From Embankments to Exteriors: Versatile Applications of UAV Photogrammetric Point Cloud Generation

Table of Contents

• Introduction

• What is UAV photogrammetric point cloud generation?

• Conventional surveying methods and their challenges

• Key efficiency points using photogrammetric point clouds

• Use cases: from embankment volume measurement to building exterior inspection

• Conclusion

• Simple surveying with LRTK

• Frequently Asked Questions

Introduction

Surveying and recording as-built conditions are routine tasks on civil engineering and construction sites. However, conventional methods that achieve accurate surveying require significant time and labor, posing a major problem for an industry chronically short of personnel. For example, understanding the topography of a large development site traditionally requires mobilizing multiple surveyors to measure each point with a total station and produce drawings. Surveying on dangerous slopes or in areas with poor footing raises safety concerns for workers. In this context, a technology that has attracted attention in recent years is UAV photogrammetric point cloud generation. By photographing a site from above with drones (UAVs) and automatically generating orthophotos (orthorectified aerial images) and high-precision point cloud data from the obtained photos, site measurements that used to take days have been dramatically streamlined. The Ministry of Land, Infrastructure, Transport and Tourism’s promotion of *i-Construction* has also supported this trend, and the technology is expected to be a key tool for improving site productivity. This article explains the benefits of UAV photogrammetric point cloud generation, which can be applied broadly “from embankments to exteriors,” and explores how surveying work on site will change.

What is UAV photogrammetric point cloud generation?

UAV photogrammetric point cloud generation refers to the process of reconstructing a three-dimensional model (point cloud data) on a computer from numerous photographs taken by a drone, and generating a composite image viewed from directly above—an orthophoto. Simply put, it is a technology for creating “map-like aerial photos.” An orthophoto is an image created by stitching together multiple aerial photos, correcting the distortions and tilts in each photo so that the result appears as if viewed from directly overhead. Because distortions caused by buildings and terrain are removed, distances and areas can be measured accurately across the entire orthophoto. A major feature of this process is that photogrammetry can be used to create a three-dimensional point cloud model while generating the orthophoto. In the past, orthorectification was performed using specialized aerial-photography software, but recent advances in photogrammetric algorithms have led to cloud services that can automatically generate high-resolution orthophotos. We have entered an era where, without conducting thousands of ground control measurements with special surveying instruments, simply having drone-acquired photos of a site can produce detailed as-built imagery and 3D models in a short time.

Conventional surveying methods and their challenges

What were the challenges of conventional surveying work before the advent of UAV photogrammetric point cloud generation? Previously, creating topographic drawings commonly required large amounts of manpower and time. Typically, a two-person team would set up and operate surveying instruments such as a total station, recording coordinates point by point. Back in the office, the points would be connected in CAD software to finally complete a plan. This method had the following problems.

• Time-consuming and labor-intensive: Teams carrying equipment would measure wide areas, and depending on site size, surveying could take a full day or more. Other tasks often had to be paused to allocate survey staff, affecting overall schedules.

• Human error and omissions: Since humans measure and record points one by one, there is always risk of misreading or recording mistakes. Also, because only limited points can be measured, fully capturing complex terrain changes is difficult. Often additional surveys are needed later when missed measurements are discovered, which is inefficient.

• Heavy equipment and safety issues: Surveying instruments like total stations are large and heavy, requiring significant effort to transport and set up. High-precision measurements need stable instrument fixation, reducing mobility. Surveyors may need to enter hazardous slopes or work on roads with vehicle traffic, demanding careful safety management.

• Requires expertise and experience: Accurate surveying and drafting require advanced skills, placing heavy burdens on experienced workers. Newcomers often find equipment operation and data processing difficult, making training time-consuming. With an aging workforce, knowledge transfer is also a challenge.

As described above, conventional manpower-centered surveying has many efficiency and safety issues. Moreover, chronic labor shortages in the construction industry make labor-saving and efficiency improvements urgent. Industry-wide DX initiatives aimed at productivity improvement, such as the government’s *i-Construction*, are accelerating, and fundamental reforms through digitization and automation of surveying work are being demanded.

Key efficiency points using photogrammetric point clouds

How does introducing UAV photogrammetric point cloud generation address the challenges above? Here are the main benefits.

• Significant time savings: Automated aerial photography by drone and cloud-based photo analysis can reduce site surveys that used to take half a day to several days down to tens of minutes to a few hours. Because high-precision orthophotos and 3D data can be obtained the same day as shooting, subsequent works can proceed immediately, shortening overall schedules.

• Safe operation with fewer personnel: Because images are captured from the air, people don’t need to enter hazardous areas. One drone and one operator can cover large areas, and work in harsh conditions such as nighttime or extreme heat is minimized. Single-operator surveying is possible, enabling surveys even at sites with staffing shortages. Remote data acquisition for high places or busy roads also reduces accident risk.

• Comprehensive data coverage and improved accuracy: Orthophotos and point clouds contain exhaustive information about the site, greatly reducing worries about missed measurements and providing a complete record of site conditions at the time of capture. By using RTK-equipped drones or ground control points (GCPs), acquired data can achieve high absolute accuracy within a few centimeters (within a few inches). Photogrammetric algorithms themselves have advanced, and with proper procedures, accuracy comparable to conventional ground surveys can be obtained.

• Automatically generated diverse deliverables: Using cloud services, the process of generating point cloud models from photos also automatically outputs orthomosaic images. Functions have emerged to extract arbitrary cross-sections from generated 3D data and download DXF drawings, among others. With a single data acquisition you can obtain orthophotos, point clouds, cross-sections, and earthwork volume calculations together, largely eliminating additional surveying or manual drafting. Creating contour lines from terrain models or applying textures to 3D models for visualization is also easy. This reduces the burden on engineers and speeds up as-built management and report preparation.

• Fast decision-making through data sharing: Digital survey data can be stored and shared in the cloud, enabling real-time information sharing between the site and the office. Meetings can be held while viewing orthophotos with supervisors or clients immediately after surveying, and remote stakeholders can simultaneously check the latest deliverables via a browser. This is far faster and more reliable than returning with paper drawings or exchanging USB drives, reducing rework and mistakes and contributing to improved quality and safety.

Use cases: from embankment volume measurement to building exterior inspection

Let’s look at concrete examples of how much surveying work can be streamlined by adopting UAV photogrammetric point cloud generation. At one development site, topographic surveying that previously required 2–3 people and more than half a day was replaced with aerial photography, enabling completion by one person in about one hour. After shooting, point cloud data and orthophotos were automatically generated in the cloud, and detailed as-built drawings were produced the same day. At the same time, volumes of fill and cut (the amount of soil placed and excavated) were automatically calculated, and discrepancies from design data were immediately determined. This is a good example of greatly improving surveying and drafting efficiency while reducing personnel.

In another case, orthophotos obtained by drone are used for as-built management of a large dam construction. Processes that used to involve many cross-section measurements and manual drafting for earthwork calculations are now completed quickly from current-condition capture to quantity calculation through regular drone flights and cloud processing. Because acquired point cloud data have coordinates in a global geodetic reference system, later-acquired data can be easily integrated, allowing drawings to be updated immediately to reflect the latest conditions as needed. This minimizes losses from remeasuring missing areas and greatly speeds up on-site decision-making.

UAV photogrammetry is also widely applied outside civil works. For building exterior (facade) inspections, drones can photograph the entire exterior wall, and the large number of images can be auto-stitched in the cloud to create high-resolution elevation orthophotos (photographic elevation drawings of a building wall viewed head-on). This makes it easier to detect deterioration and cracks across an entire wall from the office without erecting scaffolding for close visual inspection. For infrastructure inspections of hard-to-access bridges or chimneys, 3D modeling of drone photos has increasingly enabled efficient identification of damage locations.

Thus, the introduction of orthophotos and point cloud data is beginning to fundamentally change common practices on site. Surveying and as-built management tasks that used to require much time and effort are being streamlined and accelerated with digital tools, allowing limited personnel to safely and accurately grasp site conditions. Leveraging the detailed data obtained for construction management and maintenance can improve overall project quality and reduce costs. UAV photogrammetric point cloud generation can be called a “game changer” that fundamentally transforms site workflows.

Conclusion

The spread of UAV photogrammetric point cloud generation technology is dramatically improving work efficiency in the construction and surveying industries. By digitizing surveying tasks that relied on manual labor, site conditions can now be understood quickly, accurately, and safely. This is not only convenient but also directly contributes to shorter schedules, cost savings, improved working conditions, and attracting younger talent. Supported by national DX policies, smart construction using orthophotos and point cloud data will increasingly become standardized.

Some may worry whether their company can master advanced technologies. However, recent cloud services and surveying solutions are designed to be usable without specialized knowledge. Once the essentials are understood, they can be easily introduced on any site. The benefits of efficiency reach all levels, from site staff to management, and contribute to work-style reform across the organization. Combining these technologies with AI-based automatic analysis in the future is expected to enable even faster and more advanced surveying. The digital surveying revolution centered on UAV photogrammetric point cloud generation is rewriting conventional wisdom on site. Actively advancing site DX rather than sticking to traditional methods is what the construction industry needs going forward.

Simple surveying with LRTK

For those who want to realize efficiency using orthophotos and point clouds on their own sites, the LRTK series simple surveying solution is recommended. LRTK is an all-purpose surveying tool composed of a pocket-sized high-precision GNSS receiver that can be attached to a smartphone and a cloud service, allowing anyone to easily perform centimeter-level positioning (half-inch-level positioning) and 3D measurements. By uploading photos taken by a drone to the cloud, high-precision point cloud models are automatically generated, and orthophotos and cross-sections can be obtained together. No specialized high-performance PC or difficult operations are required; site-captured data can be immediately turned into deliverables. LRTK also supports smartphone-based point cloud scanning (LiDAR), enabling easy completion of details that are blind spots for drones, such as the backside of structures or beneath tree canopies. The LRTK series is manufactured domestically in compliance with *i-Construction* and offers thorough support from introduction to operation, so non-experts can use it with confidence. Harness cutting-edge surveying technology and use LRTK to powerfully promote productivity improvement and DX on your sites.

If you are interested, please feel free to contact us. We will help LRTK take your site to the next level.

Frequently Asked Questions

Q: What equipment and software are required to generate orthophotos? A: Basically, you can get started with a drone equipped with a high-resolution camera and an internet connection. Capture aerial photos with a drone and upload the image data to a cloud service, and point clouds and orthophotos can be automatically generated without preparing expensive surveying software or a high-performance PC on your own. If you want very high-precision survey results, use an RTK-capable drone or set multiple ground control points (GCP targets) to correct image coordinates. A typical PC for viewing the final deliverables only needs to run a standard web browser.

Q: How reliable is the accuracy of orthophotos and point cloud data? A: Accuracy varies somewhat depending on shooting conditions and equipment, but with proper operation can be comparable to conventional ground surveys. By ensuring sufficient photo overlap and correcting survey data with an RTK-equipped drone or ground control points (GCPs), high-precision results with horizontal and vertical errors on the order of a few centimeters (a few inches) can be expected. Even RTK-unenabled drones can produce highly accurate relative 3D models using photogrammetric algorithms alone, but for strict coordinate requirements it is recommended to correct with simple ground control points. In any case, accuracy achievable for normal civil construction management applications is generally sufficient.

Q: Is security a concern if survey data are stored in the cloud? A: Many cloud services take strong measures for security and data protection. Communications are encrypted, and servers implement strict access control and intrusion prevention, so sensitive survey data can be stored with confidence. Automatic backups mean data remain in the cloud even if a user’s PC fails. When selecting a service, check the terms of use and privacy policy and choose a reputable provider.

Q: The operation seems difficult—can beginners use it? A: Recent orthophoto generation services are designed to be beginner-friendly. The basic procedure is just to perform drone shooting on site and upload the photos to the cloud. Advanced parameter settings are automatically adjusted in the background, so you can obtain results without deep theoretical knowledge. Choosing a service with Japanese manuals and support desks allows you to ask questions when you don’t understand operations. Many cases exist where even those inexperienced with drones or surveying have implemented solutions successfully. It is also possible to adopt a phased approach—try a small project first to get accustomed to procedures before full-scale use.

Q: Are the benefits worth the cost of introducing orthophoto generation technology? A: Introducing the technology involves initial investment and operating costs such as drone hardware and cloud service fees. However, in most cases the benefits justify the costs. Labor and days previously spent on conventional surveying and measurement are drastically reduced, so the investment can be outweighed by mid- to long-term efficiency gains. In addition, reductions in high-altitude work lower occupational accident risks, and rapid data acquisition shortens overall project schedules—benefits that are hard to quantify but very significant. Using the latest technology also appeals to clients and enhances competitiveness. Overall, orthophoto generation is a cost-effective solution.