New Standard for 3D CAD Utilization: On-site DX Achieved with Smartphone Surveying (LRTK)

In the construction industry, design using 3D CAD is becoming commonplace, but there are many voices saying that those data are not being fully utilized on-site. A gap still exists between 3D models and the construction site, and discrepancies between design drawings and the field have caused rework and inefficiency. A method gaining attention in recent years as a key to solving these challenges and achieving true digital transformation on-site (on-site DX) is smartphone surveying (LRTK). By combining smartphones with high-precision positioning technology, this approach enables anyone to easily capture the field as 3D data and to link and share it with design data immediately. This article reviews the traditional issue of the disconnect between 3D CAD and the field, explains the new workflows and bidirectional use of 3D CAD data enabled by smartphone surveying (LRTK), explores the role of smartphone RTK surveying within the trends of BIM/CIM and ICT construction, and finally introduces LRTK as a simple surveying solution that supports on-site DX.

The Disconnect Between 3D CAD and the Field – Traditional Challenges

Even when detailed design models are created with advanced 3D CAD software, it has long been pointed out that that information is not sufficiently utilized at the construction site. Traditionally, work on-site has often proceeded relying on paper drawings or 2D materials, and valuable 3D data tended to remain in the office. As a result, misalignments in understanding between design and field arise, and the as-built (actual construction results) can often differ slightly from the drawings.

This “disconnect between 3D CAD and the field” caused several problems. For example, structures that fit perfectly in the design model may in reality be off in position or elevation due to surveying errors on site or lack of terrain information, requiring adjustments after construction. Traditionally, surveyors would measure key points on-site after construction and compare them to drawings to finally identify discrepancies. However, because design data and field information were not linked in real time, discovery of small inconsistencies was delayed, sometimes causing rework.

Further, information sharing between the field and the office (design staff) was not smooth. Survey data and progress information generated daily at the site did not reach designers immediately, requiring time-consuming steps such as recording on paper or bringing data back on USB and importing it into office PCs. This time lag meant the latest site conditions were not reflected in models while construction continued, risking delayed decisions and responses by stakeholders. Compatibility issues when importing point clouds or terrain models obtained by surveying into design software, and the cumbersome data conversion between specialized packages, also hindered on-site utilization. These factors combined to create a situation where the benefits of 3D CAD data were not fully realized at the site.

How Smartphone Surveying (LRTK) Changes Workflows

In recent years, smartphone surveying has emerged as a technology that can significantly change this situation. Smartphone surveying combines a smartphone with a high-precision GNSS receiver (RTK method) and, as needed, links it to the built-in LiDAR sensor or camera to easily perform surveying and 3D measurement on site. LRTK is a representative example: a small RTK-GNSS receiver attaches to a smartphone to enable centimeter-level positioning while allowing 3D scanning and AR display. Tasks that previously required expensive dedicated equipment and skilled surveying techniques are becoming performable by anyone using a smartphone and LRTK.

The main innovations smartphone surveying (LRTK) brings include:

• Easy acquisition of point cloud data: Using the latest smartphones (for example, models equipped with LiDAR), you can walk around a site and scan terrain and structures to obtain a set of many points (point cloud data). High-density 3D measurements that formerly required terrestrial laser scanners or drone photogrammetry can now be achieved with a single smartphone. By processing the acquired point cloud, you obtain detailed 3D models of the site that can be used to verify as-built conditions against design data or to record construction progress.

• Centimeter-level high-precision positioning: RTK-GNSS technology allows even a smartphone to obtain highly accurate position coordinates with errors reduced to a few centimeters. Simply attaching a dedicated small receiver to the smartphone dramatically improves errors that were several meters with conventional GPS, enabling measurements directly linked to survey control point coordinates or design coordinate systems. This makes it possible to record latitude, longitude, and height of a point with a single tap and to perform precise staking-out (layout) in plane rectangular coordinate systems.

• Immediate understanding and sharing of current conditions: With smartphone surveying, a major advantage is that data acquired on-site can be checked and shared immediately. Point clouds and measured coordinates can be uploaded to the cloud directly from the smartphone, enabling real-time sharing with designers and clients in the office. For example, if you scan the site right after a day’s work and upload the as-built data to the cloud, the office can review the 3D data the same day for quality checks or as-built approvals. Whereas processing and reporting of survey data could previously take several days, smartphone surveying makes it possible to share the site’s “now” the same day, dramatically speeding decision-making.

• Intuitive on-site visualization with AR: Point cloud data obtained from smartphone surveying and pre-prepared 3D design models can be displayed in AR (augmented reality) on smartphones or tablets. Thanks to the high-precision location information from RTK, digital models can be accurately overlaid on the real world. For example, you can visualize underground piping in a point cloud model to guide excavation, or overlay a finished building model onto the site landscape to share the completed appearance with clients. Conventional simple AR often suffered from positional drift, but RTK-based precision enhancement prevents model displacement even during extended AR use. AR conveys design intent intuitively on-site, helping prevent construction errors and facilitating stakeholder alignment.

Moreover, public recognition of smartphone+RTK-based simple 3D surveying is growing; for example, in 2022 the Ministry of Land, Infrastructure, Transport and Tourism revised its as-built management guidelines to specify 3D measurement methods using mobile devices. Validation experiments showed that point clouds captured by smartphone LiDAR had errors of about 1–2 cm compared with verification points measured by total station, confirming accuracy that easily meets conventional quality standards (within ±5 cm).

As described above, smartphone surveying dramatically streamlines on-site surveying and measurement workflows. Tasks that once required multiple people a full day can, in some cases, be completed by one person in several tens of minutes. The ease of conducting measurements simply by walking the site with a device reduces the need to enter hazardous areas and lowers labor burden, improving safety and labor savings. The environment in which anyone can perform high-precision on-site measurements routinely is taking shape, representing a major step forward for on-site DX.

Compatibility with 3D CAD Data and Bidirectional Use

As smartphone surveying becomes widespread, the linkage between data captured on-site and 3D CAD data from the design stage will become dramatically smoother. This is especially because the absolute coordinates (global geodetic or public coordinate systems) provided by RTK unify site point clouds and measured coordinates with the coordinate system of the design model. Previously, point clouds acquired by laser scanners required later alignment by assigning coordinates to control points, but smartphone+RTK provides geo-referenced 3D data at the moment of capture. With this data foundation in place, information can be used bidirectionally between design and construction.

• Using design data on-site: Digital 3D design models can be directly used for on-site tasks. Loading a design model into a smartphone app and displaying it in AR lets the team share the intended finished shape that can be hard to grasp from drawings alone, allowing all site workers to proceed with a common image. Based on coordinate values contained in the model, you can also stake out key positions (marking pile locations or guiding machine operators). In other words, rather than converting design data to paper, you can refer to and use the digital model on-site, making accurate reflection of design intent in the field easier.

• Feeding site data back into design: Point clouds and measured coordinates of as-built conditions captured by smartphone surveying can be fed back to designers and construction managers immediately. By overlaying the latest site 3D data shared via the cloud onto the office CAD model, progress and quality can be checked quickly. Small deviations or issues during construction can be detected early, and design model revisions or additional instructions can be issued responsively. After completion, the high-precision as-built data can be used to create deliverable 3D products (as-built models) or employed as digital twins for facility management.

By adopting smartphone surveying, the design→construction→verification cycle becomes seamlessly connected by data. Information that traditionally flowed in one direction (from design to construction) shifts to a bidirectional digital flow where the field also sends data digitally, keeping design models and real-world conditions synchronized. This contributes to maintaining design quality, improving and advancing construction efficiency, and accelerating the PDCA cycle targeted by BIM/CIM.

The Role of Smartphone RTK Surveying in BIM/CIM and ICT Construction

Smartphone RTK surveying (use of smartphone+RTK technology) is beginning to take an important position within the accelerating trends of BIM/CIM and ICT construction. BIM/CIM is an approach that uses 3D models across the entire construction project for unified information management, and the Ministry of Land, Infrastructure, Transport and Tourism is promoting its application to direct-managed projects, among other measures, as the industry digitizes. Supporting these initiatives at the field level requires bridging the “gap between surveying and the design model” and “connecting the field and the office in real time.” Smartphone RTK surveying is a field-side solution to precisely these challenges.

In ICT construction, attention has focused on drone-based 3D surveying and machine-guided construction equipment. In addition to these, easy-to-use smartphone surveying is expected to be a tool that further advances on-site DX. For example, in indoor or mountainous areas where drones cannot fly, or for detailed as-built checks that heavy machinery cannot handle, smartphone+RTK allows people to walk the site and collect data directly. It is suitable for small-scale works and daily progress management, and its agility—being able to measure immediately when needed without arranging large equipment—is a major strength.

Also, as smartphone surveying devices have become lower cost and simpler to use, equipping the site on a “one person, one device” basis has become realistic. If site supervisors or foremen each carry an LRTK-equipped smartphone and can quickly perform surveying, measurement, and recording at any time, delays waiting for surveys can be eliminated. Because anyone on site can obtain surveying data without relying on a specialized surveying team, parallel workflows and rapid inspections become possible, improving overall productivity. In addition, software that automates complex calculations and coordinate corrections makes the tools easy to use even for non-experts, addressing issues such as aging skilled personnel and labor shortages. Smartphone RTK surveying is poised to strengthen its presence as a next-generation standard supporting BIM/CIM and ICT construction.

Smartphone Surveying Solution Supporting On-site DX: LRTK

Finally, as one solution that makes it easy to introduce such smartphone surveying technology to the field, we introduce LRTK. LRTK (Light RTK) is a pocket-sized device that turns a smartphone into a centimeter-level surveying instrument. A dedicated ultra-compact RTK-GNSS receiver attaches to the smartphone with one touch, and high-precision positioning starts as soon as you launch the app. Then you simply move to the location you want to measure and follow on-screen instructions to operate the smartphone, enabling position measurement, point cloud scanning, photography, and AR display all with one device. Measurement data is saved to the cloud in real time, so you can confirm and share data on-site without bringing it back to the office.

As an all-in-one surveying tool, LRTK is also easy to deploy on-site. The device itself weighs only a few hundred grams and has a built-in battery, so it can be carried all day and used whenever needed. The price point is far more affordable than traditional surveying equipment, making it practical for site personnel to carry as their personal tool. In fact, sites that have adopted LRTK on a one-device-per-person basis have begun to appear, proving that an environment where you can “measure whenever you want” directly translates into productivity improvements.

A high-precision, easy-to-use smartphone surveying device like LRTK is a powerful partner for driving on-site DX. By linking digital models created with 3D CAD to the real construction site in real time and removing the barriers between design and construction, its impact is enormous. The use of such digital technologies will also dramatically improve site productivity and safety. If smartphone surveying technologies like this become established as the new standard for 3D CAD utilization, a future will come in which everyone can freely handle digital data while carrying out construction. As a first step toward on-site DX, why not consider introducing smartphone surveying LRTK?