Municipalities Take Notice! LRTK CLAS-Compatible Receivers You Can Rely On at Disaster Sites Provide High-Precision Positioning Even Outside Communication Coverage

Table of Contents

• Why high-precision positioning is needed at disaster sites

• What a CLAS-compatible receiver for Michibiki is

• Effective even when communication infrastructure is cut off during disasters

• Strengths of one-person surveying via smartphone linkage

• Applications to infrastructure inspection and photo documentation

• Supporting fieldwork with AR-based position guidance

• LRTK meets requirements for disaster response

• Adoption by municipalities and looking ahead

• FAQ

Why high-precision positioning is needed at disaster sites

In recent years, large-scale disasters such as earthquakes and heavy rains have occurred frequently across Japan, making rapid and accurate understanding of damage a major challenge for municipal disaster prevention personnel and civil engineers. At disaster sites, it is required to accurately record and share “where and what happened,” but conventional GPS can have errors on the order of several meters, which may be insufficient for identifying and recording locations. For example, typical GPS information with errors of 5–10 m (16.4–32.8 ft) cannot precisely indicate which houses have collapsed or exactly where roads have collapsed, potentially hindering restoration planning and support activities.

If precise positioning becomes possible, damaged locations can be pinpointed on maps and the extent of damage can be accurately understood. This enables accurate placement of evacuation shelters, deployment of rescue teams, and infrastructure restoration planning. In particular, subtle changes such as cracks in bridges and levees, the degree of ground subsidence, and the spread of debris can be detected by centimeter-level positioning (cm level accuracy (half-inch accuracy)). Also, if photos and reports are tagged with accurate coordinates, subsequent verification and information sharing with other departments proceed smoothly.

The national government is also promoting DX (digital transformation) of field operations, and the Ministry of Land, Infrastructure, Transport and Tourism’s i-Construction encourages high-precision surveying and construction management using ICT. Disaster response also demands higher accuracy and speed than before, and municipalities are beginning to prepare for the introduction of high-precision GNSS technology during peacetime. Against this background, new technologies that realize “centimeter-level positioning usable even outside communication coverage” are attracting attention.

What a CLAS-compatible receiver for Michibiki is

One technology that enables high-precision positioning is CLAS (Centimeter-Level Augmentation Service) provided by the Michibiki quasi-zenith satellite system (QZSS). Michibiki covers the sky above Japan, and CLAS is correction information for positioning errors directly broadcast from those satellites. Normally, to achieve centimeter-level positioning accuracy you needed RTK (real-time kinematic) using correction data via mobile networks. However, with a CLAS-compatible receiver, you can improve real-time positioning accuracy using only augmentation signals from the satellites without relying on the Internet or base stations.

A CLAS-compatible receiver is a GNSS device that can receive and use the CLAS signal (correction information transmitted on the L6 band). Specifically, it includes a high-sensitivity antenna and dedicated chips to receive correction data sent from Michibiki satellites and correct positioning results such as GPS. As a result, errors that were formerly on the order of meters can be reduced to the level of several centimeters. The biggest feature is that high-precision positioning becomes possible even in environments where mobile phone signals do not reach. Because correction information can be received directly from the satellites overhead even when outside communication coverage, high-accuracy position measurements can be performed in mountainous areas, remote islands, and at sea—places with poor infrastructure—without additional cost.

Of course, using CLAS requires a compatible receiver and some initial investment, but because it is a free augmentation service available nationwide in Japan, the cost advantage is significant. In addition, Michibiki satellites are designed to remain near the zenith over Japan, making them relatively easy to acquire even in urban canyons or valleys (assuming use outdoors with an unobstructed view of the sky). By introducing a CLAS-compatible receiver, you can gain the reassurance that “if the sky is visible, you can measure anywhere,” even under the harsh conditions of disaster sites.

Effective even when communication infrastructure is cut off during disasters

In large-scale disasters, it is common for mobile base stations and communication networks to be damaged and for the Internet to become unusable. In such situations, conventional network RTK positioning devices cannot receive correction information, and high-precision GNSS cannot demonstrate its accuracy when used standalone. This is where CLAS-compatible receivers demonstrate their power. Because CLAS does not depend on communication infrastructure, centimeter-level positioning (cm level accuracy (half-inch accuracy)) is possible at disaster sites outside communication coverage as long as satellite signals can be received, greatly improving reliability in emergencies.

There are reported cases where CLAS-compatible receivers proved useful at sites where mobile communications were down. For example, during this year’s Noto Peninsula earthquake, a technician who happened to have a “coverage-outage-capable model” high-precision GNSS device could accurately record collapsed buildings and ground fissures with photos. Even though communication networks were down, CLAS-enabled positioning allowed vital immediate field records to be preserved. From this episode, it is clear that CLAS-compatible receivers provide significant reassurance as “positioning tools that are especially useful in emergencies.”

Moreover, when performing recovery work in isolated areas after a disaster, CLAS-compatible receivers are a reliable ally. Even if widespread power outages and communication outages occur, surveyors can measure and create maps with just a receiver and a smartphone. Where previously deployment of mobile base stations or manpower-intensive surveying was necessary, immediate positioning using only satellite information significantly increases the speed and accuracy of initial response.

Strengths of one-person surveying via smartphone linkage

Manpower is limited immediately after a disaster. In such situations, CLAS-compatible receivers that link with smartphones demonstrate their true value. By combining a smartphone with a compact GNSS receiver, surveying tasks that once required multiple people and bulky equipment can be completed by a single person. For example, traditional total station operations often required an operator and an observer, or the setup of control points. But with a smartphone plus a high-precision GNSS receiver, a single person can walk and acquire survey points one after another.

Products like LRTK are designed so the receiver connects to a smartphone via Bluetooth and can be mounted on a dedicated telescoping monopod for professional surveying. By mounting the receiver on the tip of the monopod and placing the tip on the ground at the target point, high-precision single-point positioning is completed. Moreover, the app automatically applies a height offset correction according to the monopod length, eliminating complicated calculations or leveling tasks. The ease of use—even without specialized surveying skills—is a major advantage for staff who suddenly need to perform surveying during disaster response.

One-person surveying also improves mobility and safety. Personnel can promptly go to the site alone and begin measurements without heavy machinery or additional personnel. This enables investigations with minimal staff in areas at risk of secondary disasters, contributing to staff safety. Also, the latest CLAS-compatible receivers include models with tilt compensation, allowing accurate coordinates to be obtained even when the pole (monopod) cannot be held perfectly vertical by correcting tilt with built-in sensors. This makes it easier to secure survey points on rubble piles or unstable footing, dramatically improving surveying efficiency at disaster sites.

Applications to infrastructure inspection and photo documentation

High-precision location information is powerful not only for surveying but also for infrastructure inspections and damage documentation. Using a smartphone-linked CLAS-compatible receiver, you can attach accurate positioning data to each photo and inspection note. For example, in bridge inspections after an earthquake, photos of cracked piers can be taken while latitude, longitude, elevation, and camera heading are automatically recorded in the photo file. Later, plotting those photos on a map lets you intuitively share “which part of which bridge had what kind of damage.” This prevents omissions and misidentification of locations and smooths planning for restoration work and preparation of disaster reports for the national government.

Additionally, combining a CLAS-compatible receiver with a dedicated app enables recording of continuous track logs via continuous positioning. When inspectors patrol a disaster area, their movement paths can be logged with high precision, making it clear at a glance which areas have been checked and how far dangerous spots were inspected. This helps prevent omissions in wide-area inspections and facilitates progress sharing among teams.

An interesting feature is “subject positioning” using the smartphone camera. This technique estimates coordinates of objects that are dangerous to approach or out of reach from a distance through the camera. By aiming at the target on the app screen and pressing the shutter, the coordinates of that point are estimated and recorded. For example, the upper portion of a collapsing building or a crack on a steep slope can be measured safely from a distance. The app color-codes subject positioning accuracy, with green indicating high accuracy under good conditions. This function—collecting necessary data without risking safety—is a practical example for disaster sites.

Supporting fieldwork with AR-based position guidance

Linking CLAS-compatible receivers with smartphones enables new field support using AR (augmented reality) technology. By combining high-precision position data with the smartphone camera view, digital information can be overlaid on the real landscape. AR use cases in disaster response include, for example:

• Coordinate navigation: A function that guides users to pre-specified coordinates. For restoration tasks that include instructions like “install a temporary water main valve here,” AR guidance allows workers to identify installation points at a glance by following arrows or markers displayed on the smartphone screen. Tasks that previously relied on maps and compasses can be performed intuitively and accurately with AR.

• On-site projection of 3D models: Use of 3D models to present restoration proposals for collapsed structures or landslide repair plans by projecting them on site. For example, bringing BIM/CIM data for a proposed temporary bridge and overlaying it in AR at the disaster site allows on-the-spot confirmation of whether it can be installed as planned. Visual checks for interference with terrain and surroundings help validate restoration plans in the field.

• Heatmap display: Based on 3D point cloud data obtained from drones or scanners, a heatmap showing displacement amounts or sediment accumulation color-coded by location can be displayed on site. For example, calculating the sediment volume for a slope collapse by location and displaying a heatmap with red or yellow according to risk lets you identify dangerous areas at a glance. This directly supports decisions such as efficient debris removal planning and setting restricted access zones.

By incorporating AR position guidance, fieldwork becomes far more “understandable” and “reliable.” Overlaying digital information on reality reduces reliance on individual experience and intuition, allowing everyone to recognize the site by the same standards. Disaster response personnel do not always have local knowledge or specialized expertise, but with high-precision positioning and AR support, they can carry out tasks accurately even in unfamiliar terrain.

LRTK meets requirements for disaster response

When selecting equipment for use at disaster sites, it is important that it meets stricter requirements than in normal times. High-precision GNSS receivers are no exception—there are conditions they must meet to be useful in emergencies. Below are the requirements for disaster-response equipment and how LRTK satisfies them.

• Lightweight, compact, and highly portable: Being lightweight is crucial in disaster areas. The LRTK receiver weighs about 165 g and is as light as a smartphone, with thickness around 1 cm (0.4 in). It fits in a pocket and does not get in the way even when wearing a helmet or protective clothing. It is designed to minimize burden in disaster response where equipment must be as light as possible.

• Rapid deployment on site: Equipment requiring complex setup delays initial response. LRTK can start positioning immediately by wirelessly connecting to a smartphone. No complicated wiring is needed; turn on the receiver, launch the app, and you are ready. There is no need to set up tripods or base stations, so you can begin surveying and recording as soon as you decide to do so.

• Long operation time in the field: Securing power is a challenge in disaster response; LRTK’s internal battery runs for about 6 hours. It can also be charged from external batteries via USB Type-C, so with a portable power supply you can use it all day. Because it can be self-sustained without relying on generators or vehicle power, it is reliable even during blackouts.

• Can record data without relying on communications or the cloud: You need a way to store data locally when networks are down. LRTK can save positioning data and photos on the smartphone even offline, and later sync to the cloud when convenient. This enables operations that “do not stop recording” even when you cannot connect to the cloud in real time. Also, because CLAS support maintains accuracy even outside coverage, there is no need to worry that “if the network goes down, measurements stop.”

• Versatile and extensible for multiple uses: Disaster situations change rapidly and require diverse tasks. LRTK can be used handheld with a smartphone, mounted on a monopod or tripod for stationary observations, or fixed to a vehicle for continuous positioning while driving. Through its dedicated app, it provides a wide range of functions from surveying to photo capture and AR support, making it an all-purpose device for field response.

As described, LRTK is a CLAS-compatible receiver that meets the requirements for disaster response at a high level. It is designed and developed for use in harsh field conditions, with thorough attention to practicality in emergencies. For municipal staff and technicians, it can be a reliable partner when the time comes.

Adoption by municipalities and looking ahead

In earthquake-prone Japan, more municipalities are positive about adopting such cutting-edge technologies. The reasons municipalities take notice are clear: rapid and accurate disaster response is an important administrative duty, and high-precision positioning tools can be a trump card. For example, Fukui City introduced a field surveying system using iPhones and CLAS-compatible receivers to speed early recovery and reduce costs. By enabling city staff to carry out surveying that was previously outsourced to specialists, the city aimed to speed initial response and save budget. Advanced municipalities are preparing equipment and personnel during peacetime to strengthen readiness for emergencies.

Following the successful example in the Noto Peninsula earthquake, inquiries and interest in high-precision GNSS terminals have increased from other municipalities and companies. The reassurance of “being able to position even when communications are down” is very attractive to those responsible for crisis management. In preparation for potential future mega-events such as a Nankai Trough megathrust earthquake or a major metropolitan earthquake, securing positioning technology that does not depend on communication infrastructure will become an important theme nationwide.

Finally, for these technologies to truly perform in disaster response, both “technology” and “field operation” must work together. No matter how excellent the equipment, it is useless if it cannot be operated effectively in the field. In this respect, LRTK offers intuitive operation via a smartphone app and cloud-linked data sharing, making it user-friendly for field personnel. With training during peacetime and use in small-scale sites, staff can become familiar so that in a large-scale disaster they can calmly employ high-precision positioning technology. Municipalities should incorporate such new positioning solutions into disaster plans and prepare for the “next disaster that could occur at any time.”

CLAS-compatible receivers that enable high-precision positioning are reliable tools that support the field even during communication outages. Why not consider introducing this technology into your disaster prevention and crisis management practices to dramatically improve the quality and speed of disaster response?

FAQ

Q: What is Michibiki’s CLAS? A: CLAS (Centimeter-Level Augmentation Service) is a centimeter-level positioning augmentation service broadcast from Japan’s Michibiki quasi-zenith satellites. It provides real-time correction information for positioning errors such as GPS via satellite, and using a compatible receiver makes centimeter-level high-precision positioning possible. A major feature is that it can be used without mobile communication networks.

Q: Can it really measure positions outside communication coverage? A: Yes. With a CLAS-compatible receiver, you can maintain high-precision positioning by receiving correction signals directly from satellites even in mountainous areas where mobile signals do not reach or in regions where networks have been severed by disasters. However, because satellite signals must be received, indoor or tunnel use is difficult; it should be used in locations with as open a view of the sky as possible.

Q: Can a smartphone alone achieve centimeter positioning? A: The GPS built into smartphones has errors on the order of meters, but by combining a CLAS-compatible high-precision GNSS receiver with a smartphone, centimeter-level positioning becomes possible. For example, using a receiver that links with a smartphone like LRTK and an app that applies correction information, a smartphone can function as a high-precision positioning device. The key is using an external high-precision antenna and correction technology, not the smartphone alone.

Q: I’m concerned about the cost and effort to introduce CLAS-compatible receivers. A: CLAS itself is provided free from the satellites, so there is no monthly service fee. There is a cost to purchase receivers, but compact and affordable models have appeared recently, making them more accessible compared to traditional surveying equipment. Receivers are designed to be used simply by turning them on and connecting to a smartphone, so they can be operated without specialized knowledge; with basic training, municipal staff can use them effectively.

Q: Should we use CLAS or network RTK? A: Each has pros and cons, and it is recommended to use them according to the situation. In urban areas with good communication environments, network RTK (such as Ntrip services) offers stable corrections. But in disaster sites or mountainous areas where communications may become unavailable, CLAS shines. A sensible approach is “use network RTK in peacetime, CLAS in emergencies.” Fortunately, modern devices like LRTK support both CLAS and network RTK, allowing flexible use according to field conditions.

Q: Is the positioning accuracy really down to a few centimeters? A: Under appropriate conditions, horizontal positioning errors of a few centimeters or less and vertical accuracy of several centimeters to several tens of centimeters can be expected. This is a dramatic improvement over standalone positioning (errors of several meters). However, accuracy depends on the environment, satellite geometry, surrounding obstructions, and receiver performance. For CLAS, initial convergence may take a few minutes, but once a Fix solution (high-precision solution) is obtained, centimeter-level accuracy can be stably maintained. In summary, you can generally expect near-centimeter accuracy when used outdoors with a clear view of the sky.

Q: How can we make sure the system is ready to use immediately when a disaster strikes? A: Prepare by becoming proficient with the equipment during peacetime. Have CLAS-compatible receivers and smartphone apps ready, conduct trial operations at small sites, and use them in disaster drills. Regular practice with location-tagged photo recording and one-person surveying will ensure you can use them confidently in an actual disaster. Also, perform routine maintenance such as battery charging and firmware updates in peacetime so devices are always in standby and ready to go.