3.2 Route Planning and Coverage Strategy

Core Route Planning Principles

Walk Main Corridors First, Branch Into Rooms Second

Establish the spine of the floor plan before branching. The corridors give SLAM a continuous backbone to anchor everything against, and each later room entry becomes a loop closure relative to that backbone, correcting drift as you go. Branch first and the room-to-room relationships rely on weaker individual transitions.

Each Room Entry and Exit Is a Loop Closure

Enter a room, scan it completely, and leave through the same doorway. The system has now seen the corridor before and after the room, which lets it detect and correct any drift accumulated inside. Exiting through a different doorway loses this. Where a room has multiple doors, enter and exit through the same one.

Close the Final Loop

The most important loop closure of any session is the last one: returning near the startup point at the end. It corrects drift across the whole session, not one segment. Return within 5 to 10 m (15 to 30 ft) of where you started, and within 40 degrees of the original viewing angle. Ending at the start from the opposite direction does not satisfy this.

Movement Patterns Within Spaces

Inside rooms and open areas, the path determines coverage. Random movement leaves gaps; systematic patterns give multiple angles on every surface.

Long Corridors and Featureless Runs

Corridors drift faster than open spaces because repetitive walls offer fewer distinguishing features per unit of travel, so SLAM has less to compute position from.

Branching Frequency

• Corridors over 50 m (160 ft) without RTK: branch into at least one room and return before the far end. A straight out-and-back accumulates uncorrected drift.
• With RTK Fixed: length extends to about 150 m (500 ft), since absolute position is bounded by the coordinate stream. Branching is still recommended.
• Any space counts. A brief detour into a closet, electrical room, or break room creates a loop closure that resets accumulated drift.

Side Shuffle in Narrow Corridors

For corridors under 2 m (6 ft) wide, the side shuffle keeps both walls in view and gives SLAM geometry a forward walk cannot. Budget about 50 percent more time for any corridor walked sideways.

Targets in Featureless Corridors

For corridors over 60 m (200 ft) with no distinguishing features, place high-contrast SLAM anchor targets every 30 to 45 m (100 to 150 ft). They give SLAM explicit features to match when the surrounding geometry is uniform and do not require surveyed coordinates to help. See Module 4: Positioning.

Multi-Floor Coverage

Each floor is scanned in sequence, with stairwells providing geometric continuity between them.

Order of Floors

• Start at the ground floor and work up. It connects to the most exterior coordinate references, which anchors the floors above.
• Scan each floor as a continuous session from exiting the stairwell to re-entering it.
• Do not stop between floors. The stairwell is part of the session. Stopping creates separate sessions that must be joined with Map Fusion, which aligns less cleanly than a continuous scan.

Stairwells

See 3.3 Transitions. Stairwells take longer than their footprint suggests and are a high-failure transition. Plan time accordingly.

Elevators

The elevator car moves through space the scanner never sees, so SLAM loses track between floors.

• Do not scan inside elevators. Stop before entering, ride without scanning, start a new session on the next floor.
• Join sessions with Map Fusion. Each must share overlap geometry with its neighbors. Use the stairwell for at least one transition between any two floors to provide alignment data.
• Pick one canonical stairwell as the inter-floor connector when a building has several.

Three-Pass Capture Strategy

For maximum vertical coverage in interior spaces, especially for 3DGS, use three passes at different heights within a single continuous session.

• Pass 1, chest height, about 1.5 m (5 ft): primary SLAM loop and core wall geometry. Walk the full route.
• Pass 2, overhead, about 2.1 to 2.4 m (7 to 8 ft): ceiling lines, light fixtures, upper wall detail. Use an extension pole if available.
• Pass 3, low, about 0.6 to 0.9 m (2 to 3 ft): baseboards, floor textures, under-furniture detail.

Keep height consistent within each pass and change gradually between passes. All three must be one continuous session; stopping between passes creates artifacts at the joins. Three-pass scans take about 2.5 to 3 times as long as a single chest-height scan, with a significant gain in 3DGS quality.

The Continuous Session Principle

SLAM depends on continuous trajectory data. Every stop introduces a discontinuity that Map Fusion must bridge in processing, at the cost of setup, processing time, and alignment quality.

Use One Continuous Session When

• Single-floor projects. Always one session.
• Multi-floor projects. One session per floor, joined at stairwells.
• The scan fits your processing machine. If total duration fits within hardware limits, use one session.

Break Into Multiple Sessions When

• The scan exceeds your hardware. Split into manageable sessions and join with Map Fusion.
• Floors are elevator-separated. Each floor is a session, joined by stairwell traversal or Map Fusion.
• Multi-day projects. Each day is a session. Plan day-to-day overlap for Map Fusion.
• Operator fatigue past 2 hours. Break with planned rest. Hour-3 posture produces less recoverable data than a clean second session.

For Map Fusion planning, see Module 5: Map Fusion Fundamentals.