LiDAR for Heritage Preservation: Creating a Digital Record of What We Cannot Afford to Lose

Historic churches, monuments, statues, ancestral houses, and other culturally significant structures can survive for decades or even centuries. But age alone does not guarantee that they will always remain as they are today.

Natural disasters, fire, deterioration, structural failure, redevelopment, and human activity can damage or permanently alter heritage structures. In the Philippines, where earthquakes, typhoons, flooding, and other natural hazards are recurring realities, this is an especially important consideration for buildings and monuments that may be difficult or impossible to replace.

Photographs can preserve what a structure looked like. Architectural plans can document how it was designed. But what if we need to know the actual dimensions, geometry, position, and intricate architectural details of the structure as it exists today?

This is one area where LiDAR and 3D laser scanning can play an important role in heritage preservation.

By collecting millions of three-dimensional measurements across the surfaces of a structure, LiDAR can create a detailed point cloud that serves as a measurable digital record of its existing condition. Rather than waiting until something has already been damaged or lost, heritage owners and conservation teams can document it while it is still standing.

AI-generated image of Terrestrial LiDAR Scanning

When we think about heritage preservation, restoration often comes to mind. A historic building deteriorates, a monument is damaged, or a structure is affected by a disaster and only then does the question arise: How do we restore it?

But restoration depends heavily on knowing what was originally there.

A photograph may show the appearance of a church façade, for example, but it may not provide enough dimensional information to determine the exact depth of an architectural detail, the geometry of a column, the curvature of an arch, or the spatial relationship between different parts of the structure. Historical plans can provide valuable information, but they may not always reflect modifications, settlement, deformation, repairs, or other changes that have occurred throughout the life of the building.

A detailed three-dimensional survey provides another layer of documentation.

Using Terrestrial LiDAR, a laser scanner can be positioned at multiple locations around and within a structure. The scanner measures the distance and position of visible surfaces from each scanning location. These individual scans are then registered together to form a dense three-dimensional point cloud representing the structure.

Actual Terrestrial LiDAR Scanning Output of a Church done by AB Surveying and Development

The result is not simply a picture of the building. It is a measurable digital representation of its geometry at the time it was surveyed.

That distinction becomes important when the objective is preservation.

Creating a Digital Record Before It Is Needed

AB Surveying and Development has applied this approach to the documentation of an existing church using Terrestrial LiDAR.

Actual Terrestrial LiDAR Scanning Output of a Church done by AB Surveying and Development

The purpose of the survey went beyond producing measurements for an immediate construction project. The church was scanned to create a detailed record of the structure so that, should it ever suffer severe damage or destruction, spatial information about its existing form would already be available as a reference.

Multiple scanner positions can capture different portions of the structure and combine them into a comprehensive point cloud. Depending on the required scope, this can document walls, columns, arches, façades, ceilings, decorative elements, and other visible architectural features in three dimensions.

This does not mean that a LiDAR point cloud alone can automatically rebuild a historic church. Restoration or reconstruction would still require the expertise of architects, structural engineers, conservation specialists, historians, craftspeople, and other professionals. Information about original materials, construction techniques, structural systems, and historical modifications may also be necessary.

What the survey provides is something extremely valuable to those professionals: detailed dimensional information about what was physically there before it was damaged or lost.

And importantly, that information has to be collected while the structure is still available to measure.

Heritage documentation therefore does not need to begin when deterioration becomes critical. In many cases, the best time to create a detailed record of an important structure is before there is an urgent reason to need it.

Notre-Dame: Documenting Heritage Before Disaster Strikes

One of the most compelling international examples comes from Notre-Dame Cathedral in Paris.

Years before the devastating fire of April 2019, the late architectural historian Andrew Tallon had used laser scanning to study Notre-Dame and other Gothic cathedrals. At Notre-Dame, Tallon scanned the cathedral from more than 50 locations in and around the building, collecting more than one billion points of data. His objective at the time was to better understand how medieval builders had constructed the cathedral and how the building had changed over centuries.

The scans allowed Tallon to examine aspects of the cathedral that would have been extremely difficult to measure using traditional tools alone. By analysing its geometry, he was able to investigate questions about the construction sequence, movement of the building, columns, façades, and flying buttresses.

Then, in 2019, Notre-Dame burned. The fire destroyed the cathedral's roof and spire and severely damaged portions of the historic structure. Suddenly, detailed documentation that had originally been collected for architectural research had another potential value. Tallon's laser-scanning work became part of the information available to those working on the cathedral's reconstruction; National Geographic later reported that his work aided that effort.

The lesson for heritage preservation is significant. Documentation becomes most valuable when it already exists before a disaster occurs. No one conducting a heritage survey can know whether a structure will eventually be affected by fire, earthquake, deterioration, or another event. But once something has been destroyed, it is no longer possible to go back and scan its original condition.

For culturally significant buildings, creating an accurate digital record today can preserve information that may become invaluable decades from now.

Further reading: See how laser scanning was used to study Notre-Dame Cathedral before the fire — National Geographic

Heritage LiDAR Is Not Only for Reconstruction

The value of 3D documentation is not limited to preparing for a worst-case scenario.

A detailed point cloud can support architects, engineers, conservation specialists, and heritage professionals working on restoration, renovation, condition documentation, architectural recording, and conservation planning. Measurements can be taken from the dataset, sections and elevations can be derived, and the point cloud can provide a spatial reference for developing drawings or three-dimensional models depending on the requirements of the project.

LiDAR can also be useful when the structure itself is difficult to measure manually. Historic buildings often contain irregular geometry, high ceilings, intricate façades, decorative elements, columns, arches, and surfaces that do not conform perfectly to modern drawings. Rather than assuming that two seemingly identical portions of an old building have exactly the same dimensions, laser scanning records their actual visible geometry.

Actual Terrestrial LiDAR Scanning Output of a Church done by AB Surveying and Development

Repeated surveys can provide another potential application. If a structure is scanned at different points in time using appropriately controlled survey methods, datasets can be compared to help specialists investigate geometric changes. Any interpretation of movement, deformation, deterioration, or structural condition would still require the appropriate engineering or conservation expertise, but LiDAR can provide the measurable spatial information on which those assessments may be based.

The same principle applies beyond churches. Historic buildings, monuments, statues, bridges, ruins, and other culturally significant structures can all potentially benefit from detailed three-dimensional documentation.

In that sense, heritage preservation does not only mean repairing what has already been damaged. It can also mean recording what exists while it is still here.

From Preserving What We Can See to Revealing What We Cannot

LiDAR's role in heritage extends beyond documenting individual structures.

At a much larger scale, Aerial LiDAR has changed the way archaeologists study entire historic landscapes, particularly in places where dense vegetation makes archaeological features difficult to recognize from the ground.

One of the best-known examples is the archaeological landscape surrounding Angkor Wat in Cambodia.

Angkor Wat itself was not discovered using LiDAR. The temple and many other major structures at Angkor had already been known and studied for generations. What LiDAR helped reveal was that the landscape surrounding these monuments contained far more archaeological information than could easily be seen from the ground.

In 2012, researchers conducted an airborne LiDAR campaign over central Greater Angkor. By processing ground returns to derive terrain information beneath vegetation, archaeologists were able to map subtle features that had been obscured by dense and protected vegetation. The resulting data revealed settlement patterns and previously unknown relationships between archaeological features and showed that the Angkor Wat complex extended beyond what earlier interpretations had suggested.

Digital terrain model of Preah Khan of Kompong Svay, east of Angkor. Photograph: Damian Evans/Cambodian Archaeological Lidar Initiative (Source: https://www.theguardian.com)

Later LiDAR research at Phnom Kulen also helped archaeologists map Mahendraparvata, an early Angkor-period urban centre. Researchers identified an extensive network of linear axes, enclosures, ponds, shrines, water-management features, and other archaeological traces, many represented by subtle variations in terrain that were difficult to observe from the ground.

Importantly, the LiDAR findings were followed by field investigation and excavation to verify and interpret what appeared in the elevation data. This illustrates a very different heritage application from scanning a historic church, but the underlying principle is similar.

LiDAR allows us to measure physical evidence of the past in three dimensions. For an individual building, Terrestrial LiDAR can document architectural details that are standing today. Across a heavily vegetated archaeological landscape, Aerial LiDAR can help researchers identify subtle terrain patterns that may reveal roads, settlement areas, water systems, earthworks, and other traces of past human activity.

LiDAR does not replace archaeologists, historians, architects, or conservation professionals. Instead, it gives them another way to see, measure, investigate, and document heritage.

Further reading: See how LiDAR helped reveal the larger urban landscape around Angkor — The Guardian

Preserve It Digitally While It Is Still Here

Heritage is irreplaceable precisely because it carries something that a newly constructed replica cannot fully reproduce: history.

Technology cannot prevent every earthquake, fire, typhoon, structural failure, or century of deterioration. A point cloud cannot replace an original centuries-old church, monument, or historic building either.

What it can preserve is information.

A detailed LiDAR survey can record the dimensions, geometry, architectural features, and spatial relationships of a heritage structure as they exist at a particular point in time. That information can support conservation today and potentially become an important reference for restoration or reconstruction in the future.

The examples of Notre-Dame and Angkor also demonstrate how valuable that digital record can become in ways that may not have been anticipated when the data was originally collected. At Notre-Dame, laser scanning undertaken to better understand a historic cathedral created an extraordinarily detailed record that later aided reconstruction efforts after a devastating fire. At Angkor, Aerial LiDAR allowed researchers to look beyond the monumental temples and better understand traces of an extensive historic landscape hidden beneath vegetation.

At AB Surveying and Development, Terrestrial and Aerial LiDAR provide different ways of documenting the physical environment, from detailed scanning of individual structures to broader mapping across large and complex areas.

Because when it comes to heritage, surveying is not always about preparing for what will be built next.

Sometimes, it is about making sure we do not lose the record of what came before.