How to Use Location Information in Indoor Construction Management: 5 Methods to Achieve Improved Accuracy and Efficiency

Table of Contents

• Why location information is important in indoor construction management

• Method 1: Ensure layout accuracy by implementing high-precision indoor positioning

• Method 2: Improve work efficiency by real-time location management of materials, equipment, and personnel

• Method 3: Real-time verification of construction accuracy using AR and digital twins

• Method 4: Streamline progress and quality control with 3D scanning and photogrammetry

• Method 5: Enable high-precision measurements for anyone using smartphone-based simple positioning

• Summary: Recommendation for simplified surveying using LRTK

• FAQ

Why location information is important in indoor construction management

In indoor construction management, accurately understanding "what is being done where" is the key to project success. Construction sites involve many people and pieces of equipment moving around, and especially inside buildings or underground spaces where visibility is limited, pinpointing locations becomes even more difficult. For example, it can take a long time to locate required equipment within a large building, or mistakes can occur such as performing work in a location different from the one specified. Traditional indoor work relied on drawings and verbal on-site instructions to confirm locations, but on large floors or in complex structures there is a limit to what human effort alone can achieve, leading to reduced construction accuracy and operational inefficiency.

Moreover, satellite positioning such as GPS, while effective outdoors, cannot be used indoors or underground because signals do not reach those areas. Therefore, indoor construction management needs to utilize positioning technologies that serve as alternatives to GPS. In recent years, the construction industry has also been paying attention to construction management that leverages location information as part of digital transformation (DX). By incorporating location information, it is possible to achieve both construction accuracy improvement (placing work precisely at designated locations) and efficiency (reducing unnecessary movement and time spent searching). This article introduces five concrete methods for maximizing the use of location information in indoor construction management.

Method 1: Ensuring layout accuracy by implementing **high-precision indoor positioning technology**

To perform accurate surveying and layout work inside buildings, the introduction of high-precision indoor positioning technology is essential. Because satellite positioning cannot be used indoors, a total station, a fixed laser leveler, or an indoor-dedicated positioning system is used instead to establish reference coordinates. First, known reference points are set on the construction floor, and based on those, the position and elevation of each construction location are measured. Traditional layout marking work using a total station (electro-optical distance meter) is one example; because it can indicate points to the millimeter (0.04 in), you can accurately mark positions for walls and equipment installation.

In recent years, by combining such surveying instruments with digital technologies, higher-accuracy indoor positioning has become possible. For example, by using a GNSS receiver on a building's rooftop or near windows and incorporating correction signals from RTK positioning (real-time kinematic), there have been attempts to achieve centimeter-level positioning (half-inch level) indoors. If necessary, pseudo-satellite devices or IMES (indoor GPS) can be installed indoors to provide positioning in environments where GNSS signals do not reach. By introducing high-precision datum coordinates on site, you can check step by step during structural layout whether the work is being carried out in the "position and height specified in the design drawings." As a result, you can prevent rework caused by misaligned columns or walls and reduce additional surveying and rework. A layout with ensured accuracy raises the overall quality of the construction and is likely to have a significant effect in preventing problems in later stages.

Method 2: Improving work efficiency through real-time location management of equipment and workers

Another important method for leveraging location information in indoor construction management is real-time location management of equipment and workers. In a large building, time spent searching around asking, "Where is that aerial work platform?" or "Which floor is the assigned plumber on now?" leads to significant losses. Therefore, by attaching location-tracking tags to people and items on site and centrally managing them with a dedicated system, necessary information can be obtained instantly. Specifically, workers are asked to attach small beacons or RFID tags to their helmets or armbands, and active tags (radio transmitters) are attached to heavy equipment and tools. Multiple receivers (gateways) installed throughout the building receive signals from the tags and calculate each tag's current position in real time.

With this system, site supervisors can see at a glance on a PC or tablet who is working where and which floor important equipment is on. As a result, for example, the time spent searching the site for a "reserved aerial work platform that cannot be found" has been greatly reduced. Being able to locate required equipment immediately reduces waiting time for setup and improves work efficiency. In addition, real-time location management is effective for safety: it can notify via an alarm if someone enters a hazardous area, and in the event of an accident it can instantly identify the workers who were present. This enables strengthened safety management and rapid response, and consequently minimizes work interruptions and losses.

There are various technologies used for position management, such as Bluetooth beacons, Wi‑Fi positioning, and UWB (ultra-wideband wireless). Bluetooth and Wi‑Fi are relatively easy to deploy and can often work with existing devices, but their accuracy often remains on the order of several meters (several ft). On the other hand, using UWB allows positions to be determined with high accuracy of tens of centimeters or less (tens of in), but equipment costs and setup effort tend to increase. It's important to select the appropriate technology according to the scale and purpose of the site. In any case, visualizing the whereabouts of people and assets itself is a significant benefit. When information is shared across the entire site, coordination among workers becomes smoother and tasks proceed along efficient routes. Real-time position management is attracting attention as a method to increase the information available to construction managers and boost productivity across the site.

Method 3: Real-time Verification of Construction Accuracy Using AR and Digital Twins

Location information technologies, when combined with AR (augmented reality) and digital twins, also prove powerful for verifying construction accuracy. A digital twin is a representation in digital space of a building's 3D design model and construction plan, synchronized with the real site. By using this, differences between the actual construction status and the planned model can be checked in real time. For example, when the site is viewed through a tablet's camera, a BIM model (3D model of the design drawings) can be overlaid on the video feed to confirm on site whether walls and piping are in the positions specified by the design. If a construction error has caused a displacement, the discrepancy between the virtual model and the actual object becomes visually apparent, allowing immediate correction.

Using AR glasses or a smartphone’s AR features, workers can intuitively grasp on-site "where to install what". Installation positions for pipes and ducts hidden above ceilings can also be displayed in AR like a see-through diagram, making the exact installation points obvious at a glance. This makes tasks that previously required measuring and marking while referring to drawings dramatically easier, leading to a reduction in human error and an improvement in accuracy. Furthermore, if AR and positional information are stably linked, digital information will always be displayed in the correct position in the real world even as workers move. Even when walking around a large floor, they will not lose sight of design positions such as column centers and pipe routes.

On a digital twin, it is possible to display actual progress as a color-coded heat map and to visualize completed and uncompleted areas in real time. Because this information can be shared with the site office and remote managers, it also contributes to the realization of remote construction management. Even from a remote location you can check the on-site quality of work and issue instructions, which speeds up decision-making. AR and the digital twin for construction accuracy checks foster a culture of "verifying and correcting on the spot" and are an effective method for achieving high-quality construction with zero rework.

Method 4: Improving progress and quality control with 3D scanning and photogrammetry

To accurately understand construction progress and as-built conditions (the shape of the finished product), digital records created by 3D scanning and photogrammetry are effective. Traditionally, verification of as-built conditions and dimensional checks involved staff measuring various locations with tape measures and levels and comparing them to drawings. However, measuring many points manually in a large interior space is very labor-intensive and carries risks of omissions and recording errors. Therefore, an approach that uses laser-equipped surveying instruments and cameras to digitize the entire space is attracting attention.

For example, if you set up the latest 3D laser scanner on a tripod indoors and scan, you can obtain the positions of the room’s walls, floor, and equipment as point cloud data in a matter of minutes. Point cloud data is a collection of numerous points indicating positions in space, and a current 3D model can be constructed from this point cloud. Also, even in indoor spaces where drones cannot be flown, you can take many photographs with a single-lens camera or a 360-degree camera and later perform photogrammetry (photogrammetry) in software to similarly generate a 3D model. Recently, it has also become possible to easily scan interiors with LiDAR sensors built into smartphones and tablets and convert them into point cloud data.

By overlaying the on-site 3D data onto the design model, you can instantly determine whether the constructed elements are in the positions and dimensions specified by the design. For example, small discrepancies—such as a wall being off by several millimeters from the drawings or a pipe slope differing from the plan—are color-coded in the data, allowing you to identify all locations that require correction without omission. This dramatically improves the accuracy of quality control, preventing rework caused by defects discovered in later stages. In addition, because 3D point clouds and photographic data are stored as construction records, they serve as documents that enable a precise understanding of "what was where at that time" during future renovation work or inspections.

Digital on-site scans also prove powerful for progress management. By regularly acquiring indoor point cloud data, you can quantitatively assess which parts have been newly constructed since the previous acquisition and the extent of work progress. For example, because the degree to which walls have been erected and the scope of wiring installation are visualized, you can detect deviations from the plan early and use that to help revise the schedule. Furthermore, these measurements can be completed in a relatively short time and shared instantly via the cloud, reducing the need for site supervisors to return to the office to prepare reports. By incorporating highly accurate 3D records, construction management is shifting from an era of relying solely on intuition and experience to an era of making rational, data-based decisions.

Method 5: Simple Positioning Using Smartphones to Enable High-Precision Measurements by Anyone

Even if advanced positioning equipment or systems are introduced, if only a limited number of people on site can operate them, it cannot be considered true efficiency. What is attracting attention, therefore, is creating an environment in which any field staff member can easily perform high-precision measurements through simple positioning using smartphones. Today's smartphones have GPS and various sensors built in, and by combining dedicated apps and attachments they can, despite their small size, fulfill roles comparable to surveying instruments. If on-site personnel themselves carry out positioning and measurements with a smartphone in hand and can immediately share that data to the cloud, there is no need to request results from a surveying specialist team and wait, enabling real-time decision making.

As a concrete example, there are high-precision GNSS receivers that attach to smartphones. By pairing them with a smartphone and receiving network RTK correction information while measuring position, you can obtain centimeter-level coordinates (half-inch-level accuracy) that previously required dedicated equipment. Operation is also simple: by just tapping a button in the dedicated app you can record the coordinates of your current location or be navigated to a specified coordinate. This enables a person to perform tasks such as layout marking and as-built measurements alone. For example, in floor-marking position-setting work, you can reach the target position simply by walking following the arrow guidance displayed on the smartphone screen, so even non-experts can respond quickly and accurately.

Also, by using measurement apps that utilize a smartphone’s camera or LiDAR, you can measure distances, areas, heights, and so on with the same ease as taking a photo. Apps have also emerged that include a function like a "positioning photo," which automatically records the coordinates and orientation of the location at the same time as photographing the site. Many of these can be implemented with just a smartphone without purchasing special equipment, so they are affordable. If you equip sites with simple positioning tools that anyone can use, each person can check construction accuracy as needed, making early detection and correction of mistakes routine. As a result, not only will construction quality be raised, but the wasted time waiting for someone to perform verification work will be reduced, leading to a shortening of the overall construction schedule.

Summary: Promoting Simple Surveying Using LRTK

Incorporating location information into indoor construction management is the key to dramatically improving accuracy and efficiency of construction. Efforts to precisely record "when, where, and what was constructed" by leveraging digital technologies are becoming the new norm on job sites. Trends such as i-Construction, promoted by the Ministry of Land, Infrastructure, Transport and Tourism, are further encouraging this, and smart construction management that utilizes location information will increasingly become standardized.

And now, extending from that, the solution drawing attention as the next-generation field management tool is simplified surveying using LRTK. LRTK (L-R-T-K) is a solution that combines a smartphone with a compact, high-precision GNSS receiver, enabling anyone to easily achieve centimeter-level positioning and measurement (half-inch accuracy). With a dedicated app, you can acquire high-precision coordinate data and 3D point clouds in almost the same steps as taking a photo with your smartphone. In other words, tasks that previously relied on surveyors and specialized equipment can now be performed by on-site personnel themselves in a short time.

For example, in the LRTK app's "Positioning Photo" feature, simply pressing the shutter button automatically tags the photo file with the latitude, longitude, height of the capture location, and the camera's orientation. Whether indoors or outdoors, because you can leave accurate location information with the photo, it is immediately clear later which place the photo was taken. Furthermore, using LRTK, not limited to per-photo records, you can even walk around and scan the surroundings with a smartphone camera or LiDAR to turn the entire site into 3D data. All acquired point cloud data are assigned high-precision absolute coordinates, allowing them to be precisely overlaid with design drawings and existing reference point data. This enables immediate on-site construction-management decisions, such as checking the as-built condition of work areas or calculating volumes.

Thus, LRTK condenses the advantages of the various methods introduced so far into one and can be described as a groundbreaking tool that elevates construction management to a new realm of "easily performing high-precision on-site measurements". The way a smartphone itself transforms into a high-performance surveying instrument truly symbolizes construction site DX. Simply adding location information to photos and drawings can have a significant effect, but by utilizing LRTK you can achieve efficiency on a different dimension of accuracy and speed. There is no need to arrange a specialized surveying team and wait for results; you can take measurements and complete data sharing yourselves as soon as you think of it, which directly leads to shorter construction schedules and prevention of rework.

Construction management is increasingly shifting from fragmented information such as paper drawings and verbal instructions to an era driven by digital data integrated with positional coordinates. As a first step, adopting the location-information methods introduced here is highly effective. If you want greater accuracy or to simplify measurement tasks, please try simple surveying with LRTK. This cutting-edge technology, which greatly expands on-site possibilities, will strongly support improvements in the accuracy and efficiency of your construction management.

FAQ

Q. Can't GPS be used on indoor construction sites? Are there any countermeasures? A. Yes. Conventional GPS (satellite positioning) cannot be used directly inside buildings or underground because the signals are blocked. To obtain location information indoors, you need to use an alternative such as an indoor positioning system. Specific countermeasures include placing Bluetooth beacons or Wi‑Fi access points throughout the space and estimating position from proximity information, installing UWB antennas on ceilings to perform high‑precision ranging, and so on. Also used are methods that establish control points and measure with a total station, and approaches that combine smartphone sensors with known points to calculate relative positions. The important thing is to combine non‑GPS technologies to suit the indoor environment and obtain appropriate positioning information according to the situation. Recently, research into indoor positioning that leverages sensor fusion and machine learning has advanced, making it possible—by using appropriate techniques—to determine positions even on sites where GPS cannot be used.

Q. How accurate can indoor positioning systems be? A. Accuracy varies depending on the technology used. Bluetooth beacons and Wi‑Fi positioning are generally considered to have errors on the order of several meters (several ft) and are useful for a rough understanding such as "which area of a floor someone is in." If high precision is required, UWB positioning or laser-based ranging can improve accuracy to tens of centimeters to a few centimeters (tens of cm (several in) to a few cm (a few in)). For example, systems using UWB tags have been reported in ideal environments to achieve accuracies below 10 cm (3.9 in). Methods such as triangulation with multiple laser distance sensors installed on the ceiling can also achieve centimeter-level accuracy (cm level accuracy (half-inch accuracy)). However, on actual construction sites, radio interference from walls and equipment, multipath (reflections), and so on can prevent achieving the catalog specifications. From an operational standpoint, focus on whether the required and sufficient accuracy can be obtained, and consider, where appropriate, combining high-precision equipment with simpler devices to strike a balance.

Q. Doesn't implementing a location-based system require significant cost and effort? A. The implementation cost and effort depend on the scale and approach of the system. Indeed, a full-scale system that installs location-tracking antennas throughout an entire facility would entail a large upfront investment and substantial installation work. However, in recent years, small-start indoor positioning that covers only the necessary areas has become feasible. For example, a simple method of placing Bluetooth beacons at key points and receiving signals with a smartphone app is relatively inexpensive and requires no wiring work. Also, using cloud services can eliminate the need to build servers, and subscription-based solutions with monthly fees are now available. What's important is to introduce the system at your site at a scale that matches the problems you want to solve. If the only goal is confirming workers' whereabouts, you can start with the minimum necessary equipment and incrementally expand while monitoring effectiveness. On the other hand, measurement tools such as 3D scanners and high-precision GNSS receivers can have their upfront costs reduced through rentals or service use. Recently, inexpensive positioning tools that use smartphones (for example, types with dedicated attachments) have appeared, making it possible to achieve high accuracy at a more accessible cost than before.

Q. What is simple surveying using LRTK? How does it help on site? A. LRTK is a positioning system composed of a smartphone, a compact high-precision GNSS receiver, and a dedicated app, developed with the concept of “easy surveying that anyone can use.” Traditionally, achieving centimeter-level accuracy (half-inch accuracy) required expensive surveying equipment and skilled technicians, but with LRTK you can perform high-precision positioning simply by attaching the receiver to your smartphone and pressing a button. For example, with LRTK you can record survey points using the same steps as taking a photo with your smartphone, and each acquired point is immediately assigned world geodetic system coordinates (latitude/longitude and height). A major feature is that, whether indoors or outdoors, this single device can handle everything from control point surveying to as-built checks. On site, LRTK is powerful for layout confirmation and construction management. In stakeout, the guidance function will navigate you to reference points and pile-driving positions, and in as-built management, photos and point cloud data let you immediately grasp deviations from the design. In short, by introducing simple surveying with LRTK, site personnel themselves can measure, decide on the spot, and immediately move on to the next action. Because surveying processes that previously involved waiting times and communication losses are shortened and simplified, overall site efficiency and accuracy will dramatically improve.