Module 4 Quick Field Guide

Method Selection

Choose before scanning. It cannot be changed after. Full framework: 4.1.

• Relative only. No RTK, no GCPs. Local coordinates. As-builts, virtual tours, anything not tied to a real-world system
• RTK. Live GNSS corrections via NTRIP. L2 Pro uses an attachable module; K2 uses a built-in UM980. Indoor RTK requires carry-in from an outdoor Fixed position
• Surveyed GCPs (GCP1). Markers with known coordinates, marked in LixelGO during the scan. Correct method indoors and anywhere GNSS is unavailable
• Relative GCPs (GCP2). Targets marked without surveyed coordinates. Internal drift control only, no real-world frame
• Hybrid RTK + GCPs. Highest accuracy on the platform

RTK: Status and Thresholds

Status

Minimum Validity

• Status: Fixed throughout
• Satellites: more than 10
• Movement while Fixed: more than 10 m (33 ft)
• Valid RTK points logged: more than 100
• Unfixed-section max: L2 Pro 100 m (330 ft); K2 50 m (165 ft)

PPK: Thresholds

PPK is the alternative when NTRIP is unavailable or RTK will not hold Fixed.

• Base-to-rover: under 3 mi. Under 1 mi for best accuracy
• Open ground in scan: more than 10 m (33 ft) with clear sky
• Valid PPK points: more than 100, checked in LixelStudio before processing
• Base RINEX: continuous, gap-free, 1-second or finer across the full scan window
• Antenna tilt: within 20 degrees of vertical

GCP Placement

• GCP1 (Absolute): surveyed coordinates attached in LixelStudio. Aligns the scan to a real-world system and corrects IMU leveling. Use when the deliverable needs absolute coordinates
• GCP2 (Relative): marked target, no surveyed coordinate. Constrains drift only. Use when georeferencing is not required
• The same physical target is either type. The difference is whether a surveyed coordinate is attached in LixelStudio

Spacing

Use the tighter end of the range in feature-poor spaces such as data center aisles.

Distribution

• Not collinear. Points on one straight line correct only one axis
• Even, not clustered. Spread points across the full scan extent
• At boundaries and transitions: floor changes, entries, where coverage paths cross
• Reachable: the scanner must be able to sit on each point during the scan

Marking

• Write point names on paper first. Type them into the CSV and LixelGO from that list. Do not invent names in the field
• Use a floor-level target the scanner can sit on top of while staying vertical. Do not mark points on walls
• Set the scanner on the exact point, vertical, then add the control point in LixelGO with the exact name
• Hold stationary at least 5 seconds, then lift slowly and resume scanning
• Mark the same physical spot with the same name in every scan that shares it (Map Fusion)
• After the last point, keep scanning at least 15 seconds and walk a small loop before ending

Coordinate Setup Before the Scan

• Confirm the datum and ellipsoid your CORS network transmits (most networks outside Mainland China use WGS84)
• Have the target EPSG code for the deliverable ready before configuring RTK

Full configuration, datum transformations, and projection setup: 4.6.

Critical Warnings

• No recovery Georeferencing cannot be added after the scan. RTK must be active before recording. GCPs must be placed and marked during the scan. A scan delivered without it cannot be corrected without re-scanning
• Silent failure Mismatched GCP names are silently discarded. The CSV name must match what you typed in LixelGO, including case. No error appears; the point is simply dropped
• Warning Float is not a substitute for Fixed. Float embeds decimeter-level uncertainty that cannot be verified after the fact
• Warning RINEX gaps cannot be recovered. If the base station stopped logging during the scan, PPK for that period is degraded or absent. Monitor base status
• Warning Georeferencing does not fix poor technique. A scan with no loop closures and excessive speed still drifts, just with coordinates attached
• Warning Collinear GCPs are not a valid network. Distribute points so they are not all on one straight line