How to Use the Topcon LN-150 for Interior Framing Layout

The Topcon LN-150 is a purpose-built robotic layout tool for interior construction. This guide walks through the workflow for using it to lay out steel stud partitions from an architectural BIM model — the most common application for interior framing contractors. The same basic workflow applies to MEP rough-in layout, embed plate layout, and other interior layout applications; only the point list and marking protocol change.

What you need: Topcon LN-150, FC-6000 data collector, MAGNET Field software, design file with layout points, tripod, keel or marking pen.

Before You Arrive on Site: Office Preparation

Export Layout Points from the BIM Model

Good BIM-to-field layout starts in the office. Your BIM coordinator or project engineer needs to export the layout points for the floor you're working. In Revit, this typically means extracting the endpoints or centerlines of partition walls, door rough opening locations, window centerlines, and any other elements that need to be marked on the floor.

Export as:

• DXF (2D or 3D) — importable into MAGNET Field directly
• Point list (CSV with Point Number, Northing, Easting, Elevation, Description)
• MAGNET format (if your BIM coordinator has MAGNET tools)

Load the file onto the FC-6000 before leaving the office. Verify the point count on the data collector matches the exported list. A few minutes of verification now prevents a frustrating discovery on a floor 20 stories up.

Understand the Control Network

Confirm the project surveyor has established control monuments on the floor you're working. You need at least two control points with known X, Y coordinates referenced to the same coordinate system as your design model. Ask the project superintendent or surveyor for the control point list and verify the coordinates match what's in MAGNET Field.

Step 1: Set Up the Tripod and LN-150

Choose an instrument position near the center of the floor area you're laying out, with clear line-of-sight to both control monuments and across the layout area. On a large floor plate, you may need to move the instrument several times — plan your instrument positions before you start to minimize moves.

1. Set up the tripod on the concrete floor. Open the legs to a stable, wide stance.
2. Level the tripod head roughly by eye — the LN-150's onboard compensator will take care of fine leveling.
3. Mount the LN-150 on the tripod. Connect the power cable and power on.
4. The LN-150 will self-level using its dual-axis compensator. Wait for the level indicator on the display to confirm level status.
5. Power on the FC-6000 and launch MAGNET Field. Pair the FC-6000 to the LN-150 via Bluetooth.

Step 2: Perform a Free Station Setup (Resection)

The LN-150 doesn't need to be set up over a known point — it determines its own position by measuring to the control monuments you've established. This is called a free station or resection setup, and it's one of the most practical advantages of the robotic layout workflow over traditional two-person total station layout.

1. In MAGNET Field, select Survey → Free Station (exact menu path may vary by software version).
2. Select the first control point from your point list.
3. Aim the LN-150 at the first control monument (a nail or hub with a known coordinate). You can aim it manually using the instrument's physical controls, or drive the motorized head using the FC-6000.
4. Measure the control point. MAGNET Field records the angle and distance.
5. Repeat for the second control point.
6. MAGNET Field will calculate the instrument's position and orientation. Review the residuals — the difference between the measured and expected positions of the control points. A residual of less than 0.02 ft (6 mm) indicates a good setup. If residuals are higher, check that you measured the correct control points and that the monument coordinates are correct.
7. Accept the free station when residuals are acceptable.

Step 3: Begin Stakeout

With the instrument oriented to the control network, you're ready to stake out layout points.

1. In MAGNET Field, select Stakeout → Points.
2. Select the first layout point from your list. The LN-150 will rotate its motorized head to point in the direction of the target coordinate.
3. Walk toward the instrument's indicated direction, watching the FC-6000 display. The display shows your real-time position relative to the target — direction arrows and distance remaining update as you move.
4. As you approach the target, the distance displayed decreases. Slow your walk for the final few feet.
5. When the display shows you're within your tolerance (typically ±0.05 ft or ±15 mm for framing layout), make your mark with keel or a marking pen.
6. Press the store/record button on the FC-6000 to record the as-staked position. This creates a deviation record — design vs. actual — for quality documentation.
7. Advance to the next point and repeat.

Step 4: Marking Protocol for Framing Layout

Good marks are as important as accurate marks. Here's a standard framing layout marking protocol:

• Wall centerline marks: Mark the centerline of the stud wall with a dot and a short line indicating the wall direction. Mark both ends of each wall segment.
• Face-of-stud marks: If your framing crew works from face of stud rather than centerline, offset your layout point to the face-of-stud position in MAGNET Field before marking.
• Door openings: Mark both jamb sides of the rough opening. Label clearly — DOR-101L and DOR-101R, or similar.
• Color coding: Use different keel colors for different wall types if your project has many wall types (e.g., red for fire-rated walls, blue for standard partitions, yellow for shear walls).
• Photos: Photograph key layout areas after marking as a timestamped QC record. This is especially important before the floor gets dusty and marks are hard to read in photos.

Step 5: Moving the Instrument

When you've staked all points visible from the current instrument position, move the LN-150 to a new tripod position. You don't need to go back to a known point — set up anywhere with good sightlines to the control monuments, and perform a new free station setup. The entire move and re-setup typically takes less than 5 minutes with a practiced crew.

Common Issues and Solutions

• LN-150 loses lock on the handheld target: Obstructions (columns, scaffold, other workers) between the instrument and target will break the tracking link. Move to a position with clearer sightlines, or relocate the instrument to cover the obstructed area.
• Residuals too high on free station: Check that you're measuring the correct control monuments. Verify that the monument coordinates in MAGNET Field match the surveyor's point list exactly.
• Points not found in list: Confirm the design file was loaded correctly and that the coordinate system of the design model matches the project control network. A common cause is a design model in a local coordinate system vs. a state plane control network.

Products featured in this guide:

• Topcon LN-150 Layout Navigator
• Topcon FC-6000 Data Collector
• MAGNET Field Software
• Browse all Robotic Layout Tools →
• Tools Needed for BIM-to-Field Interior Layout →