A positioning revolution on smartphones! The power of centimeter-level accuracy enabled by LRTK

Table of Contents

• Basics and Mechanism of RTK Positioning

• Conventional RTK Surveying and Challenges

• The Emergence of Smartphone RTK and the Technical Background

• Components and Functions of LRTK

• Positioning Accuracy and Reliability Based on Case Studies

• Diverse Applications: Point Cloud Measurement, As-Built Management, CAD Integration, AR Display, and Cloud Sharing

• Benefits of Implementing LRTK: Labor Reduction, Shortened Work Time, and Improved Safety

• Points to Note When Implementing and Tips for Success

• The Future of Simplified Surveying Enabled by LRTK

• FAQ

Fundamentals and Mechanism of RTK Positioning

RTK stands for "Real Time Kinematic" and is a positioning technology that corrects errors in satellite positioning systems (GNSS) in real time, allowing positions to be determined with centimeter-level accuracy. In ordinary GPS positioning, slight shifts or delays in satellite signals can cause errors on the order of several meters, but with RTK, relative positioning using two GNSS receivers — a reference station (fixed station) and a mobile station (rover) — can reduce those errors to within a few centimeters.

A reference station is a receiver whose precise coordinates are known in advance; it computes the error components from the GNSS signals received at that location. A rover is the receiver installed at the point to be positioned; it receives correction data transmitted from the reference station and applies it to its own positioning calculations. In this way, the rover can determine a high-precision position relative to the reference station in real time, achieving centimeter-level positioning accuracy (cm level accuracy, half-inch accuracy) that cannot be obtained by standalone positioning (a single receiver only).

In summary, RTK positioning determines relative positions with millimeter-level (mm; approximately 0.04 in) precision by correcting various error sources contained in GNSS signals—such as atmospheric effects and satellite clock offsets—through communications from the reference station→the rover. Traditionally, transmitting these correction data required dedicated radio links (such as specified low-power radio) or an Internet connection. RTK-GNSS has long been used in civil surveying and construction sites, and is useful for various applications that require high-precision positioning, such as land boundary surveying, as-built verification (post-construction shape confirmation), and machine guidance for heavy equipment.

Conventional RTK Surveying and Challenges

RTK positioning is very attractive because it can obtain centimeter-level high-precision position information (half-inch accuracy), but there were several issues with conventional methods. First, the high cost of specialized equipment. Conventional RTK-GNSS receivers and base station equipment are very expensive when purchased as a complete set, and in some cases require an initial investment of several million yen. The equipment itself is also large and heavy—antenna-integrated pole units and stationary receivers—and is cumbersome to transport and set up in the field. In mountainous areas, for example, it was necessary to erect a tripod to install the reference station, attach the rover to a long pole, and carry it to the survey point, which also placed a significant burden on mobility.

Secondly, the difficulty of operation can also be cited. To carry out RTK surveying, a specialized procedure is required: the base station must be set on a known point, a communication link with the rover must be established, and only then can measurements begin. When communicating by radio, both stations must be placed where they have line-of-sight, and depending on the frequency band used, an application for a license to use the radio spectrum may be required. Even for network-type RTK that uses the Internet (such as VRS), subscription to the appropriate service and complex initial configuration are necessary. When problems occur on site they are difficult to deal with unless handled by skilled personnel, and as a result the technology tended to be handled only by a very small number of surveying specialists.

Third, the burden of data utilization was also a problem. With conventional equipment, survey data is recorded in the receiver or a dedicated controller, so it had to be transferred to a PC later and imported into CAD software. Even when linking location information to photos, the measured coordinates had to be manually matched afterward to images taken with a digital camera, causing cumbersome processing between the field and the office. Sharing on-site information in real time was also difficult, and many analog practices remained, such as recording information in notebooks or field books and bringing them back.

As described above, because there are hurdles such as "equipment being expensive and heavy," "operation requiring specialized knowledge," and "data processing taking time," RTK surveying, despite its accuracy advantages, has not become something that all field technicians can use on a daily basis.

The Emergence of Smartphone RTK and Its Technical Background

In recent years, a technology called Smartphone RTK (smartphone RTK positioning) has emerged that transforms this situation. Smartphone RTK is a new approach that combines a smartphone with a small RTK‑GNSS receiver to enable centimeter-level high-precision positioning in a palm-sized device. Behind this are advances in GNSS receiving devices and communication infrastructure, as well as improvements in the smartphones themselves.

First, there is the miniaturization and enhanced performance of GNSS receivers. In recent years, low-power, multi-band (L1/L2 and L5 bands) satellite positioning chipsets have emerged, making it possible to receive and process the satellite signals required for RTK in very small modules. The full-scale operation of Japan's Quasi-Zenith Satellite System "Michibiki," which provides the centimeter-level positioning augmentation service (CLAS), has also been a tailwind. CLAS is a service that directly broadcasts error correction information from satellites over a wide area, and with a compatible receiver you can obtain correction information in real time even in mountainous areas and other regions where internet connectivity does not reach. Previously, it was necessary to set up your own base stations or subscribe to network-based distribution services, but with a CLAS-compatible receiver standalone centimeter-level positioning has become possible.

Next, the advances in smartphones cannot be overlooked. Modern smartphones are equipped with high-performance CPUs and large-capacity memory, making them small computers. In addition, they carry a variety of sensors—such as cameras, LiDAR sensors, electronic compasses, and accelerometers—making them ideal platforms to be used in combination with high-precision positioning data. Furthermore, because they are constantly connected to the internet and can integrate with cloud services, they are well suited to immediately share and store information collected on site. They also allow easy functional expansion via apps, serving as a foundation for building new surveying workflows that did not exist before.

Thanks to these technological advances, "Smartphone RTK"—which combines smartphones and ultra-compact GNSS receivers—has emerged as a groundbreaking high-precision positioning solution. Positioning processes that were once carried out on desktop PCs or dedicated terminals can now be operated intuitively via smartphone apps, making tools with centimeter-level accuracy (half-inch accuracy) that anyone can use a reality.

Components and Functions of LRTK

The representative product that emerged in smartphone RTK is LRTK. LRTK is a total positioning system developed by Refixia, a startup originating from Tokyo Institute of Technology, and by attaching an ultra-compact GNSS receiver to a smartphone and linking a dedicated app with cloud services, it enables easy on-site surveying and data utilization with centimeter-level accuracy (cm level accuracy (half-inch accuracy)). The main components and their functions are as follows.

• Dedicated GNSS device (LRTK Phone): An ultra-compact RTK-GNSS receiver that attaches to and is used with a smartphone. Weighing only about 125 g and pocket-sized with a thickness of a dozen or so millimeters (about 12 mm (0.47 in)), it houses a surveying antenna, high-performance GNSS receiver circuitry, and a built-in battery. It attaches to and detaches from a dedicated smartphone cover with a single touch, and simply attaching it makes RTK positioning—previously possible only with stationary equipment—available on the smartphone. With an optional monopod (pole) you can accurately measure points on the ground, and vertical offset correction can be easily set via a button in the app.

• Smartphone app (LRTK app): A dedicated app that forms the core of the LRTK system, compatible with iPhone and Android. From this app you can start/stop positioning, record points, perform various measurements, use AR displays, and access many other features. In basic single-point positioning, you can measure latitude, longitude, and height simply by tapping a button on the smartphone at the point you want to measure, and record them together with date/time and a point name (title). As positioning modes, the app can obtain the RTK-GNSS Fix solution (fixed solution) in real time, and it can also average multiple observations to improve accuracy. For example, averaging about 60 measurements per point can achieve astonishing accuracy, reducing horizontal position errors to less than 1 cm (0.4 in). There are many other useful features. The continuous positioning function can acquire coordinates of up to 10 points per second while moving and record them as track data. The resulting tracks can be displayed like plan views or longitudinal profiles, making them useful for walking a site to check elevation differences. The photo positioning function automatically records the latitude, longitude, height of the shooting location and the camera’s orientation (azimuth) simultaneously when taking photos with the smartphone’s camera on site. This allows you to save “where and in which direction a photo was taken” with centimeter-level position information (cm level accuracy (half-inch accuracy)), eliminating the traditional need to note photo locations on paper drawings or maps. There is also a unique feature called the target positioning function, which can non‑contact acquire coordinates of locations that are difficult to enter or out of reach. For example, even measurement points where a pole cannot be placed—such as the top of a steep slope or the high part of an elevated bridge—can be measured by simply pointing the smartphone from a distance; the system estimates and records the target’s latitude, longitude, and height. This is powerful in scenes where ensuring safety is difficult because it avoids having to enter dangerous locations directly. The app also includes AR functionality, enabling surveying that leverages advanced AR technology—such as overlaying construction design 3D models onto live site images or confirming layout marking positions by virtually placing stakes.

• Cloud service (LRTK Cloud): a web platform for centralized management of positioning data, photos, and point cloud data acquired by the LRTK app in the field. Data can be uploaded to the cloud from the app with a single tap, and office staff can open a web browser to immediately check field measurement results. On the cloud map, coordinates of survey points are plotted, and each point is linked with a name, notes, and photos. If you want to share with stakeholders, you can issue a view-only URL for the data on the cloud, set a password and an expiration date, and send it. Recipients can access the map in their browser without logging in, view the results, and download them in CSV format. LRTK Cloud is not just online storage; it includes advanced features to make effective use of field data. Uploaded point cloud data can be displayed in a 3D viewer on the cloud, and volume calculations and distance measurements can be performed in the browser without installing dedicated software. You can also upload a 3D design model to the cloud and overlay it with the current point cloud data to automatically calculate differences in earthwork volumes and the like. For geotagged photos, multiple photos taken at the same survey point in time series can be displayed side by side to compare long-term changes in structures and terrain. These features allow raw information collected at the site to be stored and analyzed in the cloud, creating an environment where all stakeholders can share and utilize it.

Positioning Accuracy and Reliability Based on Case Studies

Some may doubt whether such high accuracy can really be achieved with a combination of a smartphone and a small device. However, LRTK delivers accuracy and reliability comparable to conventional professional GNSS equipment. In field tests, horizontal positioning accuracy was approximately 1-2 cm (0.4-0.8 in) even with standalone positioning, and by taking multiple short observations and averaging them the result falls below 1 cm (<0.4 in). Averaged positioning reduces errors through repeated observations, enabling point coordinates to be determined with precision approaching the millimeter level (approaching 0.04 in).

Behind LRTK’s ability to achieve such high accuracy are several technical innovations. LRTK devices support L1, L2, and L5 three-frequency GNSS, and by using multiple frequencies they can remove ionospheric errors and speed up RTK positioning initialization (accelerating integer ambiguity resolution of satellite ranges). In addition, because they also support the aforementioned CLAS, they can directly receive correction signals from the Michibiki satellites and maintain centimeter-class positioning (cm level accuracy (half-inch accuracy)) even in mountainous areas or at sea where cellular signals do not reach. This proved powerful in surveying during large-scale disasters. For example, during the 2023 earthquake in the Noto region of Ishikawa Prefecture, LRTK was used under conditions where communication infrastructure at the disaster sites had been severed. Even offline, it helped record and share the conditions of collapsed sites with coordinate data with centimeter accuracy (cm level accuracy (half-inch accuracy)), contributing to on-site verification as a reliable surveying tool.

It has received high praise from field technicians and bloggers, and there are reports that LRTK was able to obtain a Fix solution (fixed solution) even in environments such as inside forests where conventional units have difficulty acquiring satellites. On social media, comments like "I was thrilled just to receive the unit" and "When I tried measuring, the accuracy exceeded my expectations" have been posted, and its performance is being confirmed in real-world use. Thus, although compact, LRTK provides positioning accuracy and reliability sufficient for professional applications, and can be considered a high-precision tool that can be confidently deployed for field work.

Diverse Use Cases: Point Cloud Measurement・As-built Management・CAD Integration・AR Visualization・Cloud Sharing

When LRTK makes centimeter-level positioning easily achievable, the types of data that can be collected on-site and the range of their applications expand dramatically. Here, we introduce several representative application areas that use LRTK.

• Point Cloud Measurement (3D Scanning): By using LRTK together with a smartphone, you can quickly acquire three-dimensional point cloud data of terrain and structures. iPhones or iPads equipped with LiDAR can scan the surroundings on site and record high-density point clouds. Because the LRTK continuously records its own position with cm level accuracy (half-inch accuracy), distortions (positional shifts) in point cloud data that used to be a problem with smartphone-only scans are less likely to occur, enabling accurate 3D modeling of the current conditions. The acquired point clouds can be used within the app to measure distances between any two points or volumes, making them immediately useful for tasks like calculating the volume of embankments. Furthermore, by uploading them to the cloud, you can view and measure point clouds on the web or overlay them with CAD data, sharing 3D information across the office and the field.

• As-built management: LRTK also excels at verifying and recording the as-built shape after construction completion. Previously, inspection tasks in which site supervisors worked with staff to measure each point using surveying instruments and tape measures could be time-consuming, but with LRTK they can be carried out efficiently by a single person. You can measure control points and structure dimensions specified in the design drawings with LRTK and immediately compare them to the specified values on site. For example, tasks such as measuring pavement elevation and slope in roadworks or checking slope gradients at development sites can be completed quickly: with LRTK you can rapidly measure many points in a short time, and the results are plotted in real time on cloud-based maps, which automates record management. By using the photo positioning function, simply photographing the as-built areas creates location-tagged records, making it easy to review later "where and how work was carried out".

• CAD Integration: Coordinate data and point cloud data acquired by LRTK can be smoothly integrated with existing CAD software and civil engineering software. Survey point data that can be exported from the app and the cloud support standard formats commonly used in workflows, such as CSV and SIMA. Therefore, results measured on site can be imported into in-house design drawings or GIS software and used in the usual workflow. Conversely, coordinate lists and 3D models created during the design phase can also be imported into the LRTK cloud. For example, if you bulk-register a coordinate list of boundary points (CSV, GeoJSON, etc.) to the cloud, it can be synchronized to the smartphone for on-site reference. The LRTK app’s navigation feature can guide you to specified coordinates, making it easy to reconcile design drawings with the actual site or to locate boundary stakes.

• AR display: With LRTK's AR functionality, digital design data can be overlaid onto real-world jobsite scenes. The planned 3D model for construction is superimposed onto the current terrain point cloud and projected into the actual scenery, allowing designers and construction personnel to intuitively share the image of the finished project. Because the finished form, which previously could only be imagined from drawings and perspective renderings, can be checked on site at full scale, everyone's understanding is deepened. Also, by using the AR staking function, virtual markers can be shown in places where physical stakes cannot be installed. For example, even on concrete pavement or on slopes that are difficult to access, stake markings can be displayed at the designated positions on a smartphone screen, which helps when reviewing construction plans.

• Cloud sharing: Data sharing via the LRTK Cloud transforms the way field teams and stakeholders collaborate. Positioning information acquired on site is uploaded to the cloud instantly and can be shared in real time with the office and clients, dramatically accelerating decision-making. For example, when sharing survey data with partner companies, there is no need to send large files as email attachments; simply sharing a generated URL lets them always view the latest data. Because everyone can reference the same maps and data in the cloud, communication losses—such as misunderstandings resulting from transmission errors like “we thought it was measured this way on site”—are reduced. Additionally, photos and point cloud data managed in time series allow anyone to review project progress and past construction details, making information sharing and handovers smoother.

Effects of Introducing LRTK: Reduced Staffing, Shorter Work Times, and Improved Safety

The benefits of introducing LRTK to the site are significant, improving efficiency and safety across overall site management, not just surveying work. The primary effects are summarized from three perspectives.

• Labor-saving: Traditionally, each survey required a licensed surveyor or an assistant, but with LRTK on-site technicians can complete measurement work by themselves. There is no need to carry around expensive dedicated equipment; each worker can carry a smartphone and an LRTK device and perform positioning at their preferred time, eliminating wasted time waiting for surveys or waiting for personnel. Even worksites struggling with staff shortages will be able to carry out many measurement tasks with a limited number of people.

• Work time reduction: The time required for surveying and recording is greatly shortened. With a single tap, coordinate measurement and automatic recording are completed, eliminating the need to transcribe onto paper and drastically reducing on-site note-taking. Data acquired on site is organized as is and saved to the cloud, so the tasks of entering data into a PC or creating drawings after returning to the office are also reduced. Furthermore, because point cloud scanning and photo documentation can be carried out simultaneously, all necessary information can be collected in a single field operation. For example, tasks that traditionally took half a day—measuring as-built conditions and organizing photos—can be dramatically streamlined after introducing LRTK, with work completed on site and no post-processing required. Being able to share site information instantly also speeds up decision-making, contributing overall to shorter project schedules and improved productivity.

• Safety Improvements: LRTK significantly contributes to on-site safety. With its target positioning function, measurements can be taken without entering hazardous areas, allowing surveying work to be carried out safely on steep slopes or around operating heavy machinery. The miniaturization and weight reduction of the equipment also lower the risk of accidents associated with transporting devices to locations with poor footing or to high places. Furthermore, because tasks that previously required multiple people can now be performed by a single operator, human errors caused by miscommunication of signals or incorrect personnel deployment can be reduced. Even in post-disaster investigations of dangerous affected sites, LRTK enables rapid and safe situational assessment, helping to prevent further damage and to formulate early recovery plans.

Notes and Tips for Successful Implementation

LRTK is innovative, but to maximize its effectiveness there are several points to consider when implementing it.

• Preparing compatible smartphones：LRTK supports both iPhone and Android, but the features available will vary depending on the smartphone’s performance. For example, point-cloud scanning using LiDAR and advanced AR functions realize their full potential only on the latest, high-performance smartphones. If possible, it is advisable to prepare relatively recent high-end models among the supported devices (for example: iPhone Pro series). Also, to prepare for long-duration operation, battery management for both the smartphone itself and the LRTK device is important. Fully charge them before heading to the field, and prepare by carrying a portable battery (power bank) as needed.

• Ensuring a suitable positioning environment: For high-precision positioning, an environment that allows good reception of signals from GNSS satellites is important. Basically it can be used without problems in open outdoor areas, but accuracy may decrease in places with poor satellite visibility such as inside forests or under elevated structures. LRTK includes features that can help cover these situations, such as indoor positioning modes or object positioning, but for important measurements choose open locations whenever possible and use position averaging as needed—these kinds of measures to ensure accuracy. Also, when using the CLAS satellite augmentation signal within Japan, being within the service area is a prerequisite (it is available in almost the entire country, but cannot be received in some areas such as remote islands).

• In-house training and rule-making: LRTK itself is intuitive to operate, but during the initial implementation it goes more smoothly if you provide basic operation training and establish operational rules within the company. For example, agreeing in advance on naming conventions for cloud data and on who issues shared URLs and when can prevent confusion. Since this will be a first tool for field staff, a key to success is to introduce it experimentally with a small group at first to verify its effectiveness and then roll it out in stages. When performing positioning for the first time, it is reassuring to take the opportunity to deepen understanding of the equipment, for example by verifying accuracy at known points.

• Compatibility with existing operations：Even after introducing LRTK, there will likely be situations where it is used alongside conventional surveying instruments and methods for a while. If you have surveying specialists in-house or at partner companies, cross-check LRTK measurement results with the surveyed-point results obtained by total stations and the like to understand error trends and increase reliability. It is also important to pre-test whether data output from LRTK can be smoothly imported into your existing software. Fortunately, LRTK supports industry-standard data formats, but if you establish operational procedures in advance, you will be able to use it on site without confusion.

If you proceed with the implementation while keeping these points in mind, LRTK will integrate into on-site operations surprisingly easily and should fully demonstrate its effectiveness. By incorporating feedback from the field, fine-tuning settings and procedures, and exploring the usage that best fits your company, you can maximize the value of LRTK.

The Future of Simplified Surveying Achieved with LRTK

The emergence of smartphone-based LRTK is poised to dramatically change the way surveying is done. Centimeter-accurate surveying (cm level accuracy (half-inch accuracy)) that previously had to be left to specialists can now be performed with equipment that fits in anyone’s pocket. This is not merely a matter of devices becoming more convenient; it holds the potential to revolutionize on-site workflows themselves.

By leveraging LRTK, it becomes natural to measure and record on the spot whenever the need arises, and to share the necessary information via the cloud. One could say that an environment enabling high-precision surveying "anytime, anywhere, by anyone" has truly been established. This is groundbreaking not only for surveyors but also for construction managers, designers, municipal staff, and anyone who deals with spatial information. In addition to improving on-site productivity, it will contribute to better as-built and maintenance management accuracy, and ultimately to ensuring construction quality and extending infrastructure lifespans.

Simple surveying with LRTK is steadily permeating job sites. This system—aiming to be a "one-person, one-unit universal surveying device"—has, together with its reasonable pricing, already sparked a quiet boom at many sites. If you haven’t tried high-precision positioning yet, why not take this opportunity to adopt LRTK? Once you experience the labor-saving and efficiency benefits, you may find you can’t go back to the old ways. The RTK surveying revolution that starts with a smartphone will continue to broaden on-site possibilities.

FAQ

Q: Can it be used in places where mobile reception is unavailable? A: Yes, LRTK can perform high-precision positioning even outside mobile network coverage. Because the LRTK receiver supports Japan’s satellite positioning augmentation signal (Michibiki’s CLAS), it can directly receive correction information from satellites and perform centimeter-level positioning (half-inch accuracy) even in areas without internet access, such as mountainous regions or at sea. Also, positioning data is stored on the smartphone in offline environments, so when you return to an area with reception you can upload them to the cloud all at once.

Q: Is the positioning accuracy really at the centimeter level? A: Under good conditions, you can obtain accuracy within a few centimeters (a few in). In actual measurements, results have shown horizontal positions within approximately 1–2 cm (0.4–0.8 in) and vertical errors on the order of a few centimeters (a few in). By combining averaged positioning, it is also possible to achieve accuracy of less than 1 cm (less than 0.4 in). However, accuracy depends on satellite signal reception conditions, so the best results are obtained by using it in open-sky locations and measuring while stationary for a while. It may take on the order of several tens of seconds from the initial state to receive satellite correction information and obtain a fixed solution (Fix), but once a stable Fix is obtained it will thereafter stably maintain centimeter accuracy (half-inch accuracy).

Q: How is it different from a smartphone's GPS? A: Compared with the GPS built into smartphones, LRTK achieves significantly higher positioning accuracy by using a dedicated antenna and multi-frequency GNSS reception. General smartphone GPS can only receive a single frequency and typically has an accuracy on the order of several meters, whereas LRTK captures multi-frequency satellite signals and uses correction data to deliver vastly greater accuracy. The antenna is also optimized for surveying, making it less likely to lose satellites and enabling stable reception. For that reason, while using the smartphone screen as the interface, the positioning performance reaches a level equivalent to professional GNSS equipment.

Q: Is the operation difficult? Can it be used without surveying expertise? A: The operation is very simple and intuitive for anyone who has used a smartphone map app. Specialized settings are automated in the app, and the procedure is as simple as pressing a button at the point you want to measure to record it. Of course, detailed settings for surveyors—such as choosing the coordinate system (plane rectangular coordinate system, e.g. Zone ○) or setting a reference elevation—are also available, but the basic usage can be learned by anyone quickly. In fact, because tasks that used to require separate devices—“measuring, recording, taking photos, and taking notes”—can be done all in one, beginners can reliably record everything without omissions.

Q: I'm concerned about upfront costs—aren't the devices expensive? A: LRTK is offered at a much more accessible price point compared with conventional RTK surveying equipment. For detailed pricing, please contact us, but the initial cost can be kept to roughly the price of an inexpensive GNSS receiver, making it easy to get started. We also provide subscription plans that can reduce upfront costs. In many cases, equipping one unit per person still fits within budget, so it can be considered a highly cost-effective solution.

Q: Can it be used with any smartphone? A: Basically, relatively new iOS or Android smartphones can be used. It will work on models where the LRTK device can be physically attached and that support Bluetooth or USB connections. However, older models may not be supported by the app or may lack the performance to handle some features (AR display, LiDAR scanning, etc.). Recommended environments include the latest iPhone series and high-end Android models. It can also be used on iPads, and using a tablet is effective for viewing detailed point clouds on a large screen.

Q: How are survey data managed and how compatible are they with other software? A: Positioning data are automatically saved to the LRTK cloud and can be exported in formats that are convenient for work as needed. From the cloud, point data can be exported and downloaded in CSV or SIMA format, so they can be imported directly into existing CAD drawings or GIS software. Point cloud data can also be converted to common formats such as LAS. Because data can be centrally managed in the cloud, it is easy to retrieve past measurement records and share them with the team. Compared with recording in a paper field notebook on site, management is significantly easier, and data loss and entry errors can be prevented.

Q: Can it be used in rainy weather or cold regions? A: In general it can be used without problems, but because it involves a smartphone and electronic equipment, you should take care in extreme environments. The LRTK device itself is robustly designed for field use, but it is not fully waterproof, so when using it in heavy rain it is advisable to take measures such as putting the smartphone in a waterproof case. As for temperature, it will generally operate within the range where people can be active (outdoors in midwinter to direct sunlight in midsummer), but the battery may temporarily lose performance in severe cold. In any case, if you take precautions such as warming the device during breaks and preparing spare batteries, it can be used year-round.