Solar Power Sites No Longer Need Control Points｜Instant Absolute Coordinates with LRTK

Introduction: Solar Power Projects and Initial Surveying Challenges

On solar power plant construction projects, on-site surveying is indispensable from the planning stage. Accurate survey data enable smooth progress for panel layout planning, pile-driving position determination, and site development planning. However, in practice there are cases where the very first surveying steps unexpectedly consume time and effort. That is the work of installing survey control points to tie the site into a known coordinate system. On the vast land areas typical of solar power plants, this initial surveying preparation often impacts the overall project schedule. This article explains, from a field perspective, the surveying challenges at solar power sites and a solution using the new LRTK technology.

The Real Effort and Cost Structure of Installing Control Points

At a new solar power site, the first requirement is to install control points. In general surveying practice, control points within the survey area are introduced from the Geospatial Information Authority of Japan’s triangulation points or existing electronic reference stations, and those points are used as the origin to set the site-wide coordinate reference. Installing those control points requires specialized surveying personnel and equipment, and incurs the following effort and costs.

• Securing specialized staff and time: To establish control points, surveyors must visit the site and perform distance and angle measurements from known points to new control points using GNSS receivers and total stations. On large solar power sites multiple control points are often needed, so a team of several people may take half a day to several days. Labor costs and per diems directly affect the project budget.

• Equipment and outsourcing costs: High-precision surveying instruments (GNSS receivers and total stations) are expensive; if a company does not own them, rental or outsourcing to a surveying firm is required. For large-area solar projects, requesting control-point surveying from a surveying company incurs significant fees. There is also labor involved in driving and protecting stakes or bolts that serve as control points.

• Maintenance burden: Installed control points are used as reference throughout the construction period. Therefore they must be managed to avoid damage from earthworks or heavy machinery. If a control point is lost, re-surveying becomes necessary, leading to additional costs and schedule delays.

As described, establishing control points involves non-negligible upfront effort and cost. Site personnel must allocate substantial resources to “prepare before surveying,” which becomes a burden at the project start.

Why It Takes Time to Begin Survey Work

As noted, installing control points requires time and personnel, and this can delay the full-scale start of surveying. On solar power sites, before earthworks or pile driving, surveying is needed for staking out positions and understanding the current state. However, the following reasons can prevent smooth initiation of surveying at the start of construction.

• Locating known points and determining coordinates: On a new site, there may be no nearby public known points, so it is necessary first to determine the coordinates of reference points. Even when using GNSS, tens of minutes to hours of observation and post-processing may be required to derive absolute coordinates. This preparatory work can consume the morning of the first day.

• Arranging the surveying team: If a company does not have in-house surveyors, it must arrange for external surveyors to come. Scheduling with specialized vendors and travel time for remote sites add waiting time before actual surveying can start. It is not uncommon for other work to stall while “waiting for surveying.”

• Weather and site conditions: Control-point surveying must be performed under stable conditions to ensure accuracy. Heavy rain or strong winds can increase GNSS errors and force postponement. Solar power sites are often large and undulating, so ensuring lines of sight and safety requires time in preparation.

These factors combine so that even when the team is ready to “start measuring,” actual surveying can still be delayed. This initial time loss compresses the overall schedule and increases labor costs, making it a key issue field teams want to shorten.

Principle of LRTK and How It Obtains Absolute Coordinates Instantly

LRTK has emerged as a technology to lower the barrier to initial surveying. LRTK is a new positioning system that makes traditional RTK-GNSS surveying more user-friendly; its biggest feature is that it can obtain absolute coordinates instantly. Here is a brief explanation of its principle and mechanism.

RTK (real-time kinematic) surveying itself uses a reference station (base) and a rover GNSS receiver; the rover’s position is computed as a relative position to the base by correcting errors, enabling centimeter-level positioning (cm level accuracy (half-inch accuracy)). Typically, the base station has known coordinates, and the rover’s coordinates are computed relative to that base. In other words, if the base station’s coordinates are known, the rover can obtain absolute coordinates, but until the base station’s coordinates are determined, the rover’s results are not absolute.

LRTK solves the task of “providing known coordinates to the base station” by system means rather than by manual work. Specifically, an LRTK terminal (a small GNSS receiver that attaches to a smartphone) receives correction information externally and can compute its own position as a high-precision absolute coordinate in real time. There are two main ways to obtain correction information.

• Network RTK: Correction data are obtained via the Internet from the Geospatial Information Authority of Japan’s electronic reference station network or private GNSS reference station services. This enables high-precision surveying based on surrounding reference station networks anywhere in Japan.

• Satellite-based augmentation service (CLAS): In mountainous areas where mobile signals do not reach, the Quasi-Zenith Satellite System “Michibiki” transmits centimeter-class positioning augmentation signals (CLAS) (cm level accuracy (half-inch accuracy)), which can be received directly. An LRTK terminal compatible with CLAS can obtain high-precision correction information from satellites without relying on terrestrial communication infrastructure.

With these mechanisms, an LRTK terminal can acquire multiple GNSS satellites within several tens of seconds after power-up and, by applying corrections, immediately compute “absolute coordinates in the World Geodetic System.” A dedicated smartphone app displays the obtained latitude, longitude, and height in real time and automatically converts them to plane rectangular coordinate systems (JGD2011/JGD2020). In short, with LRTK you can bring equipment to the site, turn it on, and the location instantly becomes a surveyed coordinate frame.

Why LRTK Makes “No Control Points” Possible

Why does LRTK eliminate the need to install control points on site? The reason lies in the mechanism described above. Traditionally, a local control point was created on site and its coordinates measured to establish the survey basis; with LRTK, that foundation-building step can be omitted.

The correction information received by the LRTK terminal (network RTK or CLAS) is already tied to a public coordinate system. Therefore the coordinates obtained by LRTK are from the start on the same coordinate system as the Geospatial Information Authority’s reference points. For example, coordinates measured by LRTK at any point can be directly compared to coordinates on the design drawings. The intermediate process of establishing local control points, measuring them, and converting to the design coordinate system is unnecessary.

Some sites use their own local coordinate systems, but even in those cases, a simple transformation based on the absolute coordinates obtained via LRTK suffices. LRTK apps also include localization (coordinate transformation) functions, allowing correction for offsets with known points and handling data in any local coordinate system. In any case, it remains far faster to set up surveying with LRTK than to survey new control points from scratch.

In summary, LRTK realizes a “site that can be measured as soon as you arrive.” By eliminating the cumbersome procedure of installing control points, it dramatically speeds up initial surveying and can be a key technology for improving efficiency at solar power sites.

Typical Surveying Uses at Solar Power Sites (Pile Driving / Point-Cloud Scanning / As-Built Management)

With no need for control points and the ability to measure instantly, LRTK can be applied to diverse surveying needs at solar power sites. Here are three representative use cases.

• Positioning for pile driving: When installing piles for panel support structures, accurate staking is required in advance. Traditionally, a surveying team would mark pile centers based on drawings, but with LRTK the construction manager can locate pile positions themselves. Using an AR navigation function that guides the user on the smartphone screen to the set pile coordinates, one can reach the designated position without getting lost even on a vast development site. A single person can confirm and mark pile positions, allowing pile-driving work to proceed without waiting for the surveying team.

• Terrain measurement via point-cloud scanning: 3D surveying (point-cloud data acquisition) is useful for understanding terrain before and after site development or recording the as-built during construction. LRTK works with smartphone-integrated LiDAR scanners or cameras to scan surrounding terrain and structures while walking and obtain high-precision point-cloud data. (In practice, for areas of about 1～2 hectares, mobile scanning can be faster and cheaper than drone surveying in some cases.) Because absolute coordinates are attached to each point in the point cloud, there is no need to align point clouds using separate ground control points. If the point cloud obtained on site is uploaded to the LRTK cloud, the office can view the site’s 3D model and immediately perform distance, area, and volume measurements as needed.

• As-built management and inspection: LRTK is also effective for as-built checks of completed structures such as panel support frames and earthwork slopes. For example, measuring the coordinates of installed piles with LRTK allows comparison with the design pile layout data to check for deviations. Measuring many piles individually is laborious, but with LRTK one person can efficiently measure multiple points, enabling rapid full-count checks. Also, scanning ground heights after earthworks and comparing them with design cross-sections visualizes excesses or shortages in fill/cut volumes. Photo documentation for as-built records has been burdensome, but with the LRTK app, geo-tagged photos are recorded and stored in the cloud with date and location, simplifying report preparation.

Thus, with LRTK adoption, surveying at solar power sites can be streamlined across planning, construction management, and post-construction verification. Losses associated with repeatedly installing control points or stopping machinery to wait for survey teams are eliminated, contributing to smoother overall site progress.

Voices from Practitioners: Benefits of Being Able to Measure Immediately

Construction managers and survey personnel who use LRTK on site cite “the ease of starting surveying immediately upon arrival” as the biggest benefit. One site supervisor noted that previously other work was interrupted while waiting for surveying specialists, but after adopting LRTK he can start necessary measurements immediately with his own smartphone and feels that “the time spent waiting for surveying has become zero.”

Another person said that thanks to LRTK they no longer have to rush morning surveying preparations, making it easier to keep the day’s schedule on track. Especially on solar power sites where pile-driving and inspection points are scattered over wide areas, the ability to move and instantly check a point when the opportunity arises is highly valued. There are comments that “the peace of mind of being able to measure when needed” is significant on site, and LRTK’s responsiveness reduces daily work stress.

From practitioners’ perspectives, the benefits of instant positioning are being realized, and the value of LRTK in enabling the simple ability to “measure whenever you want” is increasingly recognized in the field.

Implementation Effects: Balancing Personnel Reduction, Schedule Shortening, and Accuracy Assurance

The effects expected from implementing LRTK go beyond mere surveying efficiency; they offer multifaceted benefits that contribute to workplace reform on site. Key points are summarized below.

• Personnel reduction (labor saving): Because one-person surveying becomes possible, survey teams that previously required two to three people can be significantly slimmed down. For example, tasks that always required two people for pile-positioning have been handled by one person after LRTK adoption. In the construction industry, where chronic labor shortages are an issue, being able to reassign valuable personnel to other tasks is a major benefit. Reducing the number of times external surveyors are hired also reduces costs.

• Schedule shortening (speed-up): Eliminating time for control point installation and equipment preparation dramatically shortens the lead time from mobilization to completion of surveying. With LRTK, surveying can begin immediately upon arrival on the first day, making it possible to save more than half a day compared with conventional methods. In addition, because point-cloud acquisition and cloud sharing can be done in real time, time lags associated with waiting for survey results before making design or construction decisions are removed. The overall schedule gains flexibility, and the site can respond immediately to sudden surveying needs.

• Accuracy assurance (quality maintenance): Increased speed does not come at the cost of accuracy. LRTK, with a multi-GNSS high-performance receiver, can measure positions with horizontal accuracy on the order of ±1～2 cm (±0.4～0.8 in). This is comparable to conventional large GNSS survey instruments or total stations and is sufficient for controlling errors in solar panel support structure installation. Moreover, data are digitally recorded and shared, reducing human recording errors or misreadings and improving the reliability of survey data.

In summary, LRTK’s implementation delivers the field ideal of “fewer people, faster, and accurate.” Beyond solar power projects, it can be a powerful solution for promoting DX (digital transformation) across civil engineering and construction sites.

Comparison with Other Surveying Methods (Total Station / Drone / Local Base GNSS)

Finally, here is a brief comparison between LRTK and conventional representative surveying methods. Each has strengths, but from the standpoint of practicality at solar power sites, LRTK’s advantages become clear.

• Total station (TS): Optical TS instruments can achieve millimeter-level precision, but they require known control points on site and frequent setup/backsight adjustments for each measurement. Covering large areas requires moving tripods and a team, which is time- and labor-intensive. By contrast, LRTK allows handheld surveying without control points and can provide positioning where GNSS reception is available even in areas with poor visibility. The accuracy is sufficient for pile-driving and as-built checks, so LRTK is well suited to efficiently visiting scattered survey points typical of solar parks.

• Drone surveying: Aerial photogrammetry or LiDAR scanning is effective for large-scale terrain mapping and is used for before-and-after comparisons of solar site development. However, achieving high accuracy with drone surveys requires many ground control points (GCPs) on the ground or an RTK-equipped drone, both of which require preparatory work. Additionally, flight permissions, weather constraints, and data-processing time are hurdles. With LRTK mobile scanning, one or two people can walk the ground and immediately acquire point-cloud data, offering the agility to measure specific areas. For areas up to a few hectares, mobile scanning often yields current point clouds faster and at lower cost than drone surveys.

• GNSS surveying using local base stations: RTK surveying with a local GNSS base station provides stable accuracy regardless of communication conditions. However, preparing and installing the base station equipment and entering known coordinates requires effort. Especially on new sites where base station coordinates are unknown, survey work for the base station is still needed. Network RTK services are an option but incur recurring fees. In contrast, LRTK receives corrections via the network or satellites with a minimal setup of a small terminal and smartphone, so no additional hardware or site installations are required. Initial setup on the first day takes only minutes, and the portable, pocket-size configuration is extremely convenient.

From these comparisons, for surveying needs that are “wide, scattered, and temporary” as on solar power sites, LRTK’s mobility and responsiveness are better suited than conventional methods. Of course, total stations remain effective for ultra-high-precision structural measurements, and drones are advantageous for modeling very large terrain areas in a short time. Nevertheless, LRTK is a well-balanced choice to complement these methods and streamline everyday surveying work.

Conclusion: Make Solar Surveying Lighter, Faster, and More Accurate with LRTK

We have reviewed the challenges of on-site surveying for solar power plants and the solutions that LRTK provides. Longstanding issues such as the effort of installing control points and initial-time losses are being resolved by LRTK’s arrival. As the slogan “no control points and instant absolute coordinates” suggests, bringing only a terminal and a smartphone to the site quickly turns the location into a field-ready surveying environment.

This change makes on-site surveying lighter (labor saving), faster (more efficient), and accurate (quality maintained). For construction managers and survey personnel at solar power sites, LRTK can be a lifesaver that frees them from heavy equipment and cumbersome procedures. Indeed, an era in which anyone can survey with a smartphone in hand is becoming a reality.

If you will be responsible for construction at a solar power plant, consider introducing LRTK for simplified surveying. The ease of entering a site and measuring immediately without worrying about control points is something you will not want to give up once you experience it. Why not leverage LRTK to make solar surveying lighter, faster, and more accurate?