators and students in architecture, history, and preservation also benefit from HD [4]. The records serve as a pedagogical resource, offering real-world examples of architectural styles and construction techniques. By providing a tangible connection between theoretical concepts and practical applications, the documentation enriches educators’ and students’ academic and professional development by enabling them to examine the details of historic structures, even in the absence of physical access.

Traditional HD methods, like measured drawings, large-scale photography, and written reports [5,6], while reliable, face limitations in terms of labor intensity [7], time consumption [8,9], and the precision needed in modern contexts [10]. These traditional methods can be subjective, vary among documenters [11], and struggle with capturing detailed visual information. The physical nature of their outputs also complicates effective sharing and digitalization, presenting challenges in accessibility and distribution [12]. As heritage sites face various threats, these traditional techniques often do not meet the needs for accuracy, efficiency, and accessibility required today [13,14]. This is where terrestrial laser scanning (TLS), the focal point of this study, offers transformative potential. As confirmed by Rocha and Mateus [15], Martín-Lerones et al. [16], and Moyano et al. [17], TLS, a form of advanced Light Detection and Ranging (LiDAR) technology, enables the rapid and precise collection of dense point clouds, capturing the geometry and fabric of the scanned environment in intricate detail. The incorporation of TLS into documentation processes for built heritage promises to improve the quality, accuracy, efficiency, and completeness of data collection efforts, as discussed in the works of Lemmens [18] and Olsen et al. [19]. Moreover, the rich datasets generated by TLS or 3D models developed from TLS point clouds, especially with the integration of virtual reality (VR), augmented reality (AR), or mixed reality (MR) technology [20,21,22], can transform data into immersive 3D environments that users can explore virtually. This synergy allows for a more engaging experience, enabling viewers to understand and appreciate heritage sites from remote locations, and offering a profound tool for education, restoration planning, and broader public engagement in cultural preservation [23,24]. Given these advantages, TLS has become one of the most adopted technologies for modernizing HD practices.

This research study aims to understand how TLS can be optimally utilized in the documentation of built heritage by identifying and integrating best practices and methodologies that leverage the technical strengths of TLS. Through this investigation, the research intends to enhance the process of documenting built heritage for preservation, analysis, interpretation, and educational purposes. Compared to previous studies, this research offers a more holistic and rigorous approach by employing a robust mixed-methods strategy consisting of an extensive literature review, detailed analysis of three real-world heritage documentation projects, and expert insights obtained from semi-structured interviews. This comprehensive methodology provides deeper insights and broader validation of the proposed guidelines, filling critical gaps in the existing literature. Due to page limitations, this article focuses primarily on findings from the literature review and expert interviews, with detailed findings from the case studies to be presented separately.

Many abbreviations are used in this article to refer to various terms and concepts in the field. To avoid confusion and ensure clarity, these abbreviations and their corresponding meanings are listed below:

• AI: Artificial intelligence;
• AR: Augmented reality;
• BIM: Building Information Modeling;
• CAD: Computer-aided drafting;
• GPS: Global positioning system;
• HABS: Historic American Buildings Survey;
• HAER: Historic American Engineering Record;
• HBIM: Heritage (or Historic) Building Information Modeling;
• HD: Heritage documentation;
• HDP: The Historic Documentation Programs;
• LiDAR: Light Detection and Ranging;
• MMS: Mobile Mapping System;
• MR: Mixed reality;
• NPS: National Park Service;
• RC: Reality capture;
• RBM: Reality-based modeling;
• SfM: Structure from motion;
• TLS: Terrestrial laser scanning;
• UAV: Unmanned aerial vehicle;
• VR: Virtual reality.

2. Literature Review

2.1. Overview of Heritage Documentation Methods

HD involves various methods, each contributing to the preservation and understanding of cultural heritage.

Table 1. A summary of common heritage documentation methods.

Method	Description	Outcomes	Advantages	Limitations
Manual Measurements and Sketches	Using tools like rulers and tape measures for dimensions, coupled with hand-drawn sketches.	Detailed drawings created by hand or in CAD and measurements of specific architectural features.	Detailed and customizable; low cost.	Time-consuming; subject to human error.
Large-Scale Photography	High-resolution images captured using large-format cameras.	Visual records showing fine details and textures of the building.	High detail and clarity; versatile in different conditions.	Limited perspective; requires expertise for best results.
Written Historical Reports and Field Notes	Compiling narratives and notes on the building’s history and architectural style.	Comprehensive historical and contextual documentation of the structure.	Contextually rich; covers non-visual details.	Potential for bias; time-intensive research.
Classical Optical Surveying	Traditional surveying techniques using tools like theodolites and total stations.	Precise measurements and maps showing the building’s dimensions and location.	Accurate; established and standardized methodology.	Labor-intensive; limited in capturing all details.
Laser Scanning	3D representation of structures using laser technology.	High-density 3D point clouds representing the building’s geometry.	High accuracy and detail; efficient over large areas.	Expensive equipment; requires technical expertise.
Close-Range Photogrammetry/Structure from Motion (SfM)	Multiple photographs used to reconstruct 3D models of the subject.	3D point clouds and models with high detail and texture accuracy.	High-resolution outputs; versatile and portable.	Complex data processing; dependent on lighting conditions.
Topographic Surveying	Mapping site features and large structures, often using GPS and aerial photogrammetry.	Topographic maps and digital terrain models of the site.	Comprehensive site data; versatile applications.	May require supplemental data; weather-dependent.
Aerial-Photogrammetry and UAVs	Drones with cameras capturing aerial images for large structures and 3D models.	Aerial photographs and 3D models, especially for large or complex sites.	Broad coverage; captures unique perspectives.	Regulatory restrictions; sensitive to weather and wind.

summarizes commonly used techniques for built heritage documentation, their outcomes, and their advantages and limitations [2,3,12,25,26,27,28,29,30].

2.2. TLS in Heritage Documentation

TLS, a ground-based form of LiDAR technology [31], as illustrated in Figure 1, utilizes laser sensors to collect comprehensive point clouds that depict physical objects accurately [32]. The technology plays a critical role in modern HD. It is effectively utilized to capture the existing conditions of heritage sites, facilitating structural assessments and the creation of interpretative materials. TLS significantly contributes to various aspects of HD, such as developing Building Information Modeling (BIM) or Heritage Building Information Modeling (HBIM) [21,33,34,35,36,37] and damage detection [19,38]. Furthermore, TLS data enhances public education, research, and heritage tourism by integrating VR and AR technologies to produce immersive virtual museums and tours [21,39]. TLS proves particularly beneficial in documenting heritage sites that are in poor condition, such as the Kunerad Mansion in Slovakia [40]. There, TLS successfully captured detailed data in environments plagued by poor lighting and structural instability. Its non-destructive approach allowed for meticulous documentation, laying a crucial groundwork for subsequent restoration and conservation efforts [41,42].

Scanning a heritage structure creates a comprehensive ‘snapshot’ of the target, capturing its current state and distinct architectural features in great detail. This process typically involves a detailed TLS survey. The level of detail (LoD) of the survey is especially critical for historic sites, which often feature unique architectural elements requiring precise documentation for conservation. Given their historical significance, these structures may not withstand multiple scans, emphasizing the need to capture extensive data in the initial survey. High-resolution scans are sometimes necessary to document specific details, even though they require more time and resources [43].

TLS data can generate several outputs that are instrumental in HD. While 3D point clouds, meshes, and orthographic images are the main direct outputs of TLS surveys, downstream products such as HBIM models [44,45], as shown in Figure 2, are often considered primary deliverables from a user-oriented perspective, due to their broader applicability in analysis, communication, and long-term heritage management. These models serve as structured digital environments for managing both geometric and semantic information of heritage structures, making them invaluable for tasks such as preservation planning, damage assessment, and restoration initiatives. Another significant output is the development of interactive 3D environments that merge VR or AR with the scanned data. These immersive environments provide a dynamic and engaging way for the public to explore and learn about heritage sites, making them an effective medium for interpretation and educational purposes [44,46,47]. The TLS point cloud data can also be used to produce 2D drawings. These drawings serve as a traditional form of documentation, capturing the structural and architectural details [48]. These various outputs of TLS data collectively enhance people’s ability to understand, preserve, and share the rich heritage of historical structures.

2.3. Current TLS Guidelines and Standards

This research has examined the breadth, depth, and shortcomings of existing best practice guidelines on using laser scanning for capturing the built environment, especially for documenting heritage structures. It reviewed various resources, including government agency guidelines, professional organization publications, user group and service provider documentation, and laser scanning equipment manufacturer manuals.

2.3.1. Government Agency Guidelines

The Heritage Documentation Program (HDP) of the United States National Park Service (NPS) has posted a Laser Scan Guidance on their website reflecting the assessment of laser scanning and how they incorporate the technology into their cultural resource survey work [49]. The organization claims it now uses TLS on nearly every project to produce 2D- and 3D-measured drawings in CAD format. The document also strongly stresses the importance of using traditional hand-measuring techniques to supplement digital data collection methods like TLS. While acknowledging the benefits of laser scanning, like high accuracy, extensive range, and time-savings, HDP’s guidance primarily critiques its limitations, such as the reliance on direct line-of-sight for data capture and the challenges in ensuring the long-term preservation of the captured point cloud data, which does not align with the durability and clarity standards set by the Secretary of the Interior. A notable limitation of HDP’s guidance is its lack of a detailed and practical workflow for implementing the technology in documenting built heritage. This absence leaves practitioners without a clear roadmap for effectively incorporating laser scanning into their documentation efforts.

A document under development by HDP is Field Record Requirements for Laser Scanning and Photogrammetry [50]. This document outlines HDP’s field record obligations for using laser scanning and photogrammetry to record heritage resources for the development of HDP’s documentation. The requirements detail the necessary components of maintaining records for TLS scan fieldwork, such as project information, equipment details, scanner location maps, registration accuracy reports, and scaled orthographic renders. This document is relatively more practical than HDP’s Laser Scanning Guidance mentioned above, as it includes several templates for users to take TLS scanning field notes. One template can help users sketch a scanner placement map, and another tracks the detailed execution of each scan. However, this document focuses heavily on field execution without adequate emphasis on the other phases of laser scanning documentation projects. It is also overly technical for individuals new to the technology, which may limit its accessibility for less experienced audiences.

The U.S. General Services Administration (GSA) [51] released a booklet titled 3D Laser Scanning Quality Management Program Guide with their Public Building Service branch and consultants. The document provides the recommended QA/QC (quality assurance and quality control) process required by the agency to streamline the execution and acceptance of laser scanning projects within the context of U.S. federal asset management and historic preservation. It presents a laser scanning project lifecycle framework, including procedures from project planning and data acquisition to processing and final submission. Despite its thorough approach to quality management, the guide appears too specialized and technical for those with a limited background in 3D laser scanning or related fields. It focuses heavily on quality control measures, potentially overlooking practical project planning and fieldwork aspects, and missing detailed information for recommended applications of captured scan data. Additionally, the guide lacks targeted information specifically for users in heritage preservation. This generality may limit its applicability for professionals in the field seeking detailed guidance on integrating laser scanning with heritage conservation efforts.

The California Department of Transportation (CALTRANS) [52] published recommended best practices for laser scanning technologies. The document provides detailed specifications for terrestrial and mobile terrestrial laser scanning (TLS and MTLS) projects, procedures for data collection, equipment use, and quality control, to ensure high accuracy in surveying and mapping. It includes guidelines for planning, executing, and documenting laser scanning surveys, emphasizing safety, data accuracy, and efficient project management. Soon after, the Virginia Department of Transportation (VDOT) [53] adopted this document and developed a similar guide. The technical nature and focus on specific standards and project types in both documents limit their accessibility to professionals outside the field of infrastructure project surveying or those unfamiliar with laser scanning technologies.

2.3.2. Professional Organization and Service Provider Publications

Historic England published a book titled 3D Laser Scanning for Heritage: Advice and Guidance on the Use of Laser Scanning in Archaeology and Architecture [54]. The book provides comprehensive guidance on using laser scanning in documenting archaeology and architecture. It updates professionals on technological advancements in laser scanning systems, their integration with other sensors, and offers advice for those unfamiliar with this technique. With its details on scanning hardware, software, and procedures, the book aims to assist in achieving effective heritage project outcomes. One of the most valuable pieces of information in the book might be its sixteen case studies, which include an introduction, a record of the instrument and software utilized, the purpose and justification of laser scanning for the project, the problems encountered, and the project outcomes of the real-world cases. While the book provides detailed guidance on field execution and scan data processing, it also makes a commendable effort to bridge the gap between technical experts and general practitioners. Its accessible language and inclusion of illustrative case studies support a wider audience. However, the publication places less emphasis on broader project planning and the strategic integration of TLS outputs within HD workflows, which could benefit from further elaboration. In addition to this publication, Historic England’s Geospatial Survey Specifications for Cultural Heritage [55] offers important technical standards for 3D data capture that complement the above guidance and should be considered alongside it. More generally, the Getty Conservation Institute’s publications, Recording, Documentation, and Information Management for the Conservation of Heritage Places: Guiding Principles, and its companion volume, Illustrated Examples [56], provide broader context on HD practices and how TLS integrates with other methodologies. These sources collectively demonstrate the importance of multidisciplinary, interoperable approaches in HD, of which TLS is one key component.

Professional organizations and user groups post documents on their websites regarding laser scanning. In their article, Sharma [57] explores the transformative role of 3D laser scanning in documenting heritage structures. They explain the advantages of the technology for HD, briefly introduce the process, and present the Great Wall project as a short case study. Another article, posted by Autodesk User Group and authored by Ellis [58], is informative on the role and benefits of laser scanning technology in construction projects. TruePoint [59] provides “A Complete Guide to the 3D Laser Scanning Process” to detail the procedure, from understanding the technology and equipment used to collecting data and creating point clouds for construction and engineering projects. A blog posted by PourMohammadi [60] introduces the technology to construction professionals and its workflow for capturing the as-built conditions and monitoring the progress of a construction project.

While these resources generally focus on providing useful overviews, they often miss detailed practical implementation strategies, leaving a gap for readers needing more thorough guidance on using the techniques in specific contexts. The lack of targeted advice for HD practitioners, in particular, means that those in specialized fields may not find the explicit support they need for integrating laser scanning into their unique workflows, highlighting a broader need for comprehensive, application-specific guidance within the HD community.

2.3.3. Manufacturer User Manuals

Laser scan equipment manufacturers, such as Leica^® [61], FARO^® [62], and Trimble^® [63], also offer technical manuals for using their laser scanners. These manuals usually cover setting up, operation, and maintenance of the scanners to ensure optimal use and data accuracy. Their benefits include providing detailed insights into scanner specifications, operation, maintenance, and troubleshooting tips, and enhancing user proficiency and equipment longevity. However, they tend to focus on specific models, limiting broader applicability and integration with other technologies or brands. Moreover, they generally lack comprehensive guidance for the entire TLS project lifecycle and are not tailored for HD, missing specific challenges and requirements for this discipline.

Table 2. Comparative analysis of existing TLS guidelines for HD.

Guideline Source	Title/Document Name	Key Features	Advantages	Limitations
Government Agency	HDP-NPS	Laser Scan Guidance	Discusses TLS use in heritage; emphasizes supplementing TLS with hand measurements.	Highlights TLS accuracy, range, and speed.
Government Agency	HDP-NPS	Field Record Requirements for Laser Scanning and Photogrammetry	Templates for TLS field documentation; technical recording requirements.	Practical templates; detailed field note structure.
Government Agency	GSA	3D Laser Scanning Quality Management Program Guide	Quality assurance/control processes; lifecycle framework from planning to submission.	Comprehensive QA/QC guidance; detailed lifecycle approach.
Government Agency	CALTRANS/VDOT	Recommended Best Practices for Laser Scanning Technologies	Procedures for planning, data collection, quality control, and safety management.	Detailed specifications for TLS/MTLS; thorough accuracy guidelines.
Professional Organization	Historic England	3D Laser Scanning for Heritage	Case studies; updates on hardware/software; detailed execution strategies.	Comprehensive technical reference; valuable real-world case studies.
Professional Organization & User Groups	Various Articles	General introductions and guides on laser scanning	General overviews; benefits of laser scanning; brief case studies.	Informative and accessible for new users; general understanding of TLS workflow.
Manufacturers	Leica®, FARO®, Trimble® Manuals	Technical User Manuals	Operational setup, scanner maintenance, and troubleshooting.	Detailed equipment-specific guidance; enhances user proficiency.

compares the key features of each guideline and manual included in this study along with their advantages and limitations.

2.3.4. Academic Literature on TLS Guidelines for Heritage Documentation

While most existing guidelines included in this study have emerged from government agencies, professional bodies, or equipment manufacturers, the academic literature also highlights the need for structured TLS workflows in HD. For example, the authors’ own systematic review, Static Terrestrial Laser Scanning (TLS) for Heritage Building Information Modeling (HBIM): A Systematic Review [29], found that “The absence of guidelines for using static TLS surveys for HBIM data acquisition … is a significant challenge that must be addressed.” Although this article focuses on HBIM, it underscores a broader academic consensus about the need for acquisition standards, extending directly to broader HD.

Recent work by Teppati Losè and Rinaudo [64] expanded the scope beyond HBIM, offering a systematic literature review of built HD practices and reinforcing the call for unified, practical handbook-style guidance. Additional recent studies, such as Sánchez-Aparicio et al. [65] review on damage detection in heritage constructions based on 3D point clouds and Zachos and Anagnostopoulos [66] on combined TLS, UAV, and mixed reality (MR) workflows for 3D modeling and recreation of religious heritage monuments, showcase TLS’s role in diverse heritage contexts, but also note varied methodologies and a lack of consistent procedural guidance.

In positioning this guide within current theoretical debates, the authors acknowledge the tension between standardized methodologies and the context-specific nature of HD. While prior initiatives have proposed modular or adaptable frameworks, this guide seeks to operationalize those insights through field-tested protocols and tools. This complements rather than replicates existing efforts, emphasizing practical adaptability grounded in theoretical awareness of digital heritage’s complexity.

2.3.5. European Initiatives and Multimodal Digitization Frameworks

Several large-scale European-funded initiatives, such as 3D-ICONS [67], 3D-Coform [68], Eureka3D/VIGIE [69], and 4CH (Competence Centre for the Conservation of Cultural Heritage) [70], have made substantial contributions to the development of 3D digitization frameworks for cultural heritage. These projects emphasized an integrated and multimodal documentation strategy, situating TLS within a broader methodological ecosystem that includes image-based modeling (e.g., photogrammetry, SfM, RTI) and range-based modeling (e.g., TLS, MMS). Collectively referred to as reality-based modeling (RBM), this paradigm advocates the strategic use of different technologies based on site characteristics, conservation goals, and institutional resources.

For example, the Eureka3D/VIGIE 3D Digitisation Guidelines (2024) [71] provide a typology of documentation contexts, practical workflows, and equipment selection criteria tailored to cultural heritage institutions of varying sizes and capacities. Likewise, 3D-ICONS established a comprehensive digitization pipeline, from planning and acquisition to metadata integration and dissemination via Europeana [67], while 3D-Coform advanced the state-of-the-art in 3D capture, semantic enrichment, and the socio-economic integration of 3D documentation practices [68]. Finally, 4CH has laid the groundwork for a European Competence Centre that supports capacity building, standardization, and policy development for digital heritage conservation, with a strong focus on 3D technologies [70].

While these initiatives establish a rich theoretical and institutional foundation for multimodal documentation, this study contributes a focused, field-oriented resource specifically tailored for TLS application in heritage contexts, particularly where multimodal integration is not yet fully operational.

2.4. Summary

The literature review has revealed that despite TLS’s significant benefits and acceptance in the field of HD, there remains a notable gap in holistic and practical guidance for inexperienced practitioners to utilize the technology effectively. Existing resources offered by government agencies, professional organizations, and manufacturers, while insightful, often lack specificity for the needs of HD, omitting complete project processes and focusing on technical details or specific equipment or software. Recent academic studies further highlight the critical gap in unified and practical TLS guidelines. These studies consistently emphasize the absence of structured, comprehensive standards as a key challenge facing practitioners. The published case studies reviewed in this study also indicated the absence of a comprehensive and structured workflow for planning and performing TLS HD projects. It appears that “everyone has to come up with their own game plan.” Consequently, there is a pronounced need for a holistic TLS Best Practice Guide tailored to heritage conservation. This guide should offer a streamlined framework involving project planning, fieldwork execution, data processing and application, and integration with other data acquisition methods. Furthermore, this proposed guide needs to simplify technical information and provide practical advice to make it accessible for beginners in heritage preservation.

3. Methodology

3.1. Research Approach

This research adopted a mixed-methods approach, primarily focusing on qualitative methodologies, complemented by quantitative analysis of point cloud data collected from case studies. The qualitative method involved an in-depth literature review, multiple case studies, and semi-structured expert interviews. This approach was divided into four phases: (1) review of published TLS guidelines; (2) intensive case studies of three separate HD projects; (3) semi-structured interviews with seven TLS and HD experts; and 4) development of a best practice guideline using the data acquired from the literature review, case studies, and interviews. Figure 3 shows an overview of the methodology and critical activities. Detailed methodologies, data analyses, and specific outcomes for each case study have been peer-reviewed and published [72,73,74]. Due to page constraints and the separate publication of the case studies elsewhere, this article provides only a brief overview of the case studies. Instead, it primarily focuses on findings from semi-structured expert interviews and the subsequent development of the TLS Best Practice Guide.

3.2. Case Studies

The development of the proposed TLS Best Practice Guide was substantially informed by three HD case study projects. This section summarizes their rationale, representativeness, and key insights contributing to the formulation of the guide.

3.2.1. Rationale and Selection Criteria

To ensure comprehensive representation of typical HD scenarios, the selection of these projects followed strict criteria to cover diverse historical significances, architectural styles, scales, structural complexities, environmental settings, documentation objectives, and technical challenges. Specifically, the criteria included the following:

• Historical and Cultural Significance: Sites listed on U.S. National Historic Landmarks or of substantial local or national historical importance.
• Architectural and Structural Diversity: Structures including varied styles, scales, materials, and structural compositions.
• Documentation Purposes: Different purposes such as assessment, conservation planning, restoration, and educational interpretation.
• Technical and Logistical Challenges: Projects present unique challenges such as structural instability, limited site accessibility, and environmental constraints.

Following a review of fifteen heritage projects documented by the lead author, the Edmund Pettus Bridge (Selma, AL), the Old Depot Museum (Selma, AL), and the Tankersley Rosenwald School (Hope Hull, AL) were chosen due to their collective ability to cover this comprehensive set of criteria.

3.2.2. Overview of Selected Case Studies

The Edmund Pettus Bridge [72] represents a large-scale historic infrastructure. It presented unique technical challenges such as structural vibrations from ongoing traffic, extensive coverage requirements, and difficult access points. TLS was successfully integrated with UAV-based photogrammetry, demonstrating the adaptability of TLS in complex, large-scale settings.

The Old Depot Museum [73] is situated in an urban context, presenting intricate architectural details and spatial complexity. This case highlighted the necessity and advantages of integrating TLS with supplementary data acquisition methods like photogrammetry and high-resolution imaging, ensuring comprehensive documentation of complex architectural heritage.

Tankersley Rosenwald School [74] is an unstable and historically significant building that poses substantial safety concerns. The project highlighted TLS’s capability as a non-intrusive, sensitive documentation method for deteriorating heritage structures, addressing unique preservation scenarios where safety and minimal physical intervention are paramount.

3.2.3. Representativeness and Contribution to the Guide

These three cases collectively exemplify common scenarios encountered in heritage documentation, ranging from large-scale infrastructure sites to complex architectural structures and vulnerable, deteriorating buildings. Each case represents distinct but frequently occurring field conditions, technical challenges, and heritage values that practitioners must navigate in real-world projects. As such, the projects informed both the structure and substance of the TLS Best Practice Guide, particularly with respect to field planning, data acquisition, and situational problem-solving.

However, it is also important to acknowledge the limitations in the geographic and typological scope of these case studies. All three projects were carried out in the Southeastern U.S. and focus primarily on architectural or infrastructural heritage. Other heritage typologies, such as archaeological landscapes, movable heritage, or industrial and rural sites, are not directly represented. Consequently, while the guide offers transferable workflows and tools, its direct applicability to other heritage domains may be constrained. Future research is encouraged to validate and adapt the guide across a broader spectrum of heritage types and regional contexts to strengthen its generalizability.

3.3. Semi-Structured Interviews

The choice of using semi-structured interviews was grounded in the need to capture the depth and diversity of TLS and HD expert knowledge in this specialized field. The flexible nature of semi-structured interviews allowed experts to provide detailed insights and share unique perspectives that might not emerge in ethnographic interviews [75]. Also, this method was appropriate for examining the practical, real-world aspects of TLS in heritage conservation. They offered the opportunity to discuss hands-on experiences, challenges, and solutions in detail [76]. This flexibility was crucial in a technically detailed field like TLS and allowed the researcher to adapt the conversation to explore emerging topics of interest and relevance.

3.3.1. Selection of Experts for Interview

It was essential to include diverse viewpoints, experiences, and expectations in the study. The research chose the snowball sampling method for selecting interview respondents. Snowball sampling is effective for gathering rich, in-depth data from a network of individuals who have specific expertise or experience [77]. It is especially useful when there is no readily available list of all members of the population for a study [78]. This approach starts with a few key individuals and expands through their recommendations into a rich pool of expertise.

Two TLS and HD experts whom the authors previously knew were selected as a starting point for exploring the field. During the interviews with these initial experts, each interviewee was specifically asked to recommend further experts who could contribute valuable perspectives to the study. This approach effectively broadened the pool of potential interviewees and ensured a more comprehensive coverage of experts from various backgrounds. Once a suitable candidate was identified, the next step involved a background screening of this potential interviewee using publicly available information, such as their LinkedIn profile and online CV, to confirm that the candidate had relevant experience and expertise for the study. An important aspect of the screening process was the emphasis on diversity to include professionals from different sectors and with varied experiences and geographical locations to enrich the research with comprehensive perspectives and deeper insights into the field. Once an expert was identified as suitable based on the screening criteria, a formal invitation was extended via email, explaining the aim of the study, the logistics of participation, and the benefits of their involvement. Throughout this recruitment process, ethical considerations were at the forefront. Emphasis was placed on voluntary participation and confidentiality to ensure that all respondents were fully aware of the nature of the study and their involvement.

3.3.2. Design of Interview Questions

A set of questions was prepared to guide the interviews. These questions include various themes to capture a holistic view of the experts’ perspectives regarding the use of TLS for HD. These themes are as follows:

• Demographic Information: Understanding the background of the experts.
• Experiences with TLS in HD: Gaining insights into practical applications and firsthand experiences.
• Perceptions of Benefits and Limitations: Exploring the advantages and potential drawbacks of using TLS in this field.
• Opinions on the Need for a TLS Best Practice Guide in HD: Gathering views on the importance and impact of standardized practices in TLS applications.
• Suggestions for Key Components in a Proposed Best Practice Guide: Seeking expert input on what should be included in the best practices for TLS usage.
• Future Trends in the Field: Anticipating upcoming developments and changes in TLS applications.

3.3.3. Interview Settings and Procedure

All the interviews were conducted via a virtual meeting platform, like Zoom and Microsoft Teams, to address geographical dispersion and enhance scheduling flexibility and efficiency. In addition, the virtual platforms enabled the recording and automatic transcription of interviews, which ensured accurate data capture and facilitated a thorough post-interview analysis.

The interviews took place between August and December 2023. Each participant received a list of questions three to seven days prior to their interview. This preparatory step was to provide the experts with adequate time to reflect on and formulate their responses, which enhanced the depth and thoughtfulness of the discussion. The interviews were designed to last around 90 min to offer a balance between a thorough exploration of the subject matter and consideration of the experts’ time and engagement levels. This duration proved effective in covering the topics comprehensively while allowing for a natural flow of conversation and in-depth discussions. With the consent of the participants, all interview sessions were recorded. These recordings played a crucial role in ensuring the accuracy and integrity of the data collected. They allowed for a detailed post-interview analysis and served as a reliable reference point for the research. The interviews were also recorded using handwritten notes.

3.3.4. Analysis of Interview Responses

A thematic approach was chosen for analyzing interview responses in this research. According to Harper and Thompson [79], this method is highly adaptable, making it suitable for the varied and complex nature of data gathered from the semi-structured interviews. This approach allowed for a more in-depth exploration of the data. It went beyond plain descriptions to identify underlying themes and patterns in the data collected from interviews [80]. As illustrated in Figure 4, the thematic analysis process followed a structured approach and involved the organization, categorization, and detailed analysis of the data. The objective was to extract comprehensive insights from the interviews and present them in a way that would highlight the key themes relevant to the use of TLS in HD.

In the thematic analysis process, the findings were grouped by themes rather than discussing each interview sequentially. This method allowed for a more coherent and focused discussion of the data and enabled the identification of common threads and patterns across different interviews. For instance, all responses related to the benefits of TLS were grouped under one theme, while the challenges of the technology were discussed under another. This approach ensured that each theme was explored comprehensively to cover the range of perspectives provided by the interviewees. Qualitative Color Coding (QCC) was performed for each interview transcript to derive themes and patterns from the analysis. QCC is an important tool for turning the raw qualitative research data into a more communicative and reliable format [81]. Within each thematic category, the responses were compared and contrasted to highlight both areas of consensus and differing views, and to understand the breadth and depth of the opinions and experiences shared by the experts. This approach allowed for a thorough interpretation of the data.

3.3.5. Limitation of Geographic Scope of Interviewees

While the expert interviews in this study provided valuable, practice-based insights into the topic, the authors acknowledge that the sample is geographically concentrated in the U.S. This regional bias is a reflection of the lead author’s professional network and logistical constraints during the data collection phase. Furthermore, to mitigate the limitations of the sample, the study integrated findings from an extensive review of the global academic and professional literature. Nonetheless, a more diversified geographic representation in future expert engagement would provide additional perspectives on region-specific workflows, institutional standards, and technical constraints.

3.4. Development of a “TLS for Heritage Documentation Best Practice Guide”

This phase focused on synthesizing the data obtained from case studies and semi-structured interviews. It allowed the integration of practical findings from real-world case studies with the theoretical and experiential insights gained from interviews with TLS professionals. The integration aimed to connect these two valuable data sources to establish a holistic best practice guide and to ensure that it was grounded in both practical research and expert consensus. Figure 5 illustrates the steps of the process.

The final stage of the research involved creating a “TLS for Heritage Documentation Best Practice Guide” (the guide). Building on the preliminary framework established from earlier findings, this step refined the guide and incorporated detailed tasks with their expectations to reflect practical workflows typical in heritage projects. Although it was developed to emphasize project planning and TLS fieldwork, the guide offers a comprehensive view of the TLS process, including recommendations for key aspects of scan data processing and utilization. The guide also provides information to help practitioners decide if the TLS is feasible for their documentation projects.

4. Interview Results and Analysis

Seven TLS and HD experts were successfully recruited and interviewed for this research. All interviews were recorded and transcribed for accuracy and thoroughness. The transcripts and notes taken by the researcher served as the primary data source for subsequent analysis.

4.1. Respondent Backgrounds

The group of respondents included a diverse range of professional experiences and academic backgrounds, all relevant to the application and study of TLS in HD through their professional practice and educational careers. This collective expertise, characterized by its multidisciplinary nature, provided a comprehensive understanding of the research’s technological, methodological, and practical aspects. Four respondents hold careers in academia while actively engaging in practical research, and two have over 20 years of experience contributing to the theoretical frameworks of HD. From a practical standpoint, the respondents possessed substantial experience directly applying TLS in HD projects. This included hands-on involvement in field surveys, TLS equipment, data processing, analysis, and the evaluation of various documentation technologies in heritage conservation settings. Their practical experiences were complemented by their proficiency in related technologies, such as photogrammetry, CAD, BIM, and HBIM. An international dimension was added by including experts from various geographical regions, notably North America and Europe. This international representation broadened the research scope, allowing for examining TLS applications within varied cultural and regulatory environments. Figure 6 illustrates the approximate locations of the interview respondents.

4.2. Results and Analysis

The thematic analysis of the interview transcripts yielded five key themes relevant to the research objectives. These primary themes are as follows:

• Current Status of TLS: Provided a foundational understanding of TLS’s role and application in HD, which was essential for developing relevant best practices.
• Advantages and Opportunities of TLS: Highlighted the technology’s strengths to emphasize these aspects in developing effective best practices.
• Limitations and Challenges of TLS: Identified areas for improvement, guiding the creation of best practices to address and mitigate these issues.
• Future Trends and Innovations in TLS: Informed the development of forward-thinking and adaptable best practices that stay relevant as technology evolves.
• Need for Best Practices Guidelines for TLS Usage and Their Key Scope: Gathered expert insights to shape comprehensive and applicable guidelines to ensure the practical implementation of TLS in heritage projects.

The following sections present and discuss the results and analysis of each theme. Due to the page limit, this article focuses on theme 5, the need for best practice guidelines and their key components, while briefly presenting the findings on other themes.

4.2.1. Current Status of TLS in HD

As illustrated in the QCC chart in Figure 7, the current status of TLS reflects its integration with other documentation methods, its supplemental role in the field, and its evolving adaptation amidst standardization and user skill level challenges. These findings reflect the need for a standardized TLS guideline in the field.

4.2.2. Advantages and Opportunities of TLS

TLS offers many benefits and strengths. By understanding these areas, the proposed best practices can be tailored to maximize the potential of TLS and to ensure that these advantages are effectively utilized and communicated within the practice. The insights gathered from the interview respondents on the advantages and opportunities of the technology (e.g., comprehensiveness and high accuracy, high efficiency and speed, visualization, capability to integrate with other technologies, and non-contact and non-invasive nature), as shown in Figure 8, reflected similar conclusions drawn in the literature review.

4.2.3. Limitations and Challenges of Implementing TLS

Identifying the disadvantages and drawbacks associated with TLS was also important. Addressing this theme in the best practices ensured that they provided practical solutions and strategies to mitigate the challenges, thereby enhancing the overall effectiveness and applicability of TLS. Several limitations and challenges of the use and implementation of the technology in HD (as shown in Figure 9), spanning a range of financial, technical, and methodological aspects, were noted by the interviewees and confirmed by the findings from the literature review.

4.2.4. Future Trends and Innovations in TLS

Investigating TLS’s advancement in HD allowed for the development of forward-looking best practices that will remain relevant and effective over time. By understanding upcoming technological innovations and potential shifts, the researcher established strategies to enhance the longevity and adaptability of the research findings. The respondents’ insights, as illustrated in Figure 10, painted a picture of an expanding application of TLS as a rapidly advancing technology, more accessible and adaptable, integrating with other technologies. Some interviewees noted that TLS still plays a complementary role alongside traditional documentation methods such as photogrammetry, GPS, and measured drawings. The findings from this question inspired the researchers to develop a TLS guideline with the capability to incorporate future technologies.

4.2.5. Need for Best Practices for TLS Usage and Their Key Scope

Insights from respondents on the need for and necessary components of a best practices guide were instrumental in shaping the structure and scope of the guidelines proposed by this study. By gathering expert recommendations on what should be included in the best practices guide, the research enhanced the relevance, practicality, and effectiveness of the implementation of best practices.

As a result, the respondents unanimously agreed that there was a lack of standardized frameworks and a need for best practices or guidance for implementing TLS in HD. Although Respondent #1 mentioned using an “internal workflow to help guide their TLS surveys,” and Respondent #2 stated that “there was a ‘thinking process’ for TLS documentation projects,” these appear to be isolated cases rather than a widely adopted practice. This lack of standardization reflected a primary research gap in the literature review. Respondents #3 and #4 went into detail, proposing outlines for potential TLS implementation guidelines. The contributions and insights from other respondents pointed to a collective understanding of the importance of establishing clear and practical guidelines.

The interview findings also revealed an outline of a prospective framework for a best practice guide for using TLS in HD, which consisted of four main steps: project planning, field scan execution, data processing and management, and scan data application. Figure 11 illustrates the process and key elements proposed by the experts.

The pre-scanning planning phase of a TLS survey was highlighted as extremely crucial. Respondent #4 suggested that “the best practices should focus on overarching methodologies, particularly on setting up in the field to ensure good data quality. This includes studying the project from understanding the historical significance to deciding on the focus areas for scanning.” Experts emphasized the need to define clear project goals and objectives, tailoring the approach to the specific requirements of the client. Understanding the site’s historical context and significance is essential, as Respondent #6 noted the importance of “getting to know the building, walking the site.” This preparation helps identify focus areas for scanning and recognizing site-specific considerations. According to Respondent #4, “they should provide flexibility for different types of sites, whether landscapes or smaller structures, and suggest appropriate scanning methodologies” to adapt to site-specific needs. In terms of resource allocation, it starts with the selection of appropriate TLS equipment. The respondents also recommended understanding the basics of equipment operation and using step-by-step checklists for the tools to ensure efficiency and effectiveness in the field. Developing a detailed, practical, and site-specific scan plan was also critical. This plan should include planning for site access, establishing data accuracy standards, and appropriate scanner settings. The setup of scan stations, scan routes, and targets/controls needed to be carefully planned to navigate potential obstructions and ensure comprehensive coverage of important aspects of the heritage structure.

The execution of TLS scans demands integrating the technology with other documentation methods. Complementing TLS with traditional methods, like hand measurements, and other RC techniques, such as photogrammetry, UAVs, and GPS, is critical for comprehensive data capture. As stated by the experts, field documentation using checklists and comprehensive field notes is an essential part of the fieldwork to record the technical and environmental details of the TLS survey.

Regarding processing and managing TLS scan data, the experts emphasized several critical components that should be included in best practices. Their insights offered a detailed perspective on how to handle the sophisticated processes involved in transforming raw TLS scans into usable and accessible dataset formats. Initially, scans are registered through precise alignment to form a single point cloud for the captured structure. Following this, point cloud data undergoes cleaning and refinement to remove extraneous points, enhancing clarity and usability. The subsequent phase involves converting the refined point cloud data files into practical formats and sizes for their applications in the next stage. Lastly, efficient file storing and sharing mechanisms are crucial, given the large size of TLS data files, to ensure accessibility and facilitate collaborative efforts among HD stakeholders involved.

In utilizing scan data, experts suggested focusing on creating 2D drawings and developing 3D models. Addressing future advancements in technology, especially in automating processes, was seen as beneficial by Respondent #5. Another respondent highlighted the evolution of software like “Scan to Plan,” which extracts 2D drawings directly from point clouds.

The experts’ visions concerning this theme provided critical information for the structure and process of the proposed TLS best practice guide. Challenges for developing this guide were also identified. As Respondent #5 expressed, “the case-specific nature of HD makes establishing universally applicable guidelines challenging.” Respondent #7 also made a similar statement. This perspective is rooted in the diversity of HD contexts, where variations in building typologies, preservation goals, and project environments demand flexible approaches. Therefore, the proposed guide is intended to outline broadly applicable strategies while recognizing that project-specific adaptations are essential to successful implementation.

5. TLS for Heritage Documentation Best Practice Guide

Based on the analysis of the data obtained from the case studies (not reported in this article due to the page limit), semi-structured interviews with TLS experts, and findings from the literature review, the researcher developed a “TLS for Heritage Documentation Best Practice Guide” (the guide) to help practitioners optimize data acquisition when using the technology for documenting built heritage.

The guide is designed to assist professionals who may already have basic knowledge and experience in laser scanning technology. It aims to offer them a holistic view of the procedure and techniques involved in TLS documentation projects to improve the quality and efficiency of their projects. The guide intends to cover all the key aspects of a TLS project while also trying to accommodate adjustments to meet the unique needs and circumstances of each specific project. Its primary focus lies on the project’s principal procedures and fulfilling the goals and objectives of each of its elements rather than delving into highly technical steps and details. Also, the guide steers clear of specifying particular hardware and software products. Instead, it provides recommendations on the capacity and specifications of these resources required for project execution. This approach ensures the guide’s longevity and aids users in navigating the entire TLS project process. Additionally, to align with the scope of this research, the emphasis of the guide is on the initial project planning and fieldwork execution stages, while providing an overview of TLS data processing and management and offering practical recommendations for utilizing TLS point cloud data. Figure 12 shows the guide’s table of contents. A complete copy of the guide is included as a supplemental document for this article.

5.1. TLS Feasibility Determination

According to the research findings, determining the practicality of using TLS for a documentation project involves evaluating several criteria to ensure the technology aligns with the project’s specific needs and constraints. These include the scale, complexity, and condition of the heritage site, accessibility and safety concerns, and the required level of detail and accuracy. Additionally, considerations of the project timeline, budget, and how TLS data integrates with other applications, such as BIM, structural assessments, and conservation analyses, are crucial. A decision-making flowchart was developed (as shown in Figure 13) to assist practitioners in deciding if TLS technology is feasible for their documentation projects.

5.2. Recommended Project Workflow

The research findings revealed a structured approach to employing TLS as a primary tool for data acquisition in HD. The approach includes four principal phases: pre-scanning preparation, on-site survey execution, data processing and management, and the application of the processed data. Figure 14 illustrates a recommended workflow and the main activities for this approach. This unified methodology involves every aspect of a project and engages all relevant stakeholders. It is also adaptable, allowing for customization to align with the unique characteristics of each project and fulfill the specific objectives of the documentation effort. Furthermore, it is worth noting that, as outlined in the research scope, this workflow focuses more on the pre-planning and survey execution phases.

5.3. Supporting Materials

A set of supporting documents was included to enhance the guide. These supplemental materials provided practical and hands-on tools and resources. They include the following:

• Template of Project Information Sheet: Helps users systematically collect background information to thoroughly understand the targeted built heritage.
• Site Assessment Report Template: Guides the evaluation of the site’s current condition, historical context, structural integrity, and specific documentation objectives and requirements.
• Fieldwork Safety Checklist: Ensures all safety protocols are followed during fieldwork.
• Recommended Specifications to Guide TLS Scanner Selection: Assists users in making well-informed decisions regarding choosing TLS systems.
• Scanner Optimal Performance Checklist: Guides users in fine-tuning the scanner to enhance data quality and efficiency.
• Field Record Template: Helps track the project information, site conditions, equipment, and maps for the locations of scan stations, scan targets, and controls.
• TLS Scan Log Template: Maintains a complete record of various aspects of each scan session.
• TLS Scan Data Processing and Management Checklist: Guides users through the critical steps in processing and managing TLS data.
• A Recommended Workflow for 3D BIM/HBIM Model Development: Highlights the key steps utilized in the approach using TLS point clouds to develop models in a BIM software platform.
• A Recommended Workflow for 2D CAD Drawing Creation: Details the process and activities for using TLS scan data to create CAD drawings, such as HABS and HAER.
• Resource Links: A list of useful materials and documentation.

6. Conclusion and Recommendations for Future Study

6.1. Summary of Key Findings

Documenting built heritage structures is essential for their conservation. Traditional techniques have been reliable but come with significant limitations. In contrast, digital technologies have transformed the field of HD and enhanced both the quality and efficiency of the process. Among these technologies, TLS stands out as one of the most influential and widely adopted tools, offering advantages in capturing detailed and accurate representations of heritage structures.

This research adopted a mixed-methods approach by integrating an in-depth literature review, comprehensive case studies of various heritage sites, and semi-structured interviews with experts. The findings revealed a relatively consistent workflow in TLS HD processes despite the unique characteristics and specific needs of each site. Another critical finding from the study was the identification of a knowledge gap in the field: the lack of holistic and practical guidance for practitioners, particularly those with limited TLS experiences, on leveraging the technology to capture existing condition data for documenting built heritage. This shortfall highlighted the broader need for a resource that explains the TLS fundamentals and guides its application through all phases of a documentation project, from planning and fieldwork to data processing and utilization.

To address this research gap, the study presented the development of the “TLS for Heritage Documentation Best Practice Guide” (the guide). The guide incorporated insights from the case studies and expertise shared during interviews. It aimed to streamline the optimal application of TLS technology in HD by offering practical advice and supportive resources. By simplifying technical information and making TLS more accessible, the guide was tailored to enable HD practitioners to elevate the quality and efficacy of their efforts.

Rather than seeking to supplant existing TLS guidelines or international standards, this guide is designed to complement them by contributing a field-based, practitioner-informed framework tailored to the heritage context. Its structure reflects a critical synthesis of academic theory, field-tested practices, and professional judgment, acknowledging that standardized methods must still be contextually adaptive. It addresses common challenges encountered in planning and executing TLS projects and provides field-tested tools, such as checklists and template forms, that promote consistency, efficiency, and clarity in documentation workflows. While it is especially useful for students and early-career practitioners seeking practical guidance, the guide also benefits experienced users by offering a more systematic and comprehensive approach to TLS implementation in heritage contexts. In doing so, it engages with ongoing theoretical discourse about digital HD, fulfilling the research gap between formalized standards and flexible, practice-driven applications.

This research synthesized a wide variety of information on incorporating TLS into HD by creating a structured workflow to optimize TLS implementation. It aimed to offer documentation practitioners a generalized and practical methodology. This study can assist practitioners in meeting the growing demands on the quantity and quality of HD. Therefore, it promises to contribute to contemporary and prospective heritage conservation practices and education.

6.2. Limitations of the Study and Future Research Considerations

The “TLS for Heritage Documentation Best Practice Guide” developed through this study primarily concentrates on the planning and field execution phases of documentation projects. While these initial stages are arguably the most crucial for the successful deployment of TLS, the guide does not delve deeply into the subsequent phases of scan data processing and utilization. This limitation could restrict practitioners’ ability to fully leverage the capabilities of TLS technology in their practice. Future research should aim to enhance the guide by incorporating comprehensive information on the latter stages of HD projects, specifically data processing and application. This expansion could be informed by gathering insights from diverse stakeholders, such as TLS data end users, software developers, laser scan equipment manufacturers, and heritage asset managers. Such an approach acknowledges that a successful HD campaign hinges on a holistic consideration of all procedural steps.

The development of the guide represents a context-specific effort that provides a foundational framework for optimal implementation of TLS. However, this guide has not undergone extensive validation across diverse documentation scenarios, which limits its proven applicability and adaptability, given the wide variety of built heritage characteristics and project needs. To address this limitation, future studies may focus on testing the guide through real-world documentation projects involving various scales and project types. By evaluating the guide’s effectiveness in varied contexts, researchers can identify areas for refinement and enhancement. This approach will validate the guide’s current recommendations and uncover opportunities for its adaptation to meet the unique demands of different built heritage. Engaging in such comprehensive validation efforts will ensure that the guide evolves into a robust and widely applicable tool for TLS HD practitioners.

Another limitation concerns the geographic scope of the expert interviews. Most participants were based in North America, reflecting the authors’ professional network. While these insights are valuable within their context, they may not fully capture international variations in practice. Future studies should include broader geographic representation to enhance the global applicability and inclusiveness of the guide.

The scope of this study was also shaped by the number of empirical sources utilized, including three case studies and seven expert interviews. While these numbers may appear limited, the selection was purposeful and strategically designed to ensure representativeness across a range of heritage contexts, technical conditions, and project goals. This approach follows a qualitative logic of maximum variation rather than statistical generalization. Nevertheless, future studies may expand the empirical base to include additional case studies and a more globally distributed expert cohort, thereby strengthening the guide’s adaptability and cross-cultural validity.

While the guide offers basic strategies for integrating TLS with other documentation methods, such as photogrammetry, hand survey, or UAVs, this study did not aim to systematically develop a fully multimodal workflow. Although integration is touched upon in Figure 7, Figure 10, Figure 13, and Figure 14, and in the supplementary guide, the guide remains primarily focused on TLS-centered procedures. Future research could build on this foundation by developing more robust multimodal frameworks that explicitly define how TLS interacts with other techniques across acquisition, processing, and interpretation stages. Such efforts would enhance the guide’s adaptability for broader documentation scenarios, particularly in complex heritage contexts that demand hybrid approaches. Additionally, while this research recognized the value of TLS in capturing existing condition data for documenting built heritage, it did not fully explore the technology’s potential for long-term monitoring, change detection, and condition assessment. This limitation may narrow the scope of understanding TLS’s capabilities beyond the documentation and come short of fully appreciating its significance in continuous conservation efforts and the sustained management of heritage assets over time. Future research should consider developing specific methodologies and tools that utilize TLS data for systematic long-term monitoring and change detection of heritage structures. This approach involves capturing initial conditions and employing the technology in successive phases to track changes, evaluate conditions, and inform conservation strategies over extended periods. Addressing this gap would highlight TLS’s role in sustainable heritage preservation and ensure that its application supports both immediate documentation needs and long-term conservation goals.