Table of Contents

• What is a drawing AR overlay

• Benefits of drawing AR overlay

• Basic preparations for AR overlay

• Procedure for performing AR overlay

• Precautions

• Checklist

• Simplified surveying with LRTK

• Summary

• FAQ

What is a drawing AR overlay

This refers to the technology of displaying construction drawings or design plans as an extension of reality (AR) on-site and overlaying them onto the actual work area. By compositing drawings or 3D models into the real space through a smartphone or tablet camera, you can intuitively compare and verify the design against the current conditions. Points that were difficult to fully grasp from conventional 2D drawings alone become visible with AR overlays, significantly improving on-site work accuracy and efficiency.

Benefits of drawing AR overlay

• Sharing design intent: Projecting life-size drawings or completion images on-site makes it easier to share the expected outcome among owners and construction staff.

• Improved construction accuracy: You can immediately check whether boundary lines, reference lines, foundation positions, etc., are placed according to the drawings, helping to detect and prevent construction errors early.

• Improved work efficiency: It assists traditional marking-out and staking work and reduces the need to walk around for measurements. Because you can confirm things on the spot instead of repeatedly consulting paper drawings, work time is shortened.

• Flexible response to design changes: If drawing data is updated in the app, the AR display on-site can immediately reflect the latest drawings. Design changes or corrections can be shared instantly.

Basic preparations for AR overlay

• Prepare drawing data: Prepare digital data such as CAD floor plans, sections, and 3D models. Setting a surveying coordinate system (latitude/longitude or plane rectangular coordinates) in the drawing facilitates smoother real-world alignment. If coordinates are not set, measure reference features on-site and assign coordinates.

• Prepare devices and software: Install a compatible AR app (e.g., apps supporting iOS ARKit or Android ARCore) and prepare a smartphone or tablet. To improve positioning accuracy, prepare to connect a GNSS receiver or a high-precision surveying terminal like LRTK to the smartphone. Don’t forget to check the smartphone battery level and clean the camera lens.

• Check the site environment: AR display requires sufficient space and line of sight. Choose an open area with few large obstructions and good GPS satellite reception. Be careful that strong direct sunlight, high humidity, or using in rain can reduce screen visibility or cause sensor errors on the smartphone.

• Points for alignment: Set a reference point in the field to serve as the drawing origin (for example, a staked coordinate point or a corner of an existing structure) and survey its actual position. This creates the basis for aligning the drawing origin in the AR app with the site origin so the entire drawing can be overlaid accurately.

Procedure for performing AR overlay

• Start the smartphone and stabilize positioning: Launch the AR app and ensure GNSS signals are being received stably. When using a high-precision positioning device (such as LRTK), receive correction information from a base station or a CLAS service to fix the smartphone’s current position at centimeter-level accuracy.

• Place the drawing using a reference point: Point the smartphone camera at the prepared reference point (the position with coordinates) and align the origin of the drawing data imported into the app with the site. This requires designating the on-site location corresponding to the drawing’s reference point via the camera or entering coordinates. Verify alignment against multiple points to ensure the drawing’s position and orientation on the site are correct.

• Overlay the drawing in AR: Display the drawing over the site at full scale. In addition to floor plans, sections and 3D models can also be overlaid as needed. If coordinates are mechanically matched, the drawing should appear in the smartphone camera view without shifting. Compare the displayed drawing with the real scene and confirm that wall lines, ceiling heights, and the positions of structures match the drawing.

• Check and correct errors: If discrepancies between the AR display and the site are found, recalibrate using additional feature points. For example, measure another survey point or a position with a known elevation on the drawing and adjust the alignment in the app. This will further improve the accuracy of the AR overlay.

• Use for on-site work: Perform work based on the accurately overlaid AR display. For example, use it to confirm staking locations, boundary lines, foundation and equipment installation positions. Tapping the AR-displayed drawing may reveal dimensions and notes, allowing easy access to necessary information on-site.

Precautions

• Maintain positioning accuracy: Regular smartphone GPS alone can produce errors of several meters, causing large AR display shifts. GPS signals are especially prone to blockage in high-rise city areas or mountainous regions. Use high-precision GNSS like LRTK and continuously apply position corrections whenever possible.

• Calibrate orientation and tilt: Smartphone compasses and gyroscope sensors are susceptible to magnetic interference and vibration, and their accuracy may drift over time. Perform sensor calibration before using AR or rotate slowly on a horizontal plane outdoors to maintain orientation sensor accuracy.

• Environmental conditions: Strong sunlight, low-light conditions, or rain can make it harder for the camera to accurately recognize the surroundings. If the screen is hard to see, consider using a sunshade or bright auxiliary lighting. Also, use a tripod or mount to prevent smartphone shake from wind or vibration.

• Manage drawing updates: Drawings may be revised as the site progresses. If the AR app does not always reflect the latest drawings, you may overlay based on outdated design information and make incorrect confirmations. When design changes occur, import the latest data immediately and share updates among on-site staff.

• Safety measures: Focusing on the AR display may reduce awareness of the surroundings and pose a hazard. On sites with cranes or heavy machinery, operate while checking the surroundings and station a safety observer; prioritize safety. Also confirm that the area you point the camera at does not contain third parties or confidential information, and respect privacy.

Checklist

• Drawing data: Loaded the latest CAD drawings or 2D/3D data into the AR app.

• Coordinate confirmation: Coordinates are set in the drawing, or reference points were surveyed on-site and coordinates assigned.

• GNSS / surveying equipment: Smartphone positioning is ready, high-precision devices like LRTK are powered on, and connected to a base station/correction information.

• Environment check: Selected an area with good line-of-sight and confirmed reception of GPS augmentation services (e.g., CLAS). Implemented measures for strong wind, rain, or direct sunlight.

• Device status: Smartphone battery has sufficient charge. Cleaned camera lens and sensors, and prepared a tripod or mount to stabilize the device.

• Staff assignments: Assigned roles for AR operation and safety monitoring when working with multiple people.

• Verification points: Marked or prepared to mark important drawing points—reference points, stakes, existing structures—to ensure reliable comparison with the AR display.

• Communication: Shared the drawing and AR display content with the entire construction team and explained operation procedures and objectives.

Simplified surveying with LRTK

LRTK is a small RTK-GNSS receiver that mounts on a smartphone and weighs only about 125 grams. Using this device enables centimeter-level high-precision positioning easily by one person without the need for specialized surveyors, unlike conventional surveying equipment. On AR overlay sites, the high-precision coordinates obtained with LRTK allow you to match drawings to actual conditions and further suppress placement errors. There is also a function to scan survey points with LRTK and automatically align the drawing’s coordinate data, enabling AR display while surveying feature points on-site. This reduces the burden of on-site surveying and meetings while visually supporting construction according to the design. Because no special qualifications or lengthy preparations are required, you can achieve end-to-end workflows—from simplified surveying to drawing verification—using just a smartphone, contributing to on-site DX.

Summary

Using AR to overlay drawings revolutionizes traditional measurement practices and greatly enhances on-site construction accuracy and efficiency. By following the procedures and precautions—from preparing drawing data to actual alignment and work verification—you can use it safely. Especially when combined with high-precision positioning by LRTK, even a smartphone alone can reduce on-site position errors to nearly zero. As the importance of visualizing design and site conditions grows, AR overlay is becoming a standard in construction management. Use this guide as a checklist to effectively implement AR projection on-site.

FAQ

• Q: What equipment is needed for drawing AR overlay? A: A smartphone or tablet and an AR-compatible app are the basics. For higher-precision positioning, prepare a small RTK receiver for smartphones (e.g., LRTK) or a GNSS antenna. A stable power supply and a tripod for securing the camera are also useful.

• Q: What should I do if coordinates are not set in the drawing? A: Survey reference features on-site (building corners, existing stakes, specific points, etc.) and manually enter those coordinates into the drawing data. Many AR apps provide a function to map on-site coordinates to the drawing using coordinates obtained on-site.

• Q: How do I deal with AR display drift? A: First check positioning status and sensor calibration. If possible, re-survey with LRTK and update correction information. Then recalibrate using multiple on-site points and readjust the difference between the AR display and the actual positions.

• Q: What is LRTK? A: LRTK is a small RTK-GNSS positioning device for smartphones that enables centimeter-level surveying and AR display.

• Q: How much space is required for AR overlay? A: An open area with few obstructions is preferable. In large sites or indoors, having space to step back and view the whole object helps display drawings more accurately. It can also be used in tight spaces if you reliably align points such as building corners or feature points.