Surveying and Setting-out Know-how in the i-Construction Era: Digital Practices to Improve Productivity

Introduction

The Ministry of Land, Infrastructure, Transport and Tourism’s initiative, i-Construction, is a program to fully introduce ICT (information and communication technology) on construction sites to improve productivity. It aims to dramatically increase the efficiency of construction sites amid labor shortages and transform them into more attractive workplaces. Among these, the surveying and setting-out work essential to construction management—referred to as surveying and setting-out (surveying and marking)—is a field that holds the key to the productivity revolution. Traditionally, it was commonplace to use batter boards (wooden stakes and string lines) to establish positions and elevations, but the use of digital technology is significantly changing surveying and setting-out methods. This article explains the role and changes in surveying and setting-out work required in the i-Construction era and introduces concrete measures to improve construction efficiency through digital setting-out without batter boards. We hope you gain an understanding of the latest methods that lead to labor savings, improved responsiveness, and enhanced as-built accuracy, and find hints for introducing them on your sites.

The role of surveying and setting-out and issues with traditional methods

Surveying and setting-out work in construction involves a series of tasks to accurately transfer positions and elevations from design drawings to the site. From pre-construction control point surveying to positioning of structures, batter board installation, and as-built (finished shape) verification surveys, surveying and setting-out is a critical process that affects construction quality. However, several issues have long been associated with traditional surveying methods. For example, the work known as batter boarding, which installs wooden stakes and horizontal boards to indicate reference elevations and boundaries, is a typical example of a task that is time-consuming and labor-intensive. To set batter boards, multiple survey technicians run around the site while heavy equipment operators work according to the batter boards. Batter boards must be reinstalled each time excavation or embankment work is carried out, and they are affected by weather and construction progress, becoming a cause of waiting in the schedule. Additionally, the presence of batter boards can obstruct heavy equipment movement and pose risks when workers operate near machinery.

Such traditional surveying methods required time and effort and imposed significant burdens for human error checks and verification work. With a shortage of experienced survey technicians, a shift to more efficient and highly responsive surveying and setting-out was urgently needed. This led to the appearance of the surveying innovation advocated by i-Construction: surveying and setting-out reform using ICT. In Ministry of Land, Infrastructure, Transport and Tourism demonstrations, cases have been reported where the surveying staff required, which was previously 7–8 people, was reduced by about half to 3–4 people through ICT introduction. In the next section, we will look at what “digital setting-out without relying on batter boards”—the key to this change—actually means.

What is digital setting-out without batter boards?

Digital setting-out is a method that uses GNSS positioning and 3D design data to perform on-site positioning and elevation management with minimal use of physical batter boards. Traditionally, wooden stakes and string lines were used on site to indicate elevations, and excavation and embankment were carried out to match them. In contrast, digital setting-out involves importing 3D design data into machines and surveying equipment and carrying out construction while checking position and elevation in real time, allowing significant omission of batter board installation.

Specifically, ICT-compatible construction machines (bulldozers, backhoes, etc.) are equipped with GPS/GNSS antennas and onboard computers, constantly comparing the design model with the current blade position. Operators can view guidance on the machine monitor such as “◯ cm (◯ in) to the design surface” and, if needed, automatically adjust blade height through automatic control. As a result, high-precision construction controlled by the machine can be performed without reference stakes or string lines during construction. In fact, a report by the Ministry of Land, Infrastructure, Transport and Tourism states that “by 3D-ifying the entire construction area, complete batter-board-less construction was implemented, eliminating losses due to waiting for batter boards.” Because machines can move freely without concern for batter boards, there are cases where daily work volume increased by about 1.5 times, demonstrating the significant impact digital setting-out can have on productivity.

Of course, not all stakes become unnecessary; conventional measurements using total stations and the like are still combined for precise positioning and verification of structures. However, if batter board installation can be omitted in many situations such as earthwork and site formation, the repeated manual surveying workload is drastically reduced, and construction cycles speed up. In short, digital technology enables a new i-Construction–era style in which “surveying and setting-out work is not a bottleneck on site.”

Major digital utilization measures to improve surveying efficiency

To realize digital setting-out, various technologies and operational models are being introduced on sites. Below are key initiatives that contribute to labor savings, improved responsiveness, and increased accuracy in surveying work.

• Immediate setting-out with GNSS positioning and RTK: RTK surveying using high-precision GNSS receivers enables centimeter-level (half-inch accuracy) positioning by a single person. By using dedicated base stations or correction information networks (VRS or continuous operating reference station networks), coordinates can be obtained instantly at any point. Tasks that traditionally required two people using a total station for marking can now be performed by a worker with an RTK rover device who can set points solo, leading to significant labor reduction. Also, because measurements can be taken on site while comparing them to design values, responsiveness is high and on-the-spot response to design changes and as-built confirmations is possible.

• Omitting batter boards by linking with ICT construction equipment: Use ICT construction machines (machine control/guidance systems) loaded with 3D design data to link machine operation and surveying. Since the machines themselves perform real-time positioning and comparison with the design surface, work can be carried out without creating batter boards to indicate construction references. This batter-board-less construction eliminates downtime for survey waits, achieving schedule shortening. The need to install stakes near heavy equipment is reduced, enhancing safety as well. For example, in the aforementioned case, completely eliminating batter boards achieved a reduction of 71 person-days of work (from 213 person-days to 142 person-days). This effectively leads to shorter construction periods and reduced labor costs.

• Cloud-based 3D data management: Centralize site survey data and design models in the cloud so all stakeholders share them. If a design change occurs, the latest 3D data can be immediately reflected in machines and surveying instruments, and data between the site and the office is synchronized instantly. This prevents unnecessary rework caused by “old drawings” and allows remote checking of progress and as-built data. Because information is continually updated in the cloud, construction managers can grasp surveying results and verification data even when not on site, which aids quick decision-making and instruction issuance (improving responsiveness).

• Automation of as-built inspection: Digital technologies are also active in as-built measurements after construction completion. Using photogrammetry from drone aerial surveys or point cloud data obtained with terrestrial 3D laser scanners, large areas of terrain and structures can be measured in a short time. By overlaying the acquired 3D point cloud with design data, it is possible to automatically determine whether the required elevations and shapes have been achieved. Verification work that used to involve manually cutting and measuring sections has been greatly labor-saved, and as-built documentation creation is simplified. In many cases, submitting digital inspection data directly eliminates the need for paper documents, speeding up the inspection process itself. With this automation, surveying staff are freed from tedious measurement tasks and can devote time to quality analysis and planning the next steps.

Effects of digital setting-out and future outlook

The digital practices described above bring many benefits to surveying and setting-out work. In addition to shortening on-site working hours and reducing personnel burden, real-time positioning and data linkage enable process efficiency, while sensor measurements deliver improved accuracy and quality and ensured safety simultaneously. Even in situations where surveying previously lagged and caused construction waiting times, it is now possible to proceed quickly with machines and data taking the lead. As a result, total construction period reduction and cost savings follow, directly contributing to overall site productivity improvements.

Digitalization and automation of surveying and setting-out will further advance on future construction sites. The Ministry of Land, Infrastructure, Transport and Tourism is also looking ahead to automation of construction sites through “i-Construction 2.0” up to 2040. Surveying know-how that has relied on experience and intuition will gradually be systematized, and an era when anyone can measure accurately is expected to arrive. In that process, the roles of site managers and engineers will shift from simple point-setting tasks to interpreting and utilizing data.

Conclusion – A new option: smartphone RTK

An important attitude for promoting digital setting-out is to try introducing new technologies on site. Recently, methods have appeared that combine a smartphone with a small GNSS receiver to perform RTK positioning. For example, attaching a device called LRTK to a smartphone can turn it into a palm-sized RTK instrument capable of centimeter accuracy (half-inch accuracy). Because it is cheaper and easier to use than traditional dedicated surveying instruments, it is conceivable that each site staff member could carry a high-precision positioning terminal as if one device per person. If not only surveying specialists but also construction managers and craftsmen can check points and mark out by themselves, on-site responsiveness will dramatically improve. Digital efficiency improvements in surveying are effective not only for large-scale projects but also for small and medium-sized works. Take this opportunity to add smartphone RTK and other latest solutions to your on-site implementation options, and make surveying and setting-out know-how a strength for your company in the i-Construction era.