LiDAR vs Photogrammetry: Capabilities, Comparison, When to Use

LiDAR vs Photogrammetry can be a tricky decision if a team is not aware of their capabilities, limitations, and area of use.

In this blog, we will explore what truly makes both of these technologies valuable.

And, how the implementation of either of these scanning technologies is directly related to the project’s requirement and the desired outcomes.

LiDAR Vs Photogrammetry: Foundations of Reality Capture

Between LiDAR and Photogrammetry, the latter was first developed, and dates back to the mid 19th century.

Over the decades, as lens and wireless technologies evolved, photogrammetry advanced in visual richness and accuracy. Back then, it was widely used for topographic mapping, taking aerial photos with the help of balloons or aircraft.

Photogrammetry has advanced significantly with digital imaging technology, improving its accuracy and efficiency in creating 3D models from photographs.

LiDAR, or Light Detection and Ranging, emerged when there was a need for remote sensing tech in atmospheric research and military applications.

However, as laser scanning advanced, LiDAR evolved into a 3D scanning tool. It was still not focused for construction industry, and various other industries also used it. LiDAR technology has evolved significantly since its inception in the 1960s, leading to smaller and more affordable sensors that can be mounted on drones.

Recent advancements in LiDAR technology have made it compact enough to be integrated into drone payloads, enhancing data acquisition capabilities.

On a fundamental level, any sector that needs to capture detailed spatial data uses this tech.

Now, let’s understand how these technologies work on the ground level. When you understand the underlying concept on which LiDAR and photogrammetry work, the decision will be the wisest one.

How LiDAR Works?

LiDAR stands for Light Detection and Ranging, the concept on which the technology works. So, it all starts with positioning the LiDAR system at an entry point.

This is where the system will refer to as the starting position, and then scan the remaining space.

The laser light is not directly spotted on the surface, but the system emits rapid pulses of laser light.

These pulses individually reflect back, and the system performs distance calculation. It then finds out the time to calculate the object's distance from the reference point, which gives the accurate height.

The integration of GNSS and IMU data with LiDAR technology enhances the accuracy of the 3D models generated from the collected data.

The system repeats this process, sending millions of laser pulses per second. This generates high point density that forms the geometry of buildings, infrastructure, and terrain, or even entire cities. LiDAR systems can emit hundreds of thousands of laser pulses per second, allowing for rapid data collection and high-resolution mapping.

LiDAR payload is also a specialized remote sensing unit, attached to drones for precise data 3D cloud models of uneven surfaces for creating a digital terrain model. Also, the technology can give precise measurements in coastal erosion that involves analysis of shoreline degradation.

How Photogrammetry Works?

This process has undergone several fundamental changes, and that field its evoution over the decades.

While the traditional methods involved the extraction of measurements and landscapes from overlapping photos, modern photogrammetry takes this to another level.

However, without contemporary computer engineering, there would be no vision algorithms to analyze these images. The evolution of photogrammetry has been influenced by advancements in computer processing, allowing for more automated and efficient image analysis.

It is those algorithms that analyze multiple images very fast, identifying common reference points. This helps the software reconstruct the depth and spatial relations of the objects for detailed 3D models.

Now, after the basics of how these technologies work, let's learn about the capabilities of Photogrammetry and LiDAR.

Capabilities of LiDAR and Photogrammetry

Both of these technologies offer different levels of accuracy and visual richness. However, their use differs based on project requirements.

Modern construction projects require millimeter-level accuracy, given the criticality of the projects and the associated risks with them.

There are risks during the construction phase as well as the post construction phase.

Since LiDAR and Photogrammetry are used for 3D modeling, which forms the base of construction coordination, the accuracy that these technologies deliver is pivotal.

So, let’s dissect the capabilities of LiDAR and Photogrammetry one by one.

Capabilities of LiDAR

So, LiDAR uses emission of laser pulses, which, after hitting the surface comes back to the system. The time it takes to return gives the accurate height, distance, and geometry of terrain or building, and the specific objects or building parts of it. However, the laser pulse rate varies across basic to advanced LiDAR scanning systems. LiDAR systems often require more specialized training for calibration and data management than standard camera-based workflows.

The key capabilities include:

Highly precise spatial measurement

LiDAR is highly preferred by professionals in the construction industry for the remarkable accuracy it offers. It offers detailed geometrical information from an inertial navigation system, which includes all the dimensions and provides vertical accuracy, ideally required for structural documentation and engineering analysis in infrastructure projects.

Detailed point clouds

LiDAR systems come in various ranges, and the most advanced ones can produce extremely dense point clouds. These represent the exact shape and structure of buildings, bridges, industrial facilities, and terrain. Construction projects are increasingly becoming complex, and hence, this kind of accuracy is required for further modeling and analysis.

Scan-to-BIM workflows

LiDAR integrated seamlessly into BIM workflows, as recognized software applications, Autodesk Revit supports it indigenously. Once the scanning is complete and the point cloud is generated, it can be effortlessly converted into intelligent 3D models. This enables accurate clash coordination, design efficiency, and reliable construction documentation as-built models.

Capturing Complex Structures

In projects where the scope of work involves designing complex mechanical rooms, industrial plants, and dense urban sites, LiDAR is strongly advantageous. LiDAR is the only reliable choice for creating Digital Terrain Models (DTMs) in forested or heavily vegetated areas.

It is because LiDAR collects data by using millions of points to directly measure surfaces and capture intricate details of even the most complex structures. It offers detail and accuracy, ensuring that the 3D models that are created are accurate and realistic.

Operation in Low-light Conditions

Since LiDAR is not an image-based scanning tech, it works exceptionally well in low-light conditions. Instead of relying on external lighting conditions, it uses lasers, making it the perfect suit for scanning tunnels, interiors, and night operations. However, LiDAR struggles with reflective surfaces such as water and glass, potentially creating data voids during mapping.

Penetration Through Vegetation

During terrain mapping, image-based scanning systems often fall short due to thick canopies. However, aerial drones with LiDAR penetrate through gaps in vegetation and capture accurate ground elevation beneath the trees. Hence, it is suitable when infrastructure is planned in areas with dense vegetation.

Capabilities of Photogrammetry

Photogrammetry uses multiple overlapping photographs captured from multiple angles. It uses them to reconstruct the 3D geometry of objects or terrains. It works on advanced computer vision and drone technologies, making it a scalable tool for documenting construction progress, generating spatial data, and environmental monitoring. Photogrammetry compensates for its lower precision with high-resolution textures and color information. It is used in open areas where high-resolution visual context, color texture, and cost-effectiveness are priorities.

The key capabilities include:

Large-scale site mapping

If organizations are looking to get comprehensive site images with high-level visual richness, photogrammetry should be their only choice.

With high-clarity specialized cameras mounted on drones, this process captures entire project sites. To track site progress or show progress to clients in infrastructure, highway, or large land development projects, this capability makes photogrammetry ideal.

3D Model Generation

3D model generation is possible with photogrammetry, but to the extent that high precision is still not required. Specialized algorithms process thousands of images, marking the overlapping points to reconstruct 3D models of buildings, terrain, and construction sites.

Orthomosaic Map Creation

Orthomosaic maps are 2D detailed maps that provide precise, georeferenced, and up-to-date visual records of the desired site.

Photogrammetry facilitates this process by taking high-resolution orthophotos from drones. These are further converted through software applications into accurate 2D maps, which help in progress tracking, site planning, safety inspections, and construction documentation.

Volume Measurement and Earthwork Analysis

Photogrammetry also allows project teams to measure material volumes and monitor terrain changes. It is because, in the above case, visual clarity is much more critical than measurements.

Drones are used to capture high-resolution images, further processed through photogrammetry software.

This generates accurate 3D terrain models, which allows teams to calculate the volume of materials such as soil, sand, and gravel that are stored in stockpiles. This process eliminates the issues with manual measures and our rough estimates by capturing detailed information.

Similarly, in land development projects, this capability of Photogrammetry helps in tracking excavation or landfill works. Aerial surveys conducted at each stage of the work provide construction teams with successive models.

This helps in measuring how much earth is moved, relocated, or added. Project managers can create detailed monitoring and progress reports and also ensure that site work is aligned with the proposed schedule. Photogrammetry is best suited for relatively flat and open areas, efficiently capturing details on visible surfaces.

Now that we have understood both technologies individually, let’s understand the difference between their implementations.

LiDAR vs Photogrammetry: A Technical Comparison

To capture real-world environments, both technologies are optimal, but with some major differences. And before choosing one, understanding these differences becomes crucial for any organization.

Data Capture Method

The most basic difference lies in how that data gets captured in both of these technologies.

So, LiDAR uses specialized laser systems that emit thousands to millions of laser pulses towards the targeted surface to measure distances. LiDAR uses active laser sensors to measure return times, while photogrammetry uses passive cameras that analyze pixel overlaps.

Photogrammetry uses high-resolution overlapping images captured from multiple viewpoints. Further, advanced computer vision algorithms analyze these images, identify reference points, and reconstruct depth information in the 3D and digital elevation models.

Where does the advantage lie?

Here, LiDAR uses laser pulses that make direct contact with the surface. Hence, it produces more consistent and accurate geometric data as compared to Photogrammetry.

Accuracy and Data Density

This is one of the most critical differences to consider when organizations are choosing between the two.

Both of these technologies have evolved over the decades to produce reliable outcomes. However, the difference is in the factors that affect the accuracy of the outcomes in LiDAR and Photogrammetry.

While LiDAR, using pulsed lasers, captures extremely precise measurements, it can even achieve millimeter-level accuracy. However, that depends on the capturing conditions and the type of LiDAR system used. Hence, it is suitable for tasks such as infrastructure documentation and structural analysis, where this level of precision is required.

Photogrammetry, on the other hand, is also capable of producing highly detailed models of modern infrastructure that is complex and large-scale. But this accuracy often depends on the image quality, lighting conditions, camera collaboration, and the number of images taken. Hence, Photogrammetry data is useful for capturing interiors or details of specific areas of a structure, or objects with detailed visual features and textures.

Environmental Performance

Both technologies are used to capture real-world conditions.

Hence, there is a difference between how these two work under varying environmental conditions.

For example, LiDAR is less dependent on lighting conditions since the laser pulses are highly capable of capturing details in low-light environments such as tunnels and building interiors. LiDAR is used for forest mapping, urban planning, powerline inspection, corridor mapping, archaeology, and autonomous vehicle navigation.

There are other sectors where professionals confidently use LiDAR, but Photogrammetry entirely uses images for the complete process. This makes the process vulnerable to varying or low-light conditions.

It falls short in capturing details in areas with shadows or reflective surfaces, which are very common in real-world environments. Hence, these factors heavily affect the reconstructed model.

Processing and Data Output

The interesting fact is that both technologies generate point cloud data, but following different processes.

Unlike Photogrammetry, aerial LiDAR drones directly calculate and generate point clouds almost instantly during the scanning process of Earth's surface with the help of ground control points. Collecting LiDAR data, specialized software produces fine geometric details useful for highly complex and precise work scopes.

Photogrammetry relies on further processing time of the captured images. Here, the software analyzes the overlapping points in the images and calculates camera positions. LiDAR generates direct 3D points that require less complex processing compared to photogrammetry's image stitching.

After this, it reconstructs the spatial geometry and then generates point clouds, which will be further used for 3D model generation. Photogrammetry is more suitable for well-lit and open environments.

Here is a comprehensive view of the key differences between LiDAR and Photogrammetry.

Now, with these differences clearly in mind, let’s move forward to determine the suitable application of these technologies.

When to use LiDAR vs Photogrammetry in Construction Projects

Before choosing either of the technologies, organizations need to assess their project requirements. This is because factors such as the level of measurement accuracy, the size of the site, and environmental conditions greatly influence the decision.

When LiDAR is the right choice

LiDAR provides high vertical accuracy, superior vegetation penetration, and consistent results in varied lighting.

In projects where high precision and reliable geometric data are required, LiDAR is preferred for its absolute accuracy in data points. LiDAR data acquisition is often faster, especially when covering large areas or complex terrains.

The construction industry also goes for LiDAR for Scan-to-BIM workflows, involved in the documentation and digital model preparation of existing buildings for retrofit projects.

Also, for digital twin-led facility management, professionals create as-built models by using the comprehensive data collection generated from LiDAR equipped drones. LiDAR (light detection and ranging) uses laser pulses for 3D modeling and vegetation penetration, regardless of lighting.

Further, if the project work is around mechanical rooms or industrial facilities that have confined spaces, LiDAR solutions work exceptionally well. These places generally have low to no light conditions, which does not impact the accuracy and visual clarity of the point cloud data generated.

The technology is also valuable in preparing construction documentation for infrastructures such as bridges, highways, rail corridors, mining industry, and utility networks. Raw LiDAR data is a monochromatic point cloud that lacks the visual detail provided by photogrammetry. However, LiDAR systems often require more specialized training for calibration and data management than standard camera-based workflows.

LiDAR generates a detailed and accurate 3D point cloud, while photogrammetry produces 3D models from overlapping images.

So, to conclude, LiDAR scanning is suitable for projects

• Requiring highly precise measurements
• Involve capturing confined spaces with low light
• Suitable for mechanical rooms and semiconductor facilities

LiDAR produces structural point clouds, often colorless, whereas photogrammetry provides photorealistic, textured 3D models.

When Photogrammetry is the Preferred Choice

Photogrammetry is ideal for projects where visual detail is critical, often on a smaller budget.

When projects require scanning of large site areas, or aerial view of expansive terrains, Photogrammetry serves best for accurate results.

It is faster in these environments because it works on image capturing through drones and cameras, which is faster and cost-effective than laser scanning technologies.

Hence, Photogrammetry finds extensive use in site mapping and aerial surveying. The high-resolution orthomosaic maps created from drone-based capturing help project teams track site progress, understand current conditions, and plan logistics better. Photogrammetry processing time can be more time-consuming, particularly for projects with high complexity.

For projects that involve earthwork, i.e., removing excess earth or filling deepened areas, this technology can be used for monitoring the progress. Here, complex LiDAR technology is not required to capture data, as visual data richness is what gives clarity for further planning, rather than precise measurements.

Further, this technology is highly reliable in measuring on-site stockpiles of sand, gravel, crushed stone, demolition debris, and recyclable materials such as concrete and asphalt.

It can measure stockpiles, track excavation progress, and give clarity over terrain changes as the work progresses on excavation sites.

Photogrammetry is a cost-effective solution and is easier to deploy on multiple sites, as compared to LiDAR point clouds.

Modern construction forms use both technologies to gain better accuracy and visual clarity. Let’s uncover how these are used in combination for enhanced reliability.

Combining LiDAR and Photogrammetry for Maximum Value

In modern construction workflows, conditions change rapidly. Organizations that have seasoned professionals do not see these two technologies as competitors of one another.

Rather, they look for the maximum value by combining both in various scenarios for high accuracy. LiDAR captures highly accurate geometries of infrastructures and interiors of various complex spaces, while photogrammetry offers large-scale site coverage and visual richness. Hybrid workflows in modern mapping drones combine LiDAR for structural accuracy and photogrammetry for visual realism.

Both technologies generate two separate datasets, which are integrated using specialized software. This gives construction teams more comprehensive digital models. These models offer visual clarity and highly precise measurements, which support BIM coordination, digital twin development, and project monitoring.

As we discussed the limitations of LiDAR sensors and Photogrammetry, this hybrid approach minimizes those, and lets project teams get maximum ROI from investments in scanning technologies.

Final Thoughts

In conclusion, the decision always boils down to project scale, goals, and accuracy requirements. Based on these multiple factors, project teams can either choose one or combine both to gain the maximum value and ROI. Both technologies, after evolving over decades, are reliable real-world capturing technologies in the modern construction landscape.

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