To Avoid Mistakes in RTK Surveying:
Key Points to Keep in Mind on Civil Engineering Sites

1. Common Mistakes in RTK Surveying
Although RTK surveying uses advanced GNSS equipment, even small mistakes can significantly affect positioning accuracy. According to field experts, there are several common mistakes in RTK surveying that can cause issues. Let's review some of the typical mistakes that often occur in civil engineering sites.

• Base Station (Base) Setup Mistakes:
  Incorrectly entering the known coordinates of the base station or mixing up the geodetic system or coordinate system. For example, entering the wrong zone number for Japan’s plane rectangular coordinate system can lead to a serious mistake where the entire survey result shifts by tens of meters. There have been reports of "mixing up one digit of the reference point coordinates and then realizing later that the data didn't match when trying to align it," highlighting the importance of careful base station setup.

• Communication Failure and Inability to Receive Corrections:
  RTK surveying requires constant reception of correction data from the base station to achieve high accuracy. However, issues such as poor radio connections or setup errors may prevent the rover from receiving corrections, causing the survey to proceed with autonomous (standalone) or DGPS-level accuracy. In such cases, errors of 0.5 to 1 meter in the horizontal direction can occur, leading to rework.

• RTK Remaining in Float Solution During Surveying:
  This mistake occurs when poor surrounding conditions or satellite conditions prevent obtaining a fixed RTK solution (FIX), and the survey continues with the float solution (accuracy of several tens of centimeters). If the operator overlooks the solution status on the equipment screen or casually proceeds with the measurement, they may later notice that the elevation or position is significantly off. It's crucial to always check whether the solution is FIX or FLOAT and refrain from measuring when the solution is unstable.

• Human Errors and Procedural Mistakes:
  Basic human errors such as forgetting to check the bubble level on the pole, incorrectly entering prism height or antenna height, or mistakenly taking the wrong survey point also occur frequently. While RTK-GNSS often relies on the equipment, it's essential to follow basic procedures like verifying the equipment height, checking targets, and conducting check surveys, just like with total stations, to avoid significant errors.

In this way, RTK surveying can involve a range of issues from equipment handling and communication to human error. In the next section, we will take a closer look at the main causes of reduced accuracy and their countermeasures.

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2. Main Causes of Reduced Surveying Accuracy and Countermeasures
By understanding the factors that lead to reduced accuracy in RTK surveying, you can take preventive measures beforehand or quickly address issues on-site. Here we’ll explain the main causes that affect RTK surveying accuracy and their corresponding countermeasures (error reduction strategies).

• Atmospheric Errors in Satellite Signals (Ionospheric and Tropospheric Errors):
  GNSS satellite signals are refracted and delayed as they pass through the Earth's ionosphere and troposphere, leading to distance measurement errors. These ionospheric delays and other errors are mostly canceled out in RTK through simultaneous observations from the base station. However, as the baseline length increases, the errors that cannot be corrected by the system also increase. To address this, it's important to keep the distance between the base station and rover as short as possible (generally, a few kilometers to 10 km is ideal, and no longer than 20 km). Using a dual-frequency GNSS receiver helps reduce the impact of ionospheric errors.

• Impact of Baseline Distance:
  As mentioned, the longer the distance between the base station and rover, the lower the accuracy of RTK. Even high-precision RTK receivers typically offer a "8mm + 1ppm" accuracy (1ppm = 1mm of error per 1 km of distance). For every kilometer the rover moves away from the base station, the error increases by approximately 1mm. The solution is simple: keep the base station as close as possible or use regional electronic reference points or VRS services to shorten the baseline length.

• Multipath Errors:
  Multipath occurs when satellite signals are reflected off nearby surfaces such as the ground, buildings, or vehicles and reach the receiver, mixing with the direct signal. The reflected signal takes a longer path and results in a pseudo-distance that is longer than the actual distance, causing positioning errors. For example, smooth water surfaces, metal surfaces, glass buildings, and large vehicles are strong sources of reflection. To mitigate this, avoid surveying near large reflective surfaces. If that’s unavoidable, using high-performance choke-ring antennas to reduce multipath waves can help. On-site, removing reflective objects (such as cars or tools) near the antenna or attaching a ground plane to the base station antenna can be effective.

• Satellite Obstruction and Geometric Configuration:
  If enough satellites are not visible during positioning, RTK accuracy will degrade. Forests, buildings, and mountainous terrain can obstruct satellite visibility, reducing the number of satellites or worsening geometry (increasing PDOP values). Additionally, strong electromagnetic interference from nearby high-voltage power lines, radar equipment, or large machinery can destabilize GNSS signals. To address this, place the base station in an open area with a clear line of sight (ideally with an elevation angle above 15° in all directions) and ensure that the rover is also positioned in an open area. Modern receivers that support multi-GNSS (GPS, GLONASS, Galileo, Michibiki) increase the number of satellites available for observation in obstructed environments, improving accuracy.

• Equipment Handling Mistakes and Human Errors:
  Because RTK uses high-precision equipment, even small mistakes can lead to errors. For example, even if the rover pole is intended to be vertical, a slight tilt can cause position errors (e.g., tilting a 2-meter pole by 1° results in about 3 cm of horizontal displacement). The countermeasure is simple: always check the vertical alignment using a bubble level before measuring. Recently, GNSS receivers with IMUs (Inertial Measurement Units) have been developed, which automatically correct for tilt, even if the pole is tilted. Additionally, make it a habit to perform check surveys by measuring known points and verifying errors to quickly identify the cause if abnormalities arise.

By understanding these causes, you can prevent situations that lead to accuracy reduction in advance or respond appropriately on-site. In the next section, we will further explore the environmental factors to be cautious of in civil engineering surveying.

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3. Environmental Factors to Be Cautious of in Civil Engineering Surveying

In civil engineering and infrastructure sites, there are often environmental factors that can negatively affect RTK positioning. Here, we will explain the key environmental factors to be mindful of on-site and the corresponding countermeasures.

It is ideal to secure an unobstructed sky view with an elevation angle of at least 15°. In construction sites, where there are many structures and obstacles, the choice of the base station installation location is critical. For example, installing the base station on a high place, such as a rooftop or above a temporary fence, can expand the visibility and improve satellite reception. Ideally, the surrounding area should be open 360°, but in urban areas, it’s inevitable that utility poles and buildings will block the view. Even so, it’s important to position the antenna towards the open sky as much as possible and avoid expecting satellites with low elevation angles in obstructed directions.

On the other hand, the rover (mobile station) side also requires some adjustments when the measurement point is in challenging conditions. For example, in places such as under viaducts or in forests, where GNSS signals cannot be received, you should consider using alternative methods such as total stations or the LRTK method (described later) instead of relying solely on RTK. If GNSS positioning is absolutely necessary, measures such as temporarily pausing and averaging the position in an open area nearby, or slightly moving the measurement point and applying offset corrections, should be considered.

You should also be aware of electromagnetic noise and interference sources. In addition to high-voltage lines, large machinery and radar equipment emitting strong radio waves near the site can interfere with RTK radio or GNSS signals.

If there are obstacles between the base station and rover, the signals may not reach and communication may be interrupted (this is particularly noticeable when using low-power radios like specific small-power radios). As a countermeasure, ensure that the base station antenna and radio are installed at as high a point as possible for a clear line of sight, and be mindful of potential frequency interference with the site’s work radios.

Weather and natural environmental conditions also need attention. While clear weather may not cause problems, surveying should be halted during heavy rain or thunderstorms. In heavy rain, satellite signal attenuation increases, making it harder to obtain a FIX solution. Additionally, lightning can cause equipment damage or pose a risk to life. In hot weather during summer, it’s important to prevent the receiver from overheating by providing shade, and in cold regions, be mindful of battery performance degradation. Always be prepared for weather conditions that may affect surveying.

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4. Equipment and Communication Troubleshooting Methods

To ensure smooth RTK surveying, it is essential to secure the reliability of equipment and prevent communication issues. Here, we will summarize how to handle common equipment and communication problems encountered on-site.

• Power and Battery Management:
  First and foremost, checking the battery levels and preparing backup power is essential for both the base station and rover. For long-duration surveys, prepare spare batteries and backup power sources. In cold environments, account for battery performance degradation by ensuring sufficient battery capacity. Avoid mistakes like "the base station's power turned off, causing the corrections to stop" or "the tablet’s battery ran out, and data couldn't be saved."

• Inspecting Antenna and Cable Connections:
  Poor connections in the GNSS antennas of the base station or UHF radio antennas are major causes of RTK communication issues. Surprisingly, there are often cases where antennas are not properly installed, or they are loose or damaged. Before starting work, ensure all antenna cables are securely connected, and visually inspect for any loose connections or breakages. The connectors can deteriorate from dust or moisture, so it’s important to protect them with caps and regularly clean and replace them.

• Checking Wireless Communication Settings:
  Verify that the base station and rover’s wireless connection is functioning properly. Especially when working on a new site or changing equipment configuration, mismatched frequencies or protocol settings between the base station and rover will prevent communication. For Japan’s specific low-power radio, check if the channel and group number match. When using internet-based services like NTRIP, misconfigurations in login ID or mount point settings can prevent connections, so it’s a good idea to perform a connection test before heading to the site to ensure everything is set up properly.

• Communication Range and Signal Strength:
  For wireless RTK, if the distance between the base station and rover exceeds the communication range, the rover will no longer receive corrections. Depending on the output and terrain, with low-power radios, the practical range is usually a few kilometers, while a 5W simple radio (digital) has a range of around 5–6 km. For larger sites, consider placing the base station centrally, preparing relay stations, or using mobile data to extend the coverage. In areas with no mobile signal, such as mountainous or underground locations, network RTK won’t work, so switching to your own radio system or transferring data incrementally when the rover is back within range is a good solution.

• Pre-checking Software and Equipment:
  Before going to the field, verify that the settings for your surveying controller or app (such as geodetic system, projection method, and elevation system) are correct. Make sure to update the firmware and software to the latest stable version. Recently, many systems are controlled via tablets or smartphones, so be sure to pay attention to bug fix information for the app as well. Performing a thorough pre-check and simulation will ensure you don’t face problems on-site and are ready to prevent issues in advance.

By following these practices, you can significantly reduce the risk of work stoppages due to equipment or communication issues. In the next section, we will review the comprehensive best practices for ensuring the success of RTK surveying.

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5. Best Practices for Success in RTK Surveying

Finally, we will summarize the comprehensive best practices for conducting RTK surveying safely and accurately. Let’s go over the key points to check from before heading to the site all the way to the completion of the survey.

1. Pre-planning and Satellite Prediction:
   Before conducting the survey, predict the number of GNSS satellites to be used and their configuration, and choose a time when satellite alignment is favorable. If necessary, use the Geospatial Information Authority of Japan’s GNSS prediction service or app to check the trends in PDOP values. Especially in obstructed environments, avoid times when there are fewer satellites and plan with sufficient buffer time.

2. Optimizing Base Station Installation:
   The base station should be installed in a stable location where the surrounding sky is wide open. If using a tripod, ensure that it is securely set up to avoid tipping or vibration due to wind. When installing on a known point, make sure to measure the antenna height accurately and cross-check it with the known coordinates. If possible, before starting work, conduct a few minutes of averaging at the base station and automatically compare the data with the known point to check for any discrepancies, ensuring peace of mind.

3. Accurate Equipment Settings:
   Correctly select settings for geodetic systems, coordinate systems, and geoid models on the controller or software. In Japan, the standard settings are typically the World Geodetic System (JGD2011/2022) + Plane Rectangular Coordinate System ◯ + Geoid (GSIGEO2011, etc.), but verify these according to the specifications of the order to avoid any mistakes. When configuring the base station, be careful to avoid forgetting to set it in base station mode or mistakenly setting the rover to base station mode.

4. Real-time Accuracy Management:
   During the survey, always monitor the status on the controller screen to confirm that the FIX solution has been obtained and that the PDOP value is within the appropriate range. If there is any unstable behavior (such as satellites decreasing or switching back to Float), stop temporarily to investigate the cause. For critical points, it is helpful to double-check by measuring again or performing a reverse calculation and comparing the results with known points to validate the data in real time.

5. Adapting to Environmental Changes:
   While surveying while moving, the satellite reception conditions will change constantly depending on the location. If obstructions are approaching, temporarily stop the measurement, or if certain areas are difficult to measure, have the courage to switch to an alternative method. Not clinging to RTK and switching to a total station or post-processing (PPK) method when necessary will ultimately lead to avoiding mistakes.

6. Data Recording and Backup:
   In addition to recording the coordinates of the survey points, also record metadata such as observation times, the number of satellites, and the status of the solution. Recent systems automatically save positioning logs to the cloud and tag coordinates and orientation to photos taken on-site for storage. Keeping raw data logs is useful for troubleshooting in case of issues. Always back up the data after the survey and be prepared for unforeseen situations.

By following these best practices, the risk of making fatal mistakes in RTK surveying will be significantly reduced. However, you may still find that "practical implementation on-site can be quite challenging." In the next section, we will introduce a new technology, "LRTK," which can dramatically simplify these tasks and reduce the chances of failure.

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6. Accurate and Easy RTK Surveying with LRTK

Many of you may understand the precautions introduced so far, but might find it difficult to fully implement them on-site. To address these challenges, a new RTK surveying tool has emerged: LRTK (an RTK-GNSS device developed by Lefixea).

LRTK stands out for its ease of use—there is no need for complicated wiring or installation, and anyone can use it intuitively.

By leveraging LRTK, you can significantly reduce the common risks of failure in RTK surveying. For example, with its cloud integration feature, positioning data and photos can be automatically saved and shared to the cloud on-site, eliminating concerns about data loss or recording mistakes.

When the surveyor uploads the coordinates and photos of the as-built data to the cloud, supervisors in remote offices can instantly share the information, allowing them to quickly detect any missed measurements or errors and correct them. Furthermore, LRTK supports network RTK (Ntrip), which means you can achieve centimeter-level positioning without a base station anywhere in the country, as long as there is smartphone coverage. This removes the need to worry about baseline length issues, making it flexible for use on small local sites or large-scale infrastructure inspections.

Traditionally, expensive RTK equipment was used only by a limited group of surveying teams, but thanks to LRTK’s low cost and simplicity, we are now entering an era where "one device per person" is possible.

When each site supervisor and worker can easily conduct centimeter-accurate surveys without waiting for the surveying team, productivity and efficiency will drastically improve. In fact, there is even a helmet-mounted model of LRTK, where workers can walk and automatically perform continuous positioning, which is revolutionizing the style of surveying. Not only does LRTK reduce the chances of failure in RTK surveying, but it significantly minimizes the sources of mistakes from the start.