Equipment Needed for Civil Surveying and How to Choose | Comparing the Latest Tools from RTK-GNSS to 3D Scanning

Surveying instruments for civil engineering works are an important investment that determines the quality of construction. Choosing the wrong equipment can lead to reduced measurement accuracy, schedule delays, and increased costs. There are currently various instruments on the market, each with its own characteristics and applications. As a practitioner, selecting the optimal equipment according to the scale and characteristics of the project greatly influences its success. In this article, we explain in detail the main instruments used in civil surveying, their features, and selection criteria. By choosing the right instruments, it is possible to balance measurement accuracy and efficiency, ultimately improving overall construction quality and reducing costs.

Classification and Overview of Surveying Instruments

Equipment used in civil surveying can be broadly classified into three categories. The first is the classical instruments that measure angles and distances. Total stations, theodolites, and transits fall into this category. These have decades of proven performance and are still used at many sites. They are highly reliable and are fundamental instruments widely used in the field. The second is GNSS equipment that uses satellite signals. It uses satellite systems such as GPS, GLONASS, and Galileo to determine positions. The third is non-contact measuring equipment that uses lasers and cameras. This includes laser scanners, drones, and stereo cameras.

There is a complementary relationship among the instruments in each category. GNSS is suitable for wide-area surveys, while conventional instruments are required indoors or in densely forested areas where GNSS signals cannot be received. Laser scanners are effective for capturing detailed shapes, but measuring large areas takes time. In practice, using these instruments appropriately allows for optimal measurement results. Additionally, when introducing new equipment, compatibility with existing instruments and cost-effectiveness should be carefully considered.

There are many factors to consider when selecting surveying equipment: the required accuracy (cm level accuracy (half-inch accuracy) or meter-level (m (ft))), the measurement range (a narrow area or a wide area), the measurement environment (outdoors or indoors, whether there are many trees), whether the work can be completed within the project schedule, the acquisition and operating costs of the equipment, and the skill level required to operate it. These factors must be considered comprehensively to determine the optimal combination of equipment. From a long-term perspective, selecting equipment with use across multiple projects in mind is also important.

Features and Usage of All Stations and Theodolites

Total stations (electronic distance- and angle-measuring instruments) are devices that can measure angles and distances simultaneously and automatically record measurement data to a computer. Compared with traditional theodolites, measurement efficiency has been greatly improved. Accuracy is generally on the order of a few millimeters (a few 0.1 in) to about 1 centimeter (0.4 in), a level suitable for many civil engineering works. Operating a total station requires precise setup of the instrument and aiming technique at the measurement target.

The advantages of total stations are that they can accommodate a variety of surveying environments. Whether indoors or outdoors, measurements can be taken as long as a line of sight is maintained. Because measurement results are obtained as digital data, post-processing is efficient. In addition, the equipment is more affordable compared with laser scanners and drones, making it easier for small companies to adopt. Many contractors have skills in operating total stations, so on-site work is straightforward. The operating procedures are also relatively easy to learn, so the training period for new staff is shorter.

When deploying all stations, the challenges include the need for a certain level of skill to operate the equipment and the time required for measurements. In particular, measuring complex terrain or vast areas requires many observation points and extends the measurement period. Measurements are also susceptible to weather conditions and cannot be carried out during storms. Because the accuracy of instrument setup directly affects measurement accuracy, preparation in the initial stages is important.

Characteristics and Applications of GNSS Receivers and RTK-GNSS Surveying

A GNSS receiver is a device that receives signals from satellites to determine position. Standard GPS accuracy is a few meters (a few ft), but RTK-GNSS (real-time kinematic), which combines correction signals with this, can achieve accuracy of a few centimeters (a few in). RTK-GNSS consists of a base station and a rover, with the base station installed at a known reference point. By wirelessly transmitting correction signals from the base station to the rover, high-precision positioning becomes possible.

The greatest advantage of GNSS equipment is its high measurement efficiency. Whereas conventional total station surveying required multiple operators, GNSS receivers allow measurements to be carried out by a small crew. They are particularly well suited to surveying large areas and are highly effective for large-scale land development and road construction. Because measurement data can be obtained directly in digital form, office work is also streamlined. In addition, the measuring equipment is lightweight and easy to carry, making transport to hard-to-reach locations simple. Because measurement speed is fast, wide-area surveys can be completed in a short time.

One challenge in deploying GNSS equipment is that receiving satellite signals is essential. They cannot be used indoors, inside tunnels, or in densely wooded areas. Also, because installing a base station is necessary, use is limited on projects where a base station cannot be installed. Using multiple satellite positioning systems simultaneously improves the reliability of signal reception, but receivers that support this are more expensive. It should also be considered that accuracy decreases as the distance from the base station increases.

Utilization and Processing Methods of Laser Scanners and Point Cloud Data

A laser scanner is a device that emits laser light and acquires large numbers of three-dimensional coordinates of objects from the reflected light. It is particularly well suited for measuring objects with complex shapes such as terrain, buildings, and bridges. The acquired data are called point clouds and contain millions to tens of millions of points. By processing this point cloud data, detailed topographic maps, orthophotos, and three-dimensional models of buildings can be generated.

The advantage of laser scanners is their ability to perform detailed, high-precision measurements. Detailed measurements that used to take a long time with conventional methods can now be completed in a short time. They can also be used to measure hazardous locations where people cannot take measurements directly, as well as high, hard-to-reach places. Point cloud data can be utilized at every stage of a construction project. In the design phase it provides accurate on-site information, during construction it serves as a record of construction progress, and after completion it can be used for asset management of the structure.

A primary challenge of laser measurement is the high cost of the equipment. Not only the purchase price, but also software for data processing and specialized expertise are required. Processing measurement data demands professional skills, and because it is often outsourced to specialized external contractors, total costs tend to increase. It is also susceptible to weather, with measurement accuracy decreasing in rain or dense fog. Because the equipment is heavy, transporting and setting it up at measurement sites is laborious.

Characteristics and Selection Criteria for Drone Surveying and Leveling Instruments

The technique of deriving the positions of terrain and existing structures from images captured by cameras mounted on drones has rapidly become widespread in recent years. The advantage of drones is their ability to photograph large areas in a short time. Even on slopes where ground surveying by pacing is difficult, or in mountainous areas where line of sight cannot be secured, aerial photography can provide detailed information. By processing and overlapping the captured images, orthophotos (orthorectified images) and three-dimensional point clouds can be generated.

Accuracy of aerial photogrammetry with drones varies greatly depending on flight altitude, camera performance, and processing methods. Using a drone equipped with a high-precision GNSS receiver can achieve accuracies of several centimeters (a few in). In general, accuracies of several tens of centimeters (several tens of in) to about 1 m (3.3 ft) can be obtained, making it suitable for many civil engineering projects. Aerial imaging also offers significant safety advantages. Drones play an important role in surveying hazardous locations such as cliff collapse sites and areas damaged by floods.

One of the challenges when introducing drones is the presence of legal regulations. Flights near airports, flights over densely populated areas, and flights at altitudes exceeding 150 m (492.1 ft) often require permission. They are easily affected by weather, and cannot be flown on windy or rainy days. There are also many operational challenges such as aircraft maintenance, acquiring piloting skills, and permit and authorization procedures. It is also necessary to clarify legal liability.

Accurate measurement of elevations is extremely important in civil engineering work. The level used in leveling is designed so that the line of sight is perfectly horizontal, and it is used to measure the difference in height from a reference point to each location. Levels are highly accurate, and in general measurements can be made with errors on the order of a few millimeters (a few 0.01 in) to about 1 centimeter (0.4 in). Leveling is carried out continuously from the start of construction through to its completion.

Comprehensive Decision Criteria and Long-Term Considerations for Equipment Selection

To select the surveying equipment best suited for a construction project, multiple factors must be considered comprehensively. First is the scale of the project. On small construction sites, total station surveying can often suffice. On the other hand, for land development projects covering several hundred hectares, the adoption of GNSS surveying or drone surveying should be considered. Second is the required accuracy. High accuracy is necessary for positioning structures, whereas lower accuracy may be acceptable for topographic mapping.

The measurement environment is also an important factor in decision-making. In outdoor settings where line of sight can be maintained, total station surveying is effective. Conversely, in densely wooded areas, laser scanners or drones may be more efficient. GNSS cannot be used for measurements inside tunnels, so conventional instruments are essential. The project schedule must also be considered; when a large volume of measurements must be completed within a limited timeframe, introducing equipment capable of high-speed measurement is indispensable.

From a cost perspective, you need to consider not only the purchase price of equipment but also the total operating costs and labor expenses. Even if you introduce expensive equipment, total costs can decrease if labor costs are reduced through efficiency gains. Conversely, even if you choose inexpensive equipment, the total cost can end up higher if longer measurement periods increase labor costs. Making use of existing knowledge and skills is also important. By selecting equipment that staff are already proficient with, you can expect shorter implementation times and fewer measurement errors.

Strategies for Combining Multiple Devices and Utilizing New Technologies

In practice, optimal measurement results are often obtained not with a single instrument but by combining multiple instruments. For example, using GNSS to measure positions over wide areas and a laser scanner to take high-precision measurements of detailed parts is an effective strategy; additionally, comparing and cross‑validating measurement results from different instruments improves the reliability of measurement accuracy.

There is also a phased approach to equipment-combination strategies. In the basic design stage, use low-cost drone surveys to capture the existing conditions, and in the detailed design stage, perform detailed measurements of the necessary areas with total station surveys. Proceeding in phases like this enables optimization of overall costs. Also, conducting the same measurements at different times using different methods can improve the reliability of the data.

Compatibility of instruments is also important. If measurement data formats differ, subsequent processing becomes more complicated. When integrating data measured by different instruments, it is necessary to standardize the coordinate system and convert data formats. Therefore, when planning to introduce multiple instruments, it is important to verify data compatibility in advance.

iPhone-mounted GNSS high-precision positioning devices like LRTK are further expanding the range of surveying equipment options. They offer the potential to achieve high-precision surveying, which previously required costly dedicated instruments, in a more economical way. By integrating such new technologies into existing equipment systems, a more efficient and flexible surveying framework can be realized.

Adoption and Implementation Strategies for New Technologies

New technologies are being rapidly introduced in the field of surveying equipment. Improvements in drone accuracy, image recognition using AI technologies, and data sharing via the cloud are bringing greater efficiency to construction work. However, when introducing new technologies, it is essential to thoroughly verify their compatibility with existing quality control systems. The introduction of new devices can make traditional verification methods unusable. For example, iPhone-mounted GNSS high-precision positioning devices such as LRTK are changing the conventional concept of surveying instruments. If the accuracy provided by these devices is equivalent to that of traditional instruments, they could revolutionize surveying operations. By leveraging widely available devices such as smartphones, the barrier to surveying could be lowered, potentially enabling high-precision measurements at more sites. However, in the early stages of introduction, it is important to fully understand the accuracy characteristics of these devices and to carry out comparative verification with conventional methods. Staff training is indispensable to the successful adoption of new technologies. Understanding not only how to operate new equipment but also its underlying principles and limitations enables appropriate use. In addition, planning in advance how to integrate new technologies into existing workflows allows for smooth implementation. To maximize the efficiency benefits offered by new equipment, it is often necessary not merely to introduce devices but to reexamine the entire construction process.

Comprehensive Comparison of Measurement Instruments and a Practical Selection Guide

Understanding the characteristics of various surveying instruments is a fundamental responsibility of field personnel. Total station surveying provides high precision and can be used in many environments. GNSS surveying excels at wide-area measurements. Laser scanners are ideal for measuring complex shapes. Drone surveying enables rapid measurements with a wide field of view. Levels achieve high accuracy in elevation measurements. To use these instruments effectively, it is important to accurately understand each instrument’s characteristics and select the most appropriate one according to site conditions. Combining multiple instruments can achieve both efficiency and accuracy.

Long-term Perspective and Investment Strategy in Equipment Selection

Investments in surveying equipment should be considered not with a single project in mind but with the expectation of use across multiple projects over several years. Even equipment with a high initial cost can dramatically reduce the cost per project when used across multiple projects over a long period. At the same time, it is necessary to consider the pace of technological advancement in the equipment. Because new technologies may emerge within a few years, it is important to assume how many years the equipment will remain suitable and make investment decisions accordingly. In addition, a manufacturer's support system, the availability and quality of repair services, and the availability of spare parts are important factors when planning for long-term use. Products from domestic manufacturers tend to have well-established support systems, but even for overseas products, purchasing through a reliable distributor makes it relatively easy to respond if problems arise.

Summary and Comprehensive Guide to Selecting Civil Surveying Equipment

Selecting surveying instruments for civil engineering is not merely a matter of comparing catalogs; it requires a comprehensive judgment that considers the entire construction project. By choosing the optimal equipment, improvements in measurement accuracy, work efficiency, and reductions in total cost can be achieved simultaneously. When selecting equipment, it is important to evaluate many factors comprehensively, such as the characteristics of the project, site conditions, required accuracy, feasibility of completion within the schedule, overall costs, and the difficulty of acquiring operational skills. Strategies that combine multiple instruments have also become common in modern civil engineering surveying. With the introduction of new technologies, the overall measurement accuracy and efficiency of the industry are expected to improve further. If innovative devices like LRTK become widespread, high-precision surveying will become possible at more sites, leading to an overall improvement in the quality of civil engineering works.

The Future of Civil Surveying Equipment and New Options

The field of civil surveying instruments is rapidly evolving. From conventional mechanical devices to digitized equipment, and further to advanced instruments equipped with AI technologies, this evolution is proceeding in stages. In future civil surveying, a hybrid measurement system that flexibly combines multiple technologies is expected to become the norm. Smartphone-based high-precision GNSS positioning devices like LRTK have the potential to further democratize surveying equipment. As these new technologies spread, more companies will be able to carry out high-precision surveys, raising the overall technical level of the industry and ultimately bringing benefits to society as a whole. The role of practitioners who contribute to improving the quality of civil engineering works through equipment selection will only become more important.

By deepening their understanding of the many instruments that support civil surveying, practitioners’ decision-making will improve, enabling appropriate choices on site. When practitioners accurately understand the characteristics of equipment, they can select and utilize it properly, contributing to the overall improvement of construction quality. By appropriately combining multiple instruments, more efficient and accurate measurements can be achieved, directly enhancing the value of the entire project.