Complete Guide to Overlaying Drawings in AR (Procedure + Precautions): Settings and Operational Tips to Prevent On-site Misalignment with LRTK

This article provides a detailed explanation, including procedures and precautions, on how to use AR to display drawings and 3D models on smartphones or tablets for construction verification and positional guidance on-site. It also introduces tips for “non-shifting” AR overlays achieved by combining high-precision RTK positioning.

Table of Contents

• What is drawing AR overlay

• Preparations: drawing data formats and coordinate alignment

• Device-side settings: LRTK setup for high-precision AR

• On-site overlay procedure (viewpoints, markers, offsets)

• Tips for preventing AR drift using LRTK

• Integrated solutions enabled by LRTK

• FAQ

What is drawing AR overlay

In construction and infrastructure works, “drawing AR overlay” refers to the technology that displays design drawings or 3D models superimposed onto the real scene through the camera of a smartphone or tablet (AR = augmented reality). Simply put, it is a system that lets you view as-built reality and design information together on-site. Using this technology, you can confirm on the spot whether the work is progressing according to the design, and detect positional discrepancies or dimensional mistakes in real time. Tasks that used to require surveying after completion to compare as-built with drawings can now be done instantly in AR, greatly reducing rework and improving quality control.

Outdoor AR combined with high-precision GNSS positioning (RTK) has drawn particular attention in recent years. With standard smartphone GPS accuracy (errors on the order of 5–10 m), precise alignment with drawings was difficult, but by using RTK-GNSS, smartphones can achieve position accuracy on the order of a few centimeters. Smartphone RTK technology, which makes phones RTK-capable, enables AR displays that match design models to the real world with almost no offset. This eliminates the need to place ground markers for alignment, and the model on the screen remains fixed at its real-world location even as the user walks around. It feels like projecting drawings onto the site—hold up a tablet and the lines from the drawing appear directly on the ground—and such a future for construction management is becoming reality.

Leveraging drawing AR overlays streamlines and enhances many on-site operations. For example, for underground utility visualization, pre-acquired data of buried pipes and cables can be displayed in AR, showing subsurface piping routes as lines on the screen during excavation. This makes it obvious where piping is buried and significantly reduces the risk of damaging lifelines. For stake-driving layout, virtual stakes (AR stakes) based on the design can be displayed at the planned stake positions, guiding workers to the correct spots. Even inexperienced workers can find exact positions by following on-screen arrows or virtual stakes, enabling one person to handle multiple stake layout points quickly. For as-built management, projecting the completed model or design lines in AR beforehand allows you to verify on the spot whether embankments or structures have reached the design elevation. When fill reaches the design line, the line will disappear behind the terrain on the screen, making it easy to tell at a glance that the required elevation has been achieved. It is also possible to capture current point cloud data with built-in smartphone LiDAR or photogrammetry and automatically compute differences from the design 3D model in the cloud. Thus, drawing AR overlay contributes to preventing construction errors, improving work efficiency, and enhancing safety, and its adoption is being considered across many sites in line with initiatives such as the Ministry of Land, Infrastructure, Transport and Tourism’s i-Construction and DX promotion.

That covers the overview and benefits of drawing AR overlay. Next, we will explain in detail the preparation procedures and precautions you need to actually use it on-site, step by step.

Preparations: drawing data formats and coordinate alignment

Preliminary preparation is crucial to accurately overlay drawings and models in AR. Check and prepare the following points.

• Prepare data formats: Digitize the design data you want to display on-site. For 2D drawings, prepare CAD data (e.g., DWG or DXF formats); for 3D models, export BIM/CIM data or formats such as IFC, OBJ, glTF. If you only have paper drawings, it’s better to obtain CAD data if possible, or at least create a simple 3D model rather than just scanning to an image—3D data makes AR display easier.

• Confirm coordinate systems: Verify that the prepared drawing data can be associated with real-world coordinates. If the drawing uses an absolute coordinate system such as the Geospatial Information Authority of Japan’s plane rectangular coordinate system or WGS84, it is easy to match with on-site positioning coordinates and typically requires no additional alignment. If the drawing uses a local arbitrary coordinate system (such as a site-specific reference line), coordinate alignment with the site positioning values is necessary. For example, obtain multiple measured lat/long or known point coordinates corresponding to control points on the drawing and compute translation and rotation offsets. Note: If the drawing and site coordinate systems are mismatched, AR displays can be significantly offset, so compute coordinate transformation parameters (origin differences, orientation angle differences, etc.) in advance. When using LRTK cloud, you can register a custom coordinate system and specify it at upload time to automatically convert and display the data.

• Model scale and units: Check the scale and unit system of CAD or 3D models. The data must be created at real scale (1:1) for correct dimensions in AR. For example, models in feet will not match real dimensions if displayed as-is, so standardize to metric units where appropriate. Imported 3D objects often have unit mismatches—take care.

• Lightweighting data: To ensure smooth display on smartphones, reduce data size when necessary. Loading highly detailed BIM models or very large point clouds can cause sluggish performance. Prepare simplified models that hide unused elements, reduce texture resolution and polygon count, or use DWG/DXF files limited to lines and points if you only need to check construction drawings. LRTK can handle large datasets in the cloud and synchronize only the required portions to the smartphone, so leverage cloud workflows as appropriate.

• Upload and sharing preparation: Once formats and alignment are confirmed, upload the data to your AR app or cloud service. In LRTK cloud, you can register DWG drawings and 3D models to a project in advance and synchronize them so they are instantly accessible on-site. Because data with absolute coordinates is automatically placed on the GIS map, office-side uploads remove the need for cumbersome on-site placement. For other AR apps, either transfer the necessary model files to the smartphone or prepare them to be loaded offline.

Those are the main preparation steps. Key point: align drawing data and site coordinates thoroughly. Doing this well makes on-site AR overlay go smoothly.

Device-side settings: LRTK setup for high-precision AR

Next, here are the device-side configuration steps for using a smartphone or tablet on-site for AR display. Achieving high-precision alignment requires attention to several device-side points.

• Prepare high-precision GNSS: To achieve centimeter-level accuracy in smartphone-based AR overlay, RTK GNSS reception is essential. When using a smartphone RTK system like LRTK, attach or connect a dedicated compact GNSS receiver to the smartphone and start RTK positioning from the app. For network RTK, connect to correction services such as NTRIP within the app, or in Japan you can use QZSS’s CLAS to receive augmentation signals without an internet connection. It is important to verify before entering the site that RTK is functioning and that correction data is being received. Note: In mountainous areas or urban canyons where satellites are blocked, getting an RTK Fix can be difficult; initializing in a location with clear sky view or setting up a base station can help.

• Position initialization (acquiring Fix): After starting GNSS reception, remain still for several tens of seconds until RTK resolves to a fixed (Fix) state. When Fix mode is achieved, the app will display estimated accuracy on the smartphone screen (e.g., horizontal accuracy ±1 cm (±0.4 in), vertical ±2 cm (±0.8 in)), indicating high-precision positioning is available. Do not proceed while in Float or Single mode, as errors are still large. In LRTK apps, the status display clearly shows Fix/Float.

• Calibrate internal sensors: AR requires not only accurate position but also accurate attitude (orientation and tilt). The phone’s compass is affected by local magnetic fields, so perform a compass calibration on arrival—e.g., move the device in a figure-eight motion. Modern AR frameworks such as ARKit/ARCore combine gyroscope, accelerometer, and camera imagery to track spatial position. Follow the app’s prompts to slowly scan surroundings so the app captures sufficient feature points. For example, LRTK may advise “do not cover the camera and walk about 6 m (19.7 ft). Avoid repetitive patterns (such as tiled floors) in view.” This stabilizes AR spatial recognition. Note: On feature-poor surfaces like gravel or grass, include nearby structures, signs, or other distinct features in the camera view while moving to improve tracking.

• App login and project selection: To use the prepared data, log into the app and open the relevant project or site data. In LRTK, syncing with the cloud and selecting a project displays registered drawings and model data. Other AR apps require preloading the models into the app. For offline operation, download the data to the smartphone in advance.

• Set site coordinate system (if necessary): As noted earlier, if the drawing and site coordinate systems differ, instruct the app about the coordinate transformation at this stage. The LRTK app has a “create site coordinate system” function where you can register a local coordinate system by inputting three or more corresponding survey points. Once registered, that site will automatically use converted coordinates. Manually, you might stand on a reference point and reset the current position to the drawing’s coordinate for that point (set an offset). In any case, make sure the device is set to handle coordinates using the same reference as the drawing.

• Start AR display mode: Launch AR view in the app. Camera video appears, and you can select the objects you synchronized earlier (e.g., “design plan view,” “structure 3D model”). If the data has absolute coordinates, LRTK will automatically project it to the proper position and orientation, so no special alignment steps are needed—overlay completes instantly. In other apps, verify that the model appears in the real space and that scale and rough position are correct.

With these steps the smartphone is configured and AR mode is ready. Next we’ll look at how to view and refine the overlay on-site.

On-site overlay procedure (viewpoints, markers, offsets)

Once high-precision prep is complete, execute the on-site procedure to overlay drawings with reality. Below we explain viewpoint handling, fine adjustments, and compare marker-based methods.

Basic overlay procedure

• Confirm model appearance: In AR mode, ensure the selected drawing/model appears on the smartphone screen. Stand still initially and check whether the model is roughly in the correct position. For example, verify that a design model appears at the foundation location or that design lines are drawn on the ground.

• Move viewpoints to verify: Walk around while holding the device to check for offsets between model and reality. Look from different distances and angles—approach, retreat, and view from the side—to confirm alignment from multiple viewpoints. For instance, check whether an actual stake at a designed corner corresponds to the AR corner, or whether a concrete form aligns with a wall line on the model. If the model remains fixed in the correct place from all viewpoints, you’re good; if misalignment appears from certain angles, adjustments are needed.

• Adjust alignment (if necessary): Even with high-precision RTK, the entire model may sometimes feel slightly offset due to residual errors or subtle coordinate system differences. Use the app’s offset function to fine-tune the model position. In LRTK you can tap and drag the model on-screen to move it horizontally or nudge it up/down, and you can apply small rotational (azimuth) corrections. Note: Always adjust using known reference points. Random adjustments can create discrepancies elsewhere; prioritize aligning one accurate reference point (or two) first. Once the reference points match, other areas should align closely.

• Model display settings: Display options are useful in AR overlays. For underground models, switch to semi-transparent display to indicate they’re below the surface, or hide parts of BIM models to view interiors. LRTK supports changing model opacity and toggling partial displays. Tune display settings so only necessary information is visible. In bright outdoor conditions, screen visibility can be poor—set maximum brightness or use shade, or attach a hood to the tablet if necessary.

• Use photos and measurements: After overlay alignment, record and utilize the results. Taking a screenshot of the AR view creates documentation that shows design information overlaid on site imagery. Such photos serve as evidence in as-built verification. If the app supports measuring distances between AR models and real objects on-screen, you can determine “how many centimeters remain.” LRTK offers a “geotagged photo” feature that tags captured photos with high-precision coordinates and camera orientation and uploads them to the cloud. This makes it clear from which position and direction a photo was taken and enables later AR view recreation.

Precautions during overlay

• Ensure on-site safety: Focusing on the AR overlay can distract attention from surroundings. Pay careful attention to trip hazards, approaching machinery, and other risks. If possible, have someone monitor safety or pause in risky areas to check surroundings.

• Maintain AR tracking: AR spatial tracking deteriorates if you move the device too quickly or abruptly. Move smoothly and avoid sudden swings. If the AR object drifts or floats, stop and reorient the camera to stabilize recognition. If that fails, use the app’s session reset to reinitialize tracking and reload the model.

• Use markers (for alternative methods): The above procedure assumes marker-less AR with high-precision positioning. However, some systems use dedicated markers (image targets, QR codes). In that case, place printed markers at defined positions and have the camera recognize them to display models. Marker-based systems can misalign if the camera loses sight of the marker, and outdoor markers risk being displaced by wind or weather, making placement challenging. High-precision GNSS methods remove the need for markers, but keep markers as a fallback, especially in GNSS-denied environments like indoors or tunnels.

• Overlaying multiple models: Advanced use cases include displaying point clouds alongside design models for comparison. When overlaying multiple datasets, display them sequentially and verify alignment step by step; disable unnecessary layers if things become cluttered. Showing point cloud differences as a color heatmap makes on-site deviation immediately visible. Be mindful that additional elements increase rendering load—if performance degrades, consider resetting and reloading.

Following these steps for on-site overlay will help intuitively close gaps between drawings and reality, enabling construction that prevents misalignment.

Tips for preventing AR drift using LRTK

Low-accuracy AR leaves users wondering whether the displayed line or the real thing is correct. To prevent on-site misalignment and make AR drawings and reality match precisely, use a high-precision positioning system like LRTK and follow these points.

• Ensure GNSS position accuracy: As noted, obtaining an RTK Fix is a prerequisite, but GNSS accuracy can be unstable depending on the environment. Near high-voltage lines, steel structures, or in valleys with limited sky view, corrections can be interrupted or multipath errors can arise. LRTK uses high-sensitivity antennas to stabilize reception, but always monitor the positioning accuracy and, if it degrades, pause work and move to a location with better signal or take other measures. Also pay attention to vertical datum differences: the design elevation might be referenced to Tokyo Peil (T.P.) whereas GNSS gives ellipsoidal height. LRTK apps can automatically apply regional geoid corrections, but with other systems ensure height references are matched.

• Accuracy of orientation: Even with very accurate RTK positions, a misaligned smartphone compass will rotate the model incorrectly. To reduce magnetic interference effects, consider mounting the phone on a rod to keep a constant orientation (for example, consistently pointing north) while aligning. LRTK stabilizes orientation using gyros and accelerometers, but if rotation errors persist, align using a known straight feature on site—e.g., a line that points true north or a clear east–west road curb—and rotate the AR model so its corresponding line is parallel. Tip: On sunny days, the sun’s direction (e.g., south at noon) can be a reference; having several people check the view increases objectivity during adjustment.

• Careful initial alignment: Instead of overlaying the entire site at once, first match a few reliable control points. Confirming a control point with a total station or verified stake and aligning the model point to that spot is effective. With LRTK you can verify control point coordinates on the phone; if the model differs, recheck the drawing coordinates. Once confirmed, proceed with AR display with confidence that the overlay is trustworthy.

• Continuous correction to prevent drift: AR can drift over long movement. High-precision position data mitigates this. LRTK continuously feeds absolute coordinates from smartphone RTK into the AR engine to correct tracking errors, so users typically won’t see models floating or drifting as they move. Other systems may require resetting anchors if drift occurs, but LRTK minimizes such effort. Tip: When traversing a large site, periodically check the GNSS position vs. model alignment at key locations and, if necessary, refresh positioning.

• Countermeasures for environmental conditions: AR quality is affected by environmental conditions. Direct sunlight causes screen glare—use screen films or a tablet hood. Rain requires equipment protection; raindrops on the camera degrade AR tracking. In rain or at night, consider illuminating targets or switching to a simplified navigation mode that shows directional arrows based on high-precision coordinates rather than relying on camera-based AR. LRTK is designed to provide coordinate guidance even under poor visibility, but best practice is to conduct surveying and AR checks in good weather and daylight whenever possible.

Following these tips will allow LRTK-based drawing AR overlay to maintain centimeter-level accuracy. With reliable position and orientation, AR moves from “approximately right” to “definitely here,” greatly reducing recognition mismatches and human errors in surveying and construction management.

Integrated solutions enabled by LRTK

Finally, a brief introduction to the functionality offered by the LRTK solution. LRTK integrates surveying and AR using a smartphone, and drawing AR overlay is only one of its features. With LRTK you can accomplish the following in a one-stop manner.

• High-precision 3D point cloud scanning: Use LiDAR and cameras on iPhone or iPad to capture site point clouds. Point clouds with RTK-derived absolute coordinates can be displayed over cloud maps and immediately compared with design drawings. Scan slopes or embankments in minutes and have the cloud compute volumes and cross-sections in the cloud with a single command.

• Immediate 3D measurements: Measurements that once required specialized software—distances, areas, volumes—can be computed in the cloud from point clouds. For example, measure the distance between two points in a scan, compute area enclosed by a polygon, or generate a heatmap of differences against the design model to check as-built. Complex terrain measurement is done by scanning on-site and obtaining numbers via cloud processing.

• Non-shifting AR display: The feature detailed in this article—the overlay function that requires no alignment and does not shift. Register drawings (DWG/DXF) or 3D models (OBJ, etc.) in the cloud and simply point your smartphone on-site to project them at real-world positions. From subsurface visualization to assembly checks and as-built confirmation, models remain fixed in the correct locations.

• Geotagged photos and sharing: Capture on-site photos tagged with high-precision coordinates and camera orientation and save them to the cloud. You can plot photos on a map, compare past and present images at specific locations in AR to observe changes, and office staff can instantly view and share synchronized cloud data from a PC without special software. Stakeholders can open a shared link to view 3D models, point clouds, and photos.

• Coordinate navigation and single-person operation: LRTK’s coordinate navigation guides you to a target by showing direction and distance like a compass when you input coordinates for a surveyed point. By following on-screen arrows, a single person can perform stake layout or marking accurately. This reduces risk by allowing targets to be set from safe positions even in steep or hazardous areas.

• Many other features: Additional functions include a log function that records walked tracks with cm level accuracy (half-inch accuracy), indoor positioning (inertial navigation where satellite signals do not reach), and management of multiple points (time-series comparison of inspection photos and model sharing across devices). All of this is achieved with a smartphone plus one LRTK device, and data is centrally managed in the cloud, consolidating tasks that previously required separate hardware and software.

Thus, LRTK is an all-in-one solution integrating simple surveying, as-built management, and AR visualization. It has clear value for improving on-site productivity and reducing human error. Drawing AR overlay is available seamlessly within LRTK, greatly reducing setup and configuration work while maximizing benefits.

This completes the comprehensive guide to drawing AR overlay procedures and tips. With proper preparation and high-precision techniques, eliminate on-site misalignment and achieve safe, efficient construction verification and management.

FAQ

Q1. What equipment and apps are needed for drawing AR overlay? A. Basically you need an AR-capable smartphone or tablet, an RTK-GNSS receiver that can measure positions with centimeter accuracy, and a dedicated app that connects them (e.g., LRTK app). While a phone alone can display AR, achieving high-precision alignment requires an RTK-capable receiver (internal receivers are possible but external units tend to be more stable). Attaching a dedicated GNSS unit such as the LRTK Phone to an iPhone/Android turns it into a high-precision surveying and AR device. If you use cloud services, internet connectivity is also required on-site (via the phone’s cellular connection or a mobile router).

Q2. I only have design drawings in PDF. Can I still do AR overlay? A. Direct AR display from PDF is difficult, but there are options. Import the PDF into CAD software and convert to DXF/DWG for line data usable in AR. Alternatively, use the PDF as an image texture on a plane after adjusting scale. Reality-wise, contact the client to obtain the original CAD data if possible; if that’s not feasible, create a georeferenced image from the PDF for AR overlay. LRTK supports DXF/DWG directly, so CAD conversion is preferable.

Q3. Is AR overlay accuracy really a few centimeters? How reliable is it? A. With proper RTK positioning and correct coordinate alignment of drawing data, horizontal position typically falls within an error range of ± a few cm. This is comparable to total station surveying. Note that smartphone AR can show slightly larger errors in the vertical direction depending on device attitude—farther objects may show several centimeters to around 10 cm of height projection error. For most stake layout and structural positioning tasks, the achieved accuracy is sufficient and reliable for practical on-site use.

Q4. Can AR overlay be done indoors or inside tunnels? A. In environments without GNSS, RTK positioning cannot be used, so the high-precision method described here is limited. LRTK does offer an indoor positioning mode that relies on the phone’s camera and sensors to continue estimating position. Short-term inertial navigation can maintain positioning, but error accumulates (roughly 2% drift relative to distance moved). Therefore, for long tunnels or large indoor spaces, periodically resetting at known points or combining markers (QR codes) for correction is recommended. In summary, it’s harder to achieve outdoor-level accuracy indoors, but with appropriate techniques, useful AR overlays are still possible.

Q5. How does this differ from other high-precision AR systems? A. Historically, high-precision AR for construction required specialized equipment (head-mounted displays or dedicated scopes) costing hundreds of thousands of dollars. LRTK is groundbreaking in that it realizes similar capabilities using a handheld smartphone plus a small GNSS receiver. Smartphones offer superior usability and portability, and software updates can extend functionality. LRTK also integrates surveying and photo management into a single platform, enabling centralized handling of point clouds, drawings, and photos in the cloud. In short, LRTK is cost-effective, device-agnostic, and feature-rich. Other systems may be better suited for specific niche uses, but for many sites an all-in-one solution like LRTK offers strong cost-performance.

Q6. Can beginners use it? Is special training required? A. Basic operations are done through a smartphone app with an intuitive GUI, and many report that novices quickly become comfortable. Coordinate navigation and AR displays are easy to follow like a game. However, some literacy in high-precision positioning helps when troubleshooting—understanding why Fix doesn’t occur or what a coordinate system is can be useful. LRTK provides support materials and manuals, and combined learning of operation and basic theory allows most users to become proficient in a short time.

Q7. If we adopt LRTK, what should we start with? A. Start by downloading the LRTK app from the official site and testing basic features with a trial account. You can experience AR display and point cloud viewing with sample cloud data even on your personal smartphone. High-precision measurements require the dedicated device, but rentals and demos are often available—contact the vendor. Define the on-site processes where you want to apply LRTK first (e.g., stake layout accuracy, as-built verification), prepare the necessary data and workflows, and pilot it on a small site or single process. LRTK offers support to help onboard, so begin by trying the app—touching it is the first step toward site DX.