Table of Contents

• What is tilt-correcting GNSS technology

• Challenges at survey sites and limitations of conventional methods

• Benefits of tilt-correcting GNSS paired with iPhone

• Effects of on-site adoption: labor savings, improved accuracy, and safety

• Use cases: slope surveying, solo stake setting, and confined-area surveying

• Outlook for RTK and iPhone integration with LRTK

• FAQ

What is tilt-correcting GNSS technology

Tilt-correcting GNSS is a technology that enables accurate position measurement even when the pole (survey staff) is tilted, by using tilt sensors and inertial measurement units (IMUs) built into a GNSS surveying device (high-precision GPS receiver). Normally, GNSS positioning requires the antenna’s projection on the ground to be determined, so the pole with the antenna must be held vertically. In real-world sites, however, keeping the pole perfectly vertical is time-consuming, and slight tilts have led to measurement errors. With tilt-correcting GNSS, the pole’s tilt angle and orientation are detected in real time and corrected in calculation, allowing accurate coordinates of the pole tip’s contact point (the point on the ground) to be obtained even when the pole is tilted.

The emergence of this technology has begun to change surveying work significantly. Traditionally, survey points were recorded after leveling the pole with a spirit level (bubble vial), but with tilt-correcting GNSS you can measure with the pole tilted, eliminating the need for meticulous leveling with a bubble vial. Typical IMU-equipped GNSS units can correct tilts up to around 30 degrees, and some models now support extreme tilts approaching 60 degrees. For example, high-performance models can maintain accuracy within a few centimeters even with a 30-degree tilt, making them effective in places where it is hard to stand a pole upright, such as near walls or trees. Tilt-correction is a relatively new feature in surveying GNSS receivers, but supported models are now offered by major manufacturers abroad and domestically, and the technology is attracting attention as a trump card for improving productivity on survey sites.

Challenges at survey sites and limitations of conventional methods

The construction and civil engineering survey sector has long faced issues such as labor shortages and operational inefficiencies. Conventional surveying typically uses optical instruments like total stations and levels, and is commonly performed by teams of two or more staff. For example, one person sets up and operates the surveying instrument while another holds the staff (pole) vertically at a distant point and aligns it with the target point. This naturally incurs personnel and time costs, and measuring a large site can often take a full day or more just for surveying. Manual workflows also carry the risk of human error; misreads or recording mistakes can lead to rework, construction delays, and additional costs. Furthermore, efficiency constraints often lead to a tendency to “measure only where possible,” resulting in coarse spacing between survey points and issues with missed areas.

GNSS surveying (so-called GPS surveying) is powerful because it obtains absolute coordinates using satellites overhead, and is effective in locations with poor line of sight or for long-distance point-to-point measurements. However, when high-precision RTK-GNSS equipment first became common, the equipment was large, expensive, and required specialized knowledge. Operations such as setting up a base station, using radios for communication, or connecting to correction services via the internet imposed operational burdens and required experience. As a result, even when portable GNSS receivers were available, operations often still required two or more people. In addition, narrow spaces where there is no room to set up a pole, or dangerous locations like cliff edges and slopes, forced surveyors to abandon direct measurement or resort to indirect estimation with conventional methods. Given these limitations, there is growing demand for new technologies that can digitize sites with fewer personnel and greater efficiency, and including points that could not be measured before.

Benefits of tilt-correcting GNSS paired with iPhone

The latest tilt-correcting GNSS technology combined with smartphones (especially iPhone) brings numerous benefits to on-site surveying. It eliminates many constraints inherent in traditional equipment and methods and has the potential to transform surveying workflows. The specific advantages are summarized below.

• Reduced time for pole leveling: There is no need to set the pole vertically; positioning can be done with the pole tilted. Eliminating the repetitive task of peering at a bubble vial for fine adjustments saves time, so observation time per point is greatly reduced. One test reported about a 20% time reduction compared to leveling with a bubble vial, allowing more points to be measured per day.

• Measurement without blind spots: Tilt correction enables acquisition of survey points that were previously abandoned. For example, at building edges, base of walls, under vehicles or structures, or other confined spaces where a pole cannot be stood vertically, you can simply insert the pole at an angle and place the tip on the target point to obtain a measurement. On slopes, you can safely place and tilt the pole tip to acquire accurate terrain data. This makes it possible to measure the entire site thoroughly and reduces the risk of overlooking points.

• Intuitive operation with smartphones: Linking a GNSS receiver to an iPhone or other smartphone greatly improves operability compared to traditional dedicated controllers. You can view maps and measurement points on a large color touchscreen, and beginners can operate intuitively using clear in-app menus. For example, starting and stopping positioning can be done with on-screen buttons, measurement data is saved automatically and can be synced to the cloud. Because the UI is the familiar smartphone app style, users are less likely to be confused by the complex settings typical of specialized equipment.

• AR-assisted support: Smartphone-native AR (augmented reality) features can also be applied to surveying. By overlaying virtual markers or arrows on the camera view that show planned measurement points or stake positions, you can visually identify points. Holding an iPhone and walking toward a point, the on-screen arrow can guide you with prompts like “move east by X cm,” enabling stake-setting work that previously required multiple people to be done accurately and alone. AR visual navigation helps even less-experienced staff perform effectively on site.

• Smaller, lighter equipment: Smartphone-connected GNSS receivers are very compact and lightweight. By attaching a palm-sized receiver that integrates antenna and battery to a smartphone, high-precision positioning becomes possible without carrying tripods or large cases. Equipment that once weighed several kilograms can now be a few hundred grams, dramatically increasing mobility to site and reducing the burden. Bringing equipment into tight sites, high places, or mountainous areas becomes easier and directly reduces work strain.

• Real-time data utilization: With positioning data accumulated on the smartphone, digital information sharing becomes smooth. You can attach photos and notes to point coordinates on the spot and share them with the office PC via the cloud immediately. This eliminates the need to write in paper field notebooks and later transcribe, preventing input errors. Using the smartphone’s communication function to send survey results from the site enables remote supervisors or colleagues to immediately review data and issue instructions. This is a workflow that embodies on-site surveying DX (digital transformation).

Effects of on-site adoption: labor savings, improved accuracy, and safety

Combining tilt-correcting GNSS with smartphone surveying yields immeasurable benefits on site. Here we organize the main improvements from three perspectives: labor savings (increased operational efficiency), improved surveying accuracy, and safety.

• Labor savings and efficiency gains: Surveys can be conducted with fewer people, increasing individual productivity. Survey crews that previously required two to three members can often be formed with a single person, helping to alleviate labor shortages. Time spent on setup and equipment installation is reduced, and the speed of measurement itself improves, enabling overall man-hour reductions. For example, tasks that previously took a full day for staking out have been reported to be completed in less than half a day using the new technology. Cloud integration also speeds up post-processing of survey data and drawing creation, shortening the entire process from surveying to design and construction.

• Improved surveying accuracy: Because tilt correction ensures accurate coordinates of the pole tip at all times, human error is reduced and observation accuracy stabilizes. Conventional errors caused by pole tilt or placement mistakes are eliminated by automatic correction. Being able to directly measure points in difficult locations means areas that previously relied on estimates can now be captured accurately. As a result, the reliability of survey deliverables increases, improving as-built management and quality inspections. Detailed digital records of site conditions make future verification and tracing easier and help prevent construction mistakes.

• Improved safety: A major effect is the reduction of occupational accident risks in surveying. Points on dangerous slopes or on roads can be measured by standing in a safe place and extending only the pole, reducing the need for workers to assume unsafe postures or enter hazardous areas. Simplifying surveys that previously required aerial work platforms or traffic control also lessens impacts on the surroundings. When working alone, continuous sharing of location and status via smartphone allows quick requests for assistance if trouble occurs. Lighter equipment reduces carrying strain and accident risk, raising overall site safety levels.

Use cases: slope surveying, solo stake setting, and confined-area surveying

The new tilt-correcting GNSS + smartphone surveying solves practical problems in various scenarios. Representative use cases include the following.

• Slope surveying: When measuring steep slopes or embankment faces, it can be dangerous for surveyors to balance on the slope. With tilt-correcting GNSS, you can measure points such as the top or toe of the slope by inserting the pole at an angle from below or above the slope. This avoids the need for people to walk the slope directly, improving safety and enabling rapid acquisition of detailed terrain data. It facilitates smooth creation of slope as-built management models and earthwork volume calculations.

• Solo stake setting: Positioning for buildings or structures (stake setting) previously required multiple people coordinating instrument operation and stake alignment. With a GNSS receiver and smartphone, one person can confirm their position and mark stake locations. The smartphone can display “X cm remaining to the target,” or AR can show a virtual stake for fine adjustment, allowing accurate stake placement without relying on seasoned intuition. Layout and formwork tasks are completed quickly even with small crews, improving overall construction efficiency.

• Confined-area surveying: In urban sites with dense buildings or walls, or in factory sites cluttered with obstacles, there may be no space for tripods or line-of-sight may be obstructed, making surveying difficult. Small GNSS units can fit into narrow gaps, and you can insert the pole at an angle to measure points deep inside. Capturing previously unmeasurable blind spots enables accurate tasks such as deformation monitoring of buildings or equipment installation positioning. High mobility allows many points to be measured in a short time while walking the site, proving powerful for detailed understanding of confined sites.

Outlook for RTK and iPhone integration with LRTK

As described above, using tilt-correcting GNSS and smartphones for surveying has a major effect on promoting on-site DX. One cutting-edge solution in this space is the lightweight RTK system called LRTK. LRTK is the collective name for smartphone-integrated GNSS positioning devices and cloud services developed by a venture originating from Tokyo Institute of Technology, aiming to make high-precision on-site positioning easy for anyone.

The LRTK series offers ultra-compact devices that attach directly to an iPhone as well as rugged pole-mounted devices designed for field use. All models integrate antenna, receiver, battery, and communication modules in an all-in-one design and weigh only a few hundred grams, making them extremely lightweight. For example, a smartphone-attachable model has a housing about 1 cm thick and weighing about 160 g; by mounting it on the back of an iPhone and connecting via Bluetooth, the smartphone itself quickly becomes an RTK surveying instrument. Despite pocketable size, it receives correction information and achieves centimeter-level accuracy in real time, and positioning data can be immediately tagged with photos and notes and saved to the cloud. It is designed as a digital tool for on-site surveying.

Moreover, a new-generation model built to withstand the harsh use of construction sites, the rugged receiver “LRTK Pro2,” has also appeared. This pole-mounted type supports CLAS satellite augmentation signals provided by Japan’s Michibiki and can achieve high-precision positioning standalone even in mountainous areas without cellular coverage. It also supports tilt-correction, so the pole tip position is recorded accurately even when the pole is tilted. Where RTK surveying was previously impossible without internet connectivity, LRTK Pro2 can position using satellite augmentation alone, making it powerful at sites out of cellular range or right after disasters. In practice, it has been used to record disaster-affected areas with high-precision geotagged photos when mobile networks were down. These features have promoted LRTK’s use as a portable surveying system across a wide range of applications including infrastructure inspection, disaster investigation, and construction management.

The lightweight RTK + smartphone approach represented by LRTK will continue to evolve. For example, wearable positioning devices that allow a worker to collect as-built data continuously simply by walking while wearing a GNSS antenna on a helmet are emerging. In the future, anyone on site may carry a smartphone and perform surveying and measurements, with data aggregated to the cloud in real time. Seamless collection and use of high-precision location data from across a site could fundamentally change how construction management and maintenance are conducted. Tilt-correcting GNSS + smartphone integration technology, which accelerates on-site surveying DX, will play an increasingly important role in the future of construction.

FAQ

Q: If I measure with the pole tilted using tilt-correcting GNSS, will accuracy be affected? A: If the tilt-correcting GNSS equipment is properly calibrated, it can maintain survey-grade high accuracy even with the pole somewhat tilted. Many models are designed to keep horizontal and vertical errors below a few centimeters at tilt angles around 30 degrees. However, exceeding each model’s specified limits (for example, maximum tilt angle) can increase errors, so it is important to use the device within the manufacturer’s recommended range.

Q: Up to what tilt can be corrected? A: Typical tilt-correcting GNSS receivers can correct tilts of about 15–30 degrees. Recently, higher-end models equipped with advanced IMUs can correct angles approaching 40–60 degrees. For common field situations (such as poles tilting near walls or on slopes), these ranges will generally suffice. Because capabilities vary by model, check the specifications for supported tilt angles.

Q: Are special operations or calibrations required when using tilt-correcting GNSS? A: Basic operation is generally the same as with normal GNSS surveying machines, but some models require an initial IMU initialization (calibration). In many cases this is completed in a few seconds to tens of seconds by leaving the receiver stationary or moving it in a figure-eight pattern. Once initialized, the receiver will automatically apply real-time correction when the pole is tilted. Aside from no longer needing to watch a bubble vial constantly, procedures are the same as normal RTK surveying, so no advanced skills are required.

Q: Can I really do stake setting or surveying alone by linking a smartphone and GNSS? A: Yes. There are increasing cases of single-person stake setting completed accurately by following guidance on a smartphone app. Positioning that used to require two people can be performed by one person who follows on-screen directions such as how many centimeters to move east/west/north/south, and then marks the position when in place. With AR-capable apps, a virtual stake marker appears in the camera view and the stake looks like it is standing in the correct spot as you approach, enabling even first-time users to work without confusion. Except for moments that require a verifier, many surveying tasks can now be completed by one person.

Q: Can this be used in remote mountain areas or inside tunnels where there is no cellular coverage? A: GNSS positioning itself works where satellites overhead are visible. In areas without cellular coverage, you cannot receive real-time correction information over the network, but devices that support satellite augmentation services such as Michibiki’s CLAS can achieve centimeter-level positioning without a base station. In fact, CLAS-compatible receivers like those in the LRTK family have been used for surveying in coverage-free areas. However, in tunnels, underground, or other places where satellite signals cannot reach, GNSS positioning is not possible and you must combine other methods like total stations or terrestrial laser scanning. Using GNSS and smartphones together covers most outdoor tasks, but choose the appropriate surveying method according to the environment.