How to 3D Scan Stone Monuments: 5 Key Points to Avoid Failure

3D scanning of stone monuments is an effective method for accurately recording stone objects such as cultural properties, memorials, memorial towers, precinct monuments, and stone artifacts serving as local historical materials in terms of both shape and surface information. In recent years, from the perspectives of preservation, research, restoration, public display, and disaster preparedness, there has been growing demand to preserve stone monuments not merely as photographs but as three-dimensional data. However, stone monuments are susceptible to the effects of their material and installation environment and present many factors that complicate measurement, such as worn inscriptions, reflections, shadows, moss and dirt, and confined installation locations. Therefore, it is not enough to simply bring equipment and shoot; selecting the appropriate method and planning according to the objective is important.

Especially practitioners looking for information under the search term "stone monument 3D scanning" will want to know what methods are available, how much preparation is required, and what to watch out for to avoid failure. Therefore, in this article, after laying out the basics of 3D scanning methods for stone monuments, we explain in detail a practical approach that is less likely to fail, divided into five key points. It is compiled to be useful both for personnel in the preliminary stage of planning a survey and for those who actually place orders or handle on-site operations.

Table of Contents

• Background for the need for 3D scanning of stone monuments

• Basics of 3D Scanning Methods for Stone Monuments

• How to Proceed Without Failing 1 Decide the Objective and Deliverables First

• How to Proceed Without Failing 2: Confirm On-site Conditions and Target Status in Advance

• Fail-Proof Approach 3: Designing Acquisition Methods and Accuracy Requirements

• Fail-Safe Approach 4: Align Position Information and Scale

• Fail-Proof Way to Proceed 5: Record with the Utilization Process in Mind

• Summary

Background for the Need for 3D Scanning of Stone Monuments

Stone monuments are often installed outdoors and, over long periods, are affected by various factors such as wind and rain, fluctuations in temperature and humidity, freezing, ultraviolet radiation, plant attachment, and human contact. Inscriptions and surface carvings that were clear when the monument was first erected often become shallower over time, and it is not uncommon for them to become difficult to read with the naked eye or in ordinary photographs. Even when they are important historical records for a community, if wear progresses without adequate documentation, it can hinder future research and transmission to subsequent generations.

What is effective in this case is 3D scanning, which can record a stone monument as a three-dimensional object. If obtained as three-dimensional data, it can objectively preserve aspects that are hard to grasp from frontal photographs alone, such as surface inclination, missing portions or damage, contours, carving depth, and surface undulations of the monument. Furthermore, by overlaying color and texture information onto the acquired shape data, it is possible to preserve it with an appearance close to the on-site look. Because it can be examined later from arbitrary angles, it is also suitable for cultural heritage surveys that cannot frequently access the site, for consideration of conservation and restoration, and for exhibition and educational uses.

Also, a stone monument does not exist in isolation; it can have value as an integral part of its environment, such as the plinth, surrounding stonework, ground, approach path, precincts, burial area, slopes, and trees. Therefore, in practice the issue is how to reconcile high-resolution recording of the monument itself with capturing the positional relationships that include the surroundings. Whether you aim simply to reproduce its appearance or also to include dimensional verification and condition monitoring will change the appropriate methods and required levels of accuracy, so it is important to first clarify the background and objectives.

3D scanning of stone monuments is not limited to a static record for preservation. Its uses are expanding—comparative materials for when disasters or damage occur, checking changes before and after restoration, assisting in reading inscriptions, creating materials for public release, and sharing information among researchers. That is why it is important not to miss any necessary information during the initial measurement stage. If problems arise later—“I should have captured a wider area,” “the side of the inscription is missing,” “coordinates weren’t taken so it can’t be overlaid with other materials”—the burden of re-measurement becomes great.

The key point for practitioners is not to treat 3D scanning of stone monuments as a one-off capture task. Rather, only by designing it as a step in a documentation workflow that includes preservation, deciphering, comparison, sharing, and reuse does it become valuable data.

Basics of 3D Scanning Methods for Stone Monuments

Methods for 3D scanning stone monuments can broadly be categorized into a method that creates three-dimensional models by taking numerous photographs, a method that directly acquires three-dimensional shapes using dedicated measuring equipment, and a method that combines those approaches. Which is optimal depends on the size of the object, the required accuracy, site conditions, and the final deliverable.

The photographic method involves photographing the subject from multiple directions with overlap and reconstructing the shape from correspondences between images. Its strengths are that it easily preserves the color and texture of the monument surface and can be operated relatively flexibly. For subjects like stone monuments that have surface undulations and carved lettering, securing a sufficient number of images and photographing in detail from oblique angles makes it easier to obtain rich surface information. However, conditions such as gloss, wetness, strong shadows, monotonous surfaces, or excessive backlighting can reduce stability, and on-site shooting design directly affects quality.

Using dedicated three-dimensional measurement equipment makes it easier to acquire the shape itself at high density and can capture surface details and edges more reliably. It is a strong option when you want to measure large stone monuments and the surrounding terrain, or when greater emphasis is placed on shape accuracy. On the other hand, adding sufficient visual information to the acquired shape may require an additional process, and depending on site conditions, consideration must be given to blind spots and occlusion.

In practical work, a combination can be effective in which the fine detail of the inscription surface is secured by photo-based methods while the overall shape and surrounding positional relationships are captured by other methods. For example, the idea is to separate data acquisition by purpose: high-density coverage for areas where aiding text reading is prioritized, and wide-area coverage for recording the installation environment. Simply adopting this approach makes it easier to avoid overreliance on a single method and reduces the likelihood of failure.

What is important here is not to understand the term "3D scanning method" solely as the type of equipment. In practice, the method includes everything from confirming the subject, assessing lighting conditions, the order of shooting or measurement, alignment, scale management, to data organization. On site, even if you carefully capture only the inscription surface, the data will be difficult to use if the boundary with the plinth or continuity with the back is missing. Conversely, even if you capture a wide area including the surroundings, if the crucial lettering is coarse the range of possible uses will be limited.

In short, the basics of 3D scanning for stone monuments are to clarify what to preserve and to what extent, and to design how shape, color, position, extent, and reusability will satisfy that purpose. If you proceed with these aspects left ambiguous, deficiencies are likely to become apparent in later stages.

Fail-safe Approach 1: Decide the Purpose and Deliverables First

One of the most common mistakes in 3D scanning of stone monuments is starting with the idea, "we'll just capture it at high resolution." In reality, if the purpose differs, both the information that needs to be recorded and the deliverables will change significantly. The first thing to clarify is who will use the data and for what purpose.

For example, if the primary purpose is preservation documentation, priority should be given to keeping the current form intact without loss. Not only the monument face but also the sides, back, top edge, the junction with the plinth, tilt, chips, and the condition of surface deterioration are important. If the main purpose is to assist inscription reading, the fine undulations and shadows around the engraved characters aid legibility, so attention to the surface detail of the monument and lighting conditions becomes more important. If the main purpose is exhibition or public use, visually pleasing color reproduction and the preparation of lightweight, easy-to-view data are essential. If the aim is restoration assessment or condition monitoring, consistency in coordinates and scale that makes later comparisons easy is required.

If the objectives are different but you end up shooting the same way on site, some aspect will be lacking. In practice you may not be able to narrow the objective down to a single one, but even then it is important to set the priorities between the primary and secondary objectives. If the primary objective remains unclear, confusion will arise in the field, and the acquisition scope, density, and shooting sequence will become inconsistent.

You should also define the deliverables in advance. The required processes vary depending on whether you need the 3D model itself, cross-sectional drawings or orthorectified images, a set paired with record photographs, or management with geolocation. In particular, if the person who will view the data later does not use specialized 3D software, unless you plan ahead to export lightweight viewing data or still images, the data you painstakingly acquired will be difficult to utilize.

You should also clearly define the scope of the subject. Whether you are targeting only the monument itself or also the surrounding paving stones, boundaries, and nearby structures will change the required field of view and measurement range. Because monuments are often inseparable from their installation context, it is helpful for later interpretation to ensure, at minimum, a coverage wide enough to show their positional relationship to the surroundings.

If you try to decide once you are on site, constraints such as time, weather, and permit conditions make it difficult to respond flexibly. That is precisely why, before starting work, compiling the purpose, users, required accuracy, target scope, deliverables, and methods of reuse into a single summary memo will make on-site decision-making less likely to waver. This is the first key point for bringing a 3D scan of a stone monument closer to success.

Fail-Safe Approach 2: Confirm On-site Conditions and Target State in Advance

3D scanning of stone monuments is strongly affected not only by the shape of the object itself but also by the conditions of its installation environment. If preliminary checks are neglected, many areas that are difficult to capture on site will arise, leading to data gaps and degraded quality. Therefore, verifying site conditions and the condition of the object is not merely a reconnaissance but an important process for ensuring quality.

The first thing to confirm is the location where the stone monument is installed. Access and equipment-delivery conditions vary by site — for example, temple grounds, cemeteries, mountainous areas, roadsides, parks, private property, or slopes. Whether you can get around to the back, whether there is sufficient working space around it, and whether the footing is stable greatly affect how freely you can photograph and measure it. If the stone monument is next to a wall or close to trees, blind spots increase and you may not be able to capture it from the required angles.

Next, lighting conditions and shadows are important. When you want to capture inscriptions on a monument surface accurately, strong direct sunlight is not necessarily advantageous. If only parts of the surface become overexposed or deep shadows fall, shape reconstruction and texture representation can become unstable. Conversely, if the light is too even, fine surface variations can become difficult to discern. Being aware of which time of day is suitable and how shadows from surrounding trees and buildings move makes on-site decision-making easier.

Checking the condition of the monument's surface is also essential. Whether the characters are worn, whether there is moss or mud adhered, whether it contains moisture, whether the surface is rough, or whether there are losses or cracks—all of these change the precautions to take during data capture. For example, wet stone surfaces or areas that are glossy only in places can be more difficult to digitize than they appear. Also, if washing or cleaning is to be performed, it must be aligned with cultural property protection and the decisions of the site managers. Rather than touching things carelessly based on on-site judgment, it is important to clearly define the scope of permitted actions.

Even more easily overlooked are obstructions such as surrounding vegetation, offerings, fences, signs, and ropes. These not only interfere with measurements but also increase the effort required to remove them during post-processing. By confirming in advance which items can be moved, which cannot, and which can be temporarily relocated only during shooting, on-site work can be greatly affected.

The effects of weather should not be underestimated. Outdoor stone monuments are directly exposed to wind and rain, so measurements taken in rain or immediately afterwards tend to suffer from wetness and reflections. If the wind is strong, surrounding vegetation moves and appears as unwanted changes in photo-based processing. Cloudy skies are easier to treat as uniform lighting, but for some subjects the visibility of inscriptions can be reduced. Rather than simply using weather to decide whether to postpone, it is necessary to evaluate it in terms of compatibility with the data capture objectives.

Information obtained during preliminary checks should be reflected in the sequence of on-site work. Whether you first capture the overall view, start with detailed shots of the monument face, or set priorities for each surface based on changes in sunlight will affect the outcome. A stone monument is an immovable subject, but surrounding conditions change constantly. Therefore, understanding on-site conditions and eliminating risks in advance is the second key point for proceeding without failure.

How to Avoid Failure — Step 3: Designing Acquisition Methods and Accuracy Requirements

A common problem in 3D scanning of stone monuments is that the process tends to skew toward one of two extremes: either capturing too broadly and roughly, or conversely capturing only local areas in excessive detail so that the whole doesn't connect. To avoid this, it is important to design the acquisition methods and accuracy requirements from the outset.

First, you should consider which parts require what level of resolution. If you want to see the characters and decorative patterns on the monument face, chips, or surface deterioration, those areas need to be captured at high density. On the other hand, understanding the plinth, the surrounding ground, and the installation environment may not require that level of density. Rather than treating the entire subject uniformly at the same density, it is more efficient and produces more consistent quality to design varying densities and coverage according to the information needed.

Next, the concept of capture direction is important. Even if a stone monument appears flat, it actually contains a variety of information such as carved characters, chipped edges, a rough back surface, and machining marks on the sides. Even if you carefully capture only the front, if continuity with the sides and the top edge is weak, the object will be unstable as a three-dimensional model. In particular, capturing with sufficient overlap from oblique angles relative to the monument face is effective for reproducing the fine bumps and depressions around the characters. It is not enough to simply walk around once; you need to adopt a layered approach, consciously capturing upper, middle, and lower areas, left and right, and near and far views.

Regarding accuracy requirements, it is also important not to make on-site judgments based on intuition. How you approach allowable error depends on how precisely you need to check dimensions, how much change you want to compare, and whether you need to overlay other survey results. Reproducing the appearance of a single monument may be sufficient in some cases, whereas if you intend to compare multiple time points or use the data for placement management, consistency of scale and coordinates becomes more important. If you proceed while leaving this vague, you may end up with a half-baked deliverable that is “visible but not measurable” or “measurable but hard to read” after acquisition.

It is also important how you handle surface information and shape information. For stone monuments, the distribution of color and staining can be historical information, while when deciphering inscriptions there are cases where surface relief is more effective than color. Therefore, considering data that prioritizes appearance separately from data that makes shape easier to interpret expands the possibilities for post-processing and application. Whether that mindset exists at the field stage changes the required capture conditions and how auxiliary records are taken.

Furthermore, if multiple measurements are anticipated, it is effective to establish acquisition rules that ensure reproducibility. Keeping consistent factors such as where to start when circling the object, which height ranges to capture, and how much of the surroundings to include will improve the quality of time-series comparisons. Since stone monuments tend to be subjects of long-term management, it is preferable to design for continued use rather than a one‑off field response.

Designing acquisition methods and accuracy requirements is not merely a technical matter. It is a judgment about what must be reliably preserved and where to accept compromises. When this is clear, hesitation on site is reduced and necessary information is less likely to be overlooked.

Fail-proof Procedure 4: Aligning Location Information and Scale

In 3D scanning of stone monuments, even if the shape can be reproduced cleanly, ambiguous position information and scale narrow the range of practical applications. In particular, when you want to re-measure and compare in the future, or associate the scan with surrounding topography, facilities, or drawings, properly establishing position information and scale is of great importance.

First, what you should determine is whether to complete the model as a standalone model of the stone monument, or to treat it as part of spatial information that includes the surrounding environment. If it is only a standalone model, relative shape reproduction may be sufficient. However, when you consider recording the installation location, comparing before and after relocation, understanding relationships with nearby facilities, and linking to inspection histories, it becomes valuable to provide a positional reference.

Scale management is fundamental. Even if three-dimensional data look visually correct, if their correspondence to actual dimensions is ambiguous, it hinders dimensional verification and comparative use. The reliability of scale is indispensable when evaluating the height, width, thickness of a stone monument, the step difference with its base, trends in the depth of inscriptions, and so on. Therefore, on-site you should reliably record reference dimensional information so that consistency can be verified during post-processing.

Going one step further, it becomes important to capture the position of a stone monument within its surrounding space. A stone monument is both a standalone artifact and may have relationships with precinct layout, the approach axis, cemetery plot divisions, traces of former roads, viewing directions, and so on. To preserve such context, it is effective to incorporate not only 3D documentation of the individual monument but also the concept of site coordinates and positional referencing. This makes it easier to link with other survey results and records, and facilitates integration into management registers and maintenance workflows.

What is important here is not to treat positional information as an afterthought. If you create three-dimensional data and then try to “sort out where things were,” you will often find that information needed on site is lacking. At the time of acquisition, you need to decide which positional information is necessary, what level of accuracy you want it to have, and how much of the area around the stone monument you should capture.

Also, if you want to manage multiple stone monuments and related stone artifacts collectively in the future, merely increasing the number of individual models will make operations more difficult. If you organize them so that locations are linked with attributes, they will be easier to search and reuse later. Because the management of cultural properties and historic sites often extends over long periods, organizing coordinates with an eye toward future usability—not just immediate readability—is important.

In outdoor stone monument documentation, having a system that can efficiently confirm on-site coordinates and ascertain surrounding positions elevates the value of 3D data. For example, combining a 3D scan of the monument itself with smooth on-site position verification and treatment as a control point makes downstream processing easier. In such cases, using iPhone-mounted high-precision GNSS positioning devices like LRTK can streamline the capture of on-site coordinates and the recording of surrounding positions. While this serves a different role than acquiring the monument’s fine geometry, in practice—when you want to preserve reliable information about surrounding positional relationships—the concept of combining 3D scanning with high-precision positioning is effective.

Fail-safe Approach 5: Record with the Utilization Process in Mind

The 3D scanning of a stone monument does not end at the point of data acquisition. What really matters is whether the recording was done with an eye toward subsequent organization, sharing, viewing, comparison, and practical use. Even if it appears to have succeeded on site, if it is difficult to use in later workflows, it is, in practical terms, close to a failure.

A common problem is that data were high-resolution at the time of capture but the file sizes are so large that they cannot be shared with stakeholders. Alternatively, insufficient organization of attributes such as file names, acquisition dates, object numbers, and installation locations can make it impossible to find the desired data later. For subjects where long-term preservation and continuous recording are assumed, such as stone monuments, ease of management is as important as the quality of the data itself.

Therefore, it is necessary to decide on-site which unit to use to organize the data. Whether to compile a complete set for each stone monument, separate overall shots and monument-face details, separate raw data from data prepared for use, or how to link related photos and notes—if you sort these out in advance, later processes become considerably easier. Even simply reflecting management numbers, acquisition dates, and face information in file names will greatly improve reusability.

Also, the required export format changes depending on the intended use. Whether researchers want to examine shapes in detail, maintenance personnel need data for routine inspections, or the material is intended for public dissemination, the appropriate data size and presentation differ. Rather than consolidating everything into a single heavy dataset, it is necessary to preserve the raw data while organizing it into user-friendly, purpose-specific formats.

If you plan to use the data for comparison, recording the acquisition conditions is essential. If you don't know when, under what weather, over what area, and in what order the data were acquired, it will be difficult to reproduce the same conditions at future re-measurements. Because deterioration and deformation of stone monuments progress over the long term, there is a strong likelihood the same subject will be recorded again several years later. At that time, to improve comparability with past data, it is important to retain metadata about the acquisition method.

Also, do not underestimate field notes and photographs of the surrounding conditions. Information that is difficult to judge from three-dimensional data alone includes the direction of light on the day, the presence of obstacles, whether cleaning was performed, surrounding vegetation, and access conditions. Although these may seem like supplementary information, they are extremely useful when reusing the data or conducting re-measurements. Treating the 3D scan of a stone monument not merely as a data-creation task but as part of a recording system will help preserve the value of the results over the long term.

For practitioners, leaving records in a state that will be understandable later is more important than aiming for perfection on site. If you record with the downstream use processes in mind, it becomes an asset that is easy to use for archiving, investigation, publication, and maintenance.

Summary

To make 3D scanning methods for stone monuments successful in professional practice, simply turning the object into a three-dimensional form is not enough. First, organizing the objectives—such as preservation, legibility/decipherment, restoration, publication, and comparison—and clarifying the required deliverables is the starting point. On that basis, it is important to inspect site conditions and the surface condition of the monument in advance, and to develop a capture plan that takes practical constraints such as lighting, blind spots, obstructions, and workflow into account. Furthermore, by designing in advance which parts to capture at what density, how to reconcile appearance and geometry, and how to provide scale and positional information, the data will become usable later.

In particular, stone monuments are both standalone records and materials tied to their installation locations and surrounding environments. Therefore, it is important both to carefully capture the fine surface undulations of the monument face and to accurately grasp the on-site positional relationships. The former relates to the quality of the 3D scan itself, and the latter directly affects the ease of management and reuse. Considering these two separately and combining them as needed is the perspective that leads to a way of proceeding that avoids failure.

On sites carrying out stone monument recording work, it is required not only to produce 3D models but also to consistently organize where the monuments are, over what extent, and according to what standards they were recorded. In such situations, having a system that can efficiently perform on-site coordinate checks and capture surrounding positions alongside 3D scanning of the monument itself increases the practicality of the records. LRTK, as an iPhone-mounted GNSS high-precision positioning device, is characterized by its ability to streamline on-site coordinate confirmation and simple surveying. It is also well suited for situations where you want to organize the positions of monuments and related structures on-site while advancing recording plans, making it easier to link 3D scan results to site management and preservation registers. If you want to elevate stone monument 3D scanning from a one-off task to records that can be used in the future, it is important to consider 3D acquisition and the organization of location information together. As an option to support that practical work, it is worth considering the use of LRTK.