Dramatically Streamline Plan Drawing at Civil Engineering Sites! Achieve High Accuracy with Smartphone Surveying and RTK

Introduction: Why Is Plan Drawing a Challenge on Site?

In civil engineering and infrastructure maintenance, creating plan drawings for construction planning and as-built records is indispensable. However, producing plan drawings on site traditionally required a great deal of time and effort. Surveying to obtain position coordinates and then manually drafting drawings based on those coordinates… these tasks require skilled technique, and with a worsening labor shortage they have become a major challenge. Creating drawings that accurately reflect existing conditions requires measuring a large number of points, and conventional methods are inefficient for this. This article focuses on smartphone-based surveying and high-precision positioning using RTK (Real-Time Kinematic) as the latest technologies to solve the headaches of plan drawing. We will concretely introduce how this new approach, which supports on-site DX (digital transformation), dramatically improves the efficiency of plan drawing.

Traditional Plan-Drawing Methods and Their Limits

In the past, creating plan drawings involved time-consuming procedures as a matter of course. A typical example was a two-person team using surveying instruments such as a total station: one person operated the instrument while the other stood at a distant point holding a staff (rod) to mark survey points. Each point was observed, and later the coordinates were connected in CAD software to create the plan drawing. However, this method had several limitations.

• Human and time burden: Two-person operations require time for setup and takedown, and when the area or number of points is large it can take an entire day. Because surveying at each site takes a long time, coordinating with other tasks and delays to the whole schedule were common.

• Accuracy and omissions: Since measurements were taken by humans point by point, there was a risk of human error (misreading or recording mistakes). If missed points were discovered later, re-surveying was required, which is inefficient. Also, the density of obtainable points was limited, making it difficult to fully capture complex terrain or structural shapes.

• Equipment constraints: Conventional surveying instruments are large and heavy, and setting up tripods and equipment took time. To ensure accuracy they needed to be stably mounted, which reduced mobility. They were difficult for newcomers to operate, and troubleshooting required specialized knowledge.

Because of these problems, it became normal for plan drawing on site to take considerable time. However, in recent years the construction industry has faced severe labor shortages and an aging workforce, increasing the demand for labor-saving and efficiency improvements to operate sites with limited personnel. Initiatives aimed at productivity improvement, such as *i-Construction* advocated by the Ministry of Land, Infrastructure, Transport and Tourism, have begun, and the need to move away from conventional “human-dependent surveying” is growing. Digital technologies that enable one-person surveying (one-man surveying) are attracting attention.

A New Surveying Approach Using Smartphones and RTK

To address the issues above, a new surveying approach combining smartphones and RTK-GNSS has emerged. This involves attaching a compact high-precision GNSS receiver to a smartphone, turning the phone into an advanced surveying instrument. Traditionally, RTK surveying equipment capable of centimeter-level positioning accuracy was very expensive, large, and required expert knowledge to operate. But with the smartphone surveying system “LRTK,” those capabilities are realized in palm-sized devices and an app.

First, RTK is a technology that takes differential data between a base station (reference point) and a rover to correct satellite positioning errors in real time. This RTK method can improve satellite positioning accuracy to within several centimeters (a few inches). The receiver used with LRTK is compact enough to integrate with a smartphone, weighing only about 150–170 g and with a thickness of approximately 1 cm (0.4 in); it connects to the smartphone via Bluetooth or Lightning. Attach it to the back of the smartphone and launch the app, and anyone can immediately begin high-precision positioning. No dedicated tripod or large equipment is required, and the entire system fits in a pocket.

What’s even more notable is that LRTK can use correction information available throughout Japan. Within a cellular coverage area, it can obtain correction data for network RTK (Ntrip method) using the Geospatial Information Authority of Japan’s Continuously Operating Reference Stations. Even at sites outside mobile coverage, it can directly receive free high-precision augmentation signals (CLAS) broadcast from the Quasi-Zenith Satellite System (Michibiki), allowing positioning accuracy to be maintained in offline environments. In other words, from urban areas to remote mountains, real-time centimeter-level positioning can be achieved by a single person. The simplicity of starting surveying by simply preparing a smartphone and receiver and pressing a button—without specialized knowledge—is a major advantage.

Using a smartphone transforms surveying styles. By combining the smartphone’s high-performance camera or LiDAR sensor with RTK positioning, it is even possible to perform a point-cloud scan of the surroundings while walking. Simply moving through the site with the smartphone held up automatically captures the surrounding terrain and structures, producing 3D data (point clouds) comprising countless survey points. Each point in the acquired point cloud is tagged with absolute coordinates (coordinates in the global geodetic system) by RTK, so it is immediately clear on the map where the measured data is located. Because high-density 3D surveying has become easy, detailed as-built measurements that previously required laser scanner equipment or multiple personnel can now be done with a single smartphone.

From Point Clouds to Plan Drawings: XYZ/LAS Output and Drawing Workflow

So how do you create plan drawings from the point cloud data obtained with a smartphone and RTK? The key is the procedure for converting three-dimensional information into two-dimensional drawings. Data acquired with LRTK is stored in the cloud and can be downloaded or processed directly on cloud services as needed. A typical drawing workflow is as follows.

• Point cloud inspection: Open the point cloud acquired on site with dedicated software or a cloud viewer. With LRTK you can check the point cloud model in a 3D viewer in a web browser.

• Conversion to plan view: Switch the point cloud to an overhead view (an orthographic-like projection). By removing unnecessary height information, the ground surface and structural outlines can be understood in plan.

• Tracing shapes: Trace the lines you want to represent on the plan—such as road edges and structural shapes—by drawing lines over the point cloud. LRTK’s cloud service allows drawing lines and shapes on the point cloud data via mouse operations, enabling the preliminary drafting of topographic maps and plan drawings.

• Exporting drawing data: The lines created for the plan can be exported as CAD drawings in DXF format and other formats. These can be downloaded for finishing in CAD software or used directly as deliverables.

As described above, once the point cloud is acquired, the subsequent drawing work is dramatically streamlined. Because the point cloud contains all points on site, concerns about drawing errors caused by “missed measurements” are reduced. Also, data acquired can be exported from the LRTK app in XYZ format (a text file of coordinate lists) or LAS format (a common binary point-cloud file). XYZ text files make it easy to check each point’s coordinates in spreadsheet software or import them into other systems, while LAS files can be loaded directly into dedicated point-cloud processing software or GIS for use. You can create terrain models, draw contour lines, or extract cross sections as needed, making analysis beyond plan drawings simple. In short, field-acquired data can be directly linked to digital drawing creation and quantity calculations.

How Work Changes with Cloud Use and Data Sharing

The true value of smartphone + RTK surveying is further enhanced by integration with cloud services. With LRTK, measurement data is saved on the smartphone and can be uploaded to the cloud with one tap. Because data can be shared immediately after measurement on site, by the time the surveyor returns to the office the results can already be delivered to supervisors, colleagues, or clients (such as municipal officials).

On the LRTK Web service in the cloud, measured points and photos are plotted on a map, and 3D point clouds can be viewed online. Recipients do not need to install dedicated software; they can view and inspect the data by accessing a URL from a browser. For example, remote site supervisors or municipal staff can meet while viewing the same surveying results in real time.

The LRTK cloud also includes convenient measurement functions. You can measure distances, areas, and volumes on uploaded point cloud data. Complex calculations can be executed with the click of a button, so values that were previously difficult to measure on site—such as the length at the top of a slope or the volume of an embankment—can be computed immediately. You can overlay multiple point-cloud datasets and CAD drawings, making it easy to compare as-built point clouds with design drawings to verify construction deviations. Centralized cloud data management allows all stakeholders to access the latest information and makes it easy to manage and utilize survey histories.

By leveraging the cloud in this way, a person surveying alone can still work while sharing information with others. Faster data sharing accelerates decision-making, enabling collaboration across the boundary between site and office. Compared to the old practice of exchanging paper drawings or USB drives, information coordination becomes far faster and more reliable.

Site Case Studies: Accurate Drawings Possible Even with One-Person Surveying

So, what level of results can be achieved with one-person surveying using a smartphone and RTK? Here are case studies that demonstrate the effects.

At one earthwork site, a terrain survey that previously required 2–3 people and more than half a day was completed by a single person using LRTK in about one hour. By walking the site and scanning the surroundings with a smartphone, high-density point cloud data was acquired in a short time. While checking the point cloud in the cloud service, important structures and boundary lines were traced and a detailed plan drawing was produced the same day. Simultaneously, volumes of fill and cut were calculated, and the differences in earthwork quantities relative to the design drawings were computed immediately. This case showed that surveying and drafting can be greatly streamlined while reducing manpower.

In another case, about 200 cubic meters of embankment were scanned with a smartphone in one go, and a plan drawing of the as-built condition was created from the point cloud. Traditionally, many cross-sections would have been measured to calculate volume and drawings would have been produced manually, but with LRTK the task was completed quickly. Because the acquired point clouds have absolute coordinates, data collected later in additional surveys can be easily combined and reflected in the drawings as needed. This means that data for missed areas can be supplemented and integrated later, minimizing the loss that used to occur when “re-surveying on another day” was required.

The benefits of one-person surveying go beyond reduced labor costs. The following secondary effects have also been observed.

• Improved efficiency and flexibility: Small teams can cover wide areas, and surveying can be performed whenever needed, reducing waiting times in the schedule. Tasks that used to depend on the surveying team’s schedule can now be done nimbly at the individual’s discretion.

• Improved safety: Surveys finish quickly, and because workers are not dispersed, it is easier to check each other’s safety. One person can operate the smartphone while remaining aware of the surroundings and move agilely even on sites with heavy machinery.

• Improved data quality: Reliance on human visual judgment is reduced, and drawings are produced based on machine-measured data, reducing subjective judgment errors. Drawing from comprehensive point-cloud information yields more accurate and persuasive plans.

In practice, data acquired with LRTK reaches a level of accuracy comparable to conventional surveys using total stations and the like. Comparisons with control points and existing drawings have shown results within a few centimeters (a few inches) of error, providing sufficient quality for operational use. The fact that high-precision drawings that don’t seem like they were produced by a single person can be obtained has the potential to significantly change on-site norms.

Conclusion: The Future of Drawing Creation with Digital Surveying

Digital surveying technology that combines smartphone surveying and RTK is opening the future of plan drawing in the civil engineering industry. Tasks that traditionally demanded great effort and time are being streamlined and accelerated by digital tools, enabling smart construction that is less dependent on personnel. With surveying and drawing creation seamlessly connected, current conditions can be reflected in drawings in near real time. This not only directly shortens construction periods and reduces costs but also accelerates on-site decision-making cycles, contributing to improved quality and safety.

Another advantage of handling digital data is that accumulated survey data can be useful for other projects and future maintenance. High-precision point clouds and coordinate data obtained once can be compared during later renovation planning or used to analyze long-term changes, becoming valuable assets. Long-term data utilization that was difficult with paper drawings and fragmentary records becomes easy with digital surveying.

Of course, many sites still require conventional two-dimensional deliverables (plan drawings and longitudinal/cross sections) as final outputs. However, the process of creating those drawings is undeniably evolving. Instead of humans manually picking points and drawing lines, computers are increasingly semi-automatically generating drawings from precise point-cloud data. Going forward, combining AI and automation technologies will likely enable even faster and more accurate drawing creation.

The field of plan drawing is truly at the heart of a “surveying revolution” driven by digital technology.

Appendix: A Quick Surveying Primer to Start with LRTK

If this article has piqued your interest in the innovative surveying using smartphones and RTK, here are a few simple pointers for getting started with LRTK.

What you need to prepare is simple—just these three items:

• A high-performance smartphone (a device that can run the RTK-compatible app)

• A compact LRTK GNSS receiver (to attach to the smartphone)

• The LRTK dedicated app (install on the smartphone and register for the cloud service)

Once setup is complete, all you do on site is walk to the locations you want to measure while holding the smartphone. For example, to measure boundary points or structural positions, move to the point with the smartphone and tap the on-screen button to record the coordinate of that location. For wide-area measurements, as mentioned earlier, simply hold up the smartphone and walk and the surrounding point-cloud scan is performed automatically.

After measurement, upload data to the cloud with a single click from the app and check and share results on the spot.

Even first-time users don’t need complicated settings; the operation is intuitive. Basic usage can be learned with just a few minutes of training, so experts are not required. The burden of carrying heavy equipment and spending long hours is eliminated, and the convenience of quick measurements with a single smartphone whenever needed is a major attraction. Try surveying with LRTK in a nearby field to experience its convenience and accuracy for yourself.

Even alone, with just a smartphone, you can start today. Why not take a step toward digitalization at your site with simple surveying using LRTK? ```markdown