GNSS Layout Practical Guide: Thorough Explanation from Preparation to Measurement

Table of Contents

• What "layout" means on construction sites

• Challenges of conventional layout work

• New layout methods using GNSS

• Preparation and procedures for GNSS layout

• Easy operation via smartphone linkage

• Intuitive position guidance using AR technology

• Labor savings and improved work efficiency

• Information sharing using the cloud

• Recommendation: simple surveying with LRTK

• FAQ

In construction sites and civil engineering works, the task of transferring positions and lines from drawings to the field is called "layout." Layout is a critical initial process for work, and in some cases millimeter-level accuracy is required, which historically demanded advanced skills, time, and manpower. This article unpacks the challenges of conventional layout work and explains new layout methods using GNSS (GPS). It briefly introduces the benefits that the latest technologies—such as RTK for high-precision positioning, and methods using smartphones and AR—bring to the field. Finally, we introduce "LRTK," a convenient simple-surveying tool that is ideal for trying these new technologies in practice.

Challenges of conventional layout work

"Layout" refers to the task in building and civil engineering of marking positions and lines from drawings onto the site. For example, indicating the positions of building walls or the centerlines of equipment on the ground or walls—this work is required at the start of many construction stages. Traditionally, this positioning has been performed using tools such as ink line reels (sumitsubo), chalk, ordinary tape measures, as well as precision devices and surveying equipment such as laser layout tools and total stations. The centerlines and level lines that serve as reference points on drawings are brought straight to the field and then, based on those references, actual coordinates are measured with accurate tape measures and marked… Performing this accurately requires knowledge and experience to interpret drawings, and even small errors can lead to large deviations. For that reason, layout has been a process that tests the skill of experienced technicians.

Moreover, layout is repeated at every stage from foundation work to equipment installation. Each instance can affect the overall schedule; being early or late can significantly change the overall construction period and the quality of outcomes. Conventional layout work was commonly done by teams, and the equipment—including instruments for setting up reference points—was often large and heavy, making setup and relocation difficult. It is not uncommon for marking many points across a wide site to become a full-day task. The labor and time required for these tasks placed a heavy burden on the site.

Another challenge in the construction industry, which faces aging and labor shortages, is the dependence on experienced technicians. If a particular skilled person leaves the site, other work may halt while waiting for layout, posing a risk of stoppage. Moreover, because the work is manual, inconsistencies can occur. Precise foundation positioning especially requires millimeter-level accuracy, which has limits when done by hand. For example, laying out positions on a site where heavy machinery is operating also requires careful attention to worker safety. Thus, conventional layout work, laden with challenges, required substantial labor and expert skill and was a persistent problem on sites in terms of both efficiency and personnel. To address these issues, new layout methods using GNSS have been attracting attention.

New layout methods using GNSS

A promising solution to these issues is a new layout method that uses GNSS systems. A GNSS receiver is a device that determines its position by receiving signals from multiple satellites, such as GPS and Japan’s Michibiki. Modern smartphones also have GPS capabilities, but ordinary GPS alone has positioning errors on the order of several meters (several m (several ft)), which is insufficient for construction sites. By using RTK (Real-Time Kinematic) technology, however, errors can be reduced to within a few centimeters (within a few cm (a few in)). RTK communicates with reference information from a base station installed on site or received via a network and counteracts tiny deviations and biases in satellite signals to achieve high accuracy—about ±1–2 cm horizontally and a few centimeters vertically. This level of precision is achieved by canceling out errors so that horizontal accuracy is approximately ±1–2 cm (±0.4–0.8 in), with vertical accuracy also on the order of a few centimeters.

In Japan, services such as the Ministry of Land, Infrastructure, Transport and Tourism’s active control station network and the quasi-zenith satellite system "Michibiki," which provides CLAS (centimeter-class augmentation service (cm level accuracy (half-inch accuracy)))), can also be used. With an RTK-capable GNSS receiver, you can directly designate coordinates from the design drawings—such as the intersection of building centerlines—as "target positions." GNSS terminals narrow down their position to the centimeter level (cm level accuracy (half-inch accuracy)) while automatically calculating the relative distance to the specified coordinates. This enables direct digital position guidance even for those with limited experience, allowing layout to be performed accurately without relying on subjective judgment.

Preparation and procedures for GNSS layout

When performing layout on site using GNSS, prepare and measure according to the following flow:

• Preliminary preparation: Prepare the coordinate information for the points and locations to be marked from design drawings or BIM data. At the same time, prepare GNSS receiver and RTK network settings, and if necessary install and configure a base station or distribution. In Japan, some devices can directly receive high-precision correction information (CLAS) provided by the Michibiki satellite even without mobile network connectivity, enabling RTK positioning in areas with partial lack of communication coverage. Also, set up the conversion processes between map coordinate systems such as the plane rectangular coordinate system used domestically and global coordinate systems like WGS-84 so that conversions can be performed when needed.

• Start RTK positioning: Connect the GNSS receiver to a smartphone and begin measuring position with RTK precision. If using corrections via the network or your own base station, connect the correction information; if using services like CLAS, configure the device to obtain high-precision positioning. Once RTK provides fixed information (centimeter-level positioning (cm level accuracy (half-inch accuracy)))), proceed with the following tasks.

• Specify target coordinates: Select the coordinate values of the points or lines to be laid out in the app. You can directly specify them using a preconfigured coordinate list or CAD data.

• Guided navigation: Use the app’s guidance function to approach the target point. The screen displays direction and distance from the current position to the target, which you use as a guide to move. If AR is available, the camera image can display the target points or lines as virtual overlays, making it obvious where to mark.

• Mark the point: When you reach the target position, mark and fix it on the ground or wall. Use paint, chalk, spray, or other marking methods as appropriate for the task and organization.

• Verify and save results: Check the marked positions by re-measurement or an alternative method if necessary. If everything is correct, record data such as coordinate names, timestamps, and notes in the app. Taking photos and linking them with position information makes it easy to review the work later.

Easy operation via smartphone linkage

Many modern GNSS receivers are designed to pair with smartphones or tablets via Bluetooth. Install a dedicated app on your phone and attach a palm-sized GNSS receiver, and your familiar smartphone quickly becomes a high-precision surveying device. In the past, specialized survey controllers and complex initial setups were required, but now RTK positioning start/stop and data saving can be done simply by tapping buttons on the phone screen. The interface is intuitive even without detailed technical knowledge, making the tool practical for anyone.

Smartphone linkage brings benefits beyond usability. You can fully leverage the rich functions of an existing smartphone, greatly improving convenience on site. For example, you can digitally record timestamps, point names, and notes in sync, take photos linked to position data, and save them—all easily within the app. There is no need for handwritten field notebooks; all acquired data are digitized and stored on the phone. Measured coordinates are automatically converted on the spot to domestic plane rectangular coordinate systems and elevations (geoid heights), enabling immediate practical judgment in the field. This allows site technicians themselves to perform simple measurements and checks easily, reducing the need to request survey teams and enabling on-the-spot decisions more often.

Additionally, integrating the GNSS receiver with a smartphone reduces the burden compared to traditional bulky surveying equipment. The convenience of carrying a compact device in your pocket and taking it out when needed lightens the site’s operational footprint. With the ability to perform quick, incidental measurements, previously postponed minor layout and measurement tasks can be completed immediately, improving on-site productivity.

Intuitive position guidance using AR technology

The combination of GNSS receivers and smartphone apps enables position guidance using AR (augmented reality) technology. AR overlays digital information onto images captured by a camera or tablet; AR navigation in map apps is becoming familiar to many. On construction sites, AR can visually indicate where to mark. If you load target points or reference line data from the design into the app, those points and lines can be overlaid onto the real scene. Workers can understand at a glance where layout markings are required without mentally matching drawings to the site; even inexperienced workers can accurately identify target positions without hesitation.

AR guidance is like a “car navigation system for construction sites.” Workers can walk the site holding a smartphone while on-screen arrows and guidance direct them to the target position. As they get close, the remaining distance is shown as “X cm to go,” and when they reach the target the on-screen marker aligns precisely. In some cases, planned layout lines or equipment routing can be projected onto the ground in AR so that workers can trace along virtual lines. These visual feedbacks enable accurate layout work by anyone without relying on veteran intuition and experience.

Labor savings and improved work efficiency

GNSS-based layout methods significantly contribute to labor savings on site. Work that traditionally required two people can be completed by one, substantially reducing personnel needs. In sites facing labor shortages, the ability to accomplish more work with limited staff is invaluable. Even at sites without a resident surveying specialist, if field technicians can use GNSS terminals to perform layout, the waste of work stoppage while "waiting for surveying" is eliminated. Consequently, planning and workflow become smoother, leading to shorter overall construction periods and reduced labor costs.

At the same time, introducing advanced technology dramatically improves operational efficiency. RTK-GNSS’s immediate high-precision positioning and AR guidance shorten layout time itself, and reduced measurement mistakes lower the need for rework. With automatic data recording and sharing, there is less need to manually plot measured values on drawings or compile reports. Information obtained on site can be shared with the office via the cloud immediately, enabling faster decision-making for subsequent processes. These effects raise overall productivity and quality on site, allowing small teams to achieve high performance. This labor savings and DX-driven efficiency improvement align with initiatives such as the Ministry of Land, Infrastructure, Transport and Tourism’s "i-Construction" and the broader push for construction DX, and will become increasingly important.

Information sharing using the cloud

GNSS receivers and smartphone apps also integrate with cloud services. Positioning data, photos, and notes collected on site can be uploaded to the cloud with a single tap from the app. Measurement points and their information are instantly plotted on cloud maps, allowing staff in the office to grasp the latest situation in real time. This eliminates the traditional steps of taking measured values back to the office, reflecting them on drawings, and sharing via email. Stakeholders in remote locations can always be synchronized, reducing communication losses and speeding up decision-making.

Sharing data with external parties via the cloud is also easy. You can issue web links that allow anyone to view specific survey data, smoothing communication with clients and partner companies. Accumulating data in the cloud enables centralized information management. For example, coordinate lists and drawings created during design can be imported into GNSS terminals via the cloud for use in the field, or site-marked coordinates can be saved to the cloud as as-built records—these workflows can be performed seamlessly. Because all surveying and layout data are stored digitally, later verification of measured values or review of construction results is straightforward. Cloud utilization connects the site and office, and links past and present data, substantially enhancing the accuracy and efficiency of construction management.

Recommendation: simple surveying with LRTK

Among the new solutions that leverage RTK positioning, smartphones, AR, and cloud services, a recently popular GNSS tool is "LRTK." LRTK is a system composed of an ultra-compact RTK-GNSS receiver and a smartphone app; simply attaching this receiver to your phone transforms a palm-sized device into a centimeter-class positioning tool (cm level accuracy (half-inch accuracy)). Lightweight and compact, it is easy to carry and multiple workers can each use one device on site. Using RTK’s high precision and cloud integration, measurement data are synchronized to the cloud instantly. LRTK also provides coordinate navigation and AR guidance functions, enabling both experts and novices to reach target points without difficulty.

LRTK is not limited to coordinate measurement and layout; it also leverages smartphone cameras and LiDAR for surrounding 3D point-cloud surveying and supports on-site composite display of design models via AR. It can calculate distances, areas, and volumes, covering a wide range of digital measurement needs on site—truly a versatile surveying tool. Its affordability and ease of use are notable advantages: it is relatively inexpensive as dedicated equipment and can be used immediately on site with just a smartphone. Because it is intuitive to operate without advanced training, site staff can perform measurements and layout as needed without relying on the surveying department. You can quickly enjoy the labor-saving and efficiency benefits described above on your own projects. LRTK accelerates on-site DX and transforms layout into a task anyone can perform. As you consider introducing high-precision, simple GNSS surveying on site, we encourage you to try LRTK and related information. You will likely experience surprisingly fast and accurate workflows that overturn conventional expectations. Accepting precise position guidance on site can spark a revolution in productivity—improving work quality and shortening task times. Why not update your layout work with new technologies instead of clinging to old methods? Take this opportunity to bring GNSS terminals to your site and experience their effects.

FAQ

Q: What is "layout"? A: It refers to marking and transferring target points and lines from drawings to objectively specified positions on construction sites. For example, marking foundation locations or column positions on site so subsequent construction can be performed precisely. In other words, it is also called "layout."

Q: What equipment and preparations are required for GNSS-based layout? A: You can get started with an RTK-capable GNSS receiver and a Bluetooth-capable smartphone or tablet. To correct signals received by the GNSS receiver with RTK, you also need an environment to receive correction information via a base station or over a network. In Japan, you can use government-operated active control station networks or the Michibiki high-precision service (CLAS) to enable RTK positioning without providing your own base station.

Q: What is the accuracy of GNSS stakeout? A: Using RTK technology, you can achieve measurement accuracy of about 2–3 cm horizontally and a few centimeters vertically. This level of precision is sufficient for foundation positioning and column placement. It is known to be within an appropriate accuracy range compared with manual tape methods or lasers.

Q: Can GNSS-based layout be performed on any site? A: Satellite-based GNSS signals require open outdoor environments. In areas surrounded by tall buildings, forests, or indoors, signals can be blocked or accurate positioning may be difficult or impossible. On the other hand, high-precision positioning can be achieved in mountainous areas by using services like Michibiki’s CLAS. It is advisable to use GNSS in combination with other methods such as total stations depending on the environment.

Q: What is LRTK? A: LRTK is a simple-surveying system composed of an ultra-compact RTK-compatible GNSS receiver and a smartphone app. It is a lightweight device that attaches to a smartphone and easily handles complex layout tasks and on-site confirmation surveying. With RTK high-precision positioning and AR guidance functions, anyone can achieve precise position guidance on site. Many of the advantages discussed in this article can be readily brought to your site using LRTK. Please try it once.