Five Basics to Know Before Introducing Terrestrial Laser Scanners to Cultural Properties

Interest in terrestrial laser scanners is growing year by year in the fieldwork of documenting, preserving, and planning restoration of cultural properties. For targets with complex shapes that you want to document without touching—such as buildings, stone structures, archaeological remains, gardens, stone walls, and interior ornamentation—the ability to acquire high-density three-dimensional data in a short time is a major attraction. Overseas as well, terrestrial laser scanners are becoming established as an important means for field surveys and digital recording in the cultural heritage sector, and internationally there is progress toward standardizing digital records and streamlining workflows.

However, surveying cultural properties is not simply a matter of “measuring well.” On cultural heritage sites, there are often overlapping constraints: it is hard to touch the object, access conditions are strict, there are many blind spots, one wants to re-measure later under the same conditions, and one wants to read not only shape but also condition and history. Therefore, when introducing terrestrial laser scanners, it is important not to look solely at the equipment specifications but to think through why you are introducing them, what types of deliverables you want to produce, and how to combine them with other methods.

Table of contents

• Background for the interest in terrestrial laser scanners in the cultural heritage field

• Basic 1 Articulate the purpose of introduction first

• Basic 2 Plan for blind spots rather than assuming you can capture everything at once

• Basic 3 Prioritize field conditions and coordinate management over accuracy specs

• Basic 4 Decide deliverables, preservation formats, and rights relationships up front

• Basic 5 Don’t try to complete everything with the terrestrial laser scanner alone

• Summary

Background for the interest in terrestrial laser scanners in the cultural heritage field

Recording cultural properties requires more than preserving appearance. It is necessary to record as objectively as possible information that will inform future preservation and restoration decisions: dimensions, tilts, warps, subsidence, losses, cracks, surface undulations, and relationships with surrounding terrain. Terrestrial laser scanners can acquire such spatial information as high-density three-dimensional point clouds, so they are valuable as foundational material for creating measured drawings, checking cross-sections, comparing changes, documenting before-and-after restoration, and planning post-disaster recovery. International initiatives on digital recording of cultural heritage also emphasize combining laser scanning, photogrammetry, and three-dimensional modeling to serve both preservation and utilization.

Terrestrial laser scanners also have the advantage of quickly recording wide areas, including high or dangerous places where scaffolding is difficult to erect and spaces that are hard to enter. In overseas practical work on cultural heritage recording, high accuracy, the ability to reach difficult positions, and time savings on site are identified as major benefits, and in recent years speed and portability have improved. On cultural heritage sites, where public opening times and work permissions are often strictly limited, “being able to secure the required density in a short time” can itself be a reason for introduction.

However, it must not be misunderstood that acquiring point cloud data itself is the goal. In cultural heritage surveys and preservation, point clouds are sometimes the final deliverable, but in practice it is only when those point clouds are developed into plans, elevations, cross-sections, condition maps, three-dimensional models, and explanatory visual materials that they become easy to use for internal sharing, design consultations, restoration planning, resident explanations, and exhibitions. What is truly needed in practice is not the “fact that a scan was made” but whether the data were preserved as usable records.

Furthermore, unlike typical buildings or civil structures, the value of cultural properties centers not on “creating something new” but on “how the existing state is read and preserved.” Slight deformations, traces of repairs, added members, surface deterioration, and relationships with surroundings may directly affect the assessment of a cultural property’s value. For that reason, introducing terrestrial laser scanners should be viewed not simply as adopting labor-saving equipment but as establishing infrastructure to improve the quality of records. If this point is not misunderstood, it is easier to avoid situations after introduction where “data exist but cannot be used for decision-making.”

Basic 1 Articulate the purpose of introduction first

The first thing to consider when introducing terrestrial laser scanners is not model selection but clarifying the purpose. The objectives for three-dimensional surveying in cultural heritage sites are diverse: documenting current conditions, restoration design, monitoring changes, recording prior to dismantling, disaster preparedness, academic research, public utilization, and education/exhibitions. Different objectives require different scanning densities, different color information, and different extents. For example, planning will be entirely different if the primary goal is to capture overall form, to follow fine carvings or cracks, or to capture the relationship with surrounding terrain. International digital heritage recording practices also emphasize organizing workflows and requirements up front to ensure consistency and quality of acquired data.

If the purpose remains ambiguous at introduction, two common failures occur on site. One is scanning at a higher density than necessary, increasing data volume and processing load unnecessarily. The other is insufficient density or complementary photography in crucial areas, making subsequent drawing or comparative analysis impossible. In cultural heritage work especially, opportunities for re-measurement are not easily obtained. Scheduling, permission conditions, scaffold availability, opening dates, and changes in the surrounding environment can make “we’ll re-do it next month” infeasible. Therefore, before introduction it is necessary to put into words “what decisions the data are intended to support.”

When outsourcing is assumed, articulating the purpose becomes even more important. Domestic guidance on digital recording for cultural heritage states that when outsourcing, one must clearly indicate the project’s purpose and intent and consult sufficiently so necessary information is obtained. In other words, “Please perform three-dimensional surveying” is not enough. Only when you share “which areas should be recorded at what level of accuracy, what deliverables it should be turned into, and how it will be used in the future” can specifications be determined. Whether the heritage specialist and the surveying personnel share the same understanding directly affects the quality of results.

In practice, even for the same cultural property project, the conservation officer may prioritize monitoring changes, the designer may emphasize dimensions and sections, and the public engagement officer may prioritize an easy-to-understand three-dimensional representation. Articulating the purpose first is not simply writing the use in one line but organizing who will use the data for what decisions. If this organization is done, priorities on site become clear, omissions are less likely, and post-introduction data use is less likely to stall.

Basic 2 Plan for blind spots rather than assuming you can capture everything at once

Terrestrial laser scanners are very powerful devices, but they are not omnipotent. The biggest limitation is that they can only capture what is in line of sight. Because lasers are emitted in straight lines, areas behind walls, under members, on the undersides of eaves, in the shadows of trees or fences, deep inside complex ornamentation, and low spaces near the floor will remain missing. Practical guidance in the cultural heritage field clearly points out that laser scanners cannot record elements that block line of sight—such as obstructions and vegetation shadows or upper and lower surfaces of structures—and that detection is difficult for dark, specular, water, or glass surfaces.

Therefore, it is important to abandon the idea of “set up once and be done.” In practice, the basic flow is to move around the target and scan from multiple positions, adding scans while checking where blind spots occur. Domestic materials on three-dimensional measurement of cultural resources also introduce the concept of assuming areas where data cannot be obtained and performing segmented measurements by moving to arbitrary positions while checking. If you don’t plan from the start to confirm point cloud omissions on site and conduct supplemental measurements there and then, substantial rework can occur in later stages.

Cultural properties in particular rarely have straightforward shapes. Old architecture with irregularly arranged pillars and beams, stone walls with subtle surface warps, stone works with fine reliefs and chips, spaces with many curved surfaces and alcoves, and remains covered by surrounding vegetation are not simple rectangular solids like conventional buildings. Therefore, before introduction consider where blind spots are likely to occur, which surfaces should be prioritized, and whether to add complementary photography or close-range measurement. Think of introducing a terrestrial laser scanner not as buying equipment but as establishing a system capable of designing surveys that reduce omissions; this mindset makes practical failures less likely.

Basic 3 Prioritize field conditions and coordinate management over accuracy specs

In evaluation and procurement, attention naturally focuses on advertised accuracy—“how many millimeters it can measure.” Of course accuracy is important. However, what truly matters on cultural heritage sites is not just the catalog numbers. In reality, outcomes are determined by operational conditions such as measurement distance, scan speed, portability, ease of tripod setup, ease of bringing the unit into tight spaces, power and battery management, work flow, surrounding pedestrian traffic, allowable working time, switching between indoor and outdoor, and coping with scaffolding and steps. Overseas practice shows using different models according to whether long-range performance or portability and speed are important, and combining scanners with high-accuracy control networks and positioning information.

Permissions and on-site supervision issues unique to cultural heritage cannot be ignored. For significant targets, measurement positions and movement paths may be restricted, work may only be allowed under supervision, or working hours may be limited. Domestic case studies on point cloud maintenance for important cultural properties point out that planning, measurement, noise removal and position adjustment, registration, and data provision are common workflows, and that permit applications and supervision are often required and that terrestrial laser measurement takes time. In other words, a focus on high performance without regard to field conditions often goes awry in cultural heritage contexts.

Even more important is coordinate management. If the survey is a one-off single-day measurement, this is easily overlooked, but records of cultural properties must withstand future comparisons. If you plan to check differences before and after restoration, compare deterioration over time, or overlay with surrounding terrain or other surveying results, you must design coordinate systems and reference points. Domestic examples note that managing data in a unified coordinate system, such as a plane rectangular coordinate system, facilitates linkage with geospatial information and application to time-series management. Before introducing equipment, clarify whether “it’s enough to get the point cloud this time” or “we want records that can be compared years later,” and decide on reference points and registration methods accordingly.

Especially for projects that aim to compare before-and-after restoration or to track impacts from earthquakes, heavy rain, or frost damage, vague initial coordinate management will drastically reduce comparison accuracy in later years. Deciding at the introduction stage which points will serve as references, what units will be used for management, and what will be recorded on site actually matters more than equipment selection. In many cultural heritage cases, “whether it can be measured” is less important than “whether it can be compared later.”

Basic 4 Decide deliverables, preservation formats, and rights relationships up front

A frequently overlooked aspect of three-dimensional surveying for cultural properties is planning the output after data acquisition. Even when point cloud data are acquired, they are often not directly usable. Restoration staff may want cross-sections or condition diagrams; management staff may want three-dimensional models for current-condition comparisons; exhibition staff may want easy-to-understand visualizations or shape data for replica production. Domestic materials on advanced use of technology in cultural heritage state that three-dimensional measurement data can be linked to replica production, exhibitions, and experiential uses. Thus, at introduction you should think starting from “who will use which deliverables” rather than simply “we will take point clouds.”

From the perspective of long-term preservation, initial planning is also important. While point clouds are very useful, overseas practical work on cultural heritage recording repeatedly discusses issues such as long-term preservability, data migration, the cost of maintaining files, and the permanence of electronic records. International digital cultural heritage initiatives stress consistency of data structures, sustainability of digital data, and extensibility for the future. Therefore, at introduction you must consider which formats to preserve in, how to separate raw and processed data, how to record metadata and work logs, and whether the data can be made reusable by future personnel.

In addition, rights and publication scope must be settled for cultural properties. In projects involving many stakeholders—owners, managers, municipalities, contractors, researchers, and exhibition staff—proceeding while leaving data ownership, usage permissions, publication allowances, and scope of secondary use vague will result in halted utilization later. International projects have established legal frameworks specifying data ownership, conditions of use, and copyright protection. Cultural property data are not merely three-dimensional files but historical records with value. Deciding rules for preservation, sharing, and publication is as critical as technical specifications for successful introduction.

Also organize surrounding information from the start: file naming conventions, scan position numbers, acquisition timestamps, responsible personnel, coordinate systems used, processing history, and which areas were captured at which densities. Digital records of cultural properties do not remain useful if only the person who acquired them understands them. Ensuring that future staff can reuse and compare the data even if personnel change is true preservation. Consider not only the data themselves but also the explanatory information needed to interpret them as part of the deliverables.

Basic 5 Don’t try to complete everything with the terrestrial laser scanner alone

What is most effective in measuring cultural properties is the attitude of not trying to do everything with a single technology. Terrestrial laser scanners excel at capturing shape, but photogrammetry, conventional photographic records, and on-site observations play major roles in representing color and texture, capturing fine edges, supplementing narrow areas, and showing relationships with surrounding environments. Research on three-dimensional recording of cultural heritage shows that combining imagery and laser scanning enriches point clouds and aids reliable recording and three-dimensional modeling. Because reading surface condition is as important as geometric fidelity in cultural properties, combining multiple methods is in fact a standard approach.

Also, the significance of on-site human observation should not be underestimated. Overseas practical work uses laser scanning widely while combining hand measurements and field observations, reflecting understanding of materials, construction traces, changes, and alterations in the record. Point clouds are an extremely powerful foundational resource, but the value of cultural properties becomes clear only when one can interpret where repairs have been made, where deformations occur, and where traces of use remain. Therefore, when planning introduction, do not separate equipment staff from heritage specialists; build a system that connects site interpretation with surveying technology.

In practice, it is realistic to center surveys on terrestrial laser scanners while bundling supplementary methods—photography, close inspection, existing drawings, terrain information, and coordinate data—when needed. This is even more the case if a cultural property is not an isolated building but is associated with a garden, approach, stone steps, stone walls, surrounding terrain, drainage, boundaries, or views. The terrestrial laser scanner should handle high-density shape acquisition of the object itself, while other methods support complementary information and positional consistency. Understanding this division of roles enables effective introduction without undue strain.

Summary

What matters when introducing terrestrial laser scanners to cultural properties is not simply choosing the latest equipment. Decide the purpose of introduction first; plan measurements with blind spots and omissions in mind; operate taking field conditions and coordinate management into account; finalize deliverables and preservation planning up front; and combine multiple recording methods rather than relying on a single technology. Covering just these five points will greatly reduce failures after introduction. In the cultural heritage field, the success or failure of measurement directly affects future preservation decisions and the scope of possible uses, so it is essential to design workflows before procuring equipment.

Particularly when you consider not only the cultural property itself but also the entire site, surrounding terrain, existing surveying results, and consistency with future re-measurements, positional consistency becomes a major theme. Detailed shape acquisition is the role of terrestrial laser scanners, while another positioning method supports high-precision alignment of reference points, photograph positions, and connections with surrounding spaces. In preservation and restoration of cultural properties, it is important not only to have a beautiful three-dimensional model of the object but to be able to manage “where and how it exists” without ambiguity.

In that sense, those considering introducing terrestrial laser scanners should also pay attention to means of handling wide-area positional information. For example, by combining LRTK—an iPhone-mounted GNSS high-precision positioning device—with the high-density point cloud of the cultural property, it becomes easier to organize connections between in-site and off-site positional information, site photos, and surrounding survey data. By assigning detailed shape acquisition to terrestrial laser scanners and positional unification and record linking to LRTK, digital records of cultural properties can be nurtured into spatial information assets that are easy to use in the future rather than single-shot survey results.

You do not have to aim for large-scale introduction from the start. Begin with trial measurements focused on a limited target range to confirm what density is required, where blind spots occur, and which deliverables are actually used on site, and reflect those results in the next plan. Measurement of cultural properties is not completed the moment equipment is introduced; it matures as you gradually refine the purpose, field approach, deliverables, preservation methods, and coordinate management. Cultural properties in particular are difficult to redo, and a single decision can have long-term effects on the quality of records. Therefore, spending time on the basic design before introduction is ultimately the most efficient approach. With that perspective on terrestrial laser scanners and LRTK, the record infrastructure that supports preservation, restoration, and utilization of cultural properties becomes more practical and user-friendly.