What’s different from conventional techniques? Three benefits of introducing GPS positioning

In recent years, improving productivity and efficiency has become a major challenge at construction and surveying sites. Labor shortages caused by an aging workforce and a decline in young professionals have become more serious, increasing the need to review traditional methods and streamline and sophisticate operations. Against this background, the use of GPS (satellite positioning) technology has attracted attention.

GPS is familiar from car navigation systems and smartphone map functions, but recently “GPS positioning” with millimeter-level accuracy has been introduced in surveying and construction, and the way fieldwork is conducted is starting to change significantly. This article introduces three representative benefits of incorporating GPS positioning into the field and explains concrete use cases at each stage such as surveying, construction, inspection, and maintenance management.

Differences between conventional surveying/construction techniques and GPS positioning

First, let’s look at the differences between conventional surveying methods and GPS positioning. Conventional surveying used optical surveying instruments such as total stations and levels to measure angles and distances by securing line-of-sight between the instrument and the target. This method required re-setting the instrument at each survey point, and multiple people to set reflectors or indicate targets, so measuring large areas was time-consuming and labor-intensive. Also, survey results were obtained in local coordinate systems for each site, so linking them with other data required tying to control points and conversion work.

In contrast, positioning using GPS receives radio signals from satellites with a dedicated antenna and directly calculates one’s position. Because points that cannot see each other can be positioned simultaneously in principle, a single person can efficiently observe many points simply by walking with an antenna. As long as the sky above is open, points several kilometers away can be located immediately, and terrain undulations and obstacles are less likely to interfere. Moreover, satellite positioning provides vertical information at the same time, so procedures for leveling to determine height differences can be omitted, making three-dimensional surveying easier. However, in environments where the sky view is blocked, such as among high-rise buildings or in forests, satellite signals cannot be received and positioning becomes unstable, so it is necessary to use conventional optical instruments where appropriate.

The introduction of GPS also brings major changes to construction sites. Conventionally, when laying out positions on site (so-called stakes and marks) or checking as-built conditions, surveyors would install stakes or markings on site based on dimensions on drawings using tape measures and surveying instruments. This required skilled techniques and multiple personnel, and mistakes in survey points could require time-consuming rework. On the other hand, with GPS positioning, coordinate data based on design drawings can be imported into a receiver, allowing accurate positions to be confirmed on site immediately. For example, if construction machines (bulldozers or excavators) equipped with GNSS receivers are used, the operator can work while viewing the machine’s position and height information on a monitor in the cab, and automatic control can finish the ground to the designed elevations and slopes. This is a revolutionary change that is far more efficient and reduces human error compared with work that relied on craftsmen’s experience and intuition. On some sites, construction without survey stakes is becoming feasible, and GPS is changing the style of construction management significantly.

Three benefits gained by introducing GPS positioning

1. Improved positioning accuracy

One of the greatest benefits of introducing GPS positioning is the dramatic improvement in measurement accuracy. Single-receiver GPS positioning traditionally had errors of several meters, but with high-precision positioning technologies such as the RTK methods that have become widespread in recent years, errors can be reduced to the order of several centimeters. For example, in cadastral surveys or laying out the foundations of structures, centimeter-level positioning accuracy (cm level accuracy (half-inch accuracy)) ensures that construction can be carried out according to the design drawings. Reducing rework and corrections due to subtle misalignments leads to improved final quality. In addition, coordinates obtained by GPS are given in the unified geodetic reference system, so survey data that were previously inconsistent from site to site can be handled in a common coordinate system. This makes it easier to centrally manage data even for large projects spanning multiple work zones, and the high accuracy and uniformity are major strengths for future maintenance and integration with other systems.

2. Dramatic improvement in work efficiency

Introducing GPS positioning dramatically increases on-site work efficiency. Survey tasks that previously required multiple people and a full day can, with GPS receivers, sometimes be completed quickly by a single person. There is no need for time-consuming instrument setup or line-of-sight assurance, and continuous observations can be made while moving, enabling rapid surveying of extensive terrain and as-built checks. This makes it easier to maintain and improve productivity even on sites with chronic shortages of technicians.

Also, in GPS-assisted construction, heavy-equipment operators can use positioning information themselves, eliminating intermediate staking and inspection tasks. Work can proceed based on on-site decisions without waiting for surveyors, shortening schedules and simplifying preparations. For example, in earthworks, height adjustments for embankments and excavations used to require repeated height measurements and corrections after initial work, but with GPS-linked machine control, the first pass can produce a finish that is almost design-compliant. This reduces the number of rework cycles, shortening construction periods and cutting fuel and labor costs. Furthermore, satellite positioning is less affected by weather and can be measured in rain or at night. Fewer interruptions due to bad weather make it easier to keep work on schedule within limited construction periods.

3. Compatibility with digitalization

The use of GPS positioning strongly promotes digital transformation (DX) on site. Because positioning results are obtained immediately as numerical data, there is no need to record by hand in paper notebooks or manually transcribe onto drawings. Measurement data can be imported on the spot into tablets or PCs, checked against CAD drawings or 3D models, and shared with the office via the cloud. This makes it easy to share information obtained on site in real time with stakeholders, enabling quick decision-making and remote instructions.

Moreover, GPS location data are highly compatible with other digital technologies and, when combined, create new value. For example, if a camera is linked with GPS, accurate coordinates and orientation can be automatically attached to photos, streamlining infrastructure inspections and field surveys. Previously, photos taken with a digital camera had to be matched to maps later to confirm locations, but with GPS positioning, photos are plotted on a map at the time of shooting, so it is immediately clear where and what was photographed. Seamless linking of digital data helps prevent human errors in recording and smooths information sharing. Additionally, using high-precision location information enables smooth integration with advanced technologies such as drone autonomous survey flights and AR-based on-site projection of design drawings, further enhancing site smartness.

Examples of GPS use in the surveying stage

First, examples of GPS use at the surveying stage, which is the start of a project. In land and topographic surveys, conventionally control points were installed on site and points were measured from them with total stations to create maps. With GPS positioning, you can obtain your position directly from known electronic control points (public coordinates) with high accuracy, eliminating the need to newly install many control points. In fact, the Geospatial Information Authority of Japan recommends the use of GNSS surveying for public surveys, and obtaining survey results in unified coordinates under the global geodetic system is becoming standard. GPS surveying can acquire wide-area topographic data quickly, enabling rapid understanding of existing conditions for development planning and design.

For example, in surveying ground elevations over a vast development site, a surveyor can collect large amounts of elevation data on a grid simply by walking with an antenna. The obtained point cloud data can be automatically reflected in electronic terrain maps and contour maps, directly supporting earthwork volume calculations and design studies. Even on complex terrain or sites with large elevation differences, GPS allows measurement without worrying about line-of-sight between points, making surveying in cliff areas, ravines, or other locations requiring safety precautions more efficient. Establishing digital three-dimensional data from the surveying stage also forms the foundation for ICT utilization in subsequent construction and maintenance phases.

Examples of GPS use in the construction stage

Next, examples of GPS use during actual construction. The use of GPS guidance on heavy equipment is increasing in road and development works. By equipping construction machines such as bulldozers and graders with GNSS receivers and onboard computers and preloading design surface data, operators can understand their machine position and finish elevation in real time while driving. Systems that automatically control blade up/down to grade to the design elevation are already in practical use, enabling substantial reduction of traditional staking (setting elevations with stakes) and finish verification tasks. Because initial cutting and filling can achieve high-precision finishes, the repeated surveying and rework processes previously required are reduced, leading to shorter construction periods and savings in fuel and labor costs.

Also, construction can progress without a surveyor constantly on site, enabling smooth work even when personnel are scarce. Fewer occasions for workers to approach hazardous areas also contributes to improved safety. In the Ministry of Land, Infrastructure, Transport and Tourism’s “i-Construction” initiative, construction using ICT-enabled machines with GNSS is a key pillar, and many cases of dramatically increased productivity have been reported nationwide. In addition to heavy equipment, site supervisors can use handheld GPS devices to measure as-built shapes on the spot and immediately compare them with design data to confirm quality. With GPS positioning, the era has arrived in which construction quality control and progress management can be performed in real time.

Examples of GPS use in the inspection stage

Next, examples of GPS use in the inspection and maintenance stage for structures and infrastructure. In inspections of bridges, roads, dams, and other infrastructure, the condition of target facilities is periodically surveyed to check for abnormalities. By using GPS positioning, the locations of inspection points can be accurately recorded and managed. For example, when inspecting cracks in a bridge column, traditionally photos were taken and locations were noted on paper drawings, but using a high-precision GPS terminal to take photos allows the crack coordinates to be automatically recorded with centimeter-level accuracy (cm level accuracy (half-inch accuracy)). Using high-precision GPS devices (such as LRTK) that attach to smartphones, an inspector can simply press the shutter on site and the photo will be tagged with latitude/longitude, orientation, and shooting time. This eliminates the need to recheck “which location the photo was taken at” when preparing reports later in the office, and prevents omissions or misplacement of records.

GPS positioning also enables efficient monitoring of structural displacement. By installing control points on buildings or ground and periodically measuring the coordinates of the same points, long-term changes such as settlement or tilting can be detected with several-centimeter accuracy. For example, deformation measurements of dams or tunnels that formerly required time-consuming photogrammetric surveys can be quantified quickly with GPS, aiding early detection of abnormalities. Incorporating GPS into inspection tasks allows consistent digital processing from on-site data collection to data analysis, enabling more accurate planning for maintenance management.

Examples of GPS use in the maintenance stage

Finally, examples of GPS use in the maintenance stage of infrastructure. Maintenance work for roads and structures ranges from routine repairs to long-term monitoring. With accurate GPS location data for infrastructure assets, the exact locations requiring repair can be pinpointed for work. For example, even for buried utilities such as water pipes and cables, recording their buried positions with GPS enables accurate excavation locations years later, reducing unnecessary digging and exploratory work. Registering asset coordinates in an asset management system and linking them with maintenance and inspection records enables data-driven decisions when planning future repairs.

Continuous monitoring using GPS is also a powerful means of watching infrastructure health. By installing GNSS sensors at bridge supports or on slopes and continuously observing position information, slight structural displacements or ground movements can be detected in real time. By establishing an alert mechanism for abnormal movements, signs of serious damage or impending disasters can be detected early and preventative measures can be taken. Thus, GPS positioning plays an important role not only in surveying during construction but also in maintenance throughout the service life of infrastructure. Maintenance based on high-precision location data will be a key to efficiently prolonging infrastructure lifespans with limited budgets and personnel.

Conclusion

The introduction of GPS positioning technology is transforming fieldwork across all stages—surveying, construction, inspection, and maintenance. The three benefits of centimeter-level positioning accuracy (cm level accuracy (half-inch accuracy)), dramatic efficiency gains, and ease of data integration are becoming indispensable elements in future construction. Smart construction using GPS is a promising solution to address labor shortages, workstyle reforms, and higher quality demands.

When actually introducing GPS positioning on site, it is important to choose equipment and services that match the purpose. Recently, solutions that make high-precision RTK positioning easy to use have emerged. For example, by using GPS positioning solutions based on LRTK, simply attaching a dedicated terminal to a smartphone can enable centimeter-class high-precision positioning (cm level accuracy (half-inch accuracy)) without installing a base station, allowing stable positioning anywhere nationwide. By leveraging such new technologies, the ICT and DX of sites that i-Construction aims for can be accelerated, enabling safer and more productive construction management.

The introduction of GPS positioning is not merely the adoption of the latest equipment, but a transformation of on-site work processes themselves. By maximizing the benefits of improved accuracy, efficiency, and digitalization and building new construction styles unbound by past conventions, productivity and quality at construction sites will improve dramatically. Our sites have now acquired a powerful tool in GPS positioning and are beginning to evolve to the next stage.