How to Measure Cultural Properties with LiDAR｜4 Steps to Improve Recording Accuracy

In documentation work for cultural properties, it is important to preserve shapes as much as possible and to produce data that can withstand future restoration and comparative research. In particular, in recent years attention has focused on LiDAR-based measurement as a means of recording three-dimensional information that is difficult to convey with drawings or photographs alone. That said, cultural properties differ from ordinary structures, and the difficulties of measurement are compounded by factors such as surface materials and states of preservation, site conditions, contact restrictions, and public display environments. Therefore, simply bringing in equipment and acquiring point clouds does not yield records that are usable in professional practice.

What really matters in LiDAR surveying of cultural heritage is not whether measurement is possible, but whether you can design in advance what level of accuracy, what spatial extent, and for what purpose the data should be preserved, and whether you can carry out fieldwork and data management according to that design. Whether the data will be used as archival records, for monitoring deterioration, or for mapping and 3D modeling will change the required resolution, how you operate on site, and your approach to post-processing.

This article organizes and explains a method for measuring cultural heritage with LiDAR into four steps to improve recording accuracy, so that practitioners in the field can apply it directly. To help those involved in cultural heritage surveys, preservation recording, maintenance management, and pre- and post-restoration comparisons to form a concrete image of how to proceed with measurements, we take a step-by-step deep dive from the preparation stage through fieldwork, data verification, and points to watch when creating records.

Table of Contents

• Key Concepts to Understand First in LiDAR Surveying of Cultural Heritage

• Step 1: Decide the survey objective and required accuracy in advance

• Step 2: Verify on-site conditions and develop a measurement plan

• Step 3 Conduct LiDAR measurements with consideration for cultural heritage

• Step 4 Refine record quality by organizing data and verifying accuracy

• Common causes that reduce recording accuracy in LiDAR surveys of cultural heritage

• Summary

Key Concepts to Understand First for LiDAR Surveying of Cultural Heritage

In LiDAR surveys of cultural heritage, it is important to first rethink the notion that “measuring at high density brings peace of mind.” While a larger number of points increases the amount of information, acquiring a higher density than necessary leads to increased work time, insufficient coverage of blind spots, ballooning data volume, and more complicated post-processing. Moreover, because cultural heritage sites often have restrictions on entry and contact, retaking scans is frequently difficult. What matters is designing a measurement plan that is neither excessive nor insufficient for the intended purpose.

For example, the accuracy and resolution required differ depending on whether you want to preserve the overall form as a record or examine surface deterioration and deformation in detail. If the goal is to capture the shape of an entire structure, overall continuity and coordinate stability are important. On the other hand, if you are dealing with details such as sculptures, stonework, decorative elements, joints, or damaged areas, local point density, angle of incidence, handling of areas in shadow, and suppression of surface noise become important. In other words, LiDAR surveying of cultural heritage should be regarded not merely as a surveying task but as work that combines recording design and conservation planning.

Another important point is that the value of cultural properties lies not only in their form but also in their positional relationships and surrounding context. Simply creating a standalone three-dimensional model can sometimes weaken the connection to on-site placement, orientation, elevation differences, relationships with surrounding structures, and the preservation environment. Therefore, rather than measuring only the object precisely, it is necessary to adopt a perspective of designing the recording extent to include surrounding spaces as needed. For cultural heritage buildings, the relationship with surrounding terrain, approach paths, stone steps, and platforms may be important, and for indoor exhibits the positional relationship with the mounting surface or display case can also be meaningful.

Moreover, cultural properties exhibit large variability in materials, and the stability of measurement results can differ. The ease of data acquisition changes for stone, wood, earthen walls, metal, lacquer, glass-like surfaces, wet surfaces, dark surfaces, and highly reflective surfaces. Even at the same site, the way points drop out and the way noise appears differ by surface; therefore, if you proceed with uniform settings without preliminary checks, you may later find that the information you needed is missing.

In LiDAR surveys of cultural heritage, whether the survey succeeds is half decided at the stage of clarifying what should be recorded, even before deciding how to operate equipment on site. With this premise in mind, moving on to the next steps is the shortest route to improving recording accuracy.

Step 1: Decide the survey objective and required accuracy first

The first step is to clearly articulate the survey objectives and the required level of accuracy. If you begin measurements while this remains vague, on site you'll tend to collect data at a higher density without a clear reason, in post-processing you'll haphazardly stitch things together, and in the final deliverable it will be difficult to explain what the data can be used for. In cultural heritage documentation, it is important that a third party reviewing the work later can understand why the measurements were taken using that method, at that density, and over that extent.

The primary purposes of a survey can be broadly classified as preservation records, restoration planning, mapping of current conditions, identification of deterioration, longitudinal comparison, public use, or combinations of these. If preservation recording is the main objective, emphasis is placed on minimizing gaps in coverage of the entire subject and on the reproducibility of coordinates so that future reinterpretation is possible. If restoration planning is the primary objective, accuracy sufficient to detect deformations and tilting, measure component dimensions, and identify interference relationships is required. If longitudinal comparison is the main objective, it is not enough to capture good data only this time; you need a recording system that makes it easy to compare under the same conditions in subsequent surveys.

When deciding required accuracy, be explicit not only about the numerical value but also about the unit in which it will be judged. The approach differs depending on whether the accuracy is needed to capture the overall shape, to check changes in fine details, the tolerances allowable for drafting, or the accuracy required to integrate position coordinates with other data. At cultural heritage sites, rather than pursuing more detail-level accuracy than necessary, it is often more practical to balance the overall and local scales and to ensure increased density focused only on the important parts.

At this stage, what you should do is decide the form of the deliverable in advance. Whether the final deliverable will be point cloud data, a three-dimensional model, orthographic images or cross-sections, or prepared figures for a report will change how you need to capture data on site. For example, if you want to produce accurate cross-sections, you need measurement positions that minimize blind spots relative to the direction you want to section, and if you prioritize reading surface patterns or carvings, you must devise ways to approach faces that tend to be in shadow. Beginning fieldwork without deciding the final deliverable carries a risk similar to starting construction without drawings.

In addition, constraints specific to cultural properties should be identified upfront. No-touch zones, no-approach zones, conflicts with opening hours, restrictions on switching lighting, whether stepladders or auxiliary equipment may be used, and restrictions on occupying passageways all directly affect measurement accuracy. Accuracy is not determined solely by equipment performance; it depends on how reproducible the procedures you can establish under on-site conditions are. If you create an ideal plan without understanding the permit conditions, it cannot be executed on site and will only lead to reduced accuracy.

Furthermore, it is important for stakeholders to share what level of detail they expect to obtain from this measurement. In surveys of cultural properties, parties with different viewpoints may be involved, such as those responsible for conservation, facility management, design, construction, and academic research. Some may prioritize overall preservation, others may prioritize detailed understanding of damaged areas, and others may prioritize applying the results to future maintenance and management. Organizing these perspectives at an early stage clarifies on-site priorities and helps prevent oversights and unnecessary rework.

In other words, what should be done in Step 1 is to define the objective before examining the subject, specify the required accuracy and deliverables according to that objective, and organize the conditions necessary to achieve that accuracy. The more carefully this is done, the less likely subsequent steps are to deviate.

Step 2 Confirm on-site conditions and develop a measurement plan

The next step is to specify, based on site conditions, from where and how the measurements will be taken. One common failure in LiDAR surveying of cultural properties is that, although the object itself is understood, that understanding is not translated into the on-site movement flow and lines of sight. Cultural properties often have complex forms with many unseen parts—uneven surfaces, projections, shadows, narrow or confined areas, reverse sides, and ground-contact areas. Moreover, if there are fences or walls, display fixtures, trees, level changes, or visitor circulation around the object, it may not be possible to measure from the ideal positions.

Therefore, when checking site conditions, rather than simply judging whether something appears measurable, you need to concretely anticipate where blind spots will occur, which surfaces are likely to be missed, and how many separate passes will be required for the whole to be connected. For cultural heritage buildings, places that tend to become blind spots include under eaves, behind columns, around the foundation, along roof edges, and around openings. For stone monuments and statues, areas prone to being missed include constricted sections, the back, the connections to the pedestal, deep carvings, and the sides of inscriptions. Instead of assuming that a single walk-around on site will be sufficient, it is important to plan in advance to cover locations that are likely to have missing data.

In measurement planning, it is easier to organize if you separate overall acquisition and focused acquisition. First, design a measurement route to stably capture the shape and positional relationships of the entire target. Then, for areas where detailed representation is important, areas where deformation needs to be checked, and reference points to be used for future comparisons, incorporate additional close-range measurements and measurements from different angles. This two-tiered approach helps avoid failures such as having the overall dataset connected but lacking density in critical areas, or concentrating so much on details that the overall coordinates become unstable.

The influence of the surrounding environment should not be overlooked. Outdoors, sunlight, wind, humidity, wetness after rain, fallen leaves, and the swaying of vegetation all become sources of noise. Indoors, factors such as cramped spaces, surrounding exhibits, glass surfaces, reflections, and constraints on visitor flow often have a greater impact than the lighting conditions themselves. When measuring cultural heritage objects, it is insufficient to look only at the object; you must consider how the surrounding environment affects point cloud stability and the ease of post-processing. For example, in locations with unstable footing the reproducibility of equipment placement decreases, and during periods of heavy foot traffic extraneous points are more likely to be captured. Choosing the measurement time is also part of a plan to improve accuracy.

In the planning stage, you should also decide how to handle reference positional information. If you leave a cultural property's three-dimensional record as a standalone geometry dataset, you can compile it using local coordinates; however, if you anticipate future re-measurement comparisons or integration with other survey results, it is advantageous to consider how coordinates will be assigned. What matters here is not just neatly connecting point clouds, but ensuring that the positional meaning is not lost when viewed later. Records of cultural properties are not finished once created; they may be reused for future investigations, restoration, or conservation management. For that reason, not overlooking how positional information is handled at the time of measurement contributes to long-term recording accuracy.

Furthermore, the method for verifying results must also be decided at this stage. If you define in advance how much can be confirmed on site to justify packing up and which locations, if not acquired, will require re-measurement, on-site decision-making becomes easier. Because revisiting cultural heritage sites is often difficult, discovering missing measurements only after returning is the most painful failure. For that reason, the measurement plan must be both a plan for the acquisition work and a plan for on-site verification.

What matters in Step 2 is not just treating site conditions as obstacles, but anticipating and sorting out which conditions will lead to which errors or missing data. The accuracy of the plan directly becomes the foundation for the accuracy of the records.

Step 3 Conduct LiDAR Measurements with Consideration for Cultural Properties

The third step is to perform measurements as planned with minimal omissions while giving top priority to consideration for cultural properties. What is important here is not to adopt the idea that the closer you get the equipment, the better. At cultural property sites, non-contact with the object, safety, and minimizing impact on the surrounding environment are prerequisites, and technologies that ensure accuracy within those constraints are required.

The first thing to be aware of is the measurement sequence. If you collect only fine details before you have a stable grasp of the overall picture, the relationship to the whole can easily become unstable when you later integrate the data. Therefore, the basic workflow is to begin with measurements that capture the overall connections and then move on to close-range measurements of key areas. By building the overall framework first, the positioning of detailed data becomes clear and it is less likely to fail during post-processing.

On-site work requires a mindset of eliminating blind spots one by one. Cultural properties are not simple shapes, so even when an area is visible from the front, the sides, back, points of contact with the ground, and the depths of recesses may not have been captured. Moreover, even if a point cloud looks clean at first glance, important corners and boundary areas can be poorly defined. In particular, do not be reassured merely because a contour appears continuous; it is important to capture data with attention to whether the necessary edges of the shape are accurately reproduced. In cultural heritage documentation, information such as boundaries, steps, seams, losses, and tool marks is often more valuable than smooth surfaces.

Also, during measurement it is important not to have unrealistic expectations based on the characteristics of the target surface. On dark surfaces, highly reflective surfaces, wet surfaces, or surfaces with continuous fine irregularities, points may not be captured as steadily as expected. In such cases, rather than simply measuring for longer from the same position, it is more effective to change the angle, adjust the distance, or supplement from another direction. Because cultural artifacts are often composed of multiple materials, parts that are easy to capture and parts that are difficult to capture can coexist within the same object. Trying to process the entire object under the same conditions can easily reduce the reproducibility of critical areas.

On-site verification is as important as the acquisition itself. Even if you think the measurements are finished, you need to perform a quick on-site check for overlap, missing data, motion blur, and the inclusion of unnecessary points, and decide whether additional acquisition is necessary. What you should check here is not merely whether points exist, but whether there is sufficient information for the intended purpose. You must assess, for example, whether the overall shape needed for preservation records has been captured, whether the density of the areas you want to inspect for deformation is sufficient, whether there is enough thickness to be readable when cutting cross-sections later, and whether surrounding areas that indicate positional relationships remain.

Furthermore, how you keep records on site is also part of quality control. Information such as where and in what order measurements were taken, which areas were prioritized, what constraints were noticed on site, and which surfaces showed reflections or missing data is extremely useful during post-processing. In LiDAR surveys of cultural heritage, you sometimes cannot make a judgment from the point cloud alone. If you record observations made on site, it becomes much easier, when reviewing the data later, to explain why a certain area is sparse or why only a particular surface is noisy. This is also important for enhancing the reliability of the results.

Measurement conducted with respect for cultural properties is not merely about moving cautiously. It means reliably preserving the necessary information, without imposing a burden on the object, under limited conditions. To achieve this, it is essential to avoid making ad hoc decisions on site and to proceed by linking objectives, planning, and verification.

Step 4: Finalize record quality by organizing data and validating accuracy

The fourth step is to organize the acquired data and refine it to a quality that can be trusted as a record. LiDAR surveying is only half finished at the point when point clouds are captured in the field. It only becomes truly valuable as a cultural heritage record after the data have been connected, positional alignment completed, unwanted points cleaned up, and the reproducibility of necessary areas verified.

The first thing to do is to integrate the acquired data and check it for consistency. Carefully inspect whether the data taken from each position connect smoothly, whether there are any local shifts or distortions, and whether the whole has any tilt or twist. With point clouds of cultural heritage, even if the whole seems to be connected, remaining local misalignments can cause major problems later when producing cross-sections or comparison diagrams. In particular, it is useful to check whether there is any visual inconsistency in surfaces or lines that should be aligned, such as rows of columns, stonework, plinth edges, floor surfaces, and wall surfaces.

Next, an important task is the removal of unwanted points. If people passing by, swaying vegetation, surrounding equipment, or spurious points caused by reflections are included, they affect not only the visual impression but also cross-section verification and the accuracy of 3D modeling. However, removing too many unwanted points is also dangerous. Because features around cultural properties, supporting elements, or the installation environment itself can be meaningful as records, it is necessary to decide, in light of the project's purpose, what to treat as noise and what to retain as contextual information. The aim is not to make the appearance tidy but to enhance the interpretability of the record.

In accuracy verification, it is important to examine both the whole and the parts. For the whole, confirm whether positional relationships and the continuity of shapes are preserved. For the parts, check whether the representation of the areas captured with emphasis meets the intended purpose. For example, if you want to check surface wear, chipped corners, seams, or tilt, you need to judge individually whether there is sufficient density and stability to read them. Even if the overall result looks clean, if the important areas cannot be read, it is insufficient as cultural heritage documentation.

Also, in cultural heritage documentation it is essential to organize accompanying information for future use. When, where, what, to what extent, and for what purpose were measurements taken? What conditions imposed constraints? Which parts have high density and which should be treated as reference values? If this information is not organized, even if only the data remain several years later they will be difficult to use. While three-dimensional data are visually appealing, they are also the kind of record that can be hard to interpret when background information is missing. Therefore, deliverables should include not only shape data but also clear descriptions of the recording conditions and quality.

Furthermore, if you are considering future re-measurement comparisons, you need to put the current results into a form that can serve as the baseline for the next measurement. If you organize the comparable scope, the coordinates and reference planes that form the basis for comparison, and measurement positions and points of interest that are easy to reproduce, the efficiency of future work and the accuracy of comparisons will be greatly improved. Because the passage of time itself is important information for cultural heritage, records that can be used continuously are more valuable than one-off records.

The essence of Step 4 is not merely to store the acquired point cloud, but to refine it into a state in which it can serve as a cultural heritage record. Recording accuracy is not determined solely by on-site acquisition; it is guaranteed only through post-processing and verification.

Causes That Commonly Reduce Recording Accuracy in LiDAR Measurements of Cultural Heritage

We have reviewed four steps so far, but in practice several typical mistakes are repeatedly made. The most common is going to the site without distinguishing between overall acquisition and focused acquisition. As a result, everything tends to be recorded at a middling density, and both the overall picture and the details often yield inconclusive results. Because cultural heritage cannot be handled by the simple, comprehensive coverage that suffices for ordinary structures, it is necessary to prioritize which areas must be reliably recorded.

Another common mistake is focusing only on the measurement target and neglecting the surrounding conditions. In practice, factors such as passage width, access and footing conditions, obstacles, opening hours, nearby reflective surfaces, trees, and floor stability can greatly affect accuracy. Never forget that the more important the subject, the more likely it is to be constrained by surrounding conditions. Accuracy in recording cultural properties may actually be determined more by how surrounding constraints are managed than by the object itself.

Furthermore, insufficient post-acquisition checks are also a major cause. Even when it appears that data were captured on site, it is not uncommon to discover missing measurements or misalignments after returning. Especially for cultural properties, where revisiting is difficult, lax on-site verification directly limits the quality of the results. Verification should be carried out not just at the end of the work but intermittently during acquisition, and any deficiencies should be remedied on the spot.

Another commonly overlooked issue is failing to organize deliverables according to their intended use. If you are satisfied with merely saving the point cloud, later when you want to produce drawings, make comparisons, or use it in presentation materials, you may find the information insufficient or, conversely, so poorly organized that it becomes difficult to work with. In cultural heritage documentation, it is necessary to strike a balance between preserving form and ensuring that the data remains usable later.

Postponing the handling of positional information also leads to a reduction in accuracy. Even if a cultural property's 3D documentation looks good as a standalone model, weak positional validation will cause problems when making future comparisons or integrating it with other materials. If you are considering records for conservation management or combining them with the surrounding environment in particular, you cannot afford to downplay the reliability of location information. Recording accuracy is not only about the fineness of shape but also about the ability to reproduce where and how something existed.

Summary

When considering how to measure cultural properties with LiDAR, the important thing is not to chase the performance of the equipment, but to design the required accuracy according to the purpose of the recording, assemble the measurement plan to suit the site conditions, and verify quality after acquisition to finalize the record.

Specifically, first decide the research purpose and required accuracy, then make a measurement plan that takes site conditions into account, afterward conduct on-site acquisition with due consideration for the cultural property, and finally determine the recording quality through data processing and accuracy verification. If these four steps are followed, the result will be closer to a record that can be used for conservation, restoration, and comparative studies rather than mere three-dimensional data.

In cultural heritage documentation, not only the fine details of the object itself but also its positional relationship to the surroundings and reproducibility for future comparison are important. That is precisely why capturing shape with LiDAR and ensuring the reliability of coordinates and positions should not be treated separately. By making the three-dimensional shapes acquired on site easy to link later with other survey results and management information, the range of uses for cultural heritage records is greatly expanded.

In that sense, when you want to make checking reference points around cultural properties and fixing positions more efficient, the idea of combining methods that make high‑precision positioning information easy to handle is effective. As a high‑precision GNSS positioning device that can be attached to an iPhone, LRTK can streamline confirmation of reference positions around cultural properties and the capture of on‑site coordinates, and it is also well suited to situations where you want to link and organize LiDAR‑acquired shape records with the site’s coordinate information. To elevate LiDAR surveying of cultural properties beyond one‑off 3D captures and turn it into records useful for future preservation management and comparative studies, the perspective of considering shape records and position records together will become increasingly important.