What Is 3D Measurement of Important Cultural Properties? 5 Basics to Know Before Implementation

3D measurement of Important Cultural Properties is not simply the task of producing a visually appealing three-dimensional model. It is the establishment of a foundation for recording valuable materials and structures that are subject to cultural property protection in a form that can be utilized for future preservation, repair, research, public exhibition, and disaster response. The Agency for Cultural Affairs positions cultural properties as national assets, designates important items for protection, and implements measures for their preservation and utilization. Important Cultural Properties lie at the core of this framework, and the approach to measurement requires a different mindset than for ordinary buildings or general objects.

Moreover, 3D measurement itself is no longer just a matter for a subset of advanced research applications. In materials from the Agency for Cultural Affairs, three-dimensional measurement is presented as a technology for digitally recording and preserving the shape and size of cultural properties, and is described as something that can lead to replica production and public use. In addition, the Agency for Cultural Affairs’ public platform has been increasingly publishing photographs, videos, and 360-degree footage of cultural properties, including National Treasures and Important Cultural Properties, showing that digital recording and utilization are steadily becoming a given in the cultural heritage field.

However, 3D measurement of Important Cultural Properties is not something that can be started simply by bringing in equipment. Whether the subject is a building or a work of art and craft, and whether it is outdoors or under storage conditions, the appropriate method, the required accuracy, and the stakeholders who need to be coordinated will differ. Furthermore, unless the acquired data is preserved in a form that can be used in the future, the measurement effort will end up as only a transient result. Therefore, this article organizes and explains five basic points that practitioners should understand before introducing 3D measurement for Important Cultural Properties.

Table of Contents

• Background for the need for 3D measurement of Important Cultural Properties

• Basic 1 Establish the purpose of 3D measurement from the outset

• Basic 2 Combine measurement methods appropriate to the target

• Basic 3: Decide the approach to accuracy and coordinates first

• Basic 4: Design data that goes beyond mere recording

• Basic 5: Organize permits and disclosure conditions before measurement

• Summary

Background for the Demand for 3D Measurement of Important Cultural Properties

Even when speaking of “Important Cultural Properties” as a single term, their scope is wide-ranging. The Agency for Cultural Affairs classifies tangible cultural properties as buildings, paintings, sculptures, crafts, calligraphic works, classical texts, ancient documents, archaeological materials, and historical materials, and designates those among them that are important as Important Cultural Properties. In other words, even under the same “3D measurement of Important Cultural Properties,” the way a site is set up differs fundamentally when recording the roofs and pillars of temple and shrine architecture versus when recording the surface shape of Buddhist statues or craft objects. What must be recognized before introduction is that if the subject differs, the correct approach also differs.

Meanwhile, what is common to all targets is the need to balance preservation and utilization. The Agency for Cultural Affairs explains that, with respect to cultural properties, including Important Cultural Properties, it imposes certain restrictions on alterations to their current state while implementing measures such as conservation and repair, disaster prevention, and public access. For buildings as well, conservation and repair are necessary to pass them on to future generations, and because they contain many elements vulnerable to fire—such as timber and plant-based roofing—protection that includes disaster prevention is emphasized. 3D measurement is emphasized because it is a practical method of documentation for reconciling “preserving” and “making use of.”

Furthermore, the public materials of the Nara National Research Institute for Cultural Properties state that three-dimensional data of cultural properties are not only fundamental resources for investigation, research, conservation, restoration, and reconstruction, but can also contribute to use in exhibitions, school education, disaster prevention, and town planning. The reason why 3D measurement of Important Cultural Properties is attracting attention is that it is not merely visualization: a single measurement result can be applied to multiple purposes, such as future repair decision-making, comparisons before and after disasters, explanations for public display, remote viewing, and the production of replicas. This is where the value lies for practitioners considering adoption.

However, precisely because they are highly valuable, the cost of failure is also significant. The Nara National Research Institute for Cultural Properties warns that with the spread of three-dimensional cultural property data, the large data volumes, diversity of formats, lack of unified metadata, and inadequate preservation methods create a risk that the data acquired with great effort could become unusable in the future. For 3D measurement of Important Cultural Properties, true implementation means designing not only the acquisition itself but also for what purpose, at what quality, how it will be preserved, and how it will be used.

Basic 1 Establish the purpose of 3D measurement at the outset

The basic starting point is to avoid leaving the purpose of 3D measurement ambiguous. What often happens on site is that measurements proceed from the starting point of "let's just convert it to 3D for now." However, in practical work on Important Cultural Properties, that ambiguity leads to rework in later stages. Whether the primary purpose is to document the current condition before repairs, to monitor deterioration, to produce drawings and check cross-sections, or to create content for public release will affect the required resolution, color reproduction, acceptable extent of blind spots, and the rigor of coordinate control. If you rush into simply "capturing at high resolution" without defining the purpose first, the data will only become heavier and will tend to result in deliverables that do not suit their intended use.

For example, if it is used as baseline documentation for conservation and repair, dimensional reproducibility and re‑measurability take priority over visual appearance. If it is used to compare changes over time, it is important to capture the same area by the same criteria each time. If public use is the main objective, surface texture reproduction that communicates to viewers and file‑size optimization for easy viewing are required. The Agency for Cultural Affairs’ materials on the application of advanced technologies present 3D measurement not only for record preservation but also in connection with replica production and public use precisely because the design philosophy of deliverables changes with the intended use. You do not need to narrow down to a single purpose, but you do need to set priorities.

A useful reference for understanding this point is research on three-dimensional measurement applied to murals and similar subjects. In materials related to the Agency for Cultural Affairs, point clouds were created by combining laser scanning and photogrammetry, and the applicability as a monitoring method for mural surfaces was examined through difference analysis of three-dimensional models. The important point here is that three-dimensional measurement is designed not to "create a visually pleasing model" but to "compare changes." Even at sites designated as Important Cultural Properties, deciding in advance what to compare and what to judge makes it easier to develop a measurement plan that is necessary and sufficient.

Also, setting objectives is directly linked to the type of deliverable. Whether a point cloud, a mesh model, orthorectified images, or even cross-sections and plan views are required will change what needs to be captured on site.

In recent years, the procedural guidelines of the Geospatial Information Authority of Japan have systematized three-dimensional point cloud surveying, UAV laser surveying, GNSS elevation surveying, and even methods for creating cross-sections using three-dimensional point cloud data.

This indicates that 3D data is not a standalone deliverable but has become a practical foundation that is developed into drawings and comparative materials.

Even for important cultural properties, defining the final deliverable in advance is the first step to preventing implementation failures.

Basic 2 Combine measurement methods appropriate for the target

The second principle is not to try to solve everything with a single method. In 3D surveying of Important Cultural Properties, it is important to assign roles to multiple methods according to the object's shape, material, installation environment, and work constraints. For buildings, a realistic approach is to combine laser scanning, which is strong at capturing overall form; photogrammetry, which is strong at reproducing surface texture and color; aerial photography to supplement high or roof areas; and positioning to manage the location of the entire site. For works of art and crafts, priorities are reproduction of fine details, consideration of reflection and transmission, shooting workflows that avoid moving the object, and attention to the storage environment. What matters is to think in terms of roles, not equipment.

In recent years in the cultural heritage field, while three-dimensional reconstruction using photographs has been widely used, there are many cases where combining a laser scanner is more effective depending on the subject. In recent communications from the Nara National Research Institute for Cultural Properties, technology development has been progressing that, assuming photogrammetry, safely records the texture and shape of cultural properties and enables three-dimensional measurement without moving the object once it has been set up. This is because in the cultural heritage field "do not touch," "do not move," and "do not burden" are extremely important. Procedures that are allowable for measuring ordinary objects may be difficult to adopt for Important Cultural Properties.

What practitioners need to grasp here is to divide the axes for method selection into three. First, what and to what extent you want to preserve as shape. Second, how much reproduction of color and texture is required. Third, whether it can be carried out safely under the constraints of site conditions. For example, if geometric accuracy is important—such as deflection of columns and beams, floor unevenness, or roof pitch—you should prioritize shape acquisition. On the other hand, if coloration, weathering marks, surface degradation, or material feel are important, how images are taken and the lighting conditions will determine the outcome. Furthermore, site-specific conditions unique to cultural heritage settings—visitor circulation, storage room access restrictions, permitted work hours, and whether contact is allowed—can make a method that appears optimal on paper inappropriate in the field.

Therefore, at the site it is easier to organize work by separating "primary methods" and "auxiliary methods." For example, decide on one primary method that captures the overall framework and add auxiliary methods to make up for blind spots or insufficient texture. Adopting this approach allows you to improve quality without undue strain even on the initial implementation. Conversely, trying to capture everything perfectly in one go from the start increases the amount of equipment to be brought in, the number of personnel to coordinate, and the burden on the site. For important cultural properties, avoiding placing excessive burden on the site is itself part of quality assurance. Designing the process to collect the necessary information for the subject—neither more nor less—leads to good 3D measurement.

Basic 3 Decide on accuracy and coordinate conventions first

The third basic principle is to align your understanding of accuracy and coordinates before measurement. In consultations about 3D measurement, people often ask, "How accurate can you capture it?" but in practice it is more precise to ask, "What accuracy is required for what purpose?" What is needed for 3D measurement of Important Cultural Properties is not always the highest possible accuracy. What is needed is an accuracy that is appropriate for the purpose, reproducible, and comparable. If the goal is to check differences before and after repairs, it is important that repeat measurements can be overlaid to the same standard; if the goal is to understand the relationship with the entire site, it is important that positional management can be integrated with the surrounding topography and circulation routes. You should distinguish situations that require absolute coordinates from those where local coordinates are sufficient.

For Important Cultural Properties of built structures, there are often occasions when one wants to examine relationships with exterior elements, approach paths, stone steps, slopes, surrounding facilities, and disaster-prevention equipment. In such cases, rather than keeping three-dimensional data as a standalone, placing it within a coordinate system that contains control points or known points makes future comparisons and overlays with other materials easier. The Geospatial Information Authority of Japan’s procedural guidelines have progressively formalized workflows such as three-dimensional point-cloud surveying, UAV laser surveying, GNSS elevation surveying, and creating cross-sections from point clouds, and the approach of linking point clouds with coordinates and the production of drawings has matured as surveying practice. In the cultural-properties field as well, if you handle external spaces, adopting this way of thinking at an early stage is effective.

On the other hand, for artworks, crafts, and indoor collections, connection to an external coordinate system is not necessarily the highest priority. What matters is the relative relationships within the measured object and how to preserve the reference for registration when re-photographing it in the future. Here, clarity of the reference is more important than the size of the coordinate system. If information such as scale markers, imaging standards, reference points, camera orientation, object ID, measurement date, and environmental conditions is not recorded, the data cannot be reused later. This is precisely why the Nara Cultural Properties Research Institute points out the problem of inconsistent metadata. Point clouds and models alone are insufficient as comparative records of cultural properties.

Furthermore, for Important Cultural Properties, actions intended to improve accuracy may themselves run afoul of on-site restrictions. According to documents from the Agency for Cultural Affairs, a "change to the current state" of an Important Cultural Property is defined as making direct and physical alterations to parts that have value as cultural property. Considering this definition, 3D measurement itself does not necessarily pose an immediate problem; however, procedures that involve marking valuable surfaces, contact, securing equipment, or moving the object require careful judgment. This is a general principle and subject to case-by-case judgment, but precisely for that reason a design philosophy that places control points and auxiliary markers at safe positions around the cultural property rather than on the object itself, and that fundamentally prioritizes non-contact methods, is important.

Principle 4: Design data that goes beyond mere recording

The fourth basic principle is not to let 3D measurement become a one-off deliverable that ends on the spot. A common failure in 3D measurement of important cultural properties is delivering a visually appealing three-dimensional model and stopping there, only to find years later that the original data location, processing conditions, coordinate information, and rights conditions are unknown and the data cannot be reused. The Nara National Research Institute for Cultural Properties points out that the diversity of data formats, inconsistent metadata, and inadequate preservation methods for cultural property three-dimensional data hinder long-term use. Practitioners need to decide before commissioning measurements "which data to keep."

At minimum, what should be retained are the original photos and raw measurement data, the data before and after processing, the export formats of the deliverables, coordinate system information, work dates, the photographer or measurer, the object name, the measurement range, missing areas, the equipment used, the approach to accuracy, whether publication is permitted, and the conditions for secondary use. If these items are retained, a different person in the future will find it easier to reorganize them. Conversely, if only the completed three-dimensional model remains, the flexibility for repair comparisons, difference verification, re-editing, creating lightweight versions, and creating public-release versions is greatly reduced. For objects that are expected to be handled over long periods, such as important cultural properties, there are many cases where reusability is more important than the deliverables.

Also, if you are considering public use, you should separate archival and public-use copies from the outset. As can be seen from the Agency for Cultural Affairs’ public infrastructure and museum DX-related materials, digital data of cultural properties are increasingly being used not only for in-house management but also for search, viewing, educational use, and public relations. For this reason, designing a hierarchy of data by purpose — for example, a high-resolution archival master, an internal shared version, and an external public version — stabilizes operations. The archival master prioritizes completeness, while the public version prioritizes ease of viewing, file size, and release conditions. If the initial design is ambiguous, you will end up altering the source data every time you publish, and management will break down.

Additionally, the location where data is stored is also important. If you rely only on an individual staff member’s device or temporary external media, the organization cannot sustain its use. Records of important cultural properties must be traceable according to consistent rules even when personnel change. By putting in place file naming conventions, version control, backup frequency, update logs, and publication history, only then do 3D measurements become organizational assets. When introducing 3D measurement for important cultural properties, it is better to think of it not as buying equipment but as establishing a record system that can be used long-term; this approach will prevent failures in practice.

Basic 5: Clarify permissions, approvals, and disclosure conditions before measurement

The fifth basic principle is to organize permissions and public-access conditions before measurement. Important Cultural Properties cannot necessarily be surveyed immediately just because the owner agrees, as is the case with ordinary properties. The Agency for Cultural Affairs states that, for cultural properties designated by the state, certain restrictions on changes to their current condition are imposed depending on their type, and that permission is required when altering the current condition of Important Cultural Properties. In addition, owners and managers of Important Cultural Properties have obligations and responsibilities regarding preservation, management, and public access. Therefore, when introducing 3D measurement, it is essential to clarify, before technical matters, who needs to be consulted and what needs to be confirmed.

A common misconception here is to assume that non-contact measurement requires no adjustments at all. In reality, there are many things to check, such as worker access areas, equipment delivery routes, shooting times, use of lighting, handling of scaffolding and ladders, coordination with visitor circulation, environmental conditions in storage rooms, and placement of signage around the subject. In particular, buildings often involve high-altitude photography and outdoor equipment placement, while artworks and crafts require different considerations—temperature and humidity, gloves, unpacking routes, and the handling of worktables. For important cultural properties, the preparation of measurement conditions itself should be regarded as part of preservation management.

If publication is planned, additional issues that need to be clarified arise. The Agency for Cultural Affairs' museum DX materials state that four points are important when publishing digital archives: the intentions of the collection holder, copyright, portrait rights and personal information, and consideration for privacy and cultural sensitivity. Even for 3D measurement of Important Cultural Properties, it is necessary to decide before measurement not only whether measurement is feasible but also how much of the acquired data can be released, whether secondary use will be permitted, whether to limit the resolution, and how much site location information to disclose. It is not uncommon for projects to be halted after measurement due to rights or publication conditions.

What is especially important for practitioners is not to add stakeholders later. If owners, managers, surveyors, conservation staff, public relations staff, and external contractors proceed with misaligned understanding, decision-making tends to stall on the day of the fieldwork. At cultural heritage sites, a single deferred decision directly affects that day’s measurement scope and quality. Conversely, if policies are agreed in advance—such as “this time the purpose is preservation documentation and only selected areas will be published at low resolution,” “control points will be placed around the periphery and will not touch the object,” and “deliverables will be divided into an archive version and a public version”—the fieldwork stabilizes remarkably. The single most important condition for successfully 3D surveying Important Cultural Properties is the quality of prior agreement, not the latest equipment.

Summary

3D measurement of Important Cultural Properties is not simply the visualization of cultural assets in three dimensions; it is about establishing a recording framework that can be used for preservation, repair, research, and public access into the future. The five basics to settle before implementation are: fixing the purpose, combining methods appropriate to the subject, aligning the approaches to accuracy and coordinate systems, designing data with long-term use in mind, and first organizing permissions and publication conditions. If this order is not violated, 3D measurement will not be a one-off event but will become an ongoing practical activity in cultural property conservation.

Especially for Important Cultural Properties that include buildings and outdoor spaces, point clouds and photographs alone tend to leave positional relationships ambiguous in later stages, and reconciling them with surrounding topography, circulation routes, disaster-prevention facilities, and the scope of repairs often causes rework. As indicated by the Geospatial Information Authority of Japan's institutional arrangements, coordinate management that includes 3D point clouds, cross-sections, and GNSS is no longer a set of separate tasks but an integrated practice. Even in 3D surveying of Important Cultural Properties, carefully documenting surrounding reference points and camera positions in ways that do not impose a burden on the cultural property itself greatly affects the reusability of the results.

In that sense, at sites where you want to organize positional information including the surrounding spaces of an Important Cultural Property, the idea of using LRTK — which is deployed as a high-precision GNSS positioning device that can be attached to an iPhone — is practical. It streamlines tasks from checking control points and recording the locations of supplementary photos to organizing the coordinates of exterior structures, approach paths, and ancillary facilities, and it makes it easier to link the acquired 3D data later to drawings, point clouds, and comparisons over time. If you want to improve recording quality including the surroundings without placing excessive burden on the Important Cultural Property itself, it is important not to treat 3D measurement and positioning separately but to organize them as an integrated workflow. As an entry point, LRTK is a well-suited option.