Table of Contents

• The significance of overlaying drawings and AR on site (purpose and benefits)

• General workflow for AR drawing overlay (3D models / floor plans / DXF, etc.)

• Concrete steps to overlay drawings on site using AR

• Common failure examples and their causes

• Points to note for correct overlay (positioning errors, perspective mismatch, anchor settings, etc.)

• Benefits of alignment correction using LRTK high-precision positioning

• On-site use cases for drawing AR (confirming pile locations, sharing completion images, overlaying underground utilities, etc.)

• Case studies and effects of introducing drawing AR with LRTK

• FAQ

Significance of overlaying drawings and AR on site (purpose and benefits)

When working on a construction site based on drawings, misreading the design or insufficient sharing of the intended image often leads to construction mistakes and rework. For example, overlooking a slight positional offset on a plan can result in a finished structure being located off the neighboring boundary, or misinterpreting the indicated drainage slope can lead to rainwater not flowing properly in the completed work. Behind these problems lies the difficulty of grasping the finished image from two-dimensional drawings alone and a gap in conveying the designer’s intent to everyone on site.

AR (augmented reality) has attracted attention as a powerful means to bridge these gaps and improve construction quality. Because design drawings and 3D models can be overlaid on the real scene through a smartphone or tablet camera, the finished form can be intuitively checked while on site. From site supervisors to workers and owners, everyone can view the same image and share “what will be built here and how,” preventing troubles caused by mismatched understanding. Below are the main benefits of overlaying drawings on site with AR.

• Visualization of the finished result: You can realistically experience the post-completion appearance that was hard to grasp from plans or sections alone, aligned with the actual scene. Placement and height of structures that are hard to imagine from drawings can be checked at a glance, enabling accurate sharing of design intent.

• Prevention of construction mistakes: By overlaying design models on the current situation in AR and checking them, deviations or interferences during construction can be detected immediately. For example, confirming formwork positions with AR before concrete pouring allows corrections before construction if offsets are found. Early detection and correction of errors significantly reduce the risk of rework.

• Consensus building and improved customer satisfaction: Using AR to explain to owners and stakeholders enables sharing the completed image that is difficult to convey with paper drawings. This prevents mismatches like “it’s different from what I expected,” and enables concrete feedback during proposal stages. Gaining agreement after previewing the completed image contributes to higher satisfaction after handover.

• Streamlining surveying and layout marking: AR overlay helps simplify positioning and layout marking. By visualizing design reference lines and positions in AR and marking on site, stakeout positions that previously required skilled surveyors can be accurately placed by anyone. This can shorten work time and reduce personnel burden.

General workflow for AR drawing overlay (3D models / floor plans / DXF, etc.)

To perform AR overlay of drawings, you first need digital design data. This can take various forms: 3D model data (BIM/CIM models or 3D CAD data) or 2D floor plan data (CAD drawings or images). If a 3D model is available, you can reproduce the shapes of columns, walls, and other three-dimensional structures in real space, making the check most intuitive. Even if only 2D floor plans or CAD drawings (DXF, etc.) are available, you can display the plan laid on the ground in AR or draw design lines as virtual glowing lines on the ground surface to achieve necessary alignment. The key is to project the design information (points, lines, shapes) onto the site at the correct scale.

Next, you must align the prepared design data with the actual site coordinates. Common AR apps use several methods to place virtual objects in real space. For example, you can set printed markers or QR codes at on-site reference positions and read them with the camera to align the model. Alternatively, you may manually move and rotate the virtual model in the AR app to match on-site feature points (corner positions or reference lines) and visually align them. What is important is to unify the coordinate system of the drawing data with the site’s coordinate system. If the design data already has absolute coordinates such as latitude/longitude or plane rectangular coordinates, you can automatically place the model in the correct position by matching it with the device’s position information. If the drawing uses a site-specific local coordinate system, you can correct the model’s position and orientation in virtual space by measuring several known points on site and mapping them (for example, specifying two or more corresponding points).

Once coordinate alignment is complete, the device screen will display the camera image overlaid with the design data in AR. Users can then confirm through the screen that virtual structures or lines exist on site in the positions shown on the drawings. This sequence—data preparation → coordinate alignment → AR display—is fundamentally common whether using 3D models or 2D drawings.

Concrete steps to overlay drawings on site using AR

Now let’s look at the actual on-site flow to display drawings in AR step by step.

• Prepare data: Load the prepared design data (3D models or drawing files) into the AR app. It is convenient to upload them in advance to a platform such as the LRTK cloud so they can be selected on site.

• Measure reference positions: To improve AR overlay accuracy, first measure reference positions on site. Connect a high-precision GNSS receiver (RTK-capable) to the smartphone to obtain latitude, longitude, and altitude to centimeter-level accuracy. Alternatively, you may align the device to known on-site points (layout marks or boundary markers) and input those coordinates as references. This step minimizes discrepancies between virtual and real-world coordinates.

• Start AR display: In the smartphone or tablet AR app, start displaying the design data. Select the previously loaded 3D model or drawing data, and virtual objects will appear overlaid on the camera image. The model may initially appear somewhat offset from the actual position, which you will adjust in the next step.

• Adjust alignment: Confirm and adjust the position and orientation of the virtual model so it accurately matches the actual site. Compare drawing markers such as building corners or road centerlines with their on-site counterparts, and make micro-adjustments in AR if there are offsets. With high-precision positioning like LRTK, major adjustments are usually unnecessary, but verify alignment from multiple viewpoints. If the model appears buried in the terrain or floating, make vertical corrections as needed.

• Utilize and record: Once the drawing and reality are precisely overlaid, use the AR display for work. If marking is required, follow the AR guide to mark the ground. When explaining to stakeholders, show the screen or capture AR photos and videos to share. Save the current AR display state and measurement data to the cloud as needed to support office records and reporting.

Common failure examples and their causes

Here are typical failure cases when overlaying drawings with AR and their main causes.

• The drawing in AR is displayed meters off: The model appears significantly displaced relative to the actual position. The cause may be low GPS accuracy on the device (meter-level positioning errors), leading to initial alignment errors. Large offsets can also occur when the design data and site coordinate systems do not match.

• It looks aligned from one viewpoint but shifts when the viewpoint changes: From a single spot the drawing seems to match reality, but discrepancies become obvious when you move. This is often caused by aligning visually from a single viewpoint only, failing to achieve precise positioning. Without sufficient real-space reference, the AR model may not be placed at the correct scale or angle.

• The model gradually drifts during AR use: The model was initially aligned but drifts away from reality while walking around. This can be caused by insufficient AR tracking accuracy or unstable anchor settings. Standard smartphone AR can accumulate small errors with movement, causing the model to appear misaligned over time.

• Model orientation or scale is incorrect: The building model faces 90 degrees off or the size is too large or small. This typically results from the design data’s orientation or scale settings not matching reality. For example, if the north direction in the drawing is rotated relative to true north, or unit system differences cause scale errors, such problems will occur.

Points to note for correct overlay (positioning errors, perspective mismatch, anchor settings, etc.)

To prevent the above failures and achieve accurate overlay, consider the following points.

• Use high-precision positioning: Consumer smartphone GPS can have errors of around 5 meters, so use RTK-GNSS or other centimeter-level positioning devices if possible. Improving absolute coordinate accuracy minimizes initial alignment errors.

• Confirm the drawing coordinate system in advance: Identify which coordinate system the design drawings are based on and convert it to the site survey coordinates if necessary. If local coordinates are used per site, prepare by calibrating with known points or using the app’s coordinate registration features to place the drawing data correctly.

• Check from different viewpoints: After placing the model, always move around and verify consistency from multiple angles; an appearance that matches from one spot may still be misaligned elsewhere. If the virtual model and real objects match in position and angle from multiple directions, the overlay is reliable.

• Use anchors and reference points: Make use of anchor or fixed alignment features provided by AR apps. If you use ground markers, fix them securely so they don’t move. When using environmental feature anchors, choose areas with distinct features (e.g., patterned walls or terrain) so tracking is stable. Systems like LRTK that manage anchors with absolute coordinates prevent model drift even when moving across a wide area.

• Calibrate device sensors: Calibrating smartphone or tablet sensors is important. Stimulate the AR kit’s environment recognition by moving the device on first startup and adjust the electronic compass to improve measurement accuracy. Devices with LiDAR can scan the surroundings to recognize ground height and obstacles, helping prevent vertical mismatches.

Benefits of alignment correction using LRTK high-precision positioning

Even considering the precautions above, there are inherent limits to standard smartphone-only AR. One such limit is positioning accuracy: standard GPS has meter-level errors, which may be adequate for rough checks but insufficient for precise overlay. Also, common AR frameworks like ARKit/ARCore track device motion using relative coordinates, so traveling across a large site gradually accumulates drift and a model initially aligned may slowly shift.

LRTK’s high-precision positioning (RTK-GNSS) addresses these challenges. LRTK is a compact positioning device attached to a smartphone that combines satellite positioning signals with correction information to calculate current position with errors on the order of centimeters. As a result, AR apps can know the device’s position in global coordinates accurately, enabling absolute alignment of design data. Specific benefits include:

• Reduced effort for initial alignment: With LRTK the coordinates match automatically, eliminating tedious fine-tuning or marker placement. Launch the app and select the model, and the virtual model will appear almost instantly at the design location.

• Stable model positioning: LRTK continuously provides centimeter-level position information even while moving, so the displayed model is less likely to drift as users walk around. The common AR issue of the model floating when viewed from a distance is mitigated, maintaining stable overlays across wide areas.

• Construction-grade accuracy: Traditional AR tolerated tens of centimeters of offset, but LRTK-enabled AR achieves the precision needed for construction tasks like pile driving or placing structural elements. When AR display dimensions match drawing dimensions, virtual layout marking can be trusted for work.

• Vertical alignment: RTK-GNSS can provide vertical positioning, enabling accurate height alignment of models. This allows precise AR representation in cases requiring vertical accuracy, such as the depth of underground utilities or fill height in earthworks.

By combining LRTK high-precision positioning, drawing AR overlay becomes practical at the accuracy level required in the field. On site, it is valued as “AR that does not shift,” allowing layout tasks that once relied on skilled surveyors’ judgement to be performed accurately by anyone with a smartphone.

On-site use cases for drawing AR (confirming pile locations, sharing completion images, overlaying underground utilities, etc.)

Below are concrete on-site use cases for drawing AR.

• Confirming pile locations: AR is a powerful guide when laying out pile locations for foundations and structures. Register pile center coordinates in advance from the design and display them in AR on site; virtual piles or markings will appear on the ground. Following those marks to drive piles enables correct positioning without tape measures or surveying instruments. With LRTK’s coordinate guidance, users can be directed with cues like “move north by X cm,” allowing accurate layout by non-experts.

• Sharing the completion image: Before construction, AR helps owners and other stakeholders understand the finished appearance. For example, displaying 3D models of exterior landscaping or equipment on a vacant lot lets customers visualize the final scene overlaid on the actual view. Immediate feedback such as “lower the height a bit” can be obtained, enabling early alignment of expectations. During construction, showing progress in AR helps intuitively report that work is proceeding according to drawings, building trust.

• Overlaying underground utilities: Visualizing buried pipes and cables in AR improves excavation safety and efficiency. If utility drawings and survey data are loaded into LRTK beforehand, simply pointing the camera on site can display the pipes and cables that should be beneath the ground. This reduces the risk of damaging existing infrastructure and helps intuitively understand how deep to dig until the utilities appear. Excavation planning and site walkthroughs become smoother, greatly improving safety management.

Other applications include checking as-built results against design models in the field for quality control, guiding machine operators with AR cues during high-elevation work, and many more. Drawing AR’s applicability across construction tasks continues to expand.

Case studies and effects of introducing drawing AR with LRTK

Sites that have actually used LRTK with AR report various benefits. Here are several case examples.

• Large reductions in work time and personnel: At mid-sized general contractor A, after introducing LRTK Phone, foundation layout work that previously took two people half a day was completed by a single site staff in about an hour. The labor of measuring from paper drawings and marking was eliminated, allowing redeployment of personnel to other tasks.

• Zero rework in construction: Exterior works company B introduced a process of sharing completion images with owners using AR before construction. As a result, specification changes and “it’s different from what I expected” disputes after start of work disappeared, and they achieved zero rework until completion. Owner trust increased and led to additional project orders, creating a virtuous cycle.

• Safe, faster infrastructure work: A municipal road project trialed AR visualization of buried pipes using LRTK. Tasks that had required cautious excavation using drawings became faster because AR conveyed accurate pipe positions, contributing to shorter schedules and improved safety. The anxiety of “you don’t know until you dig” decreased and worker confidence improved.

Combining drawing AR with high-precision positioning dramatically improves on-site productivity and quality. Because it can be used with just a smartphone and a small device, adoption is rapidly increasing, and it is becoming a key technology supporting digital transformation in construction and civil engineering. By incorporating LRTK-based simple surveying on site, you can enjoy benefits not possible with traditional methods.

FAQ

Q: What equipment and preparations are needed to perform AR overlay on site? A: You need a smartphone or tablet and an AR app. Modern iPhones and iPads come with AR functionality (ARKit) built in, so they can be used without additional devices, but to improve alignment accuracy it is recommended to use a high-precision GNSS receiver such as LRTK Phone. Also prepare the design data you will use (3D models or drawing files) on the device or in the cloud in advance, and perform coordinate system adjustments as needed for a smooth start.

Q: Can 2D drawing data be displayed in AR, or is a 3D model necessary? A: 2D floor plan data can be displayed in AR. Even without 3D models, you can project lines and shapes onto the ground or display markers and symbols at important points. For example, you can overlay DXF or image files as a background in AR to check offsets with current positions. However, 3D models provide height information and allow interference checks in three dimensions, so providing 3D data is preferable if possible.

Q: What level of alignment accuracy can drawing AR achieve? A: Standard smartphone-only GPS and AR may have offsets from tens of centimeters to several meters. This may be acceptable for rough checks but is insufficient for precise layout. Using high-precision positioning like LRTK, horizontal and vertical errors can be reduced to within a few centimeters, enabling AR overlays that nearly match the design drawings and providing construction-grade accuracy (centimeter-level).

Q: Is specialized knowledge or training required? Can site staff use it? A: No specialized CG software skills are required; basically anyone can use it by following the smartphone app instructions. LRTK systems are designed with UIs that make them usable by staff with little surveying experience, allowing positioning and AR display via button operations. A short on-site training for staff will enable immediate, practical use in daily construction management.

Q: Is it necessary to set markers or reference points in advance? A: When using LRTK, special marker installation is generally not necessary. The GNSS makes the device itself the reference point, allowing models to be displayed at the designated coordinates. However, indoors or where GPS cannot reach, you will need to rely on ARKit’s plane detection or visual markers. In those cases, using clear landmarks (e.g., wall corners or floor patterns) as references improves accuracy. For wide outdoor sites, coordinate alignment with LRTK is the most efficient method.