How to record cultural heritage in 3D with UAV photogrammetry: 7 steps to avoid failure

In the field of cultural property preservation and investigation, balancing recording accuracy and work efficiency is becoming increasingly important. Until now, cultural property documentation has often proceeded by combining on-site measurements, photography, drafting, and manual organization, and the larger the subject, the more labor-intensive the process tends to become. For targets with complex shapes and variations in elevation—such as buildings, stone walls, burial mounds, archaeological features, gardens, and shrine or temple architecture—producing sufficiently comprehensive records within a limited timeframe is itself a major burden.

One approach attracting attention for these challenges is 3D documentation using UAV photogrammetry. This method, which acquires numerous photographs from the air and reconstructs three-dimensional shapes from them, has the advantage of making it easy to record wide areas in a short time and to capture the current condition as surfaces. Because it can preserve topography that is difficult to convey with plan views alone and shapes that are hard to organize with elevation photographs alone as three-dimensional data, it can be readily applied to a variety of uses such as preservation management, repair planning, condition monitoring, and education and outreach.

However, 3D recording of cultural heritage is a field that is prone to failure if carried out with the same mindset used for photogrammetry of typical development sites or infrastructure projects. This is because cultural properties often have access and contact restrictions, their surfaces are delicate, and the purpose of recording goes beyond mere shape capture. The required quality is multi-faceted: design details and material texture, condition and extent of damage, the relationship with surrounding terrain, reproducibility for future comparisons, and so on. The idea that “just take the photos” or that point clouds or models alone are sufficient is not adequate.

Therefore, this article organizes and explains the practical workflow to follow when creating 3D documentation of cultural heritage using UAV photogrammetry, presenting it as seven steps to avoid failure. It is intended to be useful not only for staff considering adoption but also for those already working on it who have concerns about accuracy or how to compile deliverables; we delve into the common on-site pitfalls.

Table of Contents

• Reasons why UAV photogrammetry is chosen for 3D documentation of cultural heritage

• Step 1 Clarify the purpose for recording and the deliverables from the start

• Step 2: Identify the constraints of the target cultural property in advance

• Step 3: Plan your capture to prevent blind spots and reduced accuracy

• Step 4 Carefully set up the control point and auxiliary observations on site

• Step 5: Acquire on the day of shooting while managing environmental changes

• Step 6: In the analysis process, ensure both shape reproduction and recordability.

• Step 7 Organize and store for reuse after delivery

• Important considerations for successfully documenting cultural heritage in 3D

• Summary

Reasons UAV Photogrammetry Is Chosen for 3D Documentation of Cultural Heritage

UAV photogrammetry is used in the cultural heritage field not simply because it is a new technology. It tends to provide a rational solution to on-site problems. First and foremost, it makes it easy to record large areas in a short time. For subjects that extend both planimetrically and three-dimensionally—such as castle ruins, kofun clusters, gardens, shrine and temple precincts including approach paths, and stone-built remains on slopes—information gaps are likely to occur if only ground-based photography and surveying are used. By combining aerial viewpoints, it becomes easier to grasp the overall layout and to organize spatial relationships.

Next, the fact that it is suitable for repeated comparisons is also important. In cultural property conservation management, it is required not only to preserve the current condition but also to produce data that can be used for future repairs or for comparisons after disasters. For that purpose, it is important that the data can be rechecked by anyone according to the same standards. Three-dimensional data produced by photogrammetry, if the reproduction conditions are standardized, are easy to compare with observations made at other times and are useful for detecting the presence or absence of deterioration, changes in terrain, and for confirming differences before and after repairs.

It is also characteristic of cultural heritage surveys that there are many stakeholders. Preservation, survey, design, construction, and education/outreach staff, among others, require different viewpoints depending on their roles. Three-dimensional data makes it easy to cross-reference drawings, images, dimensions, and spatial relationships, helping stakeholders share a common understanding. Even when it is not possible to enter the site multiple times, having records that are easy to review later at a desk is a major advantage.

On the other hand, UAV photogrammetry has its limits. Areas beneath trees or eaves, deep recesses, and the inner parts of small defects, for example, may not be adequately reproduced by aerial photography alone. Surfaces that are monotonous and lack distinctive features, or areas with strong reflections, can also lead to unstable shape reconstruction. Therefore, when documenting cultural heritage, it is important not to treat UAV photogrammetry as an all-purpose method but to plan on combining it with supplementary observations and ground-based photography as appropriate for the subject.

Step 1 Clarify the purpose of the record and the deliverables at the outset

The first thing to do in 3D documentation of cultural heritage is neither to fly nor to take photographs. It is to clarify why you are documenting and which deliverables you will ultimately use. If you proceed while this remains unclear, you may end up with many images but insufficient necessary information, or with analysis results that are produced but difficult to use.

For example, if the purpose is preservation management, it is important that the overall shape can be stably retained. If the purpose is to consider repair planning, it is necessary that the elevations’ undulations, deformations, tilting, and the positional relationships of missing parts be easy to read. If educational display or public use is also within scope, visually appealing three-dimensional models or high-resolution image representations may be required. When the purpose differs, the required resolution, the shooting angles to prioritize, and the delivery format also change.

What is important here is that the deliverables of cultural heritage documentation are not necessarily limited to a single item. On site, it is not uncommon for them to span multiple purposes, such as 3D point clouds, 3D models, orthophotos, base data for creating plans, data for checking cross-sections, and visualization materials for explanatory purposes. Determining the priority of deliverables at the outset brings consistency to the data capture plan and analysis approach.

Also, expectations regarding accuracy should be clarified here. In 3D documentation of cultural heritage, it is often assumed that the higher the accuracy the better, but if you do not set the accuracy required for the purpose, you can end up with excessive capture and processing burdens. Conversely, if you assume that a rough overview will suffice, the data may later be unusable for dimensional verification, requiring re-surveying. The necessary conditions change depending on whether the goal is overall understanding, comparison of local deterioration, or production of drawings.

Furthermore, building consensus among stakeholders is also important. Cultural properties involve many stakeholders, and concerns differ by the responsible department. If you align in advance on the scope that may be photographed, the scope that may be published, who the data may be shared with, and assumptions about future reuse, you can reduce rework in later stages. If, after shooting, mismatches occur—such as the material being unusable for publication or lacking sufficient information for internal records—the effort invested in the survey can end up incomplete.

In other words, what’s needed in the initial steps is not just checking the technical conditions. It is articulating the purpose of the records, the deliverables, the accuracy requirements, and the operational assumptions, and thereby creating the foundation for the entire survey plan. With that foundation in place, subsequent decisions are less likely to waver.

Step 2 Identify constraints of the target cultural property in advance

At cultural heritage sites, confirming constraints is even more important than at typical aerial photography sites. It’s not just whether flight or filming is permitted, but also the allowable proximity, what may be installed, the times when entry is permitted, and consideration for the surrounding environment — these detailed conditions directly affect quality.

First, what you need to confirm are the conservation restrictions. Because cultural properties themselves are objects of protection, there may be limits on equipment placement on the ground, temporary placement of markers, close-range flights, access routes, and so on. There are also places—such as gardens, cobblestones, or exposed archaeological surfaces—where foot traffic itself should be avoided. If you do not clarify in advance how close you can approach and where you can place auxiliary items, you may not be able to carry out the observations you had planned on site.

Next, checking the surrounding environment is also essential. Cultural properties are found in a variety of locations: mountain areas, residential districts, tourist destinations, the precincts of shrines and temples, and densely built-up urban areas. Many factors affect the difficulty of photography, including wind, dense vegetation, visitor movement patterns, shadows cast by adjacent structures, crowding at certain times of day, and nearby power lines or other obstacles. In places with many tourists or worshippers in particular, attention must be paid not only to the act of photographing itself but also to safety management and to preventing unwanted people or reflections from appearing in images.

A difficulty specific to cultural properties is the condition of the object’s surface. For example, homogeneous soil surfaces, dark-colored roofs, stones that are prone to overexposure, highly reflective tiles, and areas covered with moss or grass can affect feature point extraction in photogrammetry. If the shape cannot be reliably determined from information visible only from above, oblique photography or ground-based supplementation will be necessary. Understanding the material, color, and how shadows fall in advance is crucial for making the shooting plan realistic.

Furthermore, the effects of season and time of day should not be overlooked. When foliage is dense, parts of the ground and stonework tend to be concealed, and even in winter the angle of light can make shadows excessively deep. Morning and evening light brings out a sense of depth, but shadows move quickly then, which can cause inconsistencies during processing. The conditions suited to shooting directly overhead are not necessarily the same as those suited to shooting at an angle.

What matters in this procedure is not merely treating constraints as obstacles, but planning with those constraints in mind. Rather than judging only whether you can fly or whether you can take the shots, you need to consider under which conditions you can reliably produce stable records. In cultural property surveys, the quality of advance preparation has a much greater impact on the results than the ability to respond on site.

Step 3 Plan your shooting to prevent blind spots and loss of accuracy

Whether UAV photogrammetry succeeds or fails is largely determined at the planning stage. In 3D documentation of cultural heritage, the more complex the features you want to capture, the more likely simple overhead-only photography will be inadequate. The idea that uniformly shooting straight down is sufficient may capture roofs and flat areas, but it tends to be weak for facades, under eaves, the fronts of stone walls, slopes, stepped sections, and parts hidden in the shadows of trees.

First, what you should be aware of is which face of the subject you want to reproduce. If you prioritize planar terrain and layout, grid-pattern aerial photography from directly overhead is the basic approach. Conversely, when three-dimensional lateral shapes—such as stone walls, earthen embankments, building exteriors, and the slopes of burial mounds—are important, you need to combine oblique-angle photography to achieve adequate 3D reconstruction. For cultural properties, side information and elevation differences are often more important, so a survey design that relies solely on nadir/vertical shots is not sufficient.

When setting the shooting area, it is effective to include not only the object itself but also a slightly wider surrounding area. Having surrounding terrain and background information makes connections more stable during analysis and also leaves room to crop later. If you shoot exactly to the object's edges, edge information tends to be lacking and analysis can become unstable. Because cultural heritage objects often have complex contours, designing with some margin is safer.

Also, the concept of overlap rate is important. In photogrammetry, adjacent photos must overlap sufficiently, but for cultural heritage the surface relief, vegetation, and changes in shading can make the apparent overlap rate insufficient. Because the visible area can vary greatly from photo to photo, planning with more margin than for typical flat terrain is required. In particular, on slopes and stone masonry, even a slight change in shooting position can change which faces of the stones are visible, which can result in reduced alignment accuracy.

Additionally, the shooting order is often overlooked. By considering times when the wind tends to pick up, when tourist numbers increase, and when shadows lengthen, and planning which areas to shoot first, you can more easily reduce variations in quality. Because cultural properties often make it difficult to re‑fly the same spot multiple times, you need to plan to reliably capture the required data during a single site visit.

A shooting plan is not just the setting of a flight route. It is the very design meant to ensure that no necessary information is omitted and to avoid unnecessary failures. Especially for cultural heritage, assuming that revisiting the site afterward is difficult, it is important to plan from the perspective of leaving no blind spots, ensuring comparable quality, and assembling materials that are unlikely to fail during processing.

Step 4 Carefully establish reference points and auxiliary observations on site

The concept of control points and auxiliary observations is extremely important for stabilizing quality in 3D documentation of cultural heritage. While it is possible to reconstruct three-dimensional shapes from photographs alone, establishing on-site reference points is indispensable to improve the reliability of position and scale and to ensure the results can be used later for comparison and mapping.

A common misconception here is the belief that UAV photogrammetry can be left entirely to the aircraft. In practice, the more an object is a cultural property, the more the records must be able to withstand later accountability. If it is not clear which coordinate system was used to organize the data, what was used as the reference, and how it will be matched during re-survey, the value of the records diminishes. Even if three-dimensional data looks visually coherent, if positional accuracy and comparison standards are ambiguous, it becomes difficult to apply in practice.

When establishing reference points, consideration must be given not only to visibility and the safety of installation but also to the protection of cultural properties. On the premise of not touching the object, leaving no traces, and not obstructing the scenery or circulation routes, the basic approach is to place them in stable locations around the object. It is not a matter of simply increasing the number of points; it is important to place them so they surround the subject, without bias, in positions that are effective for analysis. Placement skewed to one side tends to compromise the overall consistency.

It is also necessary to assess the need for auxiliary observations. There are many areas of cultural properties that aerial photographs alone cannot adequately capture—surfaces that are hard to see from above, missing fine details, warped wall surfaces, areas near eaves, and so on. In such cases, combining supplementary ground photography and spot dimensional checks makes it easier to verify the validity of the analysis results. Three-dimensional processing is convenient, but on-site verification is important in order to trust the final deliverables.

Moreover, the records of the reference information themselves should be retained. Information about where and what was installed, in what order observations were made, what the weather and lighting conditions were, and which on-site aspects were notable will be useful for later reprocessing or revisits. In cultural heritage surveys, it is not uncommon to reuse data collected once several years later. Organizing the information in a form that future personnel can understand supports the quality of the records.

In 3D documentation of cultural heritage, unglamorous groundwork is more effective than flashy technology. Carefully preparing control points and auxiliary observations not only increases accuracy but also enhances the explainability of the deliverables. With this perspective, the result becomes a record usable for preservation and transmission, rather than mere aerial imagery.

Step 5 Capture on the day of shooting while managing environmental changes

No matter how carefully you plan, if operations on the day of shooting are sloppy the quality will not be consistent. In 3D documentation of cultural properties, how well you can control environmental changes on the day of shooting greatly affects the outcome. Particular attention should be paid to light, wind, the movement of people, and changes in shadows.

First, regarding light: in photogrammetry, if the way photos look differs greatly, processing tends to become unstable. Cultural heritage objects often have many surface irregularities and are highly susceptible to shadows, so changes in lighting over time easily affect geometry reconstruction. If sunlight becomes stronger partway through, or if brightness suddenly changes due to clouds moving in and out, the same surface may appear different from photo to photo, making it difficult to achieve consistency. If possible, it is important to capture the same area in a short period of time and avoid widening differences in conditions.

Next is the wind. When the wind is strong, not only the aircraft’s stability but also the swaying of trees and grass becomes a problem. There may be abundant vegetation around cultural heritage sites, and if moving branches and leaves appear differently in each photo, noise can easily be introduced into point clouds and models. Even if the target itself does not move, fluctuating elements in the surroundings often reduce analysis accuracy. In particular, when grass overlaps the edges of stone walls or archaeological features, the contours you want to see can become unstable.

The movement of people is also a factor that cannot be overlooked. At tourist sites and places of worship, visitors not only appear in images but can also linger or move through the same areas, disrupting the consistency of consecutive photographs. In the recording of cultural properties the primary objective is to accurately preserve the condition of the subject, and temporary human presence tends to become noise. Therefore, operations need to include selection of time slots and management of pedestrian flows.

And on site you should always proceed while performing checks. Even if you think you’ve captured everything, a quick on-site check can reveal omissions or weak areas. Problems such as the elevation not being as well captured as expected, shadows so deep that parts are lost, or insufficient overlap at the edges can be nonfatal if you can reshoot them on site. However, if you only notice these issues after returning, a revisit may be required, and that is often difficult in cultural heritage surveys.

On the day of capture, what is required is making judgments that protect quality rather than simply proceeding as planned. It is not uncommon for weather and site conditions to differ from the plan. The important thing is not to ignore those changes, but to reassess priorities and ensure that the necessary data are reliably acquired. In 3D documentation of cultural heritage, each opportunity carries great weight, so flexible and careful operations determine the outcome.

Step 6 Ensure both shape reproduction and recordability in the analysis process

After a shoot, it's easy to assume that simply leaving things to processing software will produce 3D data, but in cultural heritage documentation the approach to analysis and processing is extremely important. This is because visual appeal and usability as a record are not necessarily the same.

For example, a model whose surface looks smooth may appear attractive at first glance, but fine losses, edge deterioration, and signs of deformation can be rounded off. Conversely, leaving too much noise makes it difficult to tell where the true geometry ends and errors begin. In 3D documentation of cultural heritage, the reliability of the geometry and the ease of re-verification are more important than decorative appearance. Therefore, processing results should not be finalized in a single form; they need to be organized according to their intended use.

The first thing to be mindful of is preserving the original data. If you leave only the processed model and finish without properly organizing intermediate results and the original images, you will not be able to respond when you want to reprocess under different conditions later. Because cultural heritage is often intended for future comparative use, it is valuable to be able to reproduce the acquisition conditions from that time. Organizing the relationships between original images, reference information, processing conditions, and outputs is more important than short-term delivery.

Next, it is necessary to carry out checks from the perspective of shape verification. Even if the overall appearance looks fine from a distance, important parts may be failing. Focusing on meaningful locations—such as joints in stone walls, eave lines, areas with level changes or steps, collapse edges, warping of wall surfaces, and around openings—reveals weaknesses in the processing. In cultural heritage documentation, in practice it is often more important that critical parts are appropriately reproduced than the overall average accuracy.

It's also important not to be overly influenced by color reproduction. When a photograph-derived appearance looks attractive, it can easily be perceived as high-quality, but even if the colors are well rendered, the shape is not necessarily correct. In particular, areas with deep shadows or strong reflections can have geometry that is less stable than they appear. Conversely, something that looks slightly rough may still be perfectly usable in terms of shape. In cultural heritage recording, you need the composure to evaluate visual impression and geometric validity separately.

Furthermore, organizing data for secondary use—such as orthorectification and cross-section verification—is also important. Because three-dimensional data can be difficult to handle as is, producing deliverables that are easier to read as plan and elevation views makes them more accessible to stakeholders. Cultural heritage surveys span multiple specialties, so converting not only the raw 3D data but also presenting it in a format that is easy to interpret adds value.

During the analysis and processing stage, what is required is not flashy completeness but the perspective of whether it can withstand being a record. Will it still be usable when reviewed in the future, will another person in charge be able to understand it, and will it withstand comparison and diagramming? By adopting this perspective, 3D documentation of cultural heritage gains value as practical documentation rather than mere visualization.

Step 7 Organize and store for reuse after delivery

3D documentation of cultural heritage does not end with delivery. Rather, how well the deliverables can be preserved in a usable state after delivery determines true success. Cultural heritage is an object of long-term conservation, and three-dimensional data may be reused in the future for comparison, repair, interpretation, disaster response, and so on. Therefore, it is necessary to organize them so they do not end up as one-off deliverables.

First, it is important to make the file structure easy to understand. If original images, 3D data, visualization data, orthophotos, reporting materials, control point information, processing-condition notes, and the like are mixed together, it will be time-consuming to reuse them in later years. If the person in charge changes, it may be unclear which files are raw data and which are processed. You should keep things so that the record date, coverage area, coordinate system, and the processing conditions used are immediately obvious.

Next, organize things so they can be compared in the future. For cultural properties, the same location may be re-recorded several years later. At that time, how you compare it with the previous data becomes important. If positional references or naming conventions are ambiguous, extra time will be needed to investigate the differences. If you anticipate comparative use, it is useful to manage the target scope, reference points, main sections, and areas of interest in a consistent way.

It is also necessary to adopt the idea of separating viewing and archival copies. High-resolution data is heavy and not always easy for all stakeholders to handle. Conversely, over-lightening the data can cause loss of necessary information. Therefore, a realistic approach is to retain information close to the original for archival purposes and to prepare separately organized, easy-to-use data for sharing. In cultural heritage surveys, many professions are involved, so being mindful of delivery formats tailored to the users will promote greater use.

Furthermore, the context of the record should also be preserved. Information such as the purpose of the survey, what the weather was like on the day, which areas could not be photographed, and which parts were checked with particular attention may not be apparent from the data alone in the future. Three-dimensional data are powerful, but they do not automatically record the circumstances at the site. To enhance the value of the record as cultural heritage documentation, leaving background information is indispensable.

If this procedure is carried out carefully, three-dimensional data will shift from a one-off deliverable to an ongoing conservation asset. Cultural heritage is also something whose value increases over time. That is precisely why it is necessary to preserve recorded data in a form that remains usable over the long term.

Important Considerations for Successful 3D Documentation of Cultural Heritage

So far we have looked at seven steps, but to truly succeed in 3D documentation of cultural heritage, technical procedures alone are not enough. It is important to grasp the underlying principles.

First, the recording of cultural properties is not intended to be about efficiency alone. UAV photogrammetry is indeed a method that makes it relatively easy to capture large areas in a short time, but what is truly required in cultural property surveys are records that will hold up for preservation and transmission to future generations. If you judge solely by whether it can be shot quickly or whether processing is light, important aspects may be omitted and the resulting deliverables may become unusable for future comparisons. Efficiency is important, but it should be pursued only after those objectives have been met.

Second, do not underestimate judgments that can only be made on site. In cultural heritage surveys there is a great deal of information that cannot be understood from photographs alone. The way surfaces are deteriorated, surrounding movement patterns, sunlight exposure, how vegetation encroaches, access restrictions—these on-site impressions determine the accuracy of planning and treatment. It is necessary to recognize that this is not a task that can be completed at a desk, but that quality is decided by the back-and-forth between field observation and data processing.

Third, there is a recognition that creating three-dimensional data and making it a usable record are distinct. In the field of cultural heritage, it is important that data can be compared later, that stakeholders can readily understand it, and that accountability can be demonstrated. To that end, it is necessary to record the recording conditions, the criteria, the extent of missing data, and the rationale for decisions. Ensuring transparency as a record—not just visual completeness—is required.

Fourth, assume that the work cannot be completed with aerial photographs alone. Cultural properties are complex, and there are aspects that UAV photogrammetry struggles with—shadowed areas, elevations or façades, and subtle surface reliefs and details. Flexibility to combine ground observations and supplementary records as needed will, in the end, reduce failures. Rather than fixing on a single means, it is important to adopt an attitude of selecting a combination appropriate to the objective.

Summary

The effort to record cultural heritage in 3D using UAV photogrammetry is highly effective for efficiently preserving large areas and producing data that are easy to compare in the future. However, given the nature of cultural heritage, it is also true that success is hard to achieve if approached with the same mindset as general aerial surveying work. It is indispensable to clarify the recording objectives, identify constraints, develop an image-acquisition plan that prevents blind spots, carefully establish control points and auxiliary observations, acquire data while managing on-the-day environmental changes, distinguish between visual appearance and record fidelity during analysis, and finally organize and preserve the results with an eye toward future reuse.

What's especially important is not to treat 3D documentation of cultural heritage as mere digitization or visualization. To make records that can be used for preservation, repair, comparison, interpretation, and transmission, the philosophy behind survey design and data organization matters more than the choice of technology. More than the act of capturing itself, thinking about what to preserve, how to preserve it, and how it will be used later is the single most important point to avoid failure.

Also, at cultural heritage sites, the way location information is handled also affects the reliability of records. When you want to align photographic data with maps, plans, or survey results from other periods, maintaining a stable positional reference is of great importance. If you want to use current three-dimensional records not as standalone, visually appealing data but linked with other information, you need operational practices that pay attention to positional accuracy.

In that regard, if you want to carry out cultural property surveys and recording of surrounding terrain in a more practical way, the idea of utilizing an iPhone-mounted high-precision GNSS positioning device like LRTK can also be effective. By combining three-dimensional records from UAV photogrammetry with high-precision on-site position verification, it becomes easier to organize and compare subsequent workflows and to align them with drawings. For those who want to make 3D documentation of cultural properties not merely a matter of “shooting and finishing,” but a surveying and recording workflow usable on-site, considering the management of such positional information will expand the scope of operations.