No Need to Install Control Points at Solar Power Sites｜Instant Absolute Coordinates with LRTK

Introduction: Solar PV Projects and Initial Surveying Challenges

Site surveying is indispensable in solar power plant construction projects from the planning stage. Accurate survey data are essential for panel layout planning, determining pile-driving positions, and considering earthwork plans, enabling smooth project progress. However, in practice, the “initial steps” of surveying can take unexpected time and effort. That step is installing survey control points, tying the site into a known coordinate system. On large solar power sites, this initial survey preparation often impacts the overall project schedule. This article explains, from a site perspective, the surveying challenges at solar power sites and a solution using the new LRTK technology.

Practical Effort and Cost Structure of Installing Control Points

At a new solar power site, the first task is to establish control points. In typical surveying, control points are introduced into the survey area based on triangulation points from the Geospatial Information Authority of Japan or existing electronic reference stations, and the site-wide coordinate reference is defined from there. Installing these control points requires skilled surveyors and equipment, generating the following workload and costs:

• Securing specialist staff and time: Installing control points requires surveyors to go on-site and use GNSS survey receivers or total stations to measure distances and angles from known points to new control points. On large solar park sites, multiple control points may be needed, and a team of several people may take half a day to several days. Labor costs and daily allowances directly affect the project budget.

• Equipment and outsourcing costs: High-precision surveying equipment (GNSS receivers and total stations) is expensive; if not owned in-house, rentals or outsourcing to surveying companies are required. For large-area solar projects, commissioning control point surveys from a surveying company incurs significant fees. There is also the time and effort to drive and protect stakes or markers used as control points.

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

Thus, installing control points involves non-negligible effort and cost at the initial stage. For site personnel, substantial resources must be allocated to “preparations before surveying,” burdening project kick-off.

Why It Takes Time to Start Surveying Work

As described above, installing control points requires time and manpower, and this becomes a cause of delaying the actual start of full-scale surveying. On solar power sites, position-setting and site condition assessment by surveying are needed before earthworks and pile-driving. However, for the following reasons, surveying does not always start smoothly at the beginning of construction:

• Finding known points and determining coordinates: At a new site, there may be no nearby official known points (public control points), so first you must identify a reference location’s coordinates. Even when using GNSS, you must observe for tens of minutes to hours or perform post-processing to derive absolute coordinates. This preparatory work can consume the morning of the first day.

• Arranging the survey team: If you don’t have survey specialists in-house, you must arrange for external surveyors to come. Scheduling with specialist contractors and travel time for distant sites add waiting time before actual surveying can begin. It’s common on sites for other tasks to be stalled while awaiting surveying.

• Weather and site conditions: Control point surveying requires stable conditions to ensure accuracy. Heavy rain or strong winds can increase GNSS errors and lead to postponement. Solar parks are often large with varied terrain, so ensuring line-of-sight and safety also takes time in preparation.

These factors combine so that even when the team is ready to “start measuring,” it can still take time to begin actual surveying. This initial time loss pressures the overall schedule and increases labor costs, so reducing it is a key concern on-site.

Principle of LRTK and How It Obtains Absolute Coordinates

LRTK has emerged as a technology that lowers the barrier to the initial steps of surveying. LRTK is a positioning system that makes conventional RTK-GNSS surveying more convenient; its main feature is that it enables instant acquisition of absolute coordinates. Let’s briefly explain its principle and mechanism.

RTK (Real-Time Kinematic) surveying uses a fixed base station and a rover GNSS receiver, correcting errors from the difference between the two to achieve centimeter-level positioning. Typically, the base station is given an accurate coordinate, and the rover’s position is calculated relative to that base. In other words, if the base station’s coordinates are known, the rover’s coordinates are absolute; conversely, until the base station’s coordinates are determined, the rover’s results are not absolute.

LRTK resolves the task of “providing known coordinates to the base station” by system means rather than manual work. Specifically, an LRTK terminal (a small GNSS receiver that can be mounted on a smartphone) receives correction information from external sources, allowing it to compute its own position as a high-precision absolute coordinate in real time. There are two main methods to obtain correction information:

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

• Satellite-based augmentation service (CLAS): In mountainous or remote areas without mobile coverage, the quasi-zenith satellite system Michibiki broadcasts centimeter-level correction signals (CLAS). LRTK terminals compatible with CLAS can directly receive high-precision correction information from satellites without relying on terrestrial communications.

With these mechanisms, an LRTK terminal can lock onto multiple GNSS satellites within tens of seconds after startup and, by applying correction information, instantly compute absolute coordinates in the World Geodetic System. A dedicated smartphone app displays the acquired latitude, longitude, and altitude in real time and automatically converts them to the plane rectangular coordinate system (JGD2011/JGD2020). In short, with LRTK you can bring the equipment on site, power it on, and the site immediately becomes a surveyable coordinate space.

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 would be established and its coordinates determined to form the surveying basis, but LRTK lets you skip that foundation-building process.

The correction data received by an LRTK terminal (network RTK or CLAS) are already tied to public coordinate systems. Therefore, coordinates obtained via LRTK are from the outset in the same coordinate system as the Geospatial Information Authority’s control points. For example, you can directly compare coordinates measured by LRTK at any point with coordinates on design drawings. The intermediate process of installing a new control point on site, measuring it, and converting it into the design coordinate system is not required.

Some sites use their own local coordinate systems, but even in such cases you can handle them by applying simple transformations from the absolute coordinates obtained with LRTK. LRTK apps also include localization (coordinate transformation) functions, allowing you to correct offsets to existing known points and handle data in any local coordinate system. In any case, setting up a survey framework on site takes far less time than surveying control points from scratch.

In summary, LRTK makes a “site that’s ready to measure as soon as you arrive.” By omitting the cumbersome procedures for establishing control points, LRTK dramatically speeds up the survey start, making it a key efficiency technology for solar power sites.

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

By making surveying possible without control points, LRTK can be applied to various surveying needs at solar power sites. Here are three representative use cases and how they are applied.

• Positioning for pile driving: When installing piles that support solar panel racks, accurate pre-marking of pile positions is required. Traditionally, a survey team would mark pile centers based on drawings, but with LRTK the construction manager can identify pile positions themselves. Using an “AR navigation” feature that guides the user to the set pile coordinates on the smartphone screen, workers can reach designated positions even on large reclaimed sites. A single person can confirm and mark pile positions, allowing pile-driving to proceed without waiting for a survey crew.

• Topographic measurement by point cloud scanning: 3D surveying (point cloud capture) is effective for understanding terrain before and after site formation or recording site conditions during construction. LRTK integrates with smartphone-built-in LiDAR scanners or cameras to scan surrounding terrain and structures while walking, producing high-accuracy point cloud data. (In practice, for areas around 1–2 hectares, point cloud acquisition can sometimes be done faster and more cheaply than drone surveys.) Because each point in the acquired point cloud is tagged with absolute coordinates, there is no need to reference the point cloud to ground control points separately. Uploading the collected point cloud to the LRTK cloud lets office staff view the site’s 3D model remotely and immediately perform distance, area, and volume measurements as needed.

• As-built management and verification: LRTK is also powerful for as-built management—verifying whether installed components such as panel support racks and formed slopes match the design. For example, measuring the coordinates of installed piles with LRTK allows you to compare them with the design pile layout to check for deviations. Measuring many piles one by one is laborious, but with LRTK one person can efficiently measure them all, enabling full-count checks in a short time. Scanning post-formation ground elevations and comparing them with design cross-sections visualizes excesses or deficits in cut-and-fill. Photo documentation, which used to be cumbersome, can be simplified: coordinate-tagged photos recorded by the LRTK app are stored in the cloud with date/time and location, making report compilation easier.

As shown above, LRTK can streamline surveying at solar power sites from planning through construction management to post-completion verification. It eliminates losses from repeatedly installing control points for each survey or stopping machinery while waiting for survey crews, contributing to smoother on-site operations.

Voices from Practitioners: Benefits of Being Able to Start Measuring Immediately

Construction managers and surveyors using LRTK on site report that the greatest benefit is the “ease of being able to start surveying immediately upon arrival.” One site supervisor said that previously other tasks were interrupted while waiting for specialist surveyors, but after adopting LRTK he can start the necessary measurements instantly with his own smartphone and felt that “the time spent waiting for surveying has become zero.”

Another practitioner noted that they are no longer pressed by morning surveying preparations and can proceed with the day’s schedule as planned. Especially on sites where pile-driving and checkpoints are scattered across a wide area, the ability to move and instantly check any point as needed is highly valued. There is also feedback that “the peace of mind of being able to measure immediately when needed” is significant for on-site teams, and LRTK’s responsiveness reduces daily work stress.

Thus, practitioner feedback confirms the benefits of instant positioning, and LRTK’s value—enabling the simple fact of “measuring when you want to”—is increasingly recognized on-site.

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

The expected effects of introducing LRTK go beyond mere surveying efficiency. There are multifaceted benefits that can transform how a site operates. Key points include:

• Reduced personnel (labor savings): Single-person surveying becomes possible, allowing substantial slimming of survey teams that previously required 2–3 people. For example, tasks that used to require two people for pile position setting have been handled by one after LRTK adoption. In an industry chronically short of labor, redirecting valuable personnel to other tasks is a major benefit. Reducing the need to commission external survey contractors also cuts costs.

• Shortened schedules (speed-up): Eliminating time for control point installation and equipment setup dramatically shortens lead time from mobilization to survey completion. With LRTK, surveying can begin immediately upon site arrival, potentially saving half a day or more compared to conventional methods. Moreover, because point cloud acquisition and cloud sharing can be performed in real time, the time lag between obtaining survey results and making design/construction decisions disappears. The overall schedule gains slack, and sites can flexibly respond to sudden surveying needs.

• Accuracy assurance (quality maintenance): Increased speed does not come at the cost of accuracy. LRTK, using multi-GNSS capable high-performance receivers, can measure positions with horizontal accuracy around ±1–2 cm. This is comparable to surveys using conventional large GNSS machines or total stations and is sufficient for managing installation tolerances of solar panel racks. Because data are recorded and shared digitally, human recording errors and misreadings are reduced, improving the reliability of survey data.

In short, LRTK delivers the on-site ideal of “fewer people, faster, and still accurate.” It is a strong solution for promoting DX (digital transformation) in civil engineering and construction beyond solar projects.

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

Finally, here is a brief comparison of LRTK with conventional representative surveying methods. Each has strengths, but LRTK’s advantage in practicality for solar power sites becomes clear.

• Total Station (TS): Optical TSs can measure with millimeter accuracy, but they require known control points and frequent set-up and backsight adjustments for each measurement. Measuring over a wide area requires moving tripods and teams, consuming manpower and time. LRTK, by contrast, enables control-point-free handheld surveying and can provide positioning even where line-of-sight is poor as long as GNSS reception is available. Its accuracy is sufficient for pile-driving and as-built checks, making LRTK more suitable for efficiently visiting dispersed measurement points in a solar park.

• Drone surveying: Aerial photogrammetry or LiDAR is effective for large-scale terrain capture and is used for pre- and post-formation comparisons. However, obtaining high accuracy with drone surveys requires installing many ground control points (GCPs) or using RTK-equipped drones, which involves preparatory work. There are also hurdles such as flight permission procedures, weather constraints, and data processing time. With LRTK-based mobile scanning, one or two people can walk the ground and obtain point clouds immediately, enabling targeted measurement of needed areas. For areas up to several hectares, LRTK mobile scanning can often provide current point clouds faster and at lower cost than drones.

• GNSS surveying using local base stations: RTK surveying with an on-site GNSS base station offers stable accuracy independent of communications, but it requires setting up and preparing base station equipment and entering known coordinates—tasks that take time. For new sites with unknown control point coordinates, base station surveying still requires preliminary surveys. Using network RTK services avoids some of this but incurs recurring fees. LRTK, in contrast, requires only a small terminal and a smartphone to receive corrections via the network or satellites, so no additional hardware or site-installed equipment is necessary. First-day setup takes only minutes, and the portable, pocket-sized configuration is overwhelmingly convenient.

From this comparison, for surveying needs that are “wide-area, dispersed, and time-limited” as in solar power sites, LRTK’s mobility and responsiveness are better suited than conventional methods. Of course, total stations remain useful for ultra-high-precision structural measurements, and drones are advantageous for modeling very large areas quickly. Nevertheless, as a tool to complement those methods and streamline routine surveying tasks, LRTK is a well-balanced choice.

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

We have reviewed the surveying challenges at solar power sites and the solutions LRTK offers. Traditional concerns such as the effort of installing control points and initial time loss are being resolved by LRTK’s emergence. As the slogan “no control points, instant absolute coordinates” implies, with only a terminal and a smartphone on site you can instantly turn the location into a survey field.

This shift makes site surveying lighter (labor-saving), faster (more efficient), and more accurate (quality maintained). For construction managers and surveyors in the solar industry, LRTK can be seen as the savior of simple surveying, freeing them from heavy equipment and complex preparations. In practice, the era when anyone can survey with a smartphone in hand is becoming a reality.

If you will be responsible for a solar power construction site, consider adopting LRTK for simple surveying. The ease of entering a site and measuring immediately, without worrying about control points, is something you won’t want to give up once you experience it. Why not use LRTK to make your solar surveys lighter, faster, and more accurate?