Drawing AR Overlay (Procedures + Precautions) On-site Manual: Checklist to Visualize According to Drawings with LRTK

Table of Contents

• What is a drawing AR overlay

• Benefits of drawing AR overlay

• Basic preparation for AR overlay

• Procedure for performing AR overlay

• Precautions

• Checklist

• Simple surveying with LRTK

• Summary

• FAQ

What is a drawing AR overlay

This refers to the technique of displaying construction drawings or design plans on-site as augmented reality (AR) and overlaying them on 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 drawings against the actual conditions. Points that were difficult to fully grasp from conventional 2D drawings alone become visualized with AR overlays, significantly improving the accuracy and efficiency of on-site work.

Benefits of drawing AR overlay

• Sharing design intent: Projecting life-size drawings or the expected completed image on-site makes it easier to share the anticipated outcome among clients and construction staff.

• Improved construction accuracy: You can verify on the spot whether boundary lines, reference lines, foundation positions, etc., are placed according to the drawings, enabling early detection and prevention of construction errors.

• Improved work efficiency: It assists traditional staking and marking tasks and reduces the need to walk around for surveying. Because you can check on the spot rather than repeatedly referring to paper drawings, work time is reduced.

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

Basic preparation 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 drawings makes real-world alignment smoother. If coordinates are not set, measure reference features on-site and assign coordinates.

• Prepare equipment 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, also prepare to connect a GNSS receiver or a high-precision surveying device like LRTK to the smartphone. Don’t forget to check the smartphone battery level and clean the camera lens.

• Check the site environment: AR displays require sufficient space and sight lines. Choose an open area with few large obstructions where GPS satellites can be received easily. Be careful using devices in strong direct sunlight, high humidity, or rain, as these conditions can reduce screen visibility and cause sensor malfunctions.

• Points for alignment: Set a reference point that will serve as the origin of the drawing on-site (for example, a staked coordinate point or a corner of an existing structure) and survey its actual position. This establishes the basis for accurately aligning the drawing origin with the on-site origin in the AR app and overlaying the entire drawing correctly.

Procedure for performing AR overlay

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

• Place the drawing using the 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 on-site location. This may require designating the on-site position corresponding to the drawing’s reference point with the camera or entering coordinates. Confirm alignment at multiple points to ensure the drawing is correctly positioned and oriented relative to the site.

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

• Check for 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 on the drawing or a position with a known elevation and adjust the alignment within the app. This increases 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 positions, boundary lines, or foundation/equipment installation locations. Tapping the AR-displayed drawing may show dimensions or notes, making it easy to reference necessary information on-site.

Precautions

• Maintain positioning accuracy: Ordinary smartphone GPS can have errors of several meters, causing large AR display shifts. GPS signals are especially obstructed in urban canyons or mountainous areas. Use high-precision GNSS like LRTK whenever possible and continuously correct positions.

• Calibrate heading and tilt: A smartphone’s compass and gyroscope are susceptible to magnetic interference and vibration and may drift over time. Calibrate before using AR, or keep the device level and slowly rotate it outdoors to maintain heading sensor accuracy.

• Environmental conditions: Strong sunlight, low light, or rain can make it difficult for the camera to accurately recognize surroundings. Poor screen visibility can impair the overlay check, so consider using sun shades or bright auxiliary lighting. Also, use a tripod or mount to prevent device shake from wind or vibration.

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

• Safety measures: Focusing on the AR display can reduce awareness of the surroundings. On sites with cranes or heavy machinery, always operate while checking your surroundings and consider assigning a safety observer; safety comes first. Also verify that the area you point the camera at does not include third parties or confidential information, and respect privacy.

Checklist

• Drawing data: The latest CAD drawings or 2D/3D data have been loaded into the AR app.

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

• GNSS/surveying equipment: The smartphone is ready for position measurement, and high-precision equipment such as LRTK is powered on and connected to a base station/correction information.

• Environment check: Choose a site with good sight lines and confirm reception conditions for GPS augmentation services (e.g., CLAS). Take measures against strong wind, rain, and direct sunlight.

• Device condition: The smartphone has sufficient battery. Clean the camera lens and sensors, and prepare stabilization such as a tripod.

• Assignment of personnel: Assign roles such as AR display operator and safety observer when working with multiple people.

• Verification points: Mark or otherwise prepare to compare important drawing points—reference points, stakes, existing structures—with the AR display.

• Communication: Share the drawings and AR display content with the entire construction team and explain operating procedures and objectives.

Simple surveying with LRTK

LRTK is a compact RTK-GNSS receiver that attaches to a smartphone, featuring a lightweight design of only approximately 125 grams. Using this device, centimeter-level (cm level accuracy (half-inch accuracy)) high-precision positioning can be easily achieved by a single person without the need for specialized surveyors as with conventional surveying equipment. On AR overlay sites, high-precision coordinates obtained with LRTK allow you to more closely match drawings and actual conditions, further reducing placement discrepancies. LRTK can scan survey points and has functions to automatically align drawing coordinate data, enabling AR displays 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 perform simple surveying and drawing verification end-to-end with just a smartphone, contributing to on-site DX.

Summary

Using AR to overlay drawings revolutionizes traditional measurement tasks and significantly 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 AR safely. In particular, combining LRTK for high-precision positioning makes it possible to reduce on-site positional discrepancies to nearly zero using only a smartphone. As visualization of design and site becomes increasingly important, AR overlays are becoming a standard in construction management. Use this guide as a checklist to effectively carry out AR projection on-site.

FAQ

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

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

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

• Q: What is LRTK? A: LRTK is a compact RTK-GNSS positioning device for smartphones that enables centimeter-level (cm level accuracy (half-inch accuracy)) surveying to AR display.

• Q: How much space is needed for AR overlay? A: At minimum, an open area with few obstructions is preferred. On large sites or indoors, having enough distance to grasp the overall view helps display drawings more accurately. In confined spaces, it is still possible to use AR by carefully aligning at building corners or feature points.