Comparison of 3D Surveying Methods! Advantages and Disadvantages of Laser Scanners, Drones, Photogrammetry, and LRTK

3D surveying is a technique for collecting the shapes of natural terrain, structures, and other objects as XYZ three-dimensional coordinate data.

It is utilized in many fields such as construction sites and civil engineering design, recording of archaeological sites, and building 3D data for VR/games. In recent years, 3D surveying technologies have advanced and many methods have developed. This article compares and explains the characteristics, advantages and disadvantages, use cases, accuracy, and cost differences of four major 3D surveying methods: “3D laser scanner surveying,” “drone surveying,” “photogrammetry,” and “surveying using the LRTK method.” While acknowledging technical complexity, explanations are presented in plain language so general readers can understand. If diagrams showing shapes or workflows are required, display “[ 図の挿入 ]”.

3D Laser Scanner Surveying

A 3D laser scanner emits laser beams from a dedicated laser device and detects reflected light from the target to precisely measure distance and position. Because a single scan can collect tens of millions of points, it acquires “point cloud data” composed of a large number of points. It can reproduce coordinates and shapes with high accuracy, making it useful for site surveys in construction, recording ancient ruins, and scenes where detailed measurements are required. [ 図の挿入 ]

• Advantages: The biggest advantage is that extremely high-precision 3D data can be obtained in a short time. With proper maintenance, details on the order of a few mm (a few hundredths of an inch) can be captured. At the same time, it can collect large-area terrain as a large number of points per unit time, enabling labor savings and efficiency compared to traditional manual surveying. In other words, it is useful for creating detailed architectural models or 3D visualizations for presentations, and can be used as an immersive digital tool.

• Disadvantages: The laser scanner equipment itself is expensive, costing several million yen or more. Moreover, operation requires detailed knowledge and data processing skills. The collected point cloud data is huge and can easily exceed what a typical PC can handle, so processing can take time or require large, high-performance PCs. Also, areas hidden from the laser beam behind objects cannot be measured, so the data obtained depends on the scanning angles and positions. Therefore, it is often necessary to relocate the scanner to multiple positions, which can require significant effort. For these reasons, small and medium-sized companies or low-budget projects often consider alternative methods.

• Use cases/examples: Effective where high accuracy and detail are required, such as current condition surveys at construction sites, 3D scans of structures with BIM/CIM in mind, or recording ancient ruins and large fixed objects for planar data extraction.

• Accuracy: With good equipment and proper setup, very high accuracy on the order of a few mm (a few hundredths of an inch) can be achieved.

• Cost: Initial costs are particularly high, with individual units costing several million yen and in some cases exceeding 10 million yen. Operational costs and data processing environment expenses are also non-negligible.

Drone Surveying

Drone surveying uses unmanned aerial vehicles (drones) to photograph or laser-scan the ground and then reconstruct the space in post-processing. Because it can capture large areas from above at once, it is particularly strong for surveying expansive civil engineering sites that would be impractical to measure by hand: large areas can be turned into 3D models in a matter of hours. Drones can also photograph hazardous or inaccessible areas (except for occluded parts). If equipped with laser sensors, they can obtain ground surface point cloud data even under dense foliage or on complex, undulating tracks.

• Advantages: It can collect large-area data in a short time and thoroughly analyze elevation differences and terrain. Drones can safely survey dangerous areas where people cannot enter, making them useful for disaster investigations and similar scenes. Large-scale sites that previously required extensive human resources can be surveyed by a small team using drones, reducing costs compared to traditional methods.

• Disadvantages: Flight and photography are subject to legal restrictions and permits. Urban or densely populated areas in particular may face strict limits. Weather and time-of-day also affect operations—rain, strong winds, and nighttime hinder measurements. Drone battery life is short, preventing long continuous flights, so large sites often need multiple flights. Achieving high-precision coordinates requires RTK-GNSS equipped drones or the placement of ground control points, demanding specialized skills and equipment. Furthermore, performing laser surveys with drones requires the drone body plus sensor equipment costing on the order of tens of millions of yen, making it significantly more expensive than ordinary photogrammetry.

• Use cases/examples: Effective for surveys of civil engineering zones and entire construction sites, exploration of rugged mountainous areas, or ecological surveys of farmland and forests—projects that require broad understanding of terrain and conditions.

• Accuracy: Photogrammetry (including drone photography) typically yields accuracy on the order of a few cm (a few tenths of an inch), depending on settings and adjustments. With camera calibration using RTK-GNSS or ground control points, planar accuracy of around 2–3 cm (0.8–1.2 in) can be expected. Vertical accuracy may be somewhat worse in some cases.

• Cost: For photogrammetry alone, equipment costs can be kept relatively low. Productivity is high, and entry costs can start from several hundred thousand yen. However, targeting high-precision surveying requires RTK-equipped drones or laser-equipped drones, which dramatically increase costs.

Photogrammetry

Photogrammetry reconstructs points in space from multiple photographs by extracting specific features from the captured images. Its fundamental principle is based on stereopsis from binocular disparity, and by integrating photos from multiple angles, an object can be reproduced with proportional relationships. Recently, advanced algorithms called SfM (Structure from Motion) have progressed, allowing automatic reconstruction of advanced point cloud information on a PC. Historically used in aerial surveying for drafting and map-making, photogrammetry has become easier to process on personal computers due to high-resolution cameras and drones. [ 図の挿入 ]

• Advantages: A major appeal is that you can use general cameras and drones that are widely available without special equipment. Because costs can be kept down, especially small and medium-sized projects can start with modest budgets. Also, the photos provide realistic 3D data close to the actual object, enabling simultaneous capture of surface texture and appearance. For example, photogrammetry is effective for modeling ruins or creating 3D reproduction models to show clients.

• Disadvantages: Processing multiple photos takes time; processing hundreds of images can take several days on some PCs. If you do not understand the use of dedicated software or processing techniques, enormous amounts of data may be obtained but not effectively utilized, requiring specialized knowledge. Surfaces without texture, such as uniformly flat areas or transparent glass, cannot be identified and thus cannot be measured as-is; in such cases, complementing with other methods is important. As a result, photogrammetry accuracy is not as high as laser or RTK-dependent methods.

• Use cases/examples: Suitable when realistic digital reproduction is required, such as cultural property reconstruction, VR content creation, or planning designs for houses and other structures. It is useful when drone or laser options are too costly or when high visual fidelity of the subject is important.

• Accuracy: Because processing uses multiple observation points, initial measurement accuracy within the effective planar area is often on the order of a few cm (a few tenths of an inch), and can achieve high visual compatibility with the real object.

• Cost: Depending on the number of photos and coordinate processing, photogrammetry is generally the most cost- and time-efficient method. However, the final level of detail and accuracy is somewhat lower than other methods, so it is important to use multiple methods appropriately.

High-Precision Simple Surveying Using the LRTK Method

The LRTK method is a new technology realized by attaching a compact RTK-GNSS receiver to a smartphone. RTK-GNSS refers to centimeter-class GPS technology (Real-Time Kinematic positioning) that achieves high-precision global positioning. LRTK miniaturizes this further so that a pocket-sized surveying device can be carried by one person. [ 図の挿入 ]

By attaching an LRTK device to an iPhone or iPad, you can always measure high-precision coordinates immediately. Simply aligning the device to the desired location and pressing a button yields latitude, longitude, and elevation positioning results. This allows even those without extensive knowledge to obtain high-precision location information with a simple button press. You can collect coordinates with LRTK for points you want to mark on captured photos and display those points in AR on drawings, or in some cases immediately display results using the smartphone’s LiDAR sensor or camera. For example, using an iPhone’s LiDAR to perform a simple point cloud scan and overlaying LRTK position information on the acquired point cloud enables easy acquisition of high-precision point clouds with absolute coordinates using only typical power and smart devices.

• Advantages: The biggest benefit of this method is that high-precision surveying can be achieved easily without a specialized surveyor. A person can go to a site alone and collect high-precision coordinate data on the spot, and the data can be shared via the cloud regardless of whether the site is urban or mountainous. RTK methods can obtain correction data from GPS satellites, so surveying is possible at night or in rain. With power available, disaster sites can be surveyed quickly with just a smartphone. In this sense, LRTK is a growing method that allows pocket-sized, easy collection of high-precision location information. Once data is collected, it can be used immediately as practical results, enabling relatively easy verification and tracking on construction sites. If each person carries an LRTK device, site surveys that used to take days could potentially be completed in hours. Moreover, compared to other methods, fewer calibration and auxiliary measurement operations are required, and overall costs are low. It may soon be an era where anyone can obtain high-precision 3D data themselves.

• Disadvantages: Currently, LRTK is not suitable for all scenes. In urban environments, GNSS signals can be difficult to receive, and multipath errors (reflections from surrounding buildings) can reduce accuracy. Also, it is intended for outdoor use, so measurements cannot be performed indoors where GNSS signals do not reach. Even considering these drawbacks, LRTK remains a promising new option for sites and companies that require 3D surveying.

• Use cases/examples: Useful when quick, simple, high-precision surveys are needed on construction sites, when sampling several points on a single structure, or when partially replacing other methods on disaster sites or very large projects to achieve high-precision situational awareness without high cost.

• Accuracy: LRTK using RTK-GNSS can measure single points with errors within about 1 cm (about 0.4 in). By averaging multiple measurements, planar accuracy of under about 10 mm (0.39 in) has been achieved.

• Cost: Because it is pocket-sized, initial costs can often be assembled for several hundred thousand yen. Compared to drone RTK or space laser systems, it offers a more affordable way to get started. Including app and cloud service fees, it is considered a very affordable cost within construction IT initiatives.

Summary: Choosing 3D Surveying Methods and Using LRTK

Below is a simple comparison table of the accuracy and main advantages of each method.

To recap the key points of each method: Laser scanner surveying can quickly collect highly accurate 3D structures down to fine detail, but equipment and skills are required, which limits its use cases. Drone surveying can rapidly capture wide areas with high-precision data, but flight restrictions and advanced piloting qualifications may be required, demanding skilled personnel. Photogrammetry struggles with uniformly featureless surfaces and transparent glass without many photos or advanced processing, limiting its accuracy, but its lack of need for specialized equipment and ease of introduction are major attractions. For example, you could obtain wide-area terrain via drone photogrammetry while supplementing key high-precision points with LRTK or ground surveying to balance efficiency and accuracy. Complex structures can be detailed with laser scanners while the overall view is covered by photogrammetry—combining methods addresses diverse survey needs. In particular, the LRTK method is being trialed in fields that require high precision. LRTK, which allows anyone to collect high-precision coordinate data with intuitive operations like tapping a car navigation screen, has the potential to bring new innovations to future 3D surveying. For example, the ability to perform what used to require large equipment with existing personnel and minimal effort greatly expands operational possibilities. If you are interested in new surveying tools or IT technologies, consider trying the LRTK method and experiencing its results firsthand.