Easy on-site earthwork volume management with just a smartphone! High-accuracy surveying anyone can do

Table of Contents

• Why volume calculations are needed on site

• Conventional earthwork calculation methods and issues

• Volume calculation evolving with digital technology

• How to calculate earthwork volume with just a smartphone

• How high-accuracy surveying anyone can do works

• Benefits of using smartphone surveying

• Recommendation for simple surveying with LRTK

• FAQ

Why volume calculations are needed on site

On construction sites, earthwork volume management (volume calculation) associated with excavation and embankment is extremely important. For example, the amount of ground to be excavated for foundation work (excavation), the amount of fill for development (embankment), and the amount of surplus soil to be disposed of (leftover soil) all must be accurately understood. These earthwork volumes are measured in cubic meters (m³) and are fundamental data directly tied to project budgets and progress management.

However, calculating volumes on actual sites is not easy. Terrain is not flat and is complex; the shapes of mounds and excavated areas are irregular. There are often differences between the quantities estimated in design and the actual quantities on site, which can result in needing to excavate more than anticipated or incurring extra costs for disposing of leftover soil or bringing in additional fill. To prevent such unexpected issues, it is important to perform volume calculations on site as needed and manage earthwork amounts.

Conventional earthwork calculation methods and issues

Traditionally, calculating earthwork volumes on site required time and manpower. Typically, surveyors measure ground elevations using total stations (TS) or levels and calculate volumes from terrain data before and after excavation or embankment. This method requires at least two people for surveying work (to operate the instrument and hold the prism or staff), and because the collected data must be imported into a PC and processed with specialized software, it takes time to obtain results. On small sites, where specialized surveying equipment may not be available, measurements are sometimes done on an ad hoc basis using shovels and tape measures to estimate length, width, and depth, and then volumes are approximated. However, such manual visual estimation and hand calculations tend to produce large errors when terrain is complex.

Furthermore, conventional earthwork calculations are difficult to perform frequently. Because surveying requires specialized knowledge and ties up personnel, it is unrealistic to measure earthwork in detail every day or each time. As a result, accurate amounts of leftover soil or progress may not be known during earthworks, and problems such as discovering too much excavation only after the fact can occur. In short, conventional methods take too much time and effort, making real-time on-site earthwork management difficult.

Volume calculation evolving with digital technology

In recent years, the introduction of digital technology has greatly advanced on-site volume calculation. Initiatives such as the Ministry of Land, Infrastructure, Transport and Tourism’s i-Construction have popularized methods that use drone aerial photography and 3D laser scanners to measure terrain and calculate earthwork volumes with software. Drone photogrammetry captures the whole site from above to create point clouds or 3D models and calculate embankment and excavation volumes. High-precision laser scanners can acquire terrain point cloud data with millimeter-level precision. With these ICT applications, as-built shapes (post-construction shapes) can be measured more efficiently than before.

In addition to these advanced devices, attention is also turning to the familiar device of the smartphone. Attempts to measure earthwork volumes easily using smartphone cameras and AR (augmented reality) technology are progressing, and major construction companies are developing field apps. For example, some AR apps allow you to place a virtual surveying pole (marker) on the smartphone screen, specify the extent of embankment or excavation, and compute the volume on the spot. In experiments comparing smartphone measurements with high-precision laser scanners, measurement errors using smartphones were reported to be within about 3–5%. Smartphone surveying thus demonstrates sufficiently practical accuracy and is being recognized as a new productivity-improving technology, with registrations in systems such as the Ministry’s New Technology Information System (NETIS).

How to calculate earthwork volume with just a smartphone

So how exactly do you measure on-site earthwork volume with only a smartphone? The basic flow is as follows. No specialized instruments are required—just a smartphone and a compatible surveying app. Volume calculation is completed in three simple steps:

• Select the surveying mode: Launch the app and choose the mode according to the target to be measured (e.g., embankment volume, excavation volume, area measurement). The app guides you through the necessary steps according to the measurement type.

• Specify the area / scan: While viewing the site through the smartphone camera, place virtual markers (poles or pins) on the target area. For example, to measure embankment volume, tap the screen to mark the four corners of the embankment’s base and several points on the embankment top. Some apps automatically scan the terrain and acquire point cloud data simply by walking around while pointing the camera.

• Check the volume result on the spot: The volume of the specified area is displayed immediately on the smartphone screen. The earthwork amount (in m³) is calculated, and sectional views or height information can be checked as needed. Results can be saved as images or overlaid on photos for record-keeping.

As described above, on-site volume measurement can be completed with a single smartphone. There is no need to wait for PC data processing to obtain results; you can grasp the earthwork amount such as “○○ m³” on the spot, which is a major advantage. Of course, smartphone-alone measurement is positioned as a form of simplified surveying and can be affected by environmental conditions. For example, AR tracking accuracy may decrease in dark surroundings or when ground patterns are sparse. Therefore, while it may not achieve strict laboratory-level precision, it is useful enough for everyday site management and rough as-built shape verification.

How high-accuracy surveying anyone can do works

Although smartphones make measurement easy, there are needs for “higher accuracy” or “use for official measurements.” This is where high-accuracy surveying using satellite positioning technology called RTK-GNSS comes in. RTK (Real Time Kinematic) is a technique that applies correction information to GNSS data (such as GPS) to achieve centimeter-level accuracy in real time. Traditionally, RTK surveying required expensive dedicated GNSS receivers and base stations, but recently products have emerged that provide this capability as compact devices that can be used with smartphones.

By using a dedicated GNSS receiver attached to a smartphone, the positional error of the smartphone’s location information can be dramatically reduced. Typical built-in smartphone GPS accuracy is on the order of several meters, but with an RTK-compatible device, horizontal position accuracy can improve to ±1–2 cm (±0.4–0.8 in), and vertical accuracy can be around ±3 cm (±1.2 in). Because elevation is measured accurately, reliable vertical differences essential for volume calculations can be obtained. These RTK-GNSS devices are pocket-sized, weighing only a few hundred grams, and can be used wirelessly with a smartphone. A dedicated app on the smartphone, combined with this device, is designed to allow anyone to perform high-accuracy positioning and surveying easily.

The operation in high-accuracy smartphone surveying is itself simple. Bring the smartphone to the point to be measured and press the app button to record the latitude, longitude, and elevation of that point. The app performs complex calculations in the background, automatically plotting and saving measured points on a map. By combining the smartphone camera function, 3D point cloud scanning of terrain is also possible. Because RTK keeps the device’s position accurate at all times, walking while scanning causes little distortion in the point cloud, and all acquired points are assigned global coordinates (absolute coordinates based on geodetic systems). In short, we have entered an era where millimeter-level precision can be handled by relying on devices, even without expert knowledge.

Benefits of using smartphone surveying

Simple surveying technology using smartphones brings many benefits to on-site earthwork management. The main advantages are summarized below:

• Labor savings and countermeasures for manpower shortages: Smartphone surveying can be completed by one person. Tasks that previously required two or more people can be performed solo, enabling efficient earthwork management even on understaffed sites.

• Immediate real-time results: Since results are displayed immediately after measurement, decisions can be made on the spot. Excesses or shortages of soil can be identified instantly, allowing quick course corrections or truck arrangements.

• Cost reduction: The need for special surveying equipment or outsourcing to surveyors can be reduced. Because smartphones and apps are relatively low-cost, significant reductions in surveying expenses and time can be achieved.

• High-frequency measurements possible: Because measurement is easy, you can frequently measure earthwork amounts in line with daily progress. Measurements can be taken as often as daily if needed, so the current site situation can always be quantified and deviations from the plan can be detected early.

• Improved safety: Surveying can be done without approaching hazardous areas. For example, deep excavations or high embankments can be measured remotely with a smartphone camera, reducing the risk of workers entering unstable ground. Short measurement times also minimize interruptions to site work, contributing to overall safety management.

• Data accumulation and sharing: Earthwork data can be recorded digitally, making it easy to review later or share with other personnel. With cloud-enabled systems, site-collected data can be viewed from the office immediately. If saved together with photos or drawings, visualizing earthwork makes it easier for all stakeholders to understand the situation.

Thus, smartphone surveying enhances site productivity and safety and facilitates smoother communication. It is a powerful tool for promoting DX (digital transformation) in civil engineering.

Recommendation for simple surveying with LRTK

One solution that maximizes the convenience and accuracy of smartphone surveying described above is LRTK. LRTK (pronounced 'el-are-tee-kay') is a modern simple surveying system that attaches a small RTK-GNSS receiver to a smartphone, dramatically improving earthwork management on site. By attaching this device to a smartphone, centimeter-level positioning that previously required large equipment becomes possible, turning the smartphone into a high-accuracy surveying instrument. Weighing approximately 125 g and compact for easy carrying, with a built-in battery, it does not get in the way on site. It can be attached to a dedicated smartphone case with one touch, making it easy to take out and start surveying when needed.

With the LRTK app, everything from position coordinate measurement to earthwork calculation and 3D surveying via point cloud scanning can be completed on a single smartphone. Acquired data can be uploaded to the cloud, allowing office staff to check site status remotely. For example, scan the terrain with LRTK to obtain current point cloud data and overlay it on the design 3D model in the cloud to instantly calculate volume differences between design and actual conditions. Advanced surveying and as-built management that used to rely on experts can be performed accurately by anyone in a short time with LRTK.

LRTK is also designed to be affordable, making it increasingly possible for each field staff member to carry one device. It realizes a daily routine in which you pull a universal surveying tool from your pocket, measure when needed, and ascertain earthwork volumes on the spot. Smartphone surveying with LRTK is a reliable ally that dramatically improves on-site efficiency, including earthwork management. If you are interested, try this new surveying experience once to feel its ease and accuracy.

FAQ

Q: How accurate are volumes measured with a smartphone? A: When using only smartphone AR surveying apps, accuracy varies with conditions but is generally within a few percent. Comparisons with high-precision laser scanners have reported differences around 3–5%. While it is simplified surveying, it is sufficiently accurate for everyday construction management. For stricter accuracy requirements, combining with RTK-compatible devices can achieve centimeter-level accuracy.

Q: What equipment or smartphones are required to measure earthwork volume? A: Basically, many apps run on recent high-performance smartphones. Devices such as iPhone or iPad with strong AR capabilities measure particularly smoothly, and devices with LiDAR sensors can provide more stable measurements. For higher accuracy, prepare an RTK-GNSS receiver (for example, a smartphone-attachable device like LRTK). Attaching such a device to your smartphone lets you use high-accuracy positioning data that a smartphone alone cannot provide.

Q: Can it be used without specialist knowledge or surveying qualifications? A: Yes. Smartphone surveying apps and systems like LRTK are designed to be usable by beginners. Operations proceed by following on-screen instructions, so no special surveying skills are required. Tasks that used to be left to surveyors can be handled easily on site by anyone. However, official surveying work for submission to public authorities may require qualified personnel, so smartphone surveying is best considered for internal site management and daily control.

Q: How does smartphone surveying differ from drone surveying? A: Drone surveying can capture wide areas at once and is suitable for large-scale development or forest terrain surveys. It requires flight permissions and piloting skills and is more affected by weather. Smartphone surveying’s biggest advantage is ease of use and is effective on small to mid-size sites or in environments where drones cannot fly, such as indoors or inside tunnels. Smartphones also require less preparation time and can be used immediately when needed. Depending on the use case, using drones and smartphones selectively or together to complement each other allows more efficient site measurement.

Q: Can data measured with a smartphone be used as official as-built quantities? A: Currently, smartphone simplified surveying data is mainly used for construction management and internal verification. For official as-built records in public works, surveying that follows established standards (e.g., fixed surveying or measurements witnessed by supervisory personnel) may be required. Nevertheless, data obtained by smartphone surveying serves as objective evidence, useful for sharing situations among stakeholders or as references for later precise surveying. As technological reliability improves, smartphone methods may become accepted as official measurement techniques in the future.

Q: What scale or area can be measured at once? A: With smartphone-alone AR surveying, depending on the app, you can typically measure an area of roughly several hundred to several thousand square meters at once. For example, one app has reported capability to measure embankments of about 1000 m² (equivalent to 30 m (98.4 ft) × 30 m (98.4 ft)) at once. For larger sites, you can divide the area and measure in sections, then merge the data. High-accuracy smartphone surveying like LRTK has successfully scanned large earthworks exceeding 200 m³. For even larger terrain, it is realistic to combine drone aerial surveying or terrestrial laser scanning. Choose the appropriate mix of smartphone surveying and other measurement methods according to site scale.