Immediate Earthwork Volume Calculation: Improve Earthwork Management Efficiency with High-Precision GNSS Surveying

Table of Contents

• Introduction

• Traditional Challenges in Earthwork Volume Calculation

• What Is High-Precision GNSS Surveying

• Immediate Volume Calculation with GNSS Surveying

• Why High-Precision GNSS Surveying Streamlines Earthwork Management

• ICT Adoption on Construction Sites and Advances in Surveying Technology

• Recommendation: Simple Surveying with LRTK

• FAQ

Introduction

In civil engineering and construction sites, accurately determining earthwork quantities — specifically the volume of soil and excavated material — is critically important. For example, errors in volume estimates can lead to mistakes in arranging the number of dump trucks or deviations in surplus soil disposal plans, seriously affecting site operations. Misjudging how much soil has been excavated and removed, or how much has been brought in and placed as fill, can cause major deviations in project cost and schedule. Volume calculations are directly tied to cost estimation, progress management, and as-built (shape) control, and are essential for proper schedule and cost control. However, traditional earthwork volume calculations are time-consuming and labor-intensive, making it difficult to grasp volumes on site immediately. This article focuses on high-precision GNSS surveying — a technology attracting attention as an enabler of immediate volume calculation — and introduces the latest methods that can improve earthwork management efficiency.

Traditional Challenges in Earthwork Volume Calculation

First, let us organize the challenges inherent in traditional earthwork volume calculation. Generally, calculating earthwork requires understanding the ground surface before and after construction and deriving excavation and fill volumes from the differences. Traditionally, surveyors used instruments such as total stations and levels to establish control points and acquire numerous measurement points on the terrain. Then, back at the office, they created a surface model with specialized software and calculated volumes by comparing with the design surface or using cross-section calculations.

However, this process had several inefficiencies. First, surveying work requires time and manpower. On large sites, obtaining measurement points can take several personnel and multiple days. Second, there is a time lag before calculation results are available. Even at best, volume is determined the next day after surveying, so it is not possible to confirm results instantly on site. For example, you cannot judge on the spot whether “today’s excavation reached the planned volume,” leading to risks of recognizing shortages or excesses later and having to redo work. On site, problems such as “there was more leftover soil than expected” or “backfill material ran short” sometimes surface later, and one reason is the inability to measure volumes in real time. Third, many situations have had to rely on rough estimates based on experience and intuition, leaving issues with accuracy and reliability. Estimating volumes from the number of dump trucks or using ad hoc on-site fixes can result in discrepancies in final measured quantities.

Thus, traditional methods of volume calculation were time-consuming and hindered real-time earthwork management. What is needed is a surveying technology that enables rapid measurement and calculation on site.

What Is High-Precision GNSS Surveying

GNSS surveying has rapidly spread in the civil engineering and construction sectors in recent years. GNSS stands for Global Navigation Satellite System and uses satellites such as GPS, GLONASS, and Japan’s QZSS (Michibiki) to determine positions. Consumer devices like smartphones or car navigation systems can obtain position information, but their errors are on the order of several meters. To achieve the high precision required for surveying and construction management, high-precision GNSS positioning methods such as RTK (Real Time Kinematic) are used.

In high-precision GNSS surveying, a base station (reference) and a rover (mobile receiver) simultaneously observe satellite signals and determine positions to centimeter-level accuracy by using the differences between them. The base station is installed at a known location and sends correction information that accounts for distance and common error factors to the rover. By applying these corrections, the rover can calculate its accurate coordinates in real time. This is called RTK surveying. In other words, where normal GPS might have errors of several meters, RTK surveying can reduce errors to a few centimeters.

RTK surveying generally yields horizontal and vertical errors on the order of a few centimeters. In practice, instances have been confirmed on civil engineering sites of horizontal 2–3 cm (0.8–1.2 in) and vertical 3–4 cm (1.2–1.6 in) accuracy, which is orders of magnitude more accurate than conventional GPS positioning.

An advantage of RTK surveying is that it can be realized without preparing a dedicated base station by using national or regional continuously operating reference station networks and correction services. Various solutions are available, such as network RTK correction data distributed via the Internet and Japan’s QZSS-provided Centimeter Level Augmentation Service (CLAS). These make stable high-precision positioning possible even in mountainous or extensive sites.

RTK-GNSS used to be expensive and required specialized knowledge, but recent miniaturization and cost reductions in receivers have made them increasingly accessible to field technicians themselves. Pocket-sized GNSS terminals that integrate antenna and receiver have appeared, creating an environment where one person can easily perform high-precision surveying. This technological innovation is accelerating the immediate calculation of earthwork volumes.

Immediate Volume Calculation with GNSS Surveying

By utilizing high-precision GNSS surveying, earthwork volume calculations that previously took time can be dramatically sped up. Specifically, you can acquire survey data directly on site and calculate volumes there.

For example, if you obtain terrain data before and after excavation using an RTK-capable GNSS receiver, you can instantly calculate volumes from the difference between the pre-excavation ground model and the post-excavation ground model. By linking the GNSS receiver with a tablet or smartphone, software that performs volume calculations can display volumes in real time as measurement points are acquired. Processes that used to require returning to the office and processing on a PC can now be completed on site. For instance, calculating volumes for a development site on the order of 10,000 square meters (107,639 ft^2) that would have taken several days with traditional methods can, in many cases, produce results the same day with high-precision GNSS surveying.

Because high-precision GNSS surveying can measure wide areas in a short time, it becomes practical to frequently check volumes during work or at the end of each day. For example, you can immediately verify the day’s fill or backfill volume at the end of each working day and reflect that in the next day’s plan. This allows you to quickly detect issues such as “insufficient soil removal” or “required fill height not reached” and take corrective action promptly.

Furthermore, GNSS survey data are stored digitally, so it is easy to upload them to the cloud from the site, share them with stakeholders, and rapidly prepare reports. Earthwork information that a site supervisor once reported based on experience can now be presented in real time as objective data. By enabling immediate volume calculation, GNSS surveying significantly improves the speed and accuracy of on-site decision-making.

Why High-Precision GNSS Surveying Streamlines Earthwork Management

Immediate volume calculation via high-precision GNSS surveying brings various benefits to general earthwork management. Below are the main efficiency points.

• Rapid progress management: Knowing volumes immediately enables accurate day-to-day progress tracking. Deviations from plan can be corrected on the spot, enabling efficient schedule management.

• Prevention of rework and excess work: Early detection of excavation or fill shortages and excesses prevents overwork or redoing tasks, directly reducing costs and shortening the schedule.

• Labor saving and countermeasure for workforce shortages: GNSS surveying lets one person cover a wide area, allowing surveying to continue even on sites with manpower shortages. Compared with traditional multi-person surveying, labor is saved and sites without resident surveyors can still be handled.

• Improved safety: GNSS allows measurement from a distance on steep or irregular terrain. The need to enter hazardous areas for surveying is reduced, lowering the risk of occupational accidents.

• Promotion of data utilization: Digitized high-precision terrain data can be used not only for volume calculation but also for as-built management and quality records. Reusing once-acquired 3D data reduces duplicated work and facilitates integrated site management using ICT.

• Improved reliability through objective data: Quantities based on GNSS-acquired survey data make reporting and consultation with clients and authorities smoother. Explanations not relying on subjective judgment or estimates increase transparency and trust in site management.

Thus, introducing high-precision GNSS surveying not only speeds up volume calculation but also comprehensively raises the efficiency and quality of site operations.

ICT Adoption on Construction Sites and Advances in Surveying Technology

Within initiatives such as the Ministry of Land, Infrastructure, Transport and Tourism’s i-Construction and the construction industry’s DX (digital transformation), advances in surveying technology play an important role. As site digitization progresses with photogrammetry using drones and point-cloud measurement with 3D laser scanners, GNSS surveying stands out for its ease of use and immediacy, achieving rapid adoption on sites.

Where surveying was traditionally entrusted to specialized surveyors, more and more site technicians now handle the latest surveying gadgets themselves to obtain necessary data. The miniaturization and lightening of high-precision GNSS receivers have created an environment where surveying can be done anytime while carrying equipment on site. For example, using an RTK-capable drone, you can create a precise terrain model from aerial photographs and use it for volume calculation, while an RTK-GNSS rover allows a one-person survey that used to require several people to be completed in a short time.

In addition, the Ministry’s “ICT earthwork” policy has increased the number of sites encouraged to use 3D design and as-built management data. The 3D data obtained by high-precision GNSS surveying are attracting attention as a means to satisfy these ICT construction requirements. In an industry chronically short of labor, such technological innovation is a driving force for dramatically improving productivity. Especially in earthwork, managing everything from surveying to construction with digital data reduces human error and enables smooth information sharing. High-precision survey data are becoming the “common language” of the site, used from construction planning through to as-built inspection. Introducing GNSS surveying on the site can be considered one of the foundational technologies for promoting site ICT adoption.

Recommendation: Simple Surveying with LRTK

Even if you want to enjoy the benefits of high-precision GNSS surveying, you may worry that it is too specialized or difficult to use on site. Finally, we introduce the LRTK series, a high-precision GNSS surveying system notable for being easy for anyone to handle.

LRTK is a compact GNSS surveying device developed with the goal of making RTK positioning “anytime, anywhere, for anyone.” The compact terminal integrates an antenna, GNSS receiver, battery, and communication module; by wirelessly connecting to a smartphone or tablet, it achieves centimeter-level positioning without complex setup. Because it does not require a fixed base station or complicated wiring like traditional systems, you can bring it to the site and start surveying immediately.

For example, the model called “LRTK Phone” uses a receiver weighing only about 125 g attached to a smartphone. Even such a lightweight device supports network RTK and QZSS CLAS, enabling high-precision surveying by a single operator. Carrying one per person and quickly measuring to check volumes as needed is a realistic mode of operation. Pricing is designed to be more accessible than traditional surveying equipment, and it is expected to be used regardless of site scale.

By leveraging LRTK, surveying work that was previously outsourced to specialists can be easily performed in-house. If high-precision GNSS surveying becomes part of everyday operations, you can expect not only immediate volume calculation but also increased efficiency and sophistication for all on-site measurement tasks. If you are considering incorporating GNSS surveying at your sites, starting with an easy solution such as the LRTK series is recommended. Use the latest technology to elevate your company’s earthwork management to the next level. In fact, LRTK has already been adopted by local governments and public agencies and is being used in a wide range of applications such as disaster-site surveying and infrastructure inspection. For more details on the LRTK series, please visit the [LRTK official site](https://www.lrtk.lefixea.com/).

FAQ

Q: What does “calculate volumes immediately” mean? A: It means being able to compute the volume of soil on site at that moment. Traditionally, survey data had to be taken back to the office for volume calculation, which caused delays; with GNSS surveying, excavation and fill volumes can be calculated immediately on site.

Q: How reliable is the accuracy of GNSS surveying? A: With RTK GNSS surveying, horizontal and vertical errors are on the order of a few centimeters. It can achieve accuracy comparable to that obtained by experienced surveyors using a total station, and is therefore sufficiently reliable for earthwork volume management.

Q: What advantages does GNSS surveying have over traditional surveying methods? A: The greatest advantages are efficiency and immediacy. GNSS surveying lets you walk with the device and rapidly measure many points over a wide area, obtaining coordinates in real time. There is no need to worry about line-of-sight or deploying multiple personnel as with total stations. Also, because data are automatically recorded digitally, post-processing effort is greatly reduced.

Q: Can staff without specialized knowledge operate high-precision GNSS surveying equipment? A: Yes. Modern GNSS surveying equipment has improved usability and is designed so that non-specialist personnel can operate it after basic training. Products like LRTK include simple operation apps that allow surveying with the feel of using a smartphone. They are practical as one of the ICT tools used on site.

Q: I’m concerned about the cost of introducing GNSS surveying equipment; is it expensive? A: High-precision GNSS surveying equipment used to be very expensive, but technological progress has lowered prices and made adoption easier. Once introduced, you can expect economic benefits from reduced outsourcing costs and improved work efficiency. Cost-effective devices like LRTK have appeared, offering benefits that justify investment from small sites to large projects.

Q: Which is better for volume calculation: GNSS surveying or drone photogrammetry? A: It depends on site conditions. Drone photogrammetry is effective when you want to measure a large area densely, but it has constraints such as obtaining flight permissions and weather dependence. GNSS surveying, on the other hand, can be performed on the ground “anytime” by setting up the receiver and excels in real-time capability. The two are complementary: drones are ideal for broad-area overviews, while GNSS is ideal for daily progress management. Both are powerful technologies that support ICT-based construction promoted by the Ministry, so it is important to make use of their strengths.

Q: Is GNSS surveying possible in mountainous areas outside mobile coverage? A: Network RTK normally requires mobile communication to receive correction data. However, receivers compatible with QZSS CLAS (Centimeter Level Augmentation Service) can achieve centimeter-level positioning from satellite augmentation signals alone, even without mobile coverage. In other words, high-precision GNSS surveying can be continued in mountainous areas, remote islands, and other regions where base station signals or mobile coverage do not reach.