The Complete Guide to Deploying cm level accuracy (half-inch accuracy) Indoor Positioning in Factories and Warehouses

At factories and warehouses, an increasing number of on-site personnel are considering introducing cm level accuracy (half-inch accuracy) indoor positioning. However, many may have questions or concerns such as "I don't know which technology to choose," "It's unclear how much it will cost to implement," and "I'm worried whether cm level accuracy will really be achieved in actual operations."

In this article, we provide a comprehensive end-to-end explanation of the entire deployment process — from planning and technology selection to design and installation, and operation and maintenance — for achieving cm level accuracy (half-inch accuracy) indoor positioning in the specific environments of factories and warehouses.

Table of Contents

• Why cm level accuracy (half-inch accuracy) positioning is necessary in factories and warehouses

• Environment-specific challenges in factories and warehouses

• How to choose positioning technologies suitable for factories and warehouses

• Implementation Phase 1: Requirements definition and on-site survey

• Implementation Phase 2: System design

• Implementation Phase 3: Installation and calibration

• Implementation Phase 4: Operation and maintenance

• Outdoor integration: Supplying reference coordinates via LRTK

• Estimated implementation costs and considerations for cost-effectiveness

• Differences in implementation approaches between large enterprises and small and medium-sized enterprises

• Utilizing indoor positioning data and deployment for operational improvements

• Integration with AI and data science

• Summary

Why is positioning with cm level accuracy (half-inch accuracy) necessary in factories and warehouses?

Factories and warehouses are environments where precise location management directly impacts productivity, quality, and safety.

On precision manufacturing lines, mix-ups of parts and misalignment of machining positions directly translate into defective products and rework costs. By tracking in real time, with cm level accuracy (half-inch accuracy), which process each parts tray or workpiece is in, the accuracy of process management improves dramatically. Visualizing the production line’s operating status in real time enables early detection and response to bottlenecks, improving overall production efficiency.

In the autonomous navigation of automated guided vehicles (AGV) and autonomous mobile robots (AMR), the prerequisite for robot-arm picking is the ability to stop in front of shelves with cm level accuracy (half-inch accuracy). If positioning accuracy is insufficient, the risk of picking errors and collisions with shelves or people increases. In collaborative environments where humans and robots work in the same space, position information with cm level accuracy (half-inch accuracy) forms the foundation that supports the safe operation of robots.

In warehouse inventory management, understanding which pallet or container is located at which position on which shelf with cm level accuracy (half-inch accuracy) improves the accuracy and efficiency of picking instructions. It also reduces the risk of misplacement and incorrect shipments. In addition, real-time tracking of inventory items can be expected to streamline stocktaking operations and reduce stocktaking errors.

In equipment inspection and maintenance, recording the precise location of each piece of equipment allows you to link inspection histories with location information for management. When an anomaly is detected, you can quickly guide personnel to the site, and the accuracy of the asset register is improved. From a preventive maintenance perspective, accurate location information for equipment can also be used to analyze degradation trends.

Environmental Challenges Specific to Factories and Warehouses

Factories and warehouses present a more challenging environment for positioning than typical offices or commercial facilities.

First is the abundance of metal structures. Steel columns, beams, metal shelving, and large machinery reflect and absorb radio waves. In radio-based positioning technologies, multiple reflections (multipath) lengthen the apparent time of flight, increasing positioning errors. In environments where metal cargo is densely packed, radio propagation patterns can change over time, which can make accuracy unstable.

Next is the severity of environmental change. Production line changes, equipment replacements, shelf relocations, and the like cause factory and warehouse layouts to change frequently. Positioning systems may require recalibration or parameter updates. Because each change incurs response costs, a flexible design that is robust against change is required.

There is also the issue of electromagnetic noise. Electromagnetic noise generated by large motors, inverters, welding machines, and high-frequency heating equipment can degrade the accuracy of positioning sensors. Careful selection of installation locations and shielding measures are important. In particular, if welding operations are nearby, it is necessary to evaluate potential interference to the positioning sensors in advance.

There are also harsh environmental conditions such as high humidity, dust, and vibration. Some factories have environments with severe humidity, dust, and vibration, so the environmental resistance of sensors is important. Check dust and water protection standards (IP code) and select equipment suited to the environment to ensure reliable long-term operation.

In large warehouses with high ceilings, there are also issues such as radio wave attenuation and limitations in anchors' fields of view. For high ceilings, anchor placement needs to be devised with regard to elevation angles, and designing anchor heights and densities to ensure radio line-of-sight is important.

How to Choose Positioning Technologies Suitable for Factories and Warehouses

The core technologies that can achieve cm level accuracy (half-inch accuracy) in factories and warehouses are UWB and LiDAR + SLAM, but they need to be used differently depending on the application.

UWB is suitable for tracking moving targets such as people, items, and AGVs in real time with cm (in) to tens of cm (in) accuracy. It operates by permanently mounting anchors on ceilings or columns and attaching tags to the tracked targets. Although it incurs equipment costs, it offers a good balance of tracking accuracy and real-time performance and can support many applications in factories and warehouses. The system is also highly scalable, allowing tracked targets to be easily expanded simply by adding more tags.

LiDAR + SLAM is suitable when the device itself moves autonomously, such as AGVs and inspection robots. It operates simply by equipping the device with LiDAR and has the advantage of not requiring fixed infrastructure. However, device costs are high, and matching accuracy can decrease in simple environments. Because the AGV itself holds the environmental map, operations must periodically update the map to address discrepancies with reality (such as the addition of new equipment).

When tracking targets number in the dozens to hundreds, UWB offers superior scalability, while LiDAR + SLAM is efficient for a small number of autonomous mobile robots. In some sites, a hybrid combining UWB and LiDAR is used, with UWB providing an absolute positional reference and LiDAR improving local accuracy.

Magnetic mapping and high-precision Wi-Fi do not reach cm level accuracy (half-inch accuracy) on their own, but when combined as complementary technologies with UWB or LiDAR, they can contribute to improved accuracy in complex radio environments.

Implementation Phase 1: Requirements Definition and On-site Survey

Implementation projects begin with requirements definition. The accuracy at this stage will greatly influence the final system's success or failure.

As part of clarifying the positioning area, clearly mark on the floor plan the range where positioning is required. Identify the positioning area's size, shape, ceiling height, and distribution of obstacles. Considering areas planned for future expansion can reduce the cost of later expansions.

To organize the tracking targets, clarify what to track (people, forklifts, pallets, AGVs) and how many (number of tags). If the number of tags increases, it may become necessary to increase the number of anchors. Also confirm the tag mounting method, power supply (battery replacement cycle), and weight and size constraints.

As part of setting accuracy requirements, clarify which applications need which level of accuracy. Depending on the application, some require cm-level accuracy (half-inch accuracy) while others are adequately served by decimeter-level accuracy, and organizing accuracy requirements can optimize costs. It is important to set realistic target values after understanding the trade-offs between accuracy and update rate, and between accuracy and cost.

As a check on the update rate, confirm how frequently position information needs to be updated. Tracking fast-moving AGVs requires a high update rate, while static facility asset management can be sufficient with a low update rate. Because higher update rates increase communication bandwidth and system load, it is important to configure the rate with consideration for balance.

On-site surveys include a radio environment survey (survey) to understand the propagation characteristics of radio waves and the effects of obstacles. The locations and strengths of electromagnetic noise sources are also verified. Conducting the radio survey under the same conditions as the actual operational environment (machinery running; cargo present) leads to a design that reflects real conditions.

Implementation Phase 2: System Design

We will design the system based on the results of the site survey.

Anchor placement design is the most important point for achieving cm level accuracy (half-inch accuracy). Decide the number and placement of anchors to cover the positioning area. As a general design guideline, place anchors at the four corners of the positioning area, and add additional ones in the middle for larger areas. Install anchors high on ceilings or walls to ensure line of sight. Aim for arrangements that minimize the geometric dilution of precision (GDOP). It is recommended to use simulation tools during the design phase to visualize the GDOP distribution.

In network design, design the anchors' power supply (AC power or PoE) and communication connections (wired LAN, and in some cases wireless). For systems where time synchronization is important, a wired connection is recommended. Calculate the bandwidth required for data delivery from the anchors to the positioning server and verify whether the existing network infrastructure can support it.

As part of the integration design with higher-level systems, decide which systems will receive the acquired position information. Design API integrations with AGV control systems, WMS (warehouse management systems), equipment management systems, and the like. Also confirm the data reception formats, frequency, and accuracy requirements on the receiving systems’ side, and agree on the interface specifications in advance.

Deployment Phase 3: Installation and Calibration

We will install anchors according to the design and perform calibration.

When installing anchors, mount the anchors precisely at the designed locations. Measure the coordinates of the mounting positions with high precision and register them in the positioning engine. Because the accuracy of the coordinates directly affects positioning accuracy, it is important to measure them precisely using a laser rangefinder or 3D measuring equipment. After installing the anchors, choose a robust fastening method to ensure the anchors do not move. In environments with significant vibration, regularly check for anchor displacement.

As part of the system’s initial calibration, we verify the accuracy of time synchronization and adjust parameters. We place test tags at known locations to check accuracy and make adjustments until the target accuracy is achieved. Recording the calibration results provides baseline data for future maintenance.

In accuracy verification, we check accuracy at multiple known points across the entire positioning area. If there are locations where accuracy does not meet the target, we add or relocate anchors and adjust algorithm parameters. By creating an accuracy map, we visualize the accuracy distribution for each area and make it easier to identify problem locations.

Deployment Phase 4: Operations and Maintenance

We will establish an operations and maintenance framework after the system is put into operation.

As a periodic accuracy check, we conduct accuracy verification at known points on a monthly or quarterly basis. If accuracy has degraded, we identify the cause and perform calibration. Building a system to automate accuracy checks can reduce the maintenance burden.

As a response to layout changes, when the layout of a factory or warehouse is modified the radio environment will change, so a survey of the affected area and recalibration are necessary. It is important to establish a system to share change plans in advance with the person responsible for managing the positioning system.

As part of fault handling, prepare response procedures that assume failure patterns such as anchor failures, network outages, and tag battery depletion. Designing a redundant configuration (installing a surplus number of anchors) so that positioning can continue even with some failures is also effective. A monitoring dashboard that allows real-time checking of anchors' communication status makes early detection and response to faults easier.

Integration with the outdoors: Supplying reference coordinates via LRTK

When you want to coordinate indoor positioning in factories and warehouses with outdoor tasks such as construction, inspection, and inventory receiving, integrated management using absolute coordinates (real-world coordinates) becomes a challenge.

LRTK is a device that, simply by attaching it to an iPhone, can obtain absolute coordinates outdoors using RTK-GNSS with cm level accuracy (half-inch accuracy). By measuring absolute coordinates at warehouse entrances and reference points with LRTK and converting them into the coordinate system of an indoor positioning system, you can manage indoor and outdoor areas in a unified coordinate system.

Especially for facilities under construction and factories undergoing renovation, aligning the coordinate system with the design BIM data is important. By measuring outdoor reference points with LRTK and building the indoor positioning coordinate system from them, high-precision construction management and quality verification become possible.

LRTK is characterized by its simplicity, allowing field personnel to start using it immediately without specialized surveying knowledge. When used together with the deployment of an indoor positioning system, it can raise location information management across the entire site to cm level accuracy (half-inch accuracy).

Guidelines for Estimating Implementation Costs and Considering Cost-effectiveness

The implementation cost of a UWB system varies depending on the size of the positioning area, the number of anchors, and the number of tags. For a medium-sized factory floor (1,000–2,000 m^2 (10,764–21,528 ft^2)) with about 8–16 anchors, including equipment costs, installation costs, and software licenses, it often amounts to several million to several tens of millions of yen.

To evaluate cost-effectiveness, it is important to quantify the costs that can be reduced by improving positioning accuracy. Convert into monetary amounts the labor cost reductions from AGV implementation, loss reductions from fewer picking errors, reductions in equipment maintenance costs, reductions in quality-defect costs, and so on, and estimate the investment payback period.

In many workplaces, it has been demonstrated that the benefits of improved positioning accuracy—such as increased productivity, improved quality, and enhanced safety—outweigh the implementation costs, and the medium- to long-term cost-effectiveness is highly regarded. In particular, when combined with automated transport robots, labor cost savings are significant, and in many cases the investment is recovered within a few years.

Differences in Implementation Approaches between Large Enterprises and Small and Medium-sized Enterprises

Deployment of cm level accuracy (half-inch accuracy) positioning in factories and warehouses requires different approaches depending on company size. Regardless of company size, the first step is to define the purpose: what the positioning is for, what accuracy is required, and which areas will be covered. With clear objectives, you can develop an implementation plan that achieves maximum effect with minimal investment.

For large enterprises, pursuing standardization and economies of scale with deployment across multiple sites in mind is important. When replicating successful cases from pilot sites, preparing standard system configurations, implementation processes, and operation manuals can reduce deployment costs and timelines. Integration design with enterprise-wide IT platforms (ERP, MES, etc.) should also be considered from the initial stage.

For small and medium-sized enterprises, it is realistic to introduce solutions in stages, beginning with areas that offer a high return on investment (ROI). Start by implementing on a small scale, focusing on the applications with the highest ROI (such as AGV positioning and inspection and management of key equipment), verify the effects, and then expand—this phased approach is recommended. Also actively consider taking advantage of subsidies and grants that support implementation.

Also, cloud-based indoor positioning services delivered as SaaS for small and medium-sized enterprises are increasing, expanding the options for accessing high-precision positioning while keeping initial investment low.

Leveraging Indoor Positioning Data and Applying It to Operational Improvements

After deploying an indoor positioning system with cm level accuracy (half-inch accuracy), how you utilize the collected data is crucial to maximizing return on investment.

First, application to productivity analysis. By collecting and analyzing movement-path data of people, goods, and AGVs in real time, you can quantitatively identify wasted movement and bottlenecks within factories and warehouses. By reducing travel distances, cutting waiting times, and optimizing layouts, you can continuously improve productivity.

Next, its application to quality control. By linking location information of parts and products in the manufacturing process with quality data, it becomes easier to pinpoint the process step or location where a quality issue occurred. The accuracy of root cause analysis (RCA) improves, and the quality improvement cycle accelerates.

As an application for safety management, it can enhance safety management operations by detecting entry into hazardous areas, detecting worker abnormalities (falls and prolonged immobility), and confirming personnel during emergencies. For KYT (hazard prediction training), leveraging actual movement flow data enables training with more realistic scenarios.

For preventive maintenance, by combining accurate positional information of equipment with inspection histories, you can precisely manage the degradation trends of each piece of equipment. It can also be used to predict the optimal timing for parts replacement and to optimize equipment layout.

Integration with AI and Data Science

High-precision location data collected through indoor positioning can generate additional value when combined with AI and data science.

Machine learning analysis of movement path data can automatically detect abnormal movements that differ from normal patterns. It is used to estimate worker fatigue and to detect early signs of anomalies in AGVs.

Using reinforcement learning for route optimization, the system can propose and automatically configure optimal transport routes for AGVs based on real on-site data. Route calculations that maximize transport efficiency while minimizing the frequency of intersections with human movement paths are executed in real time.

When integrated with digital twins, real-time location information can be reflected in the digital twin, continuously narrowing the gap between simulation and reality. As a decision-support tool for facility management, production planning, and safety management, high-precision location information will become increasingly important.

Summary

To achieve indoor positioning with cm level accuracy (half-inch accuracy) in factories and warehouses, the key to success is to carefully carry out the series of processes: requirements definition → technology selection → on-site design → installation calibration → operation and maintenance.

UWB and LiDAR + SLAM are the leading technologies at present, and it is important to use them appropriately depending on the application. For coordinate integration with outdoor areas, using iPhone-mounted high-precision GNSS positioning devices such as LRTK is effective, and it supports the realization of integrated high-precision position information management across indoor and outdoor environments.

By carefully organizing on-site requirements and proceeding with phased deployment following a PoC (proof of concept), you can reliably achieve cm level accuracy (half-inch accuracy) indoor positioning in factories and warehouses.