3.6 Scan Plan Tool

Step 1: Scope and Constraints

Before any specific planning, document what the project is and what limits the work. The questions below are not optional and must be answered before site arrival.

• What is the total scan area in square feet or square meters, by floor or zone?
• What is the deliverable? Point cloud, 3DGS reconstruction, BIM model, ATIS.cloud project, measurement-grade survey, or a combination
• What absolute accuracy is required? 3DGS visualization (no absolute reference), 3 cm RMSE georeferenced (RTK or GCPs needed), or survey-grade (extensive GCP coverage)
• Is this a baseline scan or a rescan? Rescans must align with prior session structure: same targets, same route, same boundaries
• What is the access window? Hours on site per day, total days available, escort requirements, after-hours availability
• Are there access restrictions? Secure zones, sensitive equipment areas, photography prohibitions, adhesive placement limits
• What devices will be used? L2 Pro for large facades and long ranges, K2 for indoor and close-quarters work, PortalCam if 3DGS-only output is the deliverable
• Who is the site contact and what is the escalation path if something goes wrong during the scan?

Step 2: Route and Session Planning

Convert the scope into an executable route. Identify session boundaries, initialization points, and the order in which areas will be scanned.

Session Sizing

A session is one continuous scan from initialization to completion. Multiple sessions are joined later with Map Fusion. The constraint on session length is RAM in the processing machine.

Session Boundary Rules

• Each session ends and starts at the same physical location with at least 50 ft (15 m) of overlap geometry. Map Fusion needs the overlap to align sessions; less than 50 ft of overlap produces inconsistent alignment
• Plan session boundaries at structural features that are easy to return to precisely: cross-aisles, distinctive doorways, intersection points. Boundaries in featureless areas are harder to align
• For multi-floor scans, each floor is one session, joined at stairwells (not elevators)
• For multi-day projects, each day is at least one session by definition. Plan day-to-day overlap explicitly

Initialization Point

Choose the initialization point with the same care as the route itself. The initialization position is the reference frame for the entire session.

• Initialize in a feature-rich area with at least three visible walls or large geometric features. Open lobbies, doorway thresholds, or corners work well
• Initialize where you can return cleanly at the end of the session. The final loop closure to within 15 to 30 ft (5 to 10 m) of the initialization point is the most important loop closure in any session
• For RTK georeferencing, initialize outdoors in clear sky view, achieve Fixed status, and then carry the device to the indoor starting point. RTK position is preserved during the carry

Step 3: Georeferencing and Control Point Placement

If the deliverable requires absolute coordinates, plan ground control point (GCP) placement before the scan. The number and positioning of GCPs depend on the device used and the size of the area.

GCP Spacing

The fundamental constraint is the maximum unfixed-RTK gap that each device tolerates without significant coordinate drift. GCPs must be spaced such that no two consecutive points are farther apart than this gap.

GCP Surveying

• Surveyed coordinates required. A control point without coordinates is functionally an anchor target, useful for SLAM but not for absolute georeferencing
• Same coordinate system as RTK base if RTK is also used. Mixing coordinate systems requires transformation in processing and introduces precision loss
• Document coordinate system explicitly in the deliverables: datum, projection, zone (where applicable). Future rescans must use the same system
• Survey method depends on accuracy requirement. Total station for survey-grade work, RTK rover for general georeferencing, building geometry references for relative-only deliverables

Coverage Pattern

• Place GCPs in a triangular distribution across the area, not in a single line. Linear distribution does not constrain rotation; triangular distribution does
• Place at least one GCP near the initialization point and at least one near the final loop closure point
• Include redundancy. Place 20% more GCPs than the minimum spacing requires. If a marking failure or surveying issue affects one point, the redundant points keep the dataset usable

Step 4: Anchor Target Placement

Anchor targets are different from GCPs. GCPs provide georeferencing; anchor targets give SLAM high-contrast features to track in environments where natural geometry is uniform. Some projects need both. Some need only one.

When to Place Anchor Targets

• Long featureless corridors over 200 ft (60 m) in length
• Dark environments where visual feature tracking is unreliable
• Repetitive-geometry environments: data centers, warehouses with uniform racking, tunnel systems
• Multi-session projects where Map Fusion alignment depends on shared anchor points
• Rescan engagements where target continuity between visits is essential for change detection

Target Spacing

For all environments where anchor targets are appropriate, plan placement every 100 to 150 ft (30 to 45 m) along the scan path. Closer spacing in higher-challenge zones (very dark, very repetitive). Wider spacing in lower-challenge zones (some natural features present).

Target Placement Checklist

• Each target is in a position where the scanner can approach within 3 to 6 ft (1 to 2 m) and circle it during the scan
• Each target is on a stable surface, not on a vibrating panel, near airflow vents, or on a flexible substrate that may shift mid-scan
• Each target's position is documented (photograph with rack ID or room reference) before the scan begins
• For rescans, target positions match the baseline scan documentation
• Adhesive policy verified with site operator before sticker placement
• Removal plan in place: targets and any tape are collected before site exit

Step 5: Time and Resource Estimation

Time estimates that miss reality by more than 25% lead to access window overruns, fatigue, or incomplete coverage. Build the estimate from realistic per-zone baselines, not from a single area-based ratio.

Baseline Scanning Time

The figures below assume 1.6 ft/s (0.5 m/s) average pace, single-pass coverage, and no significant transitions or environmental challenges. Use these as starting points, then adjust for project-specific factors.

Adjustment Factors

• Multiply by 1.5 to 2.0 for environments with significant transitions (multi-floor projects, many small rooms, complex stairwell-heavy layouts)
• Multiply by 2.5 to 3.0 for three-pass coverage in spaces requiring detailed 3DGS output
• Add 30 to 60 minutes per session for setup, initialization position selection, RTK Fixed achievement, and final site checks
• Add target placement time: approximately 3 to 5 minutes per anchor target, 10 to 15 minutes per surveyed GCP
• Add escort coordination time in secure sites: typically 15 to 30 minutes per access window
• Plan rest breaks every 45 to 60 minutes of active scanning. Five-minute breaks. Fatigue-degraded posture in hour 3 of continuous scanning produces less recoverable data than a planned break

Step 6: Risk Review

Before site arrival, review the plan against known failure modes. Most scan failures trace to a small set of recurring causes. Catching them in planning is significantly cheaper than catching them after the fact.

• Compound-challenge zones identified: Areas combining two or more challenges (dark and featureless, reflective and outdoor) are flagged with extra time and specific technique
• Session boundaries verified: No session exceeds the processing machine's RAM tolerance. Each session has at least 50 ft (15 m) of overlap with adjacent sessions
• GCP placement verified: Spacing within device tolerance, distribution triangular, redundancy included, coordinate system documented
• Anchor target inventory confirmed: Sufficient targets in the deployment kit for planned placement, with adhesive verified for sticker targets in non-ferromagnetic environments
• Site contact information current: Primary contact, escalation contact, and after-hours number all confirmed in the last 30 days
• Access window matches scan estimate: Total estimated scan time plus setup, rest breaks, and contingency fits within the available access window with 25% buffer
• Deliverable expectations documented: Format, accuracy, ATIS.cloud publishing, BIM handoff steps, and timeline confirmed with the client in writing
• Equipment ready: Devices charged, batteries swapped, mobile devices charged with LixelGO or LCC Scan installed and tested, processing machine has free disk space for incoming session data