Can weathered stone monuments still be read? Four benefits of using 3D scanning

Table of contents

• Reasons why weathered stone monuments become difficult to read

• Reasons why 3D scanning is suitable for deciphering stone monuments

• Benefit 1 Easier to perceive the three-dimensional relief of characters

• Benefit 2: You can carefully review information that is difficult to see on site afterwards.

• Advantage 3: Facilitates record keeping and comparative verification

• Benefit 4: Broadens the scope of sharing and utilization

• Practical considerations when leveraging 3D scanning

• Summary

Reasons Why Weathered Stone Monuments Become Difficult to Read

Even if the outlines of the characters on a stone monument are relatively clear when it is erected, over many years the surface gradually wears away and the carved edges become rounded. Moreover, because they are often placed outdoors, they are exposed to rain and wind, temperature fluctuations, direct sunlight, airborne dust, and the influence of surrounding vegetation, so the surface condition changes year by year. When these changes accumulate, the boundaries of the characters tend to blend into the background when viewed with the naked eye, making them difficult to read even up close.

What is particularly problematic is that it is not simply a matter of the characters becoming faint. On weathered stone monuments, the entire surface can become roughened, with small chips and grime spreading, so that irregularities beyond the lettering itself increase. As a result, it becomes difficult to distinguish the original incised lines from the irregular surface changes caused by long-term deterioration. Even shining a flashlight on the site or changing the viewing angle can actually complicate the shadows, and it is often hard to judge where the inscription ends and natural decay begins.

Also, when deciphering inscriptions on stone monuments, not only the characters themselves but their placement and line spacing, variations in carving depth, and the tilt of the stone surface are important. For example, areas that look similar may actually be part of a character if they consist of shallow grooves running continuously in a certain direction, while irregular, random depressions are more likely to be the result of weathering or damage. However, such subtle differences are difficult to convey in flat photographs alone, and there are limits to revisiting on-site observation results afterward.

Against this background, interest in 3D scanning has been growing in recent years as a means of recording and assisting the reading of stone monuments. 3D scanning is characterized by its ability to capture surface shapes as three-dimensional information, enabling it to handle fine bumps and depressions that ordinary photographs cannot fully capture. In response to the question of whether weathered monuments can be made readable, not all characters can necessarily be completely restored, but it is extremely effective as a means of improving legibility. What is important is to understand 3D scanning not as a magical restoration technique, but as a practical method for carefully extracting shape information from monuments that are difficult to read.

Why 3D Scanning Is Well Suited to Deciphering Inscriptions on Stone Monuments

The biggest reason 3D scanning is well suited to deciphering stone monuments is that it can treat characters as variations in surface height rather than as color or pattern. On weathered monuments, surface discoloration or encrustations can make inscriptions difficult to see, but if the relief itself remains even slightly, it may be captured as three-dimensional geometry. In other words, reconstructing the information as shape data can organize the details and make it easier to trace contours than the impression the human eye receives on site.

Another reason is the freedom of processing after acquisition. In on-site observation, you are affected by weather, time of day, sunlight conditions, and surrounding obstacles. What is visible changes between cloudy and sunny days, and depending on the orientation of a stone monument, legibility can differ greatly between morning and evening. However, if you capture the shape with a 3D scan, you can later virtually change the lighting, enhance shadows, or make surface reliefs from specific directions easier to see. This means you can repeatedly recreate on the data the observation conditions that can only be obtained once in the field.

Furthermore, what is significant for practitioners is that it becomes easier to retain the basis for their readings. Reading inscriptions on stone monuments tends to depend on a practitioner's experience and observational eye, and it can be difficult to explain in a report “why it was read that way.” With 3D scan data, it is easier to share which parts have what kinds of protrusions and depressions and from which viewing directions the marks are more readily recognized as characters. When multiple people review the data, they can discuss while looking at the same shape data without having to reconvene on site, making the reproducibility of judgments more likely to improve.

Of course, interpretation cannot be completed by 3D scanning alone. Many conditions affect the results—stone material, surface dirt, adhesion of moss or soil, solar reflection, scan density, positional accuracy, and the angles of photography and measurement, among others. Even so, 3D scanning is extremely powerful in that it converts information that is difficult to see on site into a state where it can be examined later from multiple perspectives. For more heavily weathered stone monuments, it becomes especially important to have a process that allows you to bring the shape back for analysis rather than relying solely on a brief on-site observation.

Advantage 1 Easier to perceive the three-dimensional relief of characters

The primary advantage of using 3D scanning is that it makes it easier to perceive the three-dimensional relief of characters. Characters carved into a stone monument remain as slight depressions in the surface. As weathering progresses, those depths become extremely shallow and may appear as a flat surface to the naked eye. However, if the entire surface can be recorded as a three-dimensional form, even very small variations in height can become easier to distinguish through magnified display or shading.

This is an advantage different from simply taking high-resolution photographs. Even if a photograph has high resolution, it is fundamentally two-dimensional information. It can record the light and dark of a surface, but it can be difficult to distinguish whether that is really due to differences in depth or to differences in color or dirt. By contrast, a 3D scan records the positional relationships of surfaces themselves, making it easier to trace which direction a character’s strokes are recessed and where they rise. For example, it becomes easier to consider whether a particular area is part of an incised line rather than just a stain, including its continuity with the surrounding area.

Also, being able to capture three-dimensional form makes it easier to pick up features that are easily overlooked in flat images, such as the start and end points of strokes, intersections, and shallow lines corresponding to sweeping strokes. When deciphering inscriptions on stone monuments, it can be more important how many partial shape clues you can collect than whether an entire character is completely visible. There are often cases where stacking fragmentary information—such as the angles of left and right sweeps, the positions of vertical strokes, the number of horizontal strokes, and the spacing between the character and its surroundings—helps narrow down the candidates. 3D scanning is well suited to laying the groundwork for interpretation because it makes it easier to secure such fragments as shape information.

Furthermore, it should not be overlooked that you can view the entire face of the stele as a single entity, not just parts of its surface. With the naked eye, if you concentrate on a nearby character you lose sight of the overall layout, and conversely, if you look at the whole you cannot follow the details. With 3D data, however, you can alternate between checking the overall layout and zooming in on local areas. Because you can examine information such as approximately how many characters are arranged at each height, where line breaks occur, and whether there are differences in carving between the title inscription and the main text, this contributes not only to improved accuracy in reading individual characters but also to an understanding of the inscription’s overall structure.

In practical work, rather than aiming for a perfect reading from the outset, it is important first to change a “state of unreadability” into a “state in which clues to the shape are visible.” In that sense, the advantage of making an object easier to grasp three-dimensionally is the most fundamental and also one of the most significant values in handling weathered stone monuments.

Benefit 2: You can carefully verify information that is difficult to see on-site later

The second advantage is that information which was hard to see on site can be reviewed calmly and carefully afterward. In stone monument surveys, time and environmental constraints are always present. Poor lighting conditions, surrounding trees or structures that limit observation positions, difficulty securing footing, wet surfaces, and the need to take traffic and safety into account mean it is not uncommon to be unable to secure sufficient time for thorough examination on site. In such situations, one is easily swayed by information that “seems to have been seen” in the moment, and even if one wants to recheck later, the original conditions cannot be reproduced.

If you perform a 3D scan, even after leaving the site you can recheck the captured data from multiple viewpoints. For example, you can change the lighting to reassess shadows, finely adjust the display magnification, tilt the monument surface to view it from an oblique angle, or extract and compare only a specific area. Areas you could observe for only a few seconds on site can be reviewed any number of times in the data. This ability to review material repeatedly is extremely important when dealing with subjects that contain ambiguous information, such as weathered stone monuments.

Additionally, a major advantage is that you can later try perspectives you didn’t notice on site. When interpreting, if you are standing alone at the location your viewpoint inevitably becomes fixed. However, if you take the data back, another person can check it from a different standpoint or assume different reading hypotheses and focus on specific parts. Shallow lines that were overlooked the first time may take on meaning during a second review. The mere fact that there is room for such re-examination improves the quality of the investigation.

Being able to check the data afterward also has the advantage of reducing the need to touch the monument more than necessary during fieldwork. Weathered stone monuments can have fragile surfaces, and excessive contact or cleaning may pose a risk. Rather than rubbing them on site to inspect details or touching them for long periods, capturing their shape non‑contact and carrying out subsequent examination on the data makes it easier to gather information while minimizing stress on the object.

For practitioners, leaving information in a reproducible form is often more important than completing an investigation in a single visit. If you create a state that can be checked later, the same information can be referenced during report preparation, stakeholder consultations, and further review. Because it does not depend on whether something was seen once in the field, the consistency of judgments is likely to improve. In deciphering weathered stone monuments, the ability to turn a momentary field observation into work that can be carefully verified afterwards is a very practical value of 3D scanning.

Benefit 3: Easy record keeping and comparative verification

The third advantage is that it makes record keeping and comparative verification easier. A stone monument’s condition at this moment is not permanent. Weathering progresses gradually, and the surface dirt and growth of vegetation also change. Earthquakes, nearby construction, falling objects, and human contact can cause fine damage. For that reason, it is important to record as objectively as possible what the condition was at a given point in time.

Photographic records are of course effective, but from the perspective of interpreting stone inscriptions, being able to preserve the surface geometry as well as the visual impression is of great significance. With 3D scan data, the distribution of surface relief on the monument face can be stored as three-dimensional information. This can serve as a reference for comparing how much of the contours remained at an earlier time if further weathering occurs in the future. Lines that are only barely legible now may disappear in a few years. Keeping such changes in a state where they can be tracked quantitatively or visually also has value for preservation management.

The ease of comparative verification is not limited to merely changes over time. By overlaying data acquired by different methods or at different times, or by comparing multiple processing results, it becomes easier to assess which appearance is most plausible. For example, a form that looks like a single character in one processing method may appear as a natural loss in another presentation. Even in such cases, if the original shape data remain, you can avoid being swayed solely by the processing results and trace back to verify the underlying evidence. This is also important for preventing overly arbitrary interpretations in downstream processes.

Furthermore, when the quality of record-keeping improves, it becomes easier to accommodate staff changes and interorganizational coordination. Work involving stone monuments often does not conclude quickly and is sometimes handed over across fiscal years. In such cases, verbal explanations or a few photographs alone may not adequately convey what the predecessor observed and how they reached their conclusions. With 3D scan data, at least the condition of the monument's surface can be passed on to successors or other departments. This reduces reliance on individual judgment and is a significant advantage for advancing continued preservation and investigation.

In practice, it's just as important to consider not only whether something can be read now but also how to preserve its current condition. A weathered stone monument cannot be restored once its condition is lost. That is precisely why 3D scanning, which can simultaneously assist readability and preserve records, is effective. Not only does it make inscriptions easier to read, but it also secures records that can be compared in the future, making it a highly worthwhile method to adopt.

Benefit 4: Expanded opportunities for sharing and use

The fourth advantage is that the range of sharing and utilizing the acquired data expands. Interpreting weathered stone monuments often cannot be completed by a single person alone. When multiple roles are involved, such as staff in charge of on-site surveys, record organization, preservation and management, research, and coordination with related organizations, having an environment in which each can verify the same subject under the same conditions makes the work considerably easier to carry out.

With 3D scan data, stakeholders who cannot visit the site can examine the condition of a stone monument in three dimensions. It also makes it easier to share nuances of surface relief that are hard to convey with photos alone, as well as the relationship of character positions across the entire inscription surface. As a result, points of discussion such as "which parts are difficult to read," "which areas should be checked intensively," and "where the weathering ends and where there may be carved characters" can be discussed using the same reference material. This is not merely about improving efficiency; it is also important for aligning the quality of judgments.

Moreover, the range of applications is not limited to reading assistance. Uses are diverse, including preservation records, exhibition descriptions, educational purposes, local archiving, comparative research, and foundational materials for future re-survey planning. For example, even a stone monument whose inscriptions are difficult to read on site can be made easier to use as explanatory material for stakeholders by using a display that adjusts shading based on 3D data. Because it can promote understanding of information without altering the condition of the original object, it makes it easier to achieve a balance between preservation and utilization.

Furthermore, when easily shareable data is available, replanning on-site work becomes more rational. Even if a single scan proves insufficient, you can later analyze which areas lack sufficient density and which acquisition angles are missing, and specifically design the next survey. This helps reduce unnecessary revisits and clarify the additional work required. It is also effective in reducing on-site burden and wasted budget.

When practitioners consider "stone monument 3D scanning," they tend to focus on whether it will make inscriptions readable, but the real value lies in being able to apply the information obtained to support interpretation across subsequent work as a whole. Taking into account the sharing of judgments, ease of explanation, long-term use of records, and improved efficiency of re-surveys, 3D scanning can be seen not as a one-off measurement but as an effort to establish an operational foundation for stone monument information.

Practical considerations when leveraging 3D scanning

So far we have looked at the advantages, but to make 3D scanning function effectively you also need to take into account several practical considerations. First and foremost, be clear about your objective. Whether you want to "create a clean 3D model of a stone monument" or "improve the legibility of characters made hard to see by weathering" will change the required acquisition conditions and processing strategy. This is because the required density and methods of verification differ depending on whether you prioritize the visual appearance of the shape or assistance in interpreting fine surface relief.

Next, be aware of the influence of on-site conditions. Conditions such as surfaces being wet, heavy moss or soil buildup, strong direct reflections, or being able to capture data only from a single direction due to surrounding obstacles increase the difficulty of shape capture and post-processing. Therefore, the success of measurements is determined not only by the equipment itself but also largely by pre-checks and reading the on-site conditions. As needed, it is important to organize which surfaces to capture from what distances, which times of day are appropriate, and which areas require additional checks.

Also, how you present the data after acquisition can greatly affect the outcome. 3D data does not, by itself, make text naturally readable. The appearance can change considerably depending on how shading is applied, where the viewpoint is placed, the zoom range, and how surface features are emphasized. For this reason, in practice you need to design not only the “scanning” itself but also “how to verify it for interpretation.” If this is left vague, you may end up having captured data that cannot be fully utilized.

Furthermore, caution is required in how decipherment results are handled. 3D scanning is a means to aid interpretation, but it does not create lost characters out of nothing. It is important to treat the data while clearly indicating which visible lines are characters and which are weathering, and where estimations are involved. In reports in particular, organizing "shapes that could be confirmed" separately from "interpretations as readings" will increase reliability when the material is reviewed later.

And what must not be forgotten is the handling of location information. Stone monument surveys do not necessarily conclude with the surface of a single stele. Installation position, orientation, relationships with surrounding features, on-site circulation, and positional relationships with related remains can all make the spatial context important. If 3D scan data can be linked to on-site positions and managed, revisits, comparative surveys, and overlaying with other materials become easier. Support for reading the monument surface and on-site position recording are, in practice, better considered not as separate tasks but as a continuous workflow.

Summary

Weathered stone monuments lose the contours of their inscriptions over time, making it difficult to tell what is carved even when viewed on site. However, unless the inscription information has been completely erased, traces may remain as slight surface irregularities. 3D scanning is a technique that captures those minute shapes as three-dimensional data, converting them into a form that allows careful examination later of clues that were difficult to see in the field.

In particular, the ease of grasping the three-dimensional relief of inscriptions, the ability to recheck information that is difficult to see on site as many times as necessary, the facilitation of record-keeping and comparative verification, and the ability to share and widely use the data among stakeholders are major advantages in the practical work on weathered stone monuments. Not all characters will necessarily become readable, but rather than leaving them unread, the value of 3D scanning lies in enabling evidence-based work to improve legibility.

In surveys and documentation of stone monuments, in addition to capturing the shape of the monument’s surface itself, location information — where it is installed on site, which direction it faces, and how it relates to its surroundings — is also important. Organizing this kind of field information together makes re-surveys, preservation management, and data sharing easier to carry out. When you want to streamline confirmation of on-site coordinates and position recording, LRTK, a high-precision positioning device that can be attached to an iPhone, is also effective. By improving the accuracy of position data acquisition alongside the 3D scanning work of the monument, it becomes easier to balance the reproducibility of records and the practicality of field operations. Considering not only preserving the shape of hard-to-read stone monuments but also accurately recording their locations further enhances survey quality.