RTK for Rapid Topographic Surveys (Terrain Surveying): Tips to Capture Many Points in Less Time

Table of Contents

• The benefits of introducing RTK in terrain surveying

• 7 tips to speed up RTK surveying

• Simple surveying with LRTK: start high-precision positioning with a smartphone

• FAQ

Introduction

Surveying tasks on construction sites—from as-built/topographic surveys (so-called “topo”) to as-built verification and stakeout/layout—require significant time and manpower across many workflows. When measuring many points over a large site, traditional surveys using total stations or levels often required multiple people and sometimes took many days. Recently, however, RTK positioning (Real-Time Kinematic) has attracted attention as a technology to streamline such surveying tasks. The Ministry of Land, Infrastructure, Transport and Tourism is also promoting the use of RTK surveying as an ICT technology through initiatives like i-Construction, and RTK is becoming a key technology for digital transformation on construction sites. RTK is a technique that uses high-precision GNSS (satellite positioning) to correct errors between a base station (reference station) and a rover in real time based on distance, enabling immediate acquisition of coordinates with errors suppressed to several centimeters (several in). This allows topographic surveys, which traditionally required two people to set up instruments and maintain line-of-sight, to be carried out efficiently by a single person simply by walking around with an RTK receiver.

Introducing RTK surveying drastically shortens the time required for as-built topographic surveys. For example, in one demonstration, ICT construction (use of RTK surveying and drone photogrammetry) reduced the number of days for initial road construction surveys from an average of 17.7 days to 2.7 days—a reduction of about 70%. In another case, an as-built survey of about 50 points that used to take two people half a day was completed by one person performing continuous measurements with RTK in a few hours. Of course, results vary with site reception conditions and working conditions, but RTK can potentially compress the effort for topographic surveying to a fraction of traditional time. In this way, RTK fundamentally shortens surveying process times and directly contributes to overall construction efficiency.

This article explains key points for performing topographic (as-built) surveys faster using RTK. We summarize practical “tips” that effectively shorten work time, and conclude by introducing simple surveying using smartphone-based RTK solutions—LRTK.

The benefits of introducing RTK in terrain surveying

Large-area topographic surveys require obtaining coordinates for many points. Traditional methods required time for repositioning total stations and transferring elevations with levels, and moving between survey points and relocating equipment took time. Surveys also generally required two or more people, and the larger the site, the greater the labor and time burden.

Introducing RTK positioning greatly reduces such effort. Because RTK can directly position in absolute coordinates without being constrained by line-of-sight or local survey references, points can be observed continuously one after another. Once a base station is set up (or a network RTK service is used), a surveyor can simply walk around the site with a rover receiver and measure key terrain points one after another. Eliminating interruptions due to equipment relocation allows a large number of points to be acquired in a short time once surveying begins. Moreover, because RTK provides coordinate values in real time, data can be checked immediately on site to verify that nothing has been missed. The entire workflow can be handled by one person, reducing labor and dramatically improving surveying productivity. RTK also allows multiple rovers to connect to a single base station simultaneously and perform parallel surveying. On large sites, increasing personnel and receivers to observe simultaneously can achieve major schedule reductions that were difficult with conventional methods.

7 tips to speed up RTK surveying

To efficiently acquire many survey points using RTK, keep the following points in mind.

• Check satellite geometry and choose good time windows GNSS satellite geometry strongly affects positioning accuracy and stability. If usable satellites are clustered in one area of the sky, geometry degrades and positional errors tend to increase. Before work, check satellite geometry with a GNSS planner and conduct observations at times when DOP values (which indicate position quality) are low. If possible, use receivers that support multi-GNSS such as GLONASS, Galileo, and QZSS (Michibiki) in addition to GPS to ensure a sufficient number of satellites and more stable accuracy.

• Position in open locations with no obstructions For RTK surveying, select open environments where satellite signals can be stably received. In canyons between tall buildings or under trees, signals may be blocked or reflected (multipath) by walls and the ground, causing unstable positioning. Signal reflections can prevent achieving a Fix (high-precision solution) even with small errors, so observe in locations with a wide view of the sky whenever possible. If you must survey near buildings, raise the antenna as high as possible to reduce reflection effects, or attach a ground plane (metal plate) to the antenna to block reflections from below. High-performance GNSS antennas and receivers may include multipath-reduction features, but creating an environment that avoids reflections is the most reliable measure.

• Set up the base station nearby and use network RTK RTK achieves high precision through relative positioning between a reference station and a rover, so correction accuracy decreases with longer baseline lengths (distance between base and rover) due to spatial variations in ionospheric delay and satellite clock errors. Longer distances also tend to increase time to initialize (obtain a Fix). Generally, it is desirable to be within 10 km (32808 ft) of the base station; beyond that, obtaining a fixed solution may take longer or accuracy may be unstable. When deploying your own base station, place it as close to the survey area as possible. If that is difficult, use electronic reference point data or network RTK services provided by public and private entities. The VRS method, which allows virtual reference points to be set via the network, effectively keeps baseline lengths short and enables rapid, high-precision surveying even over wide areas.

• Avoid communication interruptions and ensure stable delivery of correction data If correction data communication from the base station to the rover is interrupted, RTK cannot maintain a fixed solution and positioning becomes unstable. When communicating by radio, pay attention to antenna line-of-sight and transmission range. If obstacles lie between base station and rover antennas, signals may not reach, so install antennas as high as possible and consider repeaters for long distances. In urban areas, be aware of interference from other radio stations. When using cellular network (Ntrip), connectivity may be lost in mountainous or out-of-coverage areas. Check the site’s communication environment beforehand and prepare external antennas or alternative mobile routers as needed to ensure continuous reception of correction data.

• Establish and maintain a Fix quickly when starting positioning When starting work, ensure the rover can obtain a Fix solution reliably. If the number of tracked satellites is low or the surroundings are obstructed at the start point, obtaining a fixed solution can take a long time and waste effort. Choose as open a location as possible for the survey start point and wait until the receiver has captured enough satellites to output an accurate fixed solution. Once a Fix is obtained, it is important to keep it from breaking. During surveying, avoid obstructing satellite signals as much as possible; if the Fix reverts to a Float solution (lower precision), stop again in an open area to stabilize positioning before proceeding to the next point.

• Acquire points continuously and efficiently With RTK, you do not need to re-setup equipment or sight targets for each point as with traditional methods. If a fixed solution is available, you can measure points one after another while walking. Pre-identify candidate points on the site map and follow an efficient route to minimize wasted movement. On uneven terrain, watch your footing and collect points in a logical order. Many modern GNSS receivers offer a continuous-measurement mode that automatically records points at set intervals; using this can comprehensively capture terrain data along walking paths and prevent missed points. Some rovers now automatically compensate for pole tilt, allowing measurement while the pole is tilted and enabling faster captures at points near obstacles.

• Verify acquired data on site to prevent omissions With RTK, coordinate values for measured points are available immediately on site, so you can check results and determine whether anything is missing. Plotting points in real time on a field tablet or handheld data collector makes unmeasured areas obvious at a glance. If you find missing data, you can perform additional measurements immediately and avoid re-surveys later. Cloud connectivity lets office staff share and view data instantly from the site. Real-time information sharing streamlines result checking and issuing instructions, further improving overall efficiency.

Simple surveying with LRTK: start high-precision positioning with a smartphone

Finally, we introduce LRTK, an increasingly notable solution for applying the RTK technology above more easily on site. LRTK is a surveying system composed of an ultra-compact RTK-GNSS receiver that can be attached to a smartphone and a dedicated app, turning your smartphone into a high-precision surveying device. The device itself is lightweight and compact, weighing less than a few hundred grams and small enough to carry in a pocket. Without preparing large dedicated equipment, a single smartphone can handle tasks from reference-point surveys to as-built checks and stakeout/layout. For example, by attaching an LRTK device to your smartphone and receiving network RTK correction data, you can start centimeter-level precision (half-inch accuracy) surveying as soon as you arrive on site. There’s no need for complex initial setup or cable connections—intuitive operation lets you start immediately. Models that support QZSS’s CLAS augmentation signal can receive correction information directly from satellites even in areas without cellular coverage, allowing high-precision positioning to continue in mountainous regions. This makes stable measurements possible in forests and mountainous sites where surveying used to be difficult.

LRTK’s advantages go beyond miniaturization. By combining a smartphone’s camera and AR (augmented reality) functions, surveying and construction management become more visual and intuitive. Using RTK-derived self-positioning as a reference, you can overlay design lines or 3D models of structures onto the real world, making it immediately clear through the screen where things should be placed. Without interpreting complex drawings or performing traditional stakeout, simply pointing the smartphone enables accurate position checks, allowing less-experienced workers to carry out layout tasks without mistakes. Smartphone RTK solutions like LRTK democratize high-precision positioning technology for more site staff and enable “simple surveying” that can be done with fewer people. LRTK also integrates with cloud services, allowing immediate sharing and visualization of positioning data, photos, and point clouds collected on site, so office personnel can grasp site conditions or review survey results remotely.

To fully realize the time-saving effects discussed above, it is important to use tools that anyone can operate. In that regard, the LRTK series is a modern solution compatible with the Ministry’s i-Construction initiative and could become a trump card for site DX from surveying through construction management. If you are considering labor and efficiency savings with RTK, consider adopting smartphone-based LRTK for smart surveying.

FAQ

Q: How accurate is RTK positioning? Is it comparable to a total station? A: Generally, RTK-GNSS can achieve horizontal accuracy of about 1–3 cm and vertical accuracy of around 3 cm in open, favorable conditions. It does not provide the millimeter-level exactness of an optical total station in some cases, but for many civil surveying and construction-management tasks the accuracy is sufficient. Moreover, because RTK measures in absolute coordinates and does not accumulate errors between points like some relative methods, its practical results are often comparable. However, accuracy can decrease in environments with tall buildings or trees due to signal reflection and blockage. When performing RTK surveys, choose as open a location as possible.

Q: Do I need special qualifications or advanced skills to use RTK surveying? Can a beginner operate it alone? A: No special national qualifications are required for RTK surveying itself; if you understand basic instrument operation and the principles of positioning, you can use RTK even without being a licensed surveyor. As mentioned, RTK allows one person to observe points without an assistant holding a prism as required with traditional total stations. Field apps and controllers provide guidance, so skilled tasks like instrument setup or angle reading are unnecessary. However, basic knowledge of survey control and coordinate systems is required to evaluate coordinate accuracy and incorporate results into drawings. Also, when submitting official survey deliverables, it is still preferable to work under the supervision of a licensed surveyor.

Q: Can RTK surveying be done in mountainous areas where cellular coverage is out of range? Are there countermeasures if correction data cannot be received? A: RTK surveying can be possible even in out-of-coverage environments depending on the situation. If network RTK is unavailable, you can use the CLAS augmentation signal provided by Japan’s QZSS (Michibiki). RTK receivers that support CLAS can receive correction data directly from satellites in mountainous areas without cellular service, maintaining centimeter-class positioning. However, in dense forests or places with poor sky visibility, satellite signals may be insufficient and a fixed RTK solution may not be obtainable. In such cases, temporarily moving to an open spot to acquire positioning and then transferring relative positions, or combining RTK with traditional methods, may be necessary.

Q: Introducing RTK equipment seems expensive—does the investment pay off? A: Initial costs vary depending on equipment configuration and service contracts, but the efficiency gains from RTK often justify the investment. For example, if a survey that used to take two people a day can be completed by one person in a few hours with RTK, labor cost savings can be substantial. Recently, low-cost RTK receivers compatible with smartphones and subscription-based correction services have emerged, so you no longer need hundreds of thousands of yen of initial investment to adopt high-precision positioning. Considering productivity improvements, labor reduction, and safety gains, the cost-effectiveness of RTK adoption is generally very high.

Q: If we have RTK, do we no longer need total stations or levels? A: RTK streamlines many outdoor surveying tasks, but traditional instruments still have roles in certain situations. Inside tunnels or building interiors where satellite signals cannot reach, total stations and levels remain indispensable. Also, for very short-range tasks requiring millimeter-level control—such as precision leveling or precise equipment installation—optical methods can be more reliable. Therefore, rather than fully replacing all traditional instruments, a practical approach is to use RTK for broad outdoor surveys and complement it with optical instruments for high-precision detail work.