Table of Contents

• The importance of creating cross-sections

• Conventional cross-section creation methods and their challenges

• How RTK changes cross-section creation

• Construction DX brought by RTK cross-sections

• Summary

• Frequently asked questions

One indispensable task in construction sites and surveying is creating cross-sections. Cross-sections, which cut through terrain or structures at a given section, play an important role in verifying whether the as-built (post-construction shape) matches the design and in calculating earthwork quantities. However, conventional cross-section creation was a labor- and time-intensive task. Recently, the use of high-precision positioning technology known as RTK, which achieves centimeter-level (inch-level) accuracy, has made creating cross-sections remarkably easy. As on-site DX (digital transformation) progresses, RTK-based cross-section surveying is attracting attention as a new method that can obtain accurate cross-section data “by one person” and “in a short time.” This article explains from the basics—why cross-sections are needed—through the challenges of conventional methods, and how the latest cross-section creation methods using RTK solve those challenges and realize construction DX.

The importance of creating cross-sections

In civil engineering and construction sites, cross-sections are used in various situations such as roads, levees, developed land, and slopes. A cross-section is a drawing that shows the internal shape when terrain or a structure is cut vertically by a plane, essentially recording the site’s “cross-section.” Cross-sections serve as basic documents for as-built management and quality control and are indispensable for checking consistency with design drawings and verifying the finished form. For example, in road construction, after construction, the transverse section of the road (surface and subgrade heights and thicknesses) is measured at specified locations and compiled into cross-sections to confirm whether the construction was carried out according to the design. Cross-sections are also used for quantity calculations, not just shape confirmation. They are necessary when calculating volumes of excavation or embankment and when evaluating slope gradients and stability. Thus, cross-sections are highly reliable records used widely from construction management and quality assurance to consideration of design changes, making them very important deliverables on site.

Conventional cross-section creation methods and challenges

However, traditional surveying work for creating cross-sections has had several challenges. In the typical method, surveyors use surveying instruments such as levels and total stations to measure the elevation of each point along pre-determined cross-section lines one by one, and then draw the cross-sectional shape from the collection of points. The following problems have been pointed out in this procedure.

• Significant labor and time burden: Cross-section surveying usually requires two or more personnel (a measurer and an assistant), and setting up/moving equipment and recording readings are time-consuming. When conducting cross-section surveys over long stretches, survey staff must repeatedly move and re-set tripods to take measurements, and the more cross-sections required, the more days are needed. After surveying, there is also the office work of drafting, which is a major burden for site staff.

• Safety risks: In measurement locations such as steep slopes, riverbeds, and along busy roads, the work itself can be hazardous. Because people must enter the area directly to set up poles or staffs, there is always a risk of falls, landslides, or vehicle collisions and other occupational accidents. Having multiple people work for long periods in hazardous locations is itself a major safety management issue.

• Limits of accuracy and coverage: Manual cross-section surveying inherently limits the number of points that can be measured. Typically, only the minimum representative points are taken at intervals of several meters, so there is a risk of overlooking fine irregularities or localized areas that differ from the design. Even if one later wishes one had measured more densely, re-surveying requires returning to the site. The shape between points can only be interpolated, placing limits on the precision and comprehensiveness of the cross-section.

• Drafting effort and errors: Bringing field measurements back to the office and entering numbers into CAD software and connecting points to draw cross-section lines is tedious. The more cross-sections there are, the more repetitive drafting is required, increasing the risk of recording and input errors inherent to manual work. Forgotten photos or miswritten measurements due to busy field conditions can lead to inaccurate drawings.

• Equipment cost issues: To obtain higher-precision and more detailed cross-sections, advanced methods using the latest 3D laser scanners are available, but such sophisticated surveying equipment is very expensive. Small- and medium-scale sites often find it difficult to introduce such equipment and end up relying on traditional manual methods. The hurdle has been that high-precision cross-section measurement requires large-scale equipment and cost.

As described above, conventional cross-section creation methods have had challenges such as “requiring many personnel and time,” “involving potential danger,” “yielding partial data with risk of omissions,” and “requiring tedious drafting that can cause mistakes.” The industry has long sought “more efficient and reliable surveying methods” to solve these issues.

How RTK changes cross-section creation

Recently, a new cross-section creation method that utilizes high-precision positioning technology called RTK (real-time kinematic) has emerged. In particular, LRTK systems, which combine smartphones with small GNSS receivers for easy use, are attracting attention as solutions that overturn conventional assumptions. RTK is a technology that corrects satellite positioning errors such as GPS in real time to improve positional accuracy to within a few centimeters (a few in). With LRTK, a palm-sized RTK-GNSS receiver attached to a smartphone and a dedicated app turn an everyday smartphone into a high-precision surveying instrument. There is no need to carry heavy dedicated equipment; simply walking the site with a smartphone in hand allows you to acquire surveying data that forms the basis of cross-sections.

So, specifically, how is cross-section creation using RTK carried out? Let’s look at the process step by step.

• Field data acquisition: Using an LRTK receiver mounted on a smartphone, scan the site to acquire 3D point cloud data. By walking around the entire site with the smartphone’s camera or LiDAR sensor pointed at the surroundings, you can record the shapes of terrain and structures as a multitude of points. Because positioning errors are corrected to within a few cm (a few in) by RTK-GNSS, each point in the acquired point cloud is assigned absolute coordinates (latitude, longitude, and elevation) in a global coordinate system. In other words, simply scanning with a smartphone records the site’s shape as accurate coordinate-tagged digital data.

• Automatic processing and model generation: The large amount of point cloud data obtained can be reviewed on the smartphone on site, or uploaded to a cloud service with one tap for analysis. In the cloud, unnecessary noise points are automatically removed and data are aligned, and within minutes a detailed 3D model of the entire site is generated. Even without expensive dedicated software, environments exist where you can view point clouds and extract cross-sections in a web browser. Because the cloud handles processing of large data volumes, results can be obtained shortly after starting the on-site scan. In areas without internet connectivity, such as mountainous regions, flexible responses are possible as described later, for example by using satellite augmentation signals or processing on the smartphone alone.

• Extracting cross-sections at arbitrary positions: A major advantage is that from the 3D point cloud model uploaded to the cloud, you can freely slice out cross-sections at the locations you want and convert them into drawings. Specifying two points on the screen will automatically generate a cross-section along that line. For example, you can generate a vertical cross-section of a slope or a transverse cross-section perpendicular to a road—angle and position are up to you. Because the acquired point cloud data include fine details of the ground surface and structures, the cross-sections accurately reflect subtle undulations and shapes that manual surveying would miss. There is no need to set stakes on site with a preset plan such as “measure every 〇 m (〇 ft)”; from a single measurement dataset you can create as many required cross-sections as you like. Even if you later decide you need cross-sections at other locations, there is no need to return to the site, so there are no measurement omissions or rework.

• Utilization of drawing data: Extracted cross-sections can not only be displayed and checked in a browser but can also be output in data formats such as DXF format that are directly usable in CAD software. This lets you instantly obtain digital cross-section drawings that previously had to be hand-drafted from measured points, greatly reducing drafting time. The exported cross-section data can be used directly in design documents and as-built reports, and can be shared for review with stakeholders via email or cloud with one click. Even if printed drawings are required for submission, creating high-precision cross-sections from the data makes it efficient to produce error-free deliverables.

Through the above steps, it becomes possible to create high-precision cross-sections from point cloud data obtained on site in a short time. Tasks that traditionally took several days for surveying and several more for drafting can, with an RTK-enabled system, realistically be completed from on-site measurement to drawing completion within the same day. It is truly a workflow that overturns conventional cross-section creation practices.

Construction DX brought by RTK cross-sections

The new cross-section creation methods using RTK not only streamline surveying work but also greatly contribute to on-site construction DX (digital transformation of operations). Let’s summarize the advantages obtainable on site compared to traditional methods.

• Labor reduction and burden alleviation: With high-precision GNSS positioning and smartphone apps, cross-section surveying that used to require 2–3 people can be completed by one person. In addition to cost reductions from fewer personnel, smaller teams can handle sites facing severe labor shortages. There is no need to carry or set up heavy equipment, reducing physical burden.

• Speed-up (reduced working time): Once point cloud data are obtained, any number of cross-sections can be extracted later, eliminating the need to re-measure. Because data acquisition through to drawing can be done rapidly on site, for example you can measure in the morning and share cross-sections with design personnel in the afternoon to start discussions. This directly contributes to shortened construction periods and improved on-site responsiveness.

• Improved data accuracy and coverage: High-density point cloud measurements capture details that manual methods would miss. Variations in as-built conditions and localized defects are easier to find, improving quality management accuracy. Also, because the acquired data retain XYZ coordinates as digital information, you can prevent record omissions and transcription errors. Accumulating past measurement data enables uses such as comparing changes over time during future maintenance.

• Enhanced safety: Because terrain can be measured by LiDAR scanning from a safe distance, workers need to enter hazardous areas less often. Surveying steep terrains or disaster sites can be conducted with minimal risk. Shorter measurement times also reduce on-site exposure and lower the risk of heatstroke and accidents.

• Faster information sharing and decision-making: Digitized cross-section data can be easily shared via the cloud. Stakeholders or supervisors can simultaneously review 3D data and cross-sections in a browser while discussing, reducing communication loss and accelerating decisions. The ability to share on-site information in real time with relevant parties is a key point in construction DX.

By utilizing RTK cross-sections in this way, on-site operations themselves are transformed so that construction management can be performed “with fewer people, faster, and with high quality.” The Ministry of Land, Infrastructure, Transport and Tourism’s promotion of i-Construction recommends ICT surveying and 3D data utilization, and cross-section creation using RTK is exactly a concrete measure for that. Introducing digital construction with the latest technologies can simultaneously realize productivity improvements, safety assurance, and quality enhancement.

Summary

Creating cross-sections is an essential task at construction sites, but adopting smartphone-compatible RTK positioning systems such as LRTK dramatically evolves how it is done. Surveying work that previously required significant effort and personnel can now be completed in a short time with a smartphone in hand, obtaining high-precision cross-sections on site. The burdens of equipment and personnel and safety concerns that were unavoidable with traditional methods are greatly reduced, while the amount and accuracy of obtainable data have improved markedly.

By leveraging RTK technology, which is a next-generation solution supporting construction DX, traditional problems associated with cross-section creation can be resolved, improving both efficiency and quality of construction management. Digital technology can refresh the site’s “common sense,” enabling both productivity improvement and strengthened safety management. If you currently face challenges in reducing surveying labor or improving as-built management accuracy, consider adopting the high-precision positioning system LRTK, which is easy to use with a smartphone. LRTK allows you to start simple surveying in-house even without specialized equipment and should be a valuable tool in promoting your site’s DX. For more details, please also visit the [LRTK official site](https://www.lrtk.lefixea.com/lrtk-phone) and evolve your site to the next stage.

Frequently asked questions

Q: What equipment and preparations are needed to start creating cross-sections using RTK? A: Basically, you can start surveying with a smartphone and an LRTK device, which is a high-precision GNSS receiver. No special surveying machines or heavy equipment are required—just attach the compact receiver to your existing smartphone. Additionally, to obtain the correction information necessary for RTK positioning, you need to connect to a correction service over the internet (network RTK) or configure the system to use augmentation signals such as CLAS from Japan’s Quasi-Zenith Satellite System “Michibiki.” However, these are not difficult settings; once the environment is set up, you can start positioning and scanning on site by launching the app. Initial investment is also lower compared to conventional surveying equipment, making it easy to introduce high-precision cross-section surveying.

Q: Can you measure cross-sections with RTK positioning even in mountainous areas where mobile signals do not reach? A: Yes, it is possible. LRTK devices support the CLAS satellite augmentation signal provided by the Geospatial Information Authority of Japan, allowing reception of correction information directly from satellites and centimeter-level positioning even at sites out of mobile communication range. In places without communication infrastructure, you can operate by switching to receive CLAS signals from Michibiki (QZSS) or correction data via existing simple radio, maintaining high-precision positioning. Therefore, RTK surveying can continue in mountainous areas or remote islands where network reliance is not possible.

Q: What level of accuracy does RTK positioning provide? Is it sufficient for cross-section creation? A: RTK-GNSS generally enables high-precision positioning with planar positions of about ± a few cm (± a few in) and vertical positions also within about ± a few cm (± a few in). This is comparable to surveying using conventional levels and total stations and is sufficient for cross-section creation used in as-built management. However, because it uses satellite signals, accuracy can degrade in environments with poor sky visibility (e.g., inside tunnels or under dense tree cover). In such cases, you can obtain stable values by measuring from points with good reception or by taking multiple short measurements and averaging them. In typical site environments, RTK accuracy is generally adequate for cross-section measurement.

Q: Can this smartphone surveying method be used for official contexts such as public works? A: Yes. In recent years, national and local governments have been promoting the use of new technologies such as RTK-GNSS and photogrammetry, and their use for official as-built management under certain conditions has been accepted. As part of the Ministry of Land, Infrastructure, Transport and Tourism’s i-Construction initiative, measurement methods using RTK-GNSS have been included in draft as-built management procedures, and standards for promoting on-site DX are being developed. In actual operations, appropriate accuracy management and verification of measurement results are required, but cross-section data obtained with LRTK are positioned in public coordinate systems, making them easy to handle in subsequent processes and usable for official drawing creation. In other words, if conditions are met, smartphone+RTK cross-section surveying can be a method robust enough for official documentation.

Q: Can non-specialist surveyors operate LRTK? A: The LRTK system is designed to be easy to use with an intuitive smartphone app, so it can be handled without specialized knowledge. While basic surveying and civil engineering knowledge is beneficial, the app provides guided surveying procedures, automatic calculations, and automatic drawing generation, making it possible for even inexperienced users to obtain accurate data. The ease of use means site personnel can immediately use it when they want to “quickly check a cross-section,” allowing tasks previously outsourced to specialist contractors or in-house survey teams to be completed by the team itself. Users can become proficient with a short training period, and adoption is progressing at many sites.

Q: Besides creating cross-sections, what else can LRTK do? A: High-precision position and point cloud data obtained with LRTK can be used for various purposes beyond cross-section creation. For example, they can be used for displacement monitoring of the ground and structures, recording as-built inspections, calculating earthwork quantities by comparing terrain before and after construction, and recording the positions of buried assets or checking road alignments. As a compact positioning terminal that attaches to a smartphone, LRTK can measure in confined indoor spaces or under bridges and can be applied in surveys that integrate drones or 360° cameras. In short, LRTK is a versatile tool that meets a wide range of on-site “position measurement” needs and, once introduced, will be a powerful ally for on-site DX beyond just cross-section creation.

Creating cross-sections has never been this easy! Construction DX realized with RTK cross-sections

Table of Contents

• The importance of creating cross-sections

• Conventional cross-section creation methods and their challenges

• How RTK changes cross-section creation

• Construction DX brought by RTK cross-sections

• Summary

• Frequently asked questions

One indispensable task in construction sites and surveying is creating cross-sections. Cross-sections, which cut through terrain or structures at a given section, play an important role in verifying whether the as-built (post-construction shape) matches the design and in calculating earthwork quantities. However, conventional cross-section creation was a labor- and time-intensive task. Recently, the use of high-precision positioning technology known as RTK, which achieves centimeter-level (inch-level) accuracy, has made creating cross-sections remarkably easy. As on-site DX (digital transformation) progresses, RTK-based cross-section surveying is attracting attention as a new method that can obtain accurate cross-section data “by one person” and “in a short time.” This article explains from the basics—why cross-sections are needed—through the challenges of conventional methods, and how the latest cross-section creation methods using RTK solve those challenges and realize construction DX.

The importance of creating cross-sections

In civil engineering and construction sites, cross-sections are used in various situations such as roads, levees, developed land, and slopes. A cross-section is a drawing that shows the internal shape when terrain or a structure is cut vertically by a plane, essentially recording the site’s “cross-section.” Cross-sections serve as basic documents for as-built management and quality control and are indispensable for checking consistency with design drawings and verifying the finished form. For example, in road construction, after construction, the transverse section of the road (surface and subgrade heights and thicknesses) is measured at specified locations and compiled into cross-sections to confirm whether the construction was carried out according to the design. Cross-sections are also used for quantity calculations, not just shape confirmation. They are necessary when calculating volumes of excavation or embankment and when evaluating slope gradients and stability. Thus, cross-sections are highly reliable records used widely from construction management and quality assurance to consideration of design changes, making them very important deliverables on site.

Conventional cross-section creation methods and challenges

However, traditional surveying work for creating cross-sections has had several challenges. In the typical method, surveyors use surveying instruments such as levels and total stations to measure the elevation of each point along pre-determined cross-section lines one by one, and then draw the cross-sectional shape from the collection of points. The following problems have been pointed out in this procedure.

• Significant labor and time burden: Cross-section surveying usually requires two or more personnel (a measurer and an assistant), and setting up/moving equipment and recording readings are time-consuming. When conducting cross-section surveys over long stretches, survey staff must repeatedly move and re-set tripods to take measurements, and the more cross-sections required, the more days are needed. After surveying, there is also the office work of drafting, which is a major burden for site staff.

• Safety risks: In measurement locations such as steep slopes, riverbeds, and along busy roads, the work itself can be hazardous. Because people must enter the area directly to set up poles or staffs, there is always a risk of falls, landslides, or vehicle collisions and other occupational accidents. Having multiple people work for long periods in hazardous locations is itself a major safety management issue.

• Limits of accuracy and coverage: Manual cross-section surveying inherently limits the number of points that can be measured. Typically, only the minimum representative points are taken at intervals of several meters, so there is a risk of overlooking fine irregularities or localized areas that differ from the design. Even if one later wishes one had measured more densely, re-surveying requires returning to the site. The shape between points can only be interpolated, placing limits on the precision and comprehensiveness of the cross-section.

• Drafting effort and errors: Bringing field measurements back to the office and entering numbers into CAD software and connecting points to draw cross-section lines is tedious. The more cross-sections there are, the more repetitive drafting is required, increasing the risk of recording and input errors inherent to manual work. Forgotten photos or miswritten measurements due to busy field conditions can lead to inaccurate drawings.

• Equipment cost issues: To obtain higher-precision and more detailed cross-sections, advanced methods using the latest 3D laser scanners are available, but such sophisticated surveying equipment is very expensive. Small- and medium-scale sites often find it difficult to introduce such equipment and end up relying on traditional manual methods. The hurdle has been that high-precision cross-section measurement requires large-scale equipment and cost.

As described above, conventional cross-section creation methods have had challenges such as “requiring many personnel and time,” “involving potential danger,” “yielding partial data with risk of omissions,” and “requiring tedious drafting that can cause mistakes.” The industry has long sought “more efficient and reliable surveying methods” to solve these issues.

How RTK changes cross-section creation

Recently, a new cross-section creation method that utilizes high-precision positioning technology called RTK (real-time kinematic) has emerged. In particular, LRTK systems, which combine smartphones with small GNSS receivers for easy use, are attracting attention as solutions that overturn conventional assumptions. RTK is a technology that corrects satellite positioning errors such as GPS in real time to improve positional accuracy to within a few centimeters (a few in). With LRTK, a palm-sized RTK-GNSS receiver attached to a smartphone and a dedicated app turn an everyday smartphone into a high-precision surveying instrument. There is no need to carry heavy dedicated equipment; simply walking the site with a smartphone in hand allows you to acquire surveying data that forms the basis of cross-sections.

So, specifically, how is cross-section creation using RTK carried out? Let’s look at the process step by step.

• Field data acquisition: Using an LRTK receiver mounted on a smartphone, scan the site to acquire 3D point cloud data. By walking around the entire site with the smartphone’s camera or LiDAR sensor pointed at the surroundings, you can record the shapes of terrain and structures as a multitude of points. Because positioning errors are corrected to within a few cm (a few in) by RTK-GNSS, each point in the acquired point cloud is assigned absolute coordinates (latitude, longitude, and elevation) in a global coordinate system. In other words, simply scanning with a smartphone records the site’s shape as accurate coordinate-tagged digital data.

• Automatic processing and model generation: The large amount of point cloud data obtained can be reviewed on the smartphone on site, or uploaded to a cloud service with one tap for analysis. In the cloud, unnecessary noise points are automatically removed and data are aligned, and within minutes a detailed 3D model of the entire site is generated. Even without expensive dedicated software, environments exist where you can view point clouds and extract cross-sections in a web browser. Because the cloud handles processing of large data volumes, results can be obtained shortly after starting the on-site scan. In areas without internet connectivity, such as mountainous regions, flexible responses are possible as described later, for example by using satellite augmentation signals or processing on the smartphone alone.

• Extracting cross-sections at arbitrary positions: A major advantage is that from the 3D point cloud model uploaded to the cloud, you can freely slice out cross-sections at the locations you want and convert them into drawings. Specifying two points on the screen will automatically generate a cross-section along that line. For example, you can generate a vertical cross-section of a slope or a transverse cross-section perpendicular to a road—angle and position are up to you. Because the acquired point cloud data include fine details of the ground surface and structures, the cross-sections accurately reflect subtle undulations and shapes that manual surveying would miss. There is no need to set stakes on site with a preset plan such as “measure every 〇 m (〇 ft)”; from a single measurement dataset you can create as many required cross-sections as you like. Even if you later decide you need cross-sections at other locations, there is no need to return to the site, so there are no measurement omissions or rework.

• Utilization of drawing data: Extracted cross-sections can not only be displayed and checked in a browser but can also be output in data formats such as DXF format that are directly usable in CAD software. This lets you instantly obtain digital cross-section drawings that previously had to be hand-drafted from measured points, greatly reducing drafting time. The exported cross-section data can be used directly in design documents and as-built reports, and can be shared for review with stakeholders via email or cloud with one click. Even if printed drawings are required for submission, creating high-precision cross-sections from the data makes it efficient to produce error-free deliverables.

Through the above steps, it becomes possible to create high-precision cross-sections from point cloud data obtained on site in a short time. Tasks that traditionally took several days for surveying and several more for drafting can, with an RTK-enabled system, realistically be completed from on-site measurement to drawing completion within the same day. It is truly a workflow that overturns conventional cross-section creation practices.

Construction DX brought by RTK cross-sections

The new cross-section creation methods using RTK not only streamline surveying work but also greatly contribute to on-site construction DX (digital transformation of operations). Let’s summarize the advantages obtainable on site compared to traditional methods.

• Labor reduction and burden alleviation: With high-precision GNSS positioning and smartphone apps, cross-section surveying that used to require 2–3 people can be completed by one person. In addition to cost reductions from fewer personnel, smaller teams can handle sites facing severe labor shortages. There is no need to carry or set up heavy equipment, reducing physical burden.

• Speed-up (reduced working time): Once point cloud data are obtained, any number of cross-sections can be extracted later, eliminating the need to re-measure. Because data acquisition through to drawing can be done rapidly on site, for example you can measure in the morning and share cross-sections with design personnel in the afternoon to start discussions. This directly contributes to shortened construction periods and improved on-site responsiveness.

• Improved data accuracy and coverage: High-density point cloud measurements capture details that manual methods would miss. Variations in as-built conditions and localized defects are easier to find, improving quality management accuracy. Also, because the acquired data retain XYZ coordinates as digital information, you can prevent record omissions and transcription errors. Accumulating past measurement data enables uses such as comparing changes over time during future maintenance.

• Enhanced safety: Because terrain can be measured by LiDAR scanning from a safe distance, workers need to enter hazardous areas less often. Surveying steep terrains or disaster sites can be conducted with minimal risk. Shorter measurement times also reduce on-site exposure and lower the risk of heatstroke and accidents.

• Faster information sharing and decision-making: Digitized cross-section data can be easily shared via the cloud. Stakeholders or supervisors can simultaneously review 3D data and cross-sections in a browser while discussing, reducing communication loss and accelerating decisions. The ability to share on-site information in real time with relevant parties is a key point in construction DX.

By utilizing RTK cross-sections in this way, on-site operations themselves are transformed so that construction management can be performed “with fewer people, faster, and with high quality.” The Ministry of Land, Infrastructure, Transport and Tourism’s promotion of i-Construction recommends ICT surveying and 3D data utilization, and cross-section creation using RTK is exactly a concrete measure for that. Introducing digital construction with the latest technologies can simultaneously realize productivity improvements, safety assurance, and quality enhancement.

Summary

Creating cross-sections is an essential task at construction sites, but adopting smartphone-compatible RTK positioning systems such as LRTK dramatically evolves how it is done. Surveying work that previously required significant effort and personnel can now be completed in a short time with a smartphone in hand, obtaining high-precision cross-sections on site. The burdens of equipment and personnel and safety concerns that were unavoidable with traditional methods are greatly reduced, while the amount and accuracy of obtainable data have improved markedly.

By leveraging RTK technology, which is a next-generation solution supporting construction DX, traditional problems associated with cross-section creation can be resolved, improving both efficiency and quality of construction management. Digital technology can refresh the site’s “common sense,” enabling both productivity improvement and strengthened safety management. If you currently face challenges in reducing surveying labor or improving as-built management accuracy, consider adopting the high-precision positioning system LRTK, which is easy to use with a smartphone. LRTK allows you to start simple surveying in-house even without specialized equipment and should be a valuable tool in promoting your site’s DX. For more details, please also visit the [LRTK official site](https://www.lrtk.lefixea.com/lrtk-phone) and evolve your site to the next stage.

Frequently asked questions

Q: What equipment and preparations are needed to start creating cross-sections using RTK? A: Basically, you can start surveying with a smartphone and an LRTK device, which is a high-precision GNSS receiver. No special surveying machines or heavy equipment are required—just attach the compact receiver to your existing smartphone. Additionally, to obtain the correction information necessary for RTK positioning, you need to connect to a correction service over the internet (network RTK) or configure the system to use augmentation signals such as CLAS from Japan’s Quasi-Zenith Satellite System “Michibiki.” However, these are not difficult settings; once the environment is set up, you can start positioning and scanning on site by launching the app. Initial investment is also lower compared to conventional surveying equipment, making it easy to introduce high-precision cross-section surveying.

Q: Can you measure cross-sections with RTK positioning even in mountainous areas where mobile signals do not reach? A: Yes, it is possible. LRTK devices support the CLAS satellite augmentation signal provided by the Geospatial Information Authority of Japan, allowing reception of correction information directly from satellites and centimeter-level (inch-level) positioning even at sites out of mobile communication range. In places without communication infrastructure, you can operate by switching to receive CLAS signals from Michibiki (QZSS) or correction data via existing simple radio, maintaining high-precision positioning. Therefore, RTK surveying can continue in mountainous areas or remote islands where network reliance is not possible.

Q: What level of accuracy does RTK positioning provide? Is it sufficient for cross-section creation? A: RTK-GNSS generally enables high-precision positioning with planar positions of about ± a few cm (± a few in) and vertical positions also within about ± a few cm (± a few in). This is comparable to surveying using conventional levels and total stations and is sufficient for cross-section creation used in as-built management. However, because it uses satellite signals, accuracy can degrade in environments with poor sky visibility (e.g., inside tunnels or under dense tree cover). In such cases, you can obtain stable values by measuring from points with good reception or by taking multiple short measurements and averaging them. In typical site environments, RTK accuracy is generally adequate for cross-section measurement.

Q: Can this smartphone surveying method be used for official contexts such as public works? A: Yes. In recent years, national and local governments have been promoting the use of new technologies such as RTK-GNSS and photogrammetry, and their use for official as-built management under certain conditions has been accepted. As part of the Ministry of Land, Infrastructure, Transport and Tourism’s i-Construction initiative, measurement methods using RTK-GNSS have been included in draft as-built management procedures, and standards for promoting on-site DX are being developed. In actual operations, appropriate accuracy management and verification of measurement results are required, but cross-section data obtained with LRTK are positioned in public coordinate systems, making them easy to handle in subsequent processes and usable for official drawing creation. In other words, if conditions are met, smartphone+RTK cross-section surveying can be a method robust enough for official documentation.

Q: Can non-specialist surveyors operate LRTK? A: The LRTK system is designed to be easy to use with an intuitive smartphone app, so it can be handled without specialized knowledge. While basic surveying and civil engineering knowledge is beneficial, the app provides guided surveying procedures, automatic calculations, and automatic drawing generation, making it possible for even inexperienced users to obtain accurate data. The ease of use means site personnel can immediately use it when they want to “quickly check a cross-section,” allowing tasks previously outsourced to specialist contractors or in-house survey teams to be completed by the team itself. Users can become proficient with a short training period, and adoption is progressing at many sites.

Q: Besides creating cross-sections, what else can LRTK do? A: High-precision position and point cloud data obtained with LRTK can be used for various purposes beyond cross-section creation. For example, they can be used for displacement monitoring of the ground and structures, recording as-built inspections, calculating earthwork quantities by comparing terrain before and after construction, and recording the positions of buried assets or checking road alignments. As a compact positioning terminal that attaches to a smartphone, LRTK can measure in confined indoor spaces or under bridges and can be applied in surveys that integrate drones or 360° cameras. In short, LRTK is a versatile tool that meets a wide range of on-site “position measurement” needs and, once introduced, will be a powerful ally for on-site DX beyond just cross-section creation.