Part 9: Troubleshooting

Written By Ian Jack

Quick Field Guide

Scanner and Connection Problems

Scanner Won't Power On:

  1. Remove and firmly reinstall battery
  2. Check battery charge (press button on battery - LEDs should light)
  3. Try alternate battery if available
  4. If cold/hot weather, warm/cool battery to room temperature
  5. If still fails with charged battery, contact XGRIDS support

Can't Connect Phone to Scanner:

  1. Verify phone Bluetooth enabled (Settings → Bluetooth → On)
  2. Check hotspot settings:
    • Name: letters/numbers only, no spaces or special characters
    • Password: letters/numbers only
    • iOS: Stay on Personal Hotspot screen during initial connection
    • Android: Disable "Auto turn off hotspot"
  3. Power cycle both devices if timeout occurs
  4. Try bridge mode if direct connection repeatedly fails

Connection Drops During Scanning:

  • Most common: Phone hotspot auto-disable when screen locks
    • iOS: Settings → Display & Brightness → Auto-Lock → Never (while scanning)
    • Android: Set screen timeout to maximum
  • Battery: Charge phone before scanning, use power bank if needed
  • Range: Keep phone within 10-20m, carry in chest pocket not backpack
  • Data safe: Connection loss doesn't affect scan data, only real-time monitoring

RTK Module Won't Connect:

  1. Verify physical installation (module fully seated, no gap)
  2. Check firmware version ≥2.3 (LixelGO Settings → About)
  3. Confirm RTK Module Type matches hardware (Standard/Survey/Aerial)
  4. Power cycle scanner with RTK attached
  5. Check RTK Module Status in LixelGO (should show "Ready")
  6. Verify RTK service credentials if "Ready" but no corrections

Learn more about hardware troubleshooting →

Field Data Collection Problems

Point Cloud Has Obvious Drift:

  • Causes: Poor initialization, linear paths without loops, feature-poor environment, rapid scanner movement
  • Prevention: Stationary initialization, create frequent loops, add temporary features, walk smoothly <1 data-preserve-html-node="true" m/s
  • Processing fix: Enable Robust Mode, break into shorter segments, add control points if possible

Point Cloud Has Layers/Doubled Walls:

  • Cause: SLAM tracking loss followed by incorrect recovery
  • Common triggers: Sudden scanner movement (dropping, swinging), complete FOV blockage, extremely feature-poor areas
  • Prevention: Careful handling, maintain scanner visibility, add features to plain areas
  • Processing fix: Enable Robust Mode, try Narrow Scene mode for corridors, may require rescan

Point Cloud Has Excessive Noise:

  • Sources: Moving objects, reflective surfaces (glass/metal/water), rain/fog/dust, scanner vibration
  • Prevention: Scan during low-activity periods, avoid/angle away from reflective surfaces, dry weather, stable handling
  • Processing fix: Enable Dynamic Object Removal, increase Filter Level to Strong, use Denoising tool (Part 7)

Missing Data in Point Cloud:

  • Causes: Area never scanned (coverage gap), SLAM tracking loss (permanent), processing failure (specific sections)
  • Diagnosis: Review field notes for coverage, check processing logs for tracking loss messages
  • Solution: Rescan missed areas, improve conditions causing tracking loss, split scan for processing

Learn more about field problems →

Processing Failures

"LIO Trajectory Drift Error":

  1. Enable Robust Mode (Advanced Settings → Special SLAM Mode)
  2. Try Narrow Scene mode (for corridors/tunnels only)
  3. Enable Start-to-End Loop Closure (only if scan formed complete loop)
  4. Process only first portion (SLAM Mapping End Time Selection)
  5. Contact XGRIDS support if all fail

"Memory Exhausted" Error:

  • RAM requirements: 20-30GB for 10-min scan, 40-60GB for 20-min, 80+GB for 30-min
  1. Close other applications, verify >40GB available RAM
  2. Enable Low-Memory Reconstruction (30-50% slower)
  3. Reduce scan duration being processed
  4. Disable Point Cloud Enhancement
  5. Upgrade RAM 64GB→128GB

RTK/PPK/GCP Transformation Errors:

  • RTK: Verify Source Ellipsoid matches provider (usually WGS84), check valid data count >100
  • PPK: Verify base station data time span covers rover, check base coordinates accurate
  • GCP: Verify names match exactly (case/space sensitive), check CSV format, verify column order

Learn more about processing failures →

Accuracy Problems

Coordinates in Wrong Location (large offsets):

  1. Verify Source Ellipsoid matches RTK provider output
  2. Verify Target Coordinate System (correct zone, datum, units)
  3. Check projection parameters (central meridian, false easting/northing)
  4. Verify datum transformation parameters (WGS84↔NAD83, etc.)
  5. Test with known control points before full processing

Accuracy Worse Than Expected:

  • Diagnosis: Review accuracy report - control point residuals, RMSE statistics
  • Large residuals (>5cm): Check control point coordinates, improve SLAM with more loops
  • Gradual increase with distance: SLAM drift - add more control points (30-50m spacing)
  • Random scatter: Poor scanning conditions, improve technique, verify control surveys

Check Points Show Large Errors:

  • Systematic bias (all shifted same direction): Transformation control points have errors or insufficient quantity
  • Individual outliers: Poor marking, survey errors, or local SLAM quality issues
  • Random scatter: Overall scan quality marginal, need rescanning or more control

Learn more about accuracy problems →

Quick Diagnostic Flowchart

Scanner/Connection Issues:

Power on fails → Battery check → Try alternate → Contact support
Connection fails → Bluetooth on → Hotspot config → Power cycle → Bridge mode
Connection drops → Screen lock → Battery depleted → Range issue

Data Quality Issues:

Drift visible → Check initialization → Review loops → Feature density → Rescan
Doubling visible → Check handling → FOV blockage → Feature-poor area → Rescan
Noise excessive → Identify source → Rescanning options → Processing filters
Data missing → Coverage gap → Tracking loss → Processing failure → Rescan

Processing Errors:

Drift error → Robust Mode → Narrow Scene → Loop Closure → Reduce duration → Support
Memory error → Close apps → Low-Memory mode → Reduce duration → Disable Enhancement → More RAM
Transform error → Verify config → Check files → Test known points → Reprocess

Accuracy Issues:

Wrong location → Ellipsoid → Coordinate system → Projection → Datum → Test
Poor accuracy → Review report → Control spacing → SLAM quality → Technique → Rescan
Check point errors → Systematic? → Control points → Random? → SLAM quality → Rescan

Full Explanatory Guide

Scanner and Connection Problems

Hardware and connectivity issues prevent scanning from starting or cause scanning interruptions.

Scanner Won't Power On

Power-on failure manifests as complete unresponsiveness when pressing the power button.

Battery installation verification:

  1. Remove battery completely
  2. Examine contacts (clean, no corrosion/debris, spring-loaded)
  3. Reinsert firmly until click/lock
  4. Partial insertion makes initial contact but loses connection during scanning

Battery charge verification:

  • Press charge indicator button on battery
  • LEDs show remaining charge: 4=full, 3=75%, 2=50%, 1=25%, 0=depleted
  • If no LEDs, connect to charger
  • Charger should change from green (standby) to red (charging)
  • If no charger activity, battery defective

Alternate battery testing:

  • Install second battery if available
  • Powers on with second battery = first battery defective/depleted
  • Won't power on with known-good battery = hardware failure → XGRIDS support

Temperature-related failures:

  • Batteries less effective below 0°C or above 45°C
  • Cold: Warm battery in interior jacket pocket 10-15 min
  • Hot: Allow battery to cool in shade

Can't Connect Phone to Scanner

Phone Bluetooth verification:

  • Settings → Bluetooth → Verify On/Enabled
  • Enable if disabled, wait 10 seconds for radio activation

Hotspot configuration critical requirements:

  • Name: Letters/numbers only, no spaces/special characters
    • ✅ "MyPhone5G" ❌ "My Phone (5G)" or "Phone_WiFi"
  • Password: Letters/numbers only
    • ✅ "Password1234" ❌ "Pass@word!"

iOS-specific behavior:

  • Must stay on Personal Hotspot screen during initial connection
  • iOS auto-disables hotspot when navigating away if no devices connected
  • Sequence: Enable hotspot → Stay on screen → LixelGO connection → Wait for "1 Connection" → Navigate

Android configuration:

  • Varies by manufacturer/version
  • Navigate to hotspot advanced settings
  • Disable "Auto turn off hotspot" options

Connection Drops During Scanning

Important: Connection loss doesn't affect scan data - only real-time monitoring.

Phone hotspot auto-disable (most common):

  • Phones auto-disable hotspot when screen locks
  • iOS Solution: Settings → Display & Brightness → Auto-Lock → "Never" (while scanning)
  • Android Solution: Set screen timeout to maximum (typically 30 min)
  • Alternative: Keep screen active by touching every few minutes

Phone battery depletion:

  • Hotspot + screen + LixelGO drain battery faster than normal
  • 50% battery might deplete in 60-90 minutes
  • Solutions: Charge before scanning, USB power bank in pocket, larger battery phone

WiFi range limitations:

  • Direct connection: 10-20m range in open space
  • Walls/obstacles reduce range
  • Solutions: Keep phone closer (chest pocket vs. backpack), switch to bridge mode

WiFi interference:

  • Heavy wireless traffic causes intermittent drops
  • Check visible network count (Settings → WiFi)
  • Dozens of networks = likely interference
  • Solutions: Change hotspot channel, move location, accept intermittent connection

RTK Module Won't Connect

Physical installation:

  1. Power off scanner
  2. Examine mounting bracket (firm, screws tight)
  3. Remove RTK module
  4. Inspect connector for bent pins, debris, corrosion
  5. Clean with compressed air (don't touch pins)
  6. Reinstall ensuring complete seating (no gap)

Firmware compatibility:

  • RTK requires L2 Pro firmware ≥2.3
  • Check: LixelGO Settings → About → Firmware Version
  • Update if below 2.3

RTK type configuration:

  • LixelGO Settings → RTK Settings → RTK Module Type
  • Standard: 2.8 dBi antenna (most handheld)
  • Survey: 5.5 dBi antenna (challenging conditions)
  • Aerial: Drone mounting (not handheld)
  • Incorrect type prevents initialization

Communication status:

  • LixelGO → RTK Settings → RTK Module Status
  • "Not Detected" = physical connection problem
  • "Detected - Initializing" = communication active but incomplete
  • "Ready" = fully initialized
  • If "Not Detected" despite confirmed installation → XGRIDS support

Field Data Collection Problems

Point Cloud Has Obvious Drift

Drift manifests as curved walls, incorrect room dimensions, or loop paths that don't close.

Understanding drift accumulation: SLAM estimates position through continuous integration of IMU measurements and feature matching. Small errors compound over time. Without correction mechanisms (loop closures, RTK/GCP), errors accumulate as drift.

Common causes and solutions:

Poor initialization (movement during countdown):

  • Any movement during 15-second initialization corrupts IMU calibration
  • Corrupted calibration introduces systematic error affecting entire scan
  • Solution: Rescan with proper stationary initialization

Linear paths without loops:

  • No loop closure opportunities for error correction
  • Solution: Rescan with routes creating frequent loops (every 50-100m)

Feature-poor environments:

  • Blank walls, empty warehouses, parking garages, open fields
  • Solutions: Add temporary features (cones, boxes), use Narrow Scene mode, add RTK/GCP

Dynamic objects dominating view:

  • Moving people/vehicles confuse feature tracking
  • Solution: Rescan during quieter periods

Rapid scanner movement:

  • 1.5 m/s walking, >180°/sec rotation exceeds tracking capability

  • Solution: Rescan with controlled technique

Processing-based partial solutions:

  • Enable Robust Mode (Advanced Settings)
  • Break into shorter segments for Map Fusion
  • Add control points retroactively if possible
  • Note: Cannot fully correct drift but may improve results

Point Cloud Has Layers or Doubled Walls

Understanding the mechanism: SLAM loses position tracking when feature matching fails. When recovery matches to wrong location, all subsequent data captures in incorrect position, creating doubled geometry.

Common causes:

Sudden scanner movement:

  • Dropping, swinging rapidly, colliding with obstacles
  • Creates motion exceeding SLAM tracking capability
  • Prevention: Careful handling, maintain smooth controlled motions

Complete FOV blockage:

  • Scanner face-down during transitions
  • Operator's body blocking LiDAR window
  • Dense vegetation blocking output
  • Prevention: Maintain clear LiDAR window, position body appropriately

Extremely feature-poor environments:

  • Plain white room, uniform painted walls
  • SLAM sees identical point clouds regardless of position
  • Prevention: Add temporary features before scanning

Processing with incorrect settings:

  • Default SLAM mode for narrow corridors
  • Aggressive filter settings
  • Solutions: Reprocess with Robust Mode or Narrow Scene mode, adjust Filter Level to Weak

Solutions prioritize rescanning to address root cause most effectively.

Point Cloud Has Excessive Noise

Common noise sources and solutions:

Moving objects:

  • People/vehicles create ghost images
  • Solutions: Rescan during low-activity, enable Dynamic Object Removal, increase Filter Level to Strong

Reflective surfaces:

  • Glass, metal, water create multi-path returns
  • Solutions: Rescan at oblique angles (30-60°), accept noise as inevitable, aggressive filtering

Rain/fog/dust:

  • Airborne particles scatter laser light
  • Solutions: Wait for weather to improve, scan during dry conditions, aggressive denoising

Scanner vibration:

  • Unstable holding creates motion blur
  • Solutions: Steady handling (close to body), take breaks (prevent fatigue), stable mounting

Processing solutions:

  1. Enable Dynamic Object Removal (Advanced Settings)
  2. Increase Filter Level to Strong
  3. Use Denoising tool (Part 7): Std Dev Multiple 0.5-1.0, Neighborhood Points 10-20
  4. Trade-off: Aggressive denoising removes noise AND legitimate small features

Missing Data in Point Cloud

Diagnosis flowchart:

  1. Never-scanned vs. data-loss?

    • Review field notes about scan route
    • Never visited = coverage gap → Rescan missed areas
    • Was scanned but absent = data loss → Continue diagnosis

  2. SLAM tracking loss (permanent)?

    • Tracking fails, never recovers
    • Data abruptly ends, continuous section missing
    • Check processing logs for "Tracking lost" messages
    • Prevention: Address tracking loss cause during rescan

  3. Processing failure (specific sections)?

    • Most scan processes, discrete sections absent
    • Review processing logs for section-specific errors
    • Solutions: Reprocess with different settings, split problem sections

Processing Failures

"LIO Trajectory Drift Error"

Recovery strategies (try in order):

  1. Robust Mode (succeeds 60-70% of cases)

    • Advanced Settings → Special SLAM Mode → Robust Mode
    • More conservative estimation, tolerates higher drift

  2. Partial Processing

    • Advanced Settings → SLAM Mapping End Time Selection
    • Process only first portion (e.g., first 15 min of 25-min scan)

  3. Loop Closure (ONLY if scan formed complete loop)

    • Advanced Settings → Debug Options → Start-to-End Loop Closure
    • Forces loop closure, corrects accumulated drift
    • Critical: Using on non-loop scans degrades accuracy

  4. Narrow Scene Mode (ONLY for corridors/tunnels <500m) data-preserve-html-node="true"

    • Advanced Settings → Special SLAM Mode → Narrow Scene
    • Adjusts for limited lateral features

  5. Professional Support

    • Contact XGRIDS with project folder
    • Can analyze data, potentially split into segments

"Memory Exhausted" Error

RAM requirements:

  • 10-min scan: 20-30GB
  • 20-min scan: 40-60GB
  • 30-min scan: 80+GB (with Enhancement)

Recovery strategies:

  1. Free RAM: Close applications, verify >40GB available
  2. Low-Memory Mode: Enable Low-Memory Reconstruction (30-50% slower)
  3. Reduce Duration: Process shorter portion
  4. Disable Enhancement: Dramatically reduces RAM requirements
  5. Hardware Upgrade: 64GB → 128GB RAM

Accuracy Problems

Coordinates Are in Wrong Location

Indicates coordinate transformation configuration errors, not SLAM problems.

Diagnostic checklist:

  1. Source Ellipsoid: Verify matches RTK provider (usually WGS84, some Chinese services CGCS2000)
  2. Target System: Verify correct zone, datum, units
  3. Projection Parameters: Check central meridian, false easting/northing, scale factor
  4. Datum Transformation: Verify seven-parameter Helmert transformation (WGS84↔NAD83, etc.)
  5. Test: Use known control points to verify before full processing

Accuracy Worse Than Expected

Understanding: Total accuracy = Georeferencing accuracy + SLAM solution accuracy

Diagnostic approach:

Large control point residuals (>5cm):

  • All similar magnitude/direction = Systematic coordinate errors
  • Vary randomly = SLAM quality or marking quality

Gradual increasing error with distance:

  • SLAM drift from inadequate loops or control spacing
  • Solutions: Tighter control spacing (30-50m), more loops, RTK supplement, smaller segments

Random scatter:

  • Difficult conditions, poor technique, environmental factors
  • Review scanning conditions and technique

Check Points Show Large Errors

Check points reveal true accuracy (transformation algorithm doesn't optimize for them).

Systematic bias (all shifted same direction):

  • Transformation control points have errors OR insufficient quantity
  • Solutions: Verify control coordinates, add more transformation points

Individual outliers:

  • Poor marking, survey errors, local SLAM quality issues
  • Solutions: Verify coordinates, review coverage, accept if others verify well

Random scatter:

  • Overall scan quality marginal OR inadequate georeferencing
  • Solutions: Rescan with better technique, add control points, use hybrid RTK+GCP

Best practices:

  • Allocate 20-30% of surveyed points as check points
  • Distribute throughout project area
  • Use residuals as objective accuracy assessment
  • Don't deliver if check points exceed requirements without resolution
Ian Jack
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Part 8: Specialized Applications