Toward Zero Rework! Pre-construction Verification for Exterior Work Achieved with LRTK

In exterior (landscaping) work, small mismatches between the plan and the site often cause "rework," leading to increased costs and schedule delays. This article explains the importance of pre-construction verification for exterior work and how to prevent rework using the latest technologies. In particular, by leveraging a solution called LRTK, which combines 3D scanning and AR (augmented reality), on-site verification accuracy can dramatically improve—making zero rework an achievable goal. On sites with limited personnel and tight schedules, using advanced tools can prevent small oversights from becoming major rework issues.

LRTK is an all-in-one system composed of a high-precision GNSS receiver and a smartphone app, integrating on-site 3D scanning, surveying, AR display, and cloud sharing.

The importance of pre-construction verification in exterior/landscaping work

Residential exterior and landscaping projects involve many conditions to check, such as interactions with the building and neighboring environment, as well as ground conditions and piping. If you don’t conduct thorough on-site surveys and pre-construction verification before starting work, troubles that make you say "this wasn’t supposed to happen" can occur during construction. For example, a gate position planned on drawings might not match the actual site slope and require rework, or scheduling mismatches with the main building work might cause unnecessary waiting time. On smaller sites in particular, seemingly minor oversights can lead to overall rework, so caution is required. Traditionally, pre-construction verification on site involved measuring dimensions with tape measures and levels and comparing them to paper drawings. However, relying on visual inspection and manual measurement still carries risks of missed measurements and errors on sites with complex shapes or significant elevation changes.

Thorough pre-construction verification is essential to reduce these risks and ensure smooth progress and quality control.

Why rework happens and its costs

Why does rework occur? One reason is insufficient information gathering before construction or confirmation errors during the design stage. If the exterior plans differ from actual on-site dimensions, components may not fit during construction, resulting in rework. Lack of shared understanding with the client can also be a cause. Complaints like "this isn’t what I expected" due to differences in the final image can lead to post-construction remakes, which you want to avoid.

Rework can also result from overlooked underground utilities, boundary issues with neighboring properties, or coordination failures with building trades. For example, starting excavation without knowing pipe locations may later require pipe relocation or repair. Failing to conduct on-site surveying can lead to misidentifying property boundaries and subsequently relocating a fence. When rework occurs, not only do material and labor costs increase, but schedule extensions can damage client trust. Since exterior work is often tied to building handover dates, delays can affect the client’s move-in schedule. In some cases, this may lead to contractual penalties or extra expense obligations, which can be a serious blow to contractors. For small and medium-sized contractors, these unnecessary costs and loss of trust can significantly impact business.

Moreover, dismantling and redoing completed work is a heavy burden on site staff both mentally and timewise, and can lower morale.

Point-cloud scanning and AR: the new norm for pre-construction verification

Recently, the construction industry has begun adopting 3D surveying technologies and AR (augmented reality) for pre-construction verification. For example, point-cloud scanning using LiDAR sensors built into smartphones and similar devices can convert site topography and surroundings into high-precision 3D data. This allows on-site dimension checks that were traditionally done with plans and tape measures to be performed accurately on a digital 3D model.

Moreover, if you display the designed exterior 3D model in AR on site, you can check the full-scale finished image before starting construction. Height and depth, which are hard to grasp from drawings alone, can be intuitively understood through on-site AR. You can check whether fence or wall heights harmonize with the surroundings, or whether the approach width to the entrance is sufficient, all via AR. Using these technologies, you can identify issues before construction and share awareness among all stakeholders.

In the past, using 3D scanning and AR required expensive equipment and specialized knowledge, but more recently solutions that work with smartphones and affordable devices have emerged, making them accessible to small and medium landscaping contractors. With government initiatives like i-Construction and CIM (Construction Information Modeling) driven by the Ministry of Land, Infrastructure, Transport and Tourism, the use of 3D data and AR in exterior work will likely expand further. Improving the accuracy of pre-construction verification can greatly reduce the risk of rework after construction.

Example flow of exterior verification using LRTK

Now let’s look at a workflow for pre-construction verification in exterior work using a modern tool called LRTK.

First, use LRTK for the on-site survey before construction. The person in charge carries a smartphone and the LRTK device and scans the entire site to acquire high-precision point-cloud data. Elevation differences and the positional relationships of buildings and boundaries are converted into 3D data and saved to the cloud in minutes. Synchronized cloud data can be reviewed on office PCs for terrain checks or imported into CAD software for design adjustments. At the same time, if you take geolocated photos using a photo positioning function at key points, you can later verify site conditions in detail from the office.

Next, import the exterior 3D models and drawing data created during the design phase into the LRTK app and display them on site in AR. Through the smartphone screen, planned gate posts, carports, fences, and other elements are overlaid on the actual site. Since LRTK’s AR function places models based on high-precision coordinates, the display remains stable and accurate even when you change viewpoints. This lets you discover interferences and issues that drawings alone might not reveal. For example, you can check whether a planned gate post interferes with a swinging door, or whether a carport height will block a second-floor window. Because you can consider design changes on the spot, this leads to planning with minimal backtracking.

Additionally, LRTK’s coordinate navigation function makes it easy to stand at the exact positions specified in the design and confirm them on site. Following the directions on the smartphone screen guides you to stake or foundation points with centimeter-level accuracy, improving the precision of staking and layout markings. Once you complete this design verification by matching data with the site before construction, discrepancies between drawings and the site are largely eliminated, allowing you to start construction with confidence.

You can also scan the completed exterior with LRTK at project completion to obtain the as-built 3D data and verify whether construction was carried out according to the design. Thorough checks like this ensure solid quality control and provide lessons for future projects.

In fact, one exterior contractor used LRTK as a sales tool, projecting a planned exterior 3D model onto a customer’s site using AR. Customers reportedly praised it as "very easy to understand because the image was concrete." Sharing data via the cloud to multiple devices allows clients and designers to view the same 3D image during meetings, which increases the persuasiveness of proposals.

Benefits of introducing LRTK: reduced rework, faster work, and improved safety

• Reduced rework: The biggest benefit of using LRTK is the reduction of post-construction rework. By eliminating mistakes and mismatches before work begins, the occurrence of rework dramatically decreases. Using AR to compare the as-built result with the design at completion also prevents last-stage oversights that lead to rework. Reducing unnecessary material waste also contributes to lower environmental impact. Eliminating rework improves profit margins.

• Faster work: LRTK streamlines surveying and positioning tasks. Even without relying on the experience and intuition of skilled workers, machine assistance enables fast, accurate data acquisition and marking. For example, layout marking that used to take half a day could be completed quickly thanks to coordinate navigation. Also, tasks that traditionally required two or more people can be handled by one person, improving staffing efficiency. With fewer reworks, overall schedules shorten and the likelihood of handing over to clients on time increases.

• Improved safety: Precise pre-construction verification prevents unexpected issues during construction. Sudden on-site fixes can make work chaotic and compromise safety management, but following plan from the start reduces such risks. LRTK measurements also reduce the need for risky manual work in hazardous areas (e.g., high places or busy roads). Additionally, knowing the locations of underground utilities from point-cloud and coordinate data can prevent excavation accidents. As a result, overall site safety improves.

• Smoother client communication: Sharing the finished image via AR greatly facilitates agreement with clients. Visual understanding during the proposal stage reduces disagreements like "this isn’t what I expected," preventing post-contract changes or complaints. Reporting construction progress with 3D data during work increases client reassurance and helps build trust. Demonstrating the use of advanced technology itself conveys your company’s professionalism.

Actual LRTK users report benefits such as "survey time halved" and "client explanations became markedly smoother." In another project where LRTK was used for thorough pre-construction checks, the work was completed without a single rework occurring through to the as-built inspection.

Tips for using LRTK effectively

Finally, let’s cover key points to get the most out of LRTK on site.

• Ensure high-precision positioning: LRTK terminals incorporate high-precision RTK-GNSS, but to realize that performance you must use them in environments where satellites can be reliably received. Turn the device on in an open outdoor area and wait several tens of seconds for the positioning mode to switch from Float (about 1 m accuracy) to Fix (about 2 cm accuracy). Perform point-cloud capture and coordinate measurements after accuracy stabilizes to increase the trustworthiness of your survey data. Also note that the smartphone or tablet used must be connected to the internet to achieve high-precision positioning.

• Data sharing and cloud synchronization: Point-cloud data, photos, and coordinate data obtained on site can be synchronized to the cloud on the spot. There’s no need to copy data via USB after returning to the office; you can share data with colleagues immediately after capture. You can review terrain using cloud-based maps or 3D viewers, or download data to import into CAD software as needed. Real-time information sharing between site and design departments enables quick consideration of design changes.

• Linking 3D data with design tools: Incorporate point-cloud and coordinate data acquired with LRTK into your design workflow. For example, loading point-cloud data into CAD or civil BIM software allows design considerations based on actual site conditions. Conversely, uploading projected images and CAD drawing data to the LRTK app for AR display can be used for design checks and client presentations. LRTK supports Japan’s plane rectangular coordinate system, so standardizing your drawing coordinate system makes it easier to match drawings with site data. Start with small sites to build internal know-how and introduce the system gradually.

• On-site operational tips: When using LRTK on site, manage device and smartphone battery levels carefully and carry mobile batteries as needed. Direct sunlight in summer can make screens hard to see, so using a tablet or shade can help. Mark points to be surveyed with visible markers in advance, and observe safety around the site when checking AR displays—basic precautions that matter. Although LRTK operation is intuitive, practice beforehand so you don’t get flustered on site and can use it smoothly.

After introducing the tool, share usage and data-handling methods among all site staff and actively try it out on site. New technology can be confusing at first, but with practice it will become a strong ally in your operations.

Use LRTK’s simple surveying features to streamline pre-construction verification for exterior work

The challenge of achieving zero rework directly ties into improved site productivity and higher customer satisfaction. By using LRTK’s simple surveying features, you can dramatically streamline the surveying and verification tasks required for pre-construction verification in exterior work. Because site personnel can operate it intuitively without complicated equipment or advanced expertise, it’s easy for small contractors to adopt. The era when anyone can quickly and accurately verify a site has begun—bring advanced technology to your site and realize smart construction management that aims for zero rework.