RTK-GNSS Comparison: Cloud Sharing Changes the Job Site! LRTK Brings a Revolution in As-Built Management

Table of Contents

• What is RTK-GNSS surveying? Comparison with conventional methods

• How cloud sharing transforms the field: Utilizing real-time survey data

• Revolution in as-built management: Dramatic efficiency gains brought by LRTK

• Key comparison points between conventional RTK surveying and LRTK

• Summary: The evolution of RTK-GNSS and the new era opened by LRTK

• FAQ

What is RTK-GNSS surveying? Comparison with conventional methods

On construction sites, attention is increasing on RTK-GNSS surveying, which can measure positions with millimeter-level accuracy. RTK (Real Time Kinematic) is a technology that corrects GNSS satellite positioning errors in real time, enabling centimeter-level high-precision positioning. Standalone GPS positioning has errors on the order of several meters, but with RTK methods errors can be reduced to only a few centimeters. This improvement in accuracy has made it possible to carry out tasks such as as-built (post-construction shape) verification and precise layout work with GPS, which were previously difficult.

RTK typically uses two GNSS receivers: a reference station (base station) installed at a known coordinate and a rover (mobile unit) that performs positioning while moving. The reference station continuously sends the error information it measures to the rover, and the rover improves accuracy by applying corrections to its own position measurements. The key point is to obtain a "FIX solution" that resolves the integer ambiguity component from the phase differences of the satellite signals. Once this FIX solution is fixed, RTK achieves true centimeter-level accuracy. However, with conventional RTK surveying, setting up the reference station and performing the initial configuration takes time and effort, and it is common to require two or more personnel.

Comparison with traditional surveying methods: Optical surveying instruments such as total stations and levels, which were mainstream until not long ago, required multiple personnel and a great deal of time for precise measurements. Also, with conventional GNSS surveying, real-time accuracy was insufficient, and post-processing in the office after measurements was necessary. In contrast, RTK-GNSS surveying is revolutionary in that it can obtain high-precision positions on site without the need for prior reference-point setup or cumbersome calculations. Especially in recent years, advances in satellite positioning technology and communications infrastructure have made it possible to obtain RTK correction information without an on-site base station. For example, in Japan, services that distribute correction data from the Geospatial Information Authority's network of electronic reference points and systems that receive centimeter-level augmentation signals from quasi-zenith satellites are being put in place. By utilizing these, RTK positioning becomes possible without preparing additional base stations, lowering the barrier for small sites and for cases introducing RTK for the first time. These technological advances, together with the government's promotion of *i-Construction*, are ushering field surveying into a transition to digitalization.

How Cloud Sharing Is Changing the Field: Real-Time Use of Survey Data

With the advancement of RTK-GNSS technology, cloud-integrated data sharing is transforming on-site work efficiency. Traditionally, survey results were first compiled onto paper drawings or notes and taken back to the office for data整理・報告するのが当たり前でした。写真記録もデジカメと手書きメモを組み合わせ、あとで撮影位置を図面に書き込むような作業が必要でした。それが現在では、スマートフォンアプリとクラウドを活用して測ったその場でデータを記録・共有することが可能になっています。

For example, with the latest smartphone-compatible RTK surveying devices, because you can take photos and enter notes simultaneously with positioning, you can instantly record on-site information packaged as a set of position coordinates + photo + remarks. Since each survey point can be automatically packaged with "where and what was measured," there is no need to later match photos with measurement values. Furthermore, if you upload the data to the cloud with a single tap, the information collected on site can be shared instantly over the Internet. Office staff and clients can also view the latest measurement results and site photos in real time, dramatically speeding up reporting and communication.

With a dedicated cloud viewer, you can visualize uploaded positioning points and trajectories on a map and review captured photos and acquired 3D point cloud data together with project stakeholders. There is no longer any need to carry paper drawings or photo albums, and it becomes easy to grasp site conditions remotely. By sharing survey data in the cloud, the time lag of "measuring on site → organizing in the office" becomes zero, allowing on-the-spot verification of as-built conditions and construction decisions. The surveying workflow is truly being renewed by digitization, and on-site DX (digital transformation) is progressing.

Revolution in As-Built Management: Dramatic Efficiency Gains Brought by LRTK

In the civil engineering and construction sectors, including public works, as-built management—the important process of verifying that completed structures have been finished according to the design drawings—is essential. Traditionally, this as-built verification has been performed through manual measurements using tape measures and leveling staffs and by photographic documentation. Inspectors measure thickness, height, width, and other dimensions point by point at various locations on the structure and compare the values with the specification values on the drawings. The measurement results are compiled into an "as-built management chart" and submitted together with construction photographs. However, the conventional, predominantly manual method has many issues; the main problems are as follows.

• Significant manpower and time burden: Conducting on-site measurements required allocating many personnel and long hours, and additional office work was needed to compile the results into drawings and tables, making it a large burden. It was necessary to arrange experienced surveying technicians, and under conditions of labor shortages it could be difficult to proceed efficiently within the project schedule.

• Limited measurement points and risk of oversight: Manual measurements are physically limited in the number of points that can be measured, making it difficult to fully cover the as-built condition. With limited measurement points, slight discrepancies with the design drawings may be overlooked, and there was a risk of being told "different from the drawings" at the inspection stage and having to rush corrective work.

• Human errors such as missing records: On busy sites, mistakes like forgetting to take photos or writing measurement values incorrectly tended to occur. For example, if photos are forgotten before backfilling buried items, no evidence remains after completion, which in the worst case can lead to rework or disputes.

Due to the issues described above, conventional as-built management methods had limitations in both efficiency and accuracy. Against this backdrop, a new technology LRTK, which combines RTK-GNSS and smartphones, has emerged and is revolutionizing on-site as-built management.

LRTK is a system that attaches a pocket-sized GNSS receiver to a smartphone or tablet, designed so anyone can easily perform centimeter-precision surveying. By mounting a device weighing roughly a little over 100 grams and simply launching a dedicated app, high-precision positioning begins with no complicated initial setup required. Whereas traditional RTK surveying used to require time for tripod installation and adjustments between devices, with LRTK positioning becomes available almost immediately after power-on, allowing work to start on site without waiting. The RTK-specific FIX solution can be obtained rapidly using a proprietary algorithm, making measurements at each survey point smooth.

Moreover, ease of adoption is another attractive feature. LRTK terminals are priced lower than traditional surveying equipment, making it realistic for sites to provide "one device per person". In fact, at advanced construction sites, it's not just dedicated surveying personnel—each worker carries an LRTK, creating a system that allows precise surveying to be performed immediately when needed. That convenience and usefulness are highly valued on site.

Furthermore, the LRTK is characterized by its all-in-one capability to serve multiple purposes with a single unit. Not only can it measure positional coordinates, but by leveraging a smartphone’s camera and sensors it can scan wide areas and acquire high-density 3D point cloud data. The captured point clouds and photo data are automatically saved to the cloud on site, so they can be shared with the office the moment measurement is completed. For example, in road construction cases, using the LRTK enables rapid completion of subgrade and pavement as-built measurements, allowing all stakeholders to review the results on the same day. Survey and recording tasks that once took half a day have been greatly streamlined, leading to prevention of missed measurements and rapid corrective responses. Also, by using the AR function of the LRTK app, workers can overlay reference lines and target heights from design drawings onto live site images while working, so tasks that traditionally required two people—such as installing batter boards (establishing benchmarks) and checking heights—can be performed accurately by a single person.

LRTK also contributes from a safety perspective. In steep-slope earthworks, where surveyors traditionally entered slopes despite the danger, with LRTK the job can be completed simply by scanning point clouds from a distance. Because it can record the terrain’s 3D shape in detail without contact, it can ensure worker safety while achieving precise as-built measurements. Even on vast development sites, you can walk while automatically measuring numerous points to create a surface model, making it possible to grasp the as-built surface and embankment and excavation volumes (completed quantities). For this reason, it can be said to be revolutionary that wide-area as-built management and quantity verification can be completed with the minimum necessary personnel.

Data acquired with LRTK can be used in a form that complies with the Ministry of Land, Infrastructure, Transport and Tourism's guidelines for construction completion management. For example, by assigning absolute coordinates to LRTK point cloud data using known control points, the measurement results become suitable for submission as official construction completion inspection materials. Even today, as electronic delivery and the use of 3D data advance, with LRTK the data obtained on-site can be directly used for official documents and for creating CAD drawings. In other words, LRTK has not only made on-site surveying work accessible to anyone, but also provides results at a level that can be used for inspection and delivery in the conventional manner. It is therefore regarded as a solution that strongly promotes the DX (digitalization) of construction completion management, enabling quality control tasks to be carried out efficiently and reliably without relying on expensive specialized equipment or large numbers of skilled workers.

Comparison Points Between Conventional RTK Surveying and LRTK

There are many differences between the conventional RTK-GNSS surveying (conventional method) that has long been practiced and LRTK, a new smartphone surveying system. Below we summarize the main comparison points.

• Required equipment: In conventional methods, multiple devices such as a GNSS receiver for the base station, a GNSS receiver for the rover, a communications modem, and a dedicated controller were required. With LRTK, surveying can be completed with a smartphone and a palm-sized GNSS receiver.

• Initial setup: In conventional methods, installing reference points on site and configuring equipment took time. LRTK requires no base station; attach the device to a smartphone and turn it on to start positioning immediately.

• Personnel: Conventional methods typically required two or more people (one operating the surveying instrument and staff). With LRTK, one person can handle both positioning and recording.

• Measurement coverage: Conventional methods measured point by point, making it time-consuming to cover large areas. LRTK records the site in planar and three-dimensional detail using point-cloud scanning, reducing oversights.

• Data recording: Conventional methods required separate photography and note-taking. LRTK can take photos and record notes simultaneously with positioning, and photos are automatically linked to coordinates.

• Data sharing: With conventional methods, data was organized and shared after returning to the office following surveying. LRTK enables immediate sharing of results from the field via the cloud, allowing real-time progress tracking.

• Safety: Conventional methods posed risks when surveying hazardous areas such as steep slopes. LRTK allows non-contact measurements from a safe distance, enabling safe verification of the as-built conditions of dangerous areas.

• Implementation cost: Conventional methods required an expensive set of surveying equipment. LRTK uses low-cost devices and existing smartphones, reducing initial investment and making it easy to deploy multiple units for site-wide use.

Summary: The Evolution of RTK-GNSS and the New Era Opened by LRTK

RTK-GNSS surveying technology has advanced dramatically in recent years, and integration with cloud services and mobile devices has transformed field operations. Tasks such as positioning and as-built measurements, which were once left entirely to specialist surveying teams, can now be carried out with smart tools that anyone on site can use. At the forefront of this shift, LRTK—an all-in-one platform that integrates high-precision positioning, data recording, and cloud sharing—is being adopted at many construction sites.

Moreover, even in the construction industry—where chronic labor shortages and calls for work-style reform are prominent—the significance of introducing labor-saving and advanced tools like LRTK on-site will only grow. By leveraging LRTK, surveying tasks that were once complicated can be handled simply as simplified surveying, and results can be shared instantly. The ability to easily implement high-precision as-built management makes it possible to achieve both quality assurance and productivity improvements. With LRTK leading a new era of RTK-GNSS, on-site work practices will become even smarter going forward. At your site as well, be sure to adopt the latest technology and experience its benefits.

FAQ

Q: What is RTK-GNSS, and how does it differ from conventional GPS? A: RTK-GNSS is a positioning technology that achieves centimeter-level accuracy by correcting satellite positioning errors in real time. Standard GPS (standalone positioning) typically has errors of several meters, but RTK can reduce those errors to a few centimeters by using correction information from a reference station. As a result, it is used in applications that require high accuracy, such as land surveying and as-built management.

Q: Is a base station always necessary for RTK surveying? A: Traditionally, it was common to set up a base station (a GNSS receiver serving as the reference point) on site. However, in recent years, by using network RTK services provided by government or private entities and augmentation signals from satellites, RTK positioning has become possible without an on-site base station. For example, LRTK can utilize this correction information, allowing centimeter-accuracy positioning to begin without placing additional equipment.

Q: Can LRTK be operated without specialized surveying knowledge? A: Yes. LRTK is designed with an intuitive smartphone app and a simple hardware configuration, making it easy to use even for those who are not professional surveyors. The app places guides and menus in a clear, easy-to-understand layout, allowing you to perform everything from starting positioning to saving and sharing data with a single tap. There is no need for users to perform the complex settings or calculations required by conventional surveying equipment.

Q: Can data obtained with LRTK be used for official as-built management? A: Of course. Point cloud data and coordinate information measured with LRTK can be utilized in accordance with existing as-built management procedures. For example, if you correct the measured data to an accurate coordinate system using control points, they can be used as-is to prepare the deliverables submitted for as-built inspections of public works. The data also support electronic delivery and the method is recognized as a surveying and measurement technique that meets the Ministry of Land, Infrastructure, Transport and Tourism's i-Construction standards.

Q: Compared with traditional total station surveying, what advantages does LRTK have? A: A total station requires line of sight to a prism and may need to be re-set up at each location or operated by two people. In contrast, LRTK uses satellite positioning, so it is easier to obtain positions even in places with poor visibility, and basically allows a single person to measure each site point simply by operating a handheld smartphone. There is also a difference in the amount of data that can be acquired at once. LRTK enables capturing many points and photos in a short time with smartphone measurements and instantly recording them digitally. On the other hand, total stations excel at precise, point-by-point measurements, so using both appropriately according to the situation can further improve the efficiency and accuracy of field surveying. Note that total stations remain necessary inside tunnels or buildings where GNSS signals do not reach, so it is important to combine methods based on site conditions.

Q: Can LRTK be used at sites outside radio or cellular coverage? A: Yes. LRTK supports not only network-based corrections but also satellite augmentation signals that can be used where there is no communication coverage. Even in mountainous areas without cellular service, high-precision positioning is possible if correction information from quasi-zenith satellites overhead is received. In other words, even in locations without an Internet connection, RTK surveying with LRTK can continue as long as there is a clear view of the sky. The ability to choose the optimal correction method according to site conditions is also a strength of LRTK.