Complete with a Single Smartphone! A New Era of Mega-Solar Surveying Without Large Equipment

In mega-solar (large-scale solar power) projects, surveying vast sites is indispensable. Traditionally, this has required considerable time and labor using manpower and large surveying instruments.

However, in recent years, innovative surveying methods that can be completed with a single smartphone have begun to emerge. This article reviews the traditional challenges and background of mega-solar surveying, explains the latest trends in smartphone surveying that promote labor reduction and DX, and examines the innovation of RTK (real-time kinematic) technology. It also introduces the potential of smartphone-based point cloud scanning and AR (augmented reality) displays and describes efficiency gains through cloud integration. Finally, we propose the introduction of a smartphone surveying solution using LRTK. The new era of high-precision surveying completed with a smartphone is now imminent, and its impact is steadily reaching mega-solar survey sites.

Traditional Challenges and Background of Mega-Solar Surveying

The construction of mega-solar facilities requires vast land areas proportional to generation capacity. It is generally said that installing 1 MW of equipment requires about 1–2 hectares (10,000–20,000 m²). In other words, mega-solar plans of several MW can cover tens of hectares, equivalent to multiple soccer fields. In addition, shadow simulations due to surrounding terrain and trees are important for mega-solar. To maximize generation efficiency, it is necessary to accurately estimate the effects of shading, and for that purpose precise survey data that captures site-wide elevation differences and obstacle positions is indispensable.

For surveying such large sites, traditional methods used multiple personnel including surveyors, and instruments such as a transit (tripod-mounted optical surveying instrument) or GNSS receivers to measure each terrain elevation point and boundary. Covering a wide site often required at least two people and sometimes more than a full day, and from preparation to pack-up it involved enormous time and effort. In mountainous or hilly terrain, the physical burden on surveyors walking around is significant, and work among fallen trees or dense undergrowth can be hazardous. Furthermore, manual surveying is always accompanied by the risk of human error (misreading numbers, failing to record data, etc.), and mistakes can lead to re-surveying or redesign work.

Mega-solar planning sites are often located in rural undeveloped land or former forest areas where transport and communications infrastructure are limited, and repeated site visits for surveying increase costs. Efficiently obtaining accurate surveying data has therefore been a major issue for shortening project schedules and managing costs in mega-solar projects. In recent years, aerial surveying using drones has also emerged, enabling wider-area measurement in shorter time than before. However, drone operation requires compliance with aviation laws and specialized skills, and is affected by weather, so it is not yet a universally easy-to-use method.

The Need for Labor Reduction and DX in Surveying

Amid a severe labor shortage and aging of skilled workers across the construction and civil engineering industries, surveying sites are no exception. Numerous veteran surveyors are retiring, making it increasingly difficult to continue work that relies on experience in the traditional way. At the same time, more precise survey data than ever before is required on site, and how to efficiently carry out surveying with limited personnel has become a major challenge.

Against this backdrop, DX (digital transformation) of surveying to reduce labor and improve productivity has become urgent. The Ministry of Land, Infrastructure, Transport and Tourism’s promotion of "i-Construction" advocates “efficient surveying with fewer people and less time” and “improving on-site productivity,” accelerating surveying innovation using digital technologies. Particularly noteworthy is a new approach that leverages satellite technologies such as RTK-GNSS (real-time kinematic positioning) to the extent that surveying can be completed by a single person. Also called one-person surveying, this method is expected to be a trump card that can simultaneously resolve labor shortages and improve surveying accuracy. Employing the latest GNSS technology, even inexperienced personnel can survey wide areas in a short time, and the resulting accuracy can be equivalent to or better than traditional methods. What was once thought a pipe dream—one-person surveying—is finally becoming a reality in the field.

The Innovation of RTK Surveying with Smartphones

RTK-based high-precision positioning has long been used in surveying, but traditionally it required expensive dedicated GNSS receivers and base station equipment. Full-scale RTK surveying—setting up an antenna on a tripod as a base station and operating it together with a rover—often required investments of several million yen and specialized knowledge, making it the domain of a limited number of specialized surveying firms.

What has made RTK surveying accessible to anyone with a single smartphone is the recent emergence of smartphone-compatible ultra-compact RTK-GNSS devices. By attaching a receiver weighing only a few hundred grams to a smartphone or tablet, an everyday mobile device is transformed into a centimeter-level accuracy (cm level accuracy (half-inch accuracy)) surveying instrument. There is no need to carry tripods and heavy equipment; you can take out your smartphone on site and start measuring immediately. Tasks that were previously divided among multiple people can now be performed quickly and accurately by a single person using smartphone surveying.

The innovation of smartphone RTK surveying lies in achieving both accuracy and ease of use. Built-in smartphone GPS typically has errors of several meters, but by using RTK correction information those errors can be reduced to a few centimeters. For example, correction data can be obtained over the Internet from the nationwide network of GNSS reference stations (continuously operating reference stations), or centimeter-class augmentation signals (CLAS) from the Quasi-Zenith Satellite System Michibiki can be received directly, enabling real-time high-precision positioning regardless of location. This makes smartphone positioning sufficiently accurate for situations requiring high precision, such as terrain surveying and boundary confirmation.

Moreover, the simple configuration of smartphone plus a small RTK device significantly reduces introduction costs. Compared to conventional high-precision surveying equipment, prices are orders of magnitude more affordable, making it realistic to equip multiple field staff with one device each. If it becomes a tool that anyone can pick up and use, it will be a revolutionary improvement directly linked to strengthening surveying capabilities on site.

The Expanding Potential of Smartphone Surveying with Point Cloud Scanning and AR

Surveying with smartphones is not limited to measuring point coordinates. By utilizing smartphone-integrated LiDAR scanners and high-performance cameras, it has become easy to capture 3D point cloud data of the site. For example, a surveyor can simply walk around the site with a smartphone in hand to scan surrounding terrain and structures into dense point clouds. The captured point cloud data can be assigned accurate absolute coordinates (latitude, longitude, elevation) via RTK, allowing immediate use as an as-built site model. You can instantly calculate terrain undulations and earthwork volumes, or import the point cloud into CAD for drafting. Additionally, features that record the photo’s location and orientation when taking pictures with the smartphone camera can be used to see at a glance on a map where and in which direction a photo was taken, which helps detailed recording and sharing of site conditions.

Even more revolutionary is the smartphone AR (augmented reality) display capability. By overlaying point cloud models or design position information obtained from surveying onto the smartphone camera view, virtual objects can be projected into the real space. For example, visualizing the planned solar panel layout or pile-driving positions on the actual ground makes it possible to intuitively share the completed image on site or to perform precise stake-out alone. Traditionally, a surveyor and an assistant had to cooperate to stake out positions, but following smartphone AR guidance allows one person to set stakes without an assistant, contributing to labor reduction. With RTK’s high-precision positioning, AR objects align with real-world coordinates without positional offsets. In this way, smartphone surveying provides unprecedented value by enabling on-site data to be used in an immediately visible form.

Surveying, Recording, and Sharing Completed via Smartphone and Cloud Integration

A major feature of smartphone surveying is the ability to instantly link field-acquired data to the cloud. Coordinates measured and photos/memo information taken with a dedicated app are automatically uploaded to the cloud on the spot. Survey points and photos are plotted on cloud-based maps, and colleagues in the office can check site conditions in real time from a web browser. Measurement results can be downloaded in prescribed formats such as CSV, PDF, and SIMA, allowing immediate use for CAD drawing creation or reporting. Also, issuing a shareable link from the cloud system and sending it to stakeholders makes it easy to share the latest data with clients and partner companies.

By instantly digitizing and sharing field survey data, the time previously spent on post-survey data organization and communication can be greatly reduced. With surveying, uploading to the cloud, and sharing completed on site, there is no need to write in paper field books and bring them back, enabling seamless linkage between field and office. Managers and clients can grasp site conditions remotely, so progress checks and instructions can be given without traveling to the site. This real-time visualization of the field is a mechanism that strongly supports the DX of surveying work.

On-Site Adoption Examples and Perceived Benefits

Actual sites that have adopted smartphone surveying report efficiency and labor-saving effects not seen before. At one mega-solar development site, land surveying that previously required three people and two days was completed by one person with a single smartphone in half a day, reducing outsourcing costs to surveying companies. At another site, the ability to share high-precision point cloud data on the same day enabled design change decisions to be made the next day, directly shortening the construction schedule. Based on such examples, the main benefits brought by smartphone surveying are summarized below:

• Significant time reduction in surveying work – Surveying vast sites can be completed far more quickly than before. Surveys that previously took days have in some cases been completed within hours by leveraging smartphones and RTK technology. Shorter surveying time enables earlier start of subsequent design and construction phases, shortening the project lead time.

• Reduced personnel burden and cost savings through labor reduction – Because surveying can be performed with minimal personnel, site staffing plans gain flexibility. Tasks that previously required two to three people can be completed by one, reducing labor costs and outsourcing fees to surveying companies. Also, even if experienced surveyors are scarce, staff familiar with smartphones can handle the work, which helps with personnel procurement.

• Improved safety and reduced physical burden – Since only lightweight smartphone equipment is needed, the physical burden on surveyors in rough or steep terrain is reduced, enabling safer work. A lightweight style such as surveying with a helmet-mounted smartphone that leaves both hands free becomes possible, minimizing the number of people entering unstable areas and reducing the risk of secondary accidents.

• High-precision data and improved quality – RTK precision positioning and point cloud scanning technology enable more accurate and comprehensive capture of subtle terrain undulations and obstacle positions than before. Reduced human error makes surveying mistakes less likely, helping suppress rework. The resulting high-density 3D data visualizes site details that conventional 2D drawings might miss, improving design and schedule planning accuracy.

• Faster data sharing and decision-making – Measured data can be uploaded to the cloud on site and shared with stakeholders, smoothing information flow between field and office. This allows verification of survey results and consideration of design changes within the same day, accelerating on-site decision-making. Real-time understanding of the as-built condition helps achieve well-coordinated construction with minimal backtracking.

• Ease of introduction and operation – Smartphone surveying uses familiar smartphones, making the operation intuitive. It can be introduced on site without special qualifications or long training, lowering the barrier for team-wide adoption. This ease promotes penetration on sites and broadens the range of survey data utilization.

Proposal for Introducing a Smartphone Surveying Solution Using LRTK

LRTK is a next-generation surveying solution using smartphones. Developed by a startup from the Tokyo Institute of Technology, it is a smartphone-mounted high-precision GNSS receiver that, when attached to a smartphone, achieves positioning accuracy of 1-2 cm (0.4-0.8 in). It is an all-in-one solution that covers functions required for on-site surveying with a single smartphone: centimeter-precision positioning (cm level accuracy (half-inch accuracy)) by RTK, point cloud scanning using the smartphone’s LiDAR, AR displays without positional offset, and cloud-based data sharing. Tasks that previously required combining multiple devices and software can be performed seamlessly on a single platform with LRTK.

Introducing LRTK to mega-solar surveying enables one person to efficiently complete tasks from terrain surveying of vast sites to stake-out and as-built management. By breaking away from traditional methods that relied on heavy equipment and veteran surveyors, smartphone surveying that anyone can handle can dramatically accelerate on-site DX. LRTK is already being used across a variety of fields such as construction, civil engineering, agriculture, disaster prevention, and infrastructure management, and its effectiveness is becoming proven. As the key to realizing the new era of “complete with a single smartphone,” LRTK is poised to be a powerful partner for mega-solar developers. Advanced companies have already begun adopting smartphone surveying, improving productivity and competitiveness. The use of such new technologies will become an essential element in future mega-solar projects. Please consider smartphone surveying as an option and bring the next-generation surveying style to your sites.