Table of Contents

• High-precision indoor positioning required in factories and warehouses

• How to achieve centimeter-level positioning indoors

• What high-precision positioning using RTK is

• New indoor positioning realized by smartphone × LRTK

• Use cases and benefits in factories and warehouses

• How simple surveying with LRTK changes the field

• FAQ

High-precision indoor positioning required in factories and warehouses

On the shop floors of manufacturing plants and logistics warehouses, location information is extremely important for equipment and inventory placement, improving work flow, and safety management. Areas that used to rely on intuition and experience are increasingly being visualized using digital technologies, leading to productivity improvements and waste reduction. In particular, the demand to perform position measurement inside factories and warehouses at centimeter (cm) level accuracy (half-inch accuracy) is rising.

If you can measure positions indoors with high accuracy, you can place equipment based on precise survey data when changing layouts, and track the movements of workers and forklifts in detail to gain hints for efficiency. Fine adjustments and precise tasks that were difficult with errors of several meters can be accomplished if cm-class indoor positioning is possible. Improving factory operations (Kaizen) and optimizing warehouse operations increasingly depend on improved positional accuracy.

How to achieve centimeter-level positioning indoors

However, achieving cm-level positioning indoors is not easy. Conventional GPS (satellite positioning) cannot be received indoors because roofs and walls block the signals, resulting in errors of several meters to several tens of meters, so it cannot be used directly in indoor environments like factories and warehouses. Therefore, various methods have been tried for indoor positioning.

Representative indoor positioning technologies include:

• Positioning by BLE or Wi‑Fi: This method installs multiple radio transmitters (beacons, etc.) and estimates distance from received signal strength. It is relatively low-cost, but accuracy is at best a few meters and reflections and interference tend to cause large errors.

• UWB (ultra-wideband) positioning: A method that uses ultra-wideband radio to achieve high positioning accuracy. It requires multiple dedicated fixed stations. Depending on the environment, accuracy can be improved from several tens of centimeters down to about 10 cm (4.0 in). However, hardware and calibration costs are high, creating barriers to adoption.

• Ultrasonic or acoustic positioning: Multiple ultrasonic transmitters are placed on the ceiling, and position is calculated from the sound arrival times. Some systems are robust to obstacles and can obtain 3D positions. Some claim cm-level accuracy, but dedicated infrastructure installation and calibration work are still required.

• Camera / LiDAR-based positioning: Technologies that estimate self-position from the surrounding environment using camera image analysis or LiDAR sensors. Tags are not required, but the equipment can be expensive and in some cases a complete map of the building is required before measurement.

• PDR (pedestrian dead reckoning): A method that estimates pedestrian movement from a smartphone’s accelerometer and gyro, integrating position relative to a known start point. It works for short durations but accumulates drift over time, so accuracy cannot be maintained over long distances.

As shown, each conventional method for high-precision indoor positioning has its pros and cons. Especially to obtain centimeter-level accuracy, it has often been necessary to deploy specialized equipment extensively or invest heavily. Also, many technologies have been limited to 2D plane positions (X, Y coordinates), making precise measurement in the vertical direction (Z axis) difficult. In factories and warehouses, vertical information (which shelf height, floor slope, etc.) can also be important.

So how can one more easily achieve cm-level positioning indoors? One key is to leverage RTK (real-time kinematic) technology.

What high-precision positioning using RTK is

RTK is a technology that achieves centimeter-level accuracy by applying differential corrections to satellite positioning such as GPS. Normally, standalone GPS exhibits errors on the order of 5–10 m (16.4–32.8 ft), but by installing a base station (reference station) and sending its error information to the rover, the rover’s positioning results can be corrected. As the name real-time kinematic implies, the rover receives correction information in real time while calculating position, allowing it to know high-precision positions in real time.

Under favorable conditions, RTK positioning can achieve accuracy within about ±1–2 cm (±0.4–0.8 in) horizontally and about ±3 cm (±1.2 in) vertically. This is an order of magnitude better than standalone GPS. Originally used in civil engineering surveying, agriculture, and autonomous driving—situations requiring high-precision outdoor positioning—RTK has become more accessible recently due to cost reduction and miniaturization.

In Japan, infrastructure providing correction information is also being developed. For example, the domestic quasi-zenith satellite system “Michibiki” broadcasts CLAS (centimeter-class augmentation service), and with a compatible receiver you can receive correction data for centimeter-level positioning directly from the satellites even in environments without Internet connectivity. Therefore, even outside mobile coverage or in mountainous areas, if the sky is open, RTK can provide high-precision positioning.

Leveraging RTK in this way raises the possibility of applying it to indoor positioning—this is where the smartphone × LRTK solution appears.

New indoor positioning realized by smartphone × LRTK

LRTK is a compact high-precision positioning device that works in conjunction with a smartphone. Although palm-sized and smartphone-sized, it is equipped with a high-performance GNSS antenna and receiver and realizes centimeter-level positioning via RTK. It is battery-powered and operates for about 6 hours, and can connect wirelessly to a smartphone. Its weight is about 165 g and its thickness is about 1 cm (0.4 in), making it very compact and unobtrusive for work.

With an LRTK device, RTK positioning will Fix (resolve to a fixed solution) in about several tens of seconds to about 1 minute in an open outdoor location, allowing you to obtain your current position with accuracy within ±2 cm (±0.8 in). Unlike conventional stationary RTK base stations or large equipment, it is portable enough for field staff to carry in a pocket. For example, you can quickly measure a high-precision position near a factory entrance or on a rooftop where the sky is visible, and use that reference to perform indoor surveying.

So what happens when GPS signals cannot reach inside a building? Smartphone sensor technology becomes crucial here. Modern smartphones are equipped with cameras, LiDAR, accelerometers, and gyros, and AR (augmented reality) technology can track the device’s motion. In the smartphone × LRTK system, even after satellite positioning becomes unavailable upon entering a building, the smartphone’s AR functions continue to track the device’s position. In other words, while moving indoors the smartphone acts as a high-performance pedestrian dead reckoning device, calculating relative position from the most recent high-precision reference position.

This mechanism allows easy positioning of indoor points where GPS signals do not reach. For example, the location of equipment deep inside a factory can be obtained accurately by performing RTK position correction near an entrance and then moving with the smartphone to the equipment. Even if some error accumulates during movement, over short times and distances it can be kept to a few centimeters, and you can re-correct at an open location as needed to maintain high accuracy.

Positioning with a smartphone and LRTK also allows acquisition of vertical information. Because the 3D coordinates obtained by RTK are fused with the smartphone’s attitude data and LiDAR, position data that include height from the floor and slope can be recorded. This lets you capture shelf or machinery heights and floor unevenness—an advantage not found in many simpler indoor positioning technologies.

Furthermore, LRTK is operated intuitively via a dedicated app. The smartphone screen displays current positioning status and coordinates, and you can record points with a single tap. Just press a button at the location you want to measure to save its coordinates, and you can add notes or point names. The LRTK app also includes many useful features. For example, using an iPhone’s LiDAR sensor and camera, you can scan the surroundings to obtain high-precision 3D point cloud data (cloud points). By walking through a factory or warehouse, you can scan the entire space and create a 3D model with global coordinates attached to each point.

You can also place virtual markers at recorded points and use AR-guided navigation on the smartphone screen. For instance, when you want to mark an actual stake at a location specified on a drawing, the LRTK app can display arrows or guides to lead the user. Tasks like staking-out (position layout) that previously required surveying expertise become simple.

All of these functions are completed with just a smartphone and an LRTK device. There is no need to prepare many special devices or operate complex PC software. Data measured on site can be synced to the cloud directly from the smartphone and shared internally as 2D maps or 3D models. From the office, you can view measured points, photos, and point cloud data on the cloud. It is truly an all-in-one high-precision positioning tool that anyone can use.

Use cases and benefits in factories and warehouses

High-precision indoor positioning with smartphone × LRTK can be applied to many scenarios in factories and warehouses. Here are some concrete examples and benefits.

• Surveying for equipment layout changes and new installations: When installing new machinery or changing layouts in a factory, accurate position surveys are essential. With LRTK you can measure installation coordinates on the floor to the centimeter level. By comparing planned coordinates on drawings with survey results on site, you can mark equipment positions without misalignment. This helps prevent installation errors and reduce rework.

• Inventory management and picking efficiency in warehouses: In large warehouses, knowing exact storage locations directly affects picking efficiency. If shelf and product positions are recorded as 3D coordinates with LRTK, you can display and navigate the worker’s current position and the target inventory position in real time on a tablet. This enables optimization of picking routes and shortening of work time, ultimately reducing labor costs and lead times.

• Visualization and improvement of work flows: To analyze logistics and worker movement within a factory, you can record actual movement paths as data. If a worker carries a smartphone with LRTK for a certain period, their trajectory can be logged in continuous centimeter-level positioning. From this high-precision flow data, you can identify unnecessary back-and-forth movements and lingering points, and evaluate the effects of layout changes. For safety management, knowing precise zones traversed by people and forklifts helps reassess hazardous areas.

• Use in inspection and maintenance work: Accurate location information is useful for identifying problem areas in equipment inspections. LRTK lets you tag inspection photos with the coordinates and orientation where they were taken. Later, you can view photos on the cloud alongside maps or 3D models to immediately see “which place was repaired” or “where the next inspection should be.” As part of equipment management DX (digital transformation), this replaces handwritten records on paper drawings with digital geospatial records.

In these ways, indoor positioning with smartphone × LRTK becomes a powerful tool supporting various improvement activities on the production floor. By using high-precision positional data, you can improve quality consistently from situation grasp to planning and effect verification. For example, if you can objectively show that routing improvements reduced waste by 30% before and after, internal consensus building becomes smoother. Data-driven improvements reduce worker burden, help prevent human error, and support safer, more efficient workplaces.

How simple surveying with LRTK changes the field

With the advent of smartphone × LRTK, surveying at factories and warehouses is becoming not a special task but an extension of daily operations. Previously, centimeter-level precision surveying required hiring surveyors or specialists and handling expensive equipment. But with LRTK’s simple surveying, on-site staff themselves can complete required measurements quickly.

For example, repeatedly commissioning outside surveyors for each layout change costs time and money, but with LRTK you can handle it within your department immediately. If you mount the LRTK device on the tip of a monopod (pole), one person can achieve stable positioning. Height corrections are automatically calculated by the app, so no advanced knowledge is required. The system’s intuitive operation, stripped of the complexity typical of specialized equipment, allows even first-time users to perform surveying tasks easily.

When field staff can conduct their own surveys, decision-making speed increases dramatically. You can collect accurate data on the spot for layout simulations or to measure the effects of improvement measures and analyze immediately. You can re-measure as many times as needed, enabling flexible responses to changing conditions. This increased agility accelerates the PDCA cycle on the production floor and contributes to improved competitiveness.

Also, simple surveying with LRTK offers major cost benefits. Once you have the device and a smartphone, there are no additional measurement costs thereafter (if using Michibiki for satellite augmentation, no communication charges are required). You can reduce outsourcing survey costs and measure whenever needed, eliminating waste. Initial investment is also far lower than introducing large surveying equipment or other indoor positioning infrastructure.

Thus, the changes brought by simple surveying with LRTK are immense. As high-precision location information becomes accessible to everyone, the very methods of managing factories and warehouses will be updated. If your workplace faces issues like “we want to measure but can’t” or “we’re troubled by positioning errors,” consider the new option of smartphone × LRTK. It will surely become a strong ally in on-site improvements.

FAQ

Q. What do I need to use smartphone × LRTK? A. Basically, you only need the LRTK device itself and a compatible smartphone (currently iOS devices such as iPhone and iPad). Install the dedicated LRTK app on your smartphone and connect to the device via Bluetooth or similar. Since positioning requires receiving satellite signals in a location with a view of the sky, you first perform initial RTK positioning outside the building or near a window when measuring indoors. After that, carry the smartphone indoors and press the record button at the points you want to measure. There is no need for complex base station setup or pre-calibration; you can start measuring as soon as you arrive on site.

Q. Is the positioning accuracy really at the centimeter level? Does accuracy drop indoors? A. Yes—while RTK corrections are active, you can obtain high accuracy within a few centimeters. If you have a Fix solution (cm-level) in an open outdoor location, moving indoors immediately afterward does not cause a large drop in accuracy right away. The smartphone’s AR technology can maintain positional accuracy for short durations, so you can obtain coordinates indoors at almost a few centimeters. However, if you go without any satellite reception for an extended time, errors will gradually accumulate, so for large facilities it is advisable to occasionally reacquire satellite signals to reapply corrections. In actual operation, point surveys of around 10 points show that the variation of each point is within a standard deviation of about 1–2 cm (0.4–0.8 in). By taking dozens of measurements at one point and averaging, you can approach sub-1 cm (under 0.4 in) accuracy.

Q. How portable is the LRTK device? What about weight and battery life? A. The LRTK device is very compact and lightweight. Its weight is about 165 g, comparable to a smartphone, and its thickness is about 1 cm (0.4 in). It fits in a pocket and does not hinder field work. It has an internal battery and runs continuously for about 6 hours on a full charge. Charging is via USB Type‑C and it can be powered from a mobile battery, so you can operate for long periods without worrying about power running out.

Q. Can it be used in locations without Internet connectivity? A. Yes. The LRTK device supports the CLAS signal of Japan’s Michibiki quasi-zenith satellites. Therefore, even in remote mountains or underground facilities without mobile coverage, if the sky is visible you can receive correction information directly from the satellites and achieve high-precision positioning. For indoor positioning, if you can receive Michibiki signals from a rooftop or window without network connection, RTK accuracy can be maintained offline. However, in completely shielded underground areas where satellite signals cannot reach, this method is not feasible. In such environments, you can complement by relative surveying from reference points measured on the ground or by matching existing drawing data.

Q. How are survey data handled? Can they be shared within the company? A. Positioning data acquired with the LRTK app can be synced to the cloud for utilization. Coordinates of measured points, photos taken, and scanned point cloud data can be uploaded to a dedicated cloud service via the Internet. After uploading, you can view the data as 2D maps or 3D views in a browser and measure distances. You can issue a web-sharing URL so members in other departments or customers without the software can view it. Coordinate systems support Japan’s plane rectangular coordinate system (other systems selectable), making it easy to overlay with CAD drawings or other GIS data. In short, field-measured data can be directly compared with design drawings or existing materials and smoothly shared among stakeholders.

Q. Is specialist knowledge required for introduction and operation? Can beginners use it? A. No specialized knowledge or qualifications are required. The LRTK system is designed with a simple UI and automated processing so beginners can use it intuitively. Device setup is minimal—typically attaching to a pole and holding it level—and there is no difficult calibration. The app displays current accuracy (Fix/Float, etc.) and satellite counts, so even first-time users can easily understand the situation. Operation manuals and tutorials are provided, and support is available if needed. In practice, facility staff and survey-unexperienced workers have been able to perform LRTK surveying after short instruction. You can confidently introduce it to your site.