RTK Surveying Anyone Can Do with an iPad: New Technology Transforming Construction Sites

Table of Contents

• What is RTK surveying?

• Traditional surveying methods and their challenges

• The potential of RTK surveying with an iPad

• Advantages of RTK surveying using an iPad

• Use cases expanding on construction sites

• Simple surveying anyone can do with LRTK

• FAQ

What is RTK surveying?

In recent years, familiar devices like the iPad have made it possible to perform precise surveying that previously required specialized equipment. The key technology enabling this is RTK surveying. RTK surveying refers to Real Time Kinematic positioning using satellite positioning technology, a surveying method that can determine positions in real time with centimeter-level accuracy. Conventional GPS (GNSS) positioning can sometimes have errors of about 5-10 m (16.4-32.8 ft), but RTK can reduce errors to the order of a few centimeters. For this reason, RTK has been widely used in civil engineering and construction for tasks requiring high accuracy, such as layout staking and as-built management.

To realize RTK positioning, error corrections through simultaneous observations between a base station (a receiver with a known precise position) and a rover (the device to be positioned) are necessary. Specifically, the base station derives error information from the satellite signals it receives and delivers that correction information to the rover in real time, allowing the rover to apply corrections for high-precision positioning. Previously, deploying one’s own base station or using specialized communication equipment to receive correction data was necessary, making RTK surveying a highly specialized task. However, the recent spread of network RTK services (like Ntrip) that provide correction information via the Internet has made it easier to obtain correction data without dedicated equipment.

Traditional surveying methods and their challenges

When high-accuracy surveying is mentioned, it was once common to use a total station or expensive GNSS surveying equipment. A total station is a precision optical instrument for measuring angles and distances, but it requires time-consuming setup and sight-line assurance and is typically operated by two or more people. Regular calibration and maintenance are also essential to maintain accuracy. Meanwhile, RTK-GNSS surveying equipment requires dedicated receivers, antennas, and communication modems, and the equipment itself is expensive and requires specialized knowledge to operate. Because of these conventional methods, the image that “surveying is for specialists” was strong, and site construction managers or workers could not easily handle surveying tasks themselves.

With the construction industry facing severe labor shortages, the aging of surveying technicians and a lack of younger staff are also problems. Relying on a limited number of surveyors means that even when a site needs to quickly “check this point,” a specialist surveyor must be arranged, creating inefficiencies in scheduling and costs. Additionally, tasks such as recording measured data on paper and bringing it back to the office to reflect it in drawings took time, delaying data sharing. Traditional surveying methods had issues such as “bulky equipment,” “high personnel and time requirements,” and “a time lag in data utilization.”

The potential of RTK surveying with an iPad

Amid these trends, a new approach has emerged in recent years: RTK surveying using mobile devices like the iPad. By combining a high-performance tablet like the iPad with a compact RTK-capable GNSS receiver, centimeter-level positioning that once required specialized equipment can now be achieved easily. Specifically, by attaching a dedicated GNSS receiver to an iPad and receiving network RTK correction information via the Internet, high-precision position information can be obtained instantly. This heralds an era in which the iPad itself becomes a surveying instrument.

The biggest advantage of using an iPad for surveying is its ease of use and usability. With intuitive touch operation on a tablet, recording measurement points and processing data can be done so that people unfamiliar with specialized equipment can operate it after short training. The iPad also has a camera, LiDAR sensor, and AR capabilities, enabling advanced uses such as photography, 3D scanning, and overlaying design data in AR on a single device. Tasks that previously required separate equipment and software can now be completed on an integrated device like the iPad.

Moreover, iPad-based surveying makes real-time data sharing easy. Coordinate data and measurement results obtained during positioning can be shared instantly with the office and other stakeholders via the cloud, reducing the information gap between the field and the office. For example, coordinates of points measured on site can be uploaded to the cloud immediately and checked from an office PC. This dramatically speeds up the reflection of survey results and decision-making. The advent of RTK surveying with the iPad is turning surveying into something “anyone can do, when needed, immediately.”

Advantages of RTK surveying using an iPad

Combining an iPad with a small RTK receiver for surveying offers various advantages not found in traditional methods. The main benefits are summarized below.

• Portability and mobility: The iPad is slim and light, making it easy to carry compared to dedicated surveying equipment. Combined with a pocket-sized GNSS receiver, there is no need to carry heavy tripods or large cases, and surveying can be started quickly on site when needed.

• Single-person operation: Surveying that used to require two-person teams can basically be completed by one person with iPad surveying. There is no need to have someone hold a prism or record points, enabling efficient surveying even on sites with labor shortages.

• Ease of operation: Tablet touch operation and an easy-to-understand app UI are designed so that people without complex surveying knowledge can handle the system. The app automatically handles coordinate system transformations and height corrections, allowing site personnel to use it intuitively.

• Real-time data sharing: Data can be saved to the cloud at the time of measurement and shared immediately with office staff. This reduces the need to bring data back to the office for drawing work and smooths collaboration between field and office.

• Multipurpose use: Since the iPad itself has a camera and LiDAR, it can capture georeferenced photos and obtain 3D point cloud data from scans. Combining captured point clouds and photos with positioning data enables analysis useful for as-built management and displacement measurement, among other uses.

• Cost benefits: Initial costs can be reduced compared to equipping a site with expensive dedicated instruments. Using a general-purpose device like an iPad makes it easier to equip one device per person, and by insourcing surveying work that was previously outsourced, costs can be cut.

• Improved safety: Because surveying can be done with minimal equipment, work time is reduced, contributing to lower safety risks. For example, on busy road sites, completing surveying quickly reduces the time workers spend on the roadway, helping ensure safety.

In these ways, RTK surveying with an iPad offers significant strengths in portability, efficiency, and economics. It enables immediate response to “I want to measure this quickly” needs on site, helping to keep work that used to wait for surveying moving smoothly.

Use cases expanding on construction sites

High-precision positioning with iPad + RTK can be applied to various scenarios in construction and civil engineering. Here are some specific examples.

• Layout staking: High-precision RTK positioning is effective for layout staking that marks the placement of buildings and the location of structures on site. If coordinate values from drawings are imported into the iPad, AR functions or guidance can be used to mark precise positions. Compared to manual methods or tape measures, this enables faster work with fewer mistakes.

• As-built management and inspection: iPad surveying is powerful for as-built management, where constructed structures or shaped terrain are checked against design positions and dimensions. Measuring key points on-site and comparing them to design values on the spot allows immediate correction if problems are found. Inspection tasks that used to wait for a surveying team can now be done in a timely manner by site personnel. Faster feedback of survey results also helps minimize rework.

• Earthwork quantity calculations and terrain measurement: Combining the iPad’s LiDAR or photogrammetry with RTK positioning enables simple calculation of volumes of embankments or excavations and terrain surveys. For example, scanning a pile of excavated soil in a short time and deriving volume from the point cloud can be done by one person quickly. This improves the accuracy and speed of earthwork progress management and as-built checks.

• Infrastructure maintenance and inspection: For inspections of roads, bridges, and other infrastructure, it is useful to record photos and notes with accurate location information. If photos taken with the iPad automatically record coordinates obtained by RTK, it becomes clear later exactly where a photo was taken. This increases location reliability for records of buried pipes or structural deterioration in maintenance surveys.

• Disaster response and recovery planning: Rapid surveying is indispensable for understanding situations after landslides or floods. Previously, it was necessary to wait for specialized contractors to arrive, but with an iPad and RTK equipment, responsible personnel can quickly survey hazardous areas immediately after a disaster. Converting the terrain and damage extent into data and sharing it immediately aids initial response and recovery planning. Where accurate situation assessment used to be difficult until a specialist team arrived, simple surveying tools enable immediate data acquisition, speeding up disaster response.

• AR-based construction verification: Displaying BIM/CIM models on an iPad and overlaying them on the real scene using AR technology achieves its full potential only with RTK’s high-precision alignment. Virtual models can be displayed on the iPad screen positioned to match the real location to centimeter accuracy, allowing intuitive visualization of the finished result before construction and helping prevent construction errors. AR use, which previously suffered from positional discrepancies, has been brought to a practical level by RTK.

As shown above, RTK surveying with an iPad goes beyond merely obtaining measurement points and is expanding as a platform for construction management and investigation. As a tool that allows “measure immediately” and “share immediately,” its adoption on site is likely to continue to grow.

Simple surveying anyone can do with LRTK

One specific solution for performing RTK surveying with an iPad that has attracted attention is a product called LRTK. LRTK is a system developed by Refyxia Inc. (a startup from Tokyo Institute of Technology) that consists of a pocket-sized RTK-GNSS receiver and a dedicated app. By simply attaching an ultra-compact receiver weighing about 125 g and about 1 cm (0.4 in) thick to an iPad or iPhone, centimeter-level surveying that used to require bench-mounted equipment becomes possible. Because it is small enough to carry in a pocket, it is designed as a one-device-per-person site tool that enables measurement whenever needed. Using the dedicated app “LRTK,” everything from starting positioning to recording data can be done intuitively via touch, and the recorded latitude, longitude, and elevation of measured points are automatically converted to Japan’s plane rectangular coordinate system and geoid height.

A major feature of LRTK is its ease of use for anyone and its all-in-one functionality. Once the receiver is connected to the iPad, simply pressing the “Position” button in the app allows high-precision recording of the current position. Positioning data include timestamps and satellite reception status as ancillary information, and notes or photos can be attached as needed. Obtained point coordinates can be uploaded to the “LRTK Cloud” with a single tap, allowing office PCs and other devices to view and share survey results in real time. By automating coordinate calculations and data organization that previously required surveying expertise, the system functions as a simple surveying tool that anyone on site can use.

Furthermore, LRTK supports point cloud measurement and AR features, enabling accurate positioning to be attached to 3D point clouds scanned with the iPad’s LiDAR sensor or overlaying design data on site. Using a dedicated lightweight monopod allows the receiver to be mounted for stable positioning, enabling accuracy suitable for professional surveying tasks. Its accuracy in single-receiver positioning is about 1–2 cm (0.4-0.8 in) horizontally and vertically, and averaging multiple measurements can reduce errors to less than 1 cm (less than 0.4 in). Despite this level of performance, operation is as simple as using a smartphone, and the price point makes it easy to equip one device per person, creating a quiet boom among field practitioners.

The arrival of LRTK is overturning the conventional wisdom that “surveying must be done by specialists.” By enabling construction site managers and technicians to perform surveying themselves when needed, operational efficiency will improve dramatically. In fact, some municipalities have used LRTK in disaster response to immediately measure and share damage information, demonstrating its usefulness. The new technology of RTK surveying that anyone can do with an iPad may become an indispensable everyday tool on future construction sites. Moreover, this familiar survey style using smart devices is likely to appeal to younger generations and help attract talent to the construction industry. These trends align with initiatives such as the Ministry of Land, Infrastructure, Transport and Tourism’s “i-Construction” and the promotion of construction DX, and the dissemination of high-precision positioning technology on site is expected to accelerate further.

FAQ

Q: What is RTK surveying?

A: RTK surveying is a surveying method using Real Time Kinematic satellite positioning technology. By using correction information from a base station, it reduces GPS positioning errors to a few centimeters, enabling high-precision positioning in real time.

Q: What is needed to perform RTK surveying with an iPad?

A: An iPad alone cannot provide high-precision positioning; a GNSS receiver that supports centimeter-level positioning is required. For example, attaching a small RTK receiver like LRTK to an iPad and receiving correction information over the Internet enables RTK surveying. A dedicated surveying app is also required; in the case of LRTK, the app can be obtained from the App Store.

Q: Can it be used without specialized knowledge?

A: Yes. iPad-based RTK surveying systems are designed with intuitive operation so that anyone on site can use them. Coordinate system setup and height correction calculations are automated, so high-precision data can be obtained by simply pressing the positioning button without difficult knowledge. With a short familiarization period, site staff can operate it sufficiently.

Q: Is the accuracy inferior to conventional surveying equipment?

A: Positioning with an iPad + RTK receiver can match the accuracy of conventional full-scale surveying equipment. Under good conditions, accuracy within a few centimeters horizontally and vertically can be expected, meeting the needs of many construction sites. However, like conventional equipment, accuracy can be affected by surrounding obstructions and radio environments. With appropriate operation, surveying can be performed with practically sufficient accuracy.

Q: How are survey data managed and shared?

A: Survey data acquired on the iPad can be uploaded to the cloud and managed on the spot. For example, with LRTK, measured points are automatically plotted on a cloud map and can be accessed and shared from a PC. Cloud integration allows data measured on site to be used immediately by everyone, which is another advantage of iPad-based surveying.

Q: Can iPad surveying be done in locations without a communication environment?

A: Network RTK positioning generally requires Internet communication. In places without cellular reception, obtaining centimeter-level accuracy in real time is difficult. However, in some situations it is possible to set up a temporary base station and use radio communication. In general, perform iPad RTK surveying where mobile communication (4G/5G) is available at the site.