Rigorous Scan Data Adjustment for kinematic LIDAR systems

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1 Rigorous Scan Data Adjustment for kinematic LIDAR systems Paul Swatschina Riegl Laser Measurement Systems ELMF Amsterdam, The Netherlands 13 November

2 Contents why kinematic scan data adjustment? adjustment strategies rigorous adjustment approach adjustment workflow results and applications conclusions

3 Kinematic Laser Scanning Mobile Laser Scanning RIEGL VMX-450

4 Mobile Laser Scanning Kinematic Laser Scanning

Kinematic Laser Scanning GNSS/IMU solution truth Laser Scanners scanner coordinate systems highly accurate and precise ~ some mm System Calibration lever

5 Kinematic Laser Scanning GNSS/IMU solution truth Laser Scanners scanner coordinate systems highly accurate and precise ~ some mm System Calibration lever arms and orientation highly accurate and precise ~ mm ~ mdeg Platform Trajectory from GNSS/IMU comparably low accuracy ~ some cm m ~ several mdeg

6 Platform Trajectory Errors GNSS/IMU trajectory error sources: IMU inertial measurements biases noise drifts GNSS pseudo range measurements biases noise GNSS satellite visibility condition (esp. for MLS) rapidly changing field of view (FOV) number of tracked satellites multipath effects cycle slips

7 Platform Trajectory Errors estimated Trajectory Position Accuracy 20 cm Time

8 Platform Trajectory Errors estimated Trajectory Orientation Accuracy 20 mdeg Time

9 Kinematic Laser Scanning Point Clouds How do trajectory errors affect point clouds from kinematic laser scanning?

10 Colosseum Rome, Italy Effects on the Point Cloud

11 height deviation between all scans 10 cm 40 cm 80 cm 70 cm 60 cm Effects on the Point Cloud 20 cm

12 Kinematic Laser Scanning Point Clouds precise laser scanner data deviations between different passes 12 scans (6 passes with 2 scanners) 70 cm vertical separation 50 cm horizontal separation trajectory errors in all 6 DOF errors are time-varying 70 cm 50 cm

13 Kinematic Laser Scanning Point Clouds 70 cm 50 cm

14 Adjustment Strategies Strategies for a better trajectory solution: use measurements from additional sensors Laser Scanners point cloud geometrical point cloud features amplitude, reflectance, deviation Cameras image correlation matching image features

15 Adjustment Strategies modeling disparities of point clouds: point-to-point distance ICP (Iterative Closest Points) point-to-local plane distance modified ICP feature-to-feature distance planes, spheres, cubes, cylinders, edges, corners,... requires feature extraction as pre-processing step additional radiometrical features of markers on geometrical features

16 Adjustment Strategies Rigid adjustment: especially for ALS each strip treated as a block rigid shift rigid rotation

17 Adjustment Strategies sparse locally-rigid approach: determination of 6 DOF correction for minimizing discrepancies in each local region interpolation in between

18 Adjustment Strategies dense locally-rigid adjustment approach (semi-rigid approach):

19 Adjustment Strategies dense locally-rigid adjustment approach (semi-rigid approach): determination of 6 DOF correction for minimizing discrepancies between overlapping local regions previous block serves as reference adding-up of corrections

20 Rigorous Adjustment Strategy thorough modeling of all system components propagation of raw sensor data quality to final data product appropriate error models incorporation of all available information statistically most rigorous fully flexible trajectory adjustment no rigid or semi-rigid treatment fully non-rigid and seamless floating estimation no fixed scan as reference simultaneous adjustment of all 6 DOF continuous over time

21 Adjustment Working Principle Trajectory Accuracy Initial Trajectory Point Cloud Features Statistical Estimation Engine Feature Correspondences Laser Scanner Accuracy optional: External Control Objects Trajectory Model Data Handling Rigorous Statistics robust Algorithms

22 Adjustment Working Principle Trajectory Accuracy Initial Trajectory Point Cloud Features Statistical Estimation Engine Feature Correspondences Laser Scanner Accuracy optional: External Control Objects Trajectory Model Data Handling Optimized Trajectory Optimized Point Cloud Rigorous Statistics robust Algorithms

23 Rigorous Adjustment Workflow GNSS/IMU trajectories raw laser scan data georeferencing point cloud

24 Rigorous Adjustment Workflow GNSS/IMU trajectories control objects raw laser scan data georeferencing point cloud Rigorous Trajectory Adjustment optimized trajectories

25 Rigorous Adjustment Workflow GNSS/IMU trajectories control objects raw laser scan data georeferencing point cloud Rigorous Trajectory Adjustment optimized point cloud optimized trajectories

26 Rigorous Adjustment Implementation RiPRECISION Adjustment Software for kinematic laser scan data embedded in kinematic data handling software RiPROCESS selection of trajectories / scans fully automatic processing

27 orientation position Trajectory Corrections scan data acquired Position RMS max along [cm] 7 33 side [cm] 6 29 up [cm] Time Orientation RMS max roll [mdeg] pitch [mdeg] yaw [mdeg]

28 60 cm Adjusted Point Cloud before RiPRECISION

29 Adjusted Point Cloud after RiPRECISION 1 cm

30 before adjustment Adjusted Point Cloud

31 Adjusted Point Cloud after adjustment

32 Adjusted Point Cloud Details trajectory adjustment trajectory adjustment

33 Adjusted Point Cloud Details Street detail: 12 scans (6 passes) 60 cm before RiPRECISION after RiPRECISION 1 cm after RiPRECISION detail

34 Trajectory Accuracy Position Accuracy scan data acquired 6 cm before RiPRECISION Time 6 cm after RIPRECISION

35 Trajectory Accuracy Accuracy of Orientation 20 mdeg before RiPRECISION Time 20 mdeg after RIPRECISION

36 Adjustment Performance project number of points 670 mio size of project 100 GB up to 18 overlapping scans adjustment performance point cloud feature extraction 5 Mio feature correspondences found RiPRECISION georeferencing Total time 15 min 4 min 30 sec 20 min 40 min deviations to a few cm no user interaction

37 Absolute Adjustment in addition to relative adjustment: absolute adjustment to Control Objects Control Point Tie Point TPT CPT

38 Absolute Adjustment in addition to relative adjustment: absolute adjustment to Control Objects Control Point Tie Point Control Point Tie Plane TPL CPT

39 Absolute Adjustment in addition to relative adjustment: absolute adjustment to Control Objects Control Point Tie Point Control Point Tie Plane TPL Control Plane TiePlane CPL

40 Absolute Adjustment Modes non-rigid mode Control Object 2 Control Object 3 Control Object 1 local adjustments

41 Absolute Adjustment Modes non-rigid mode Control Object 2 Control Object 3 Control Object 1 local adjustments

42 Absolute Adjustment Modes non-rigid with frame transformation mode Control Object 2 Control Object 3 Control Object 1 local adjustments global shift

43 Absolute Adjustment Modes non-rigid with frame transformation mode Control Object 2 Control Object 3 Control Object 1 local adjustments global shift

44 Absolute Adjustment Modes rigid frame transformation only Control Object 2 Control Object 3 Control Object 1 global shift only

45 Absolute Adjustment Modes rigid frame transformation only Control Object 2 Control Object 3 Control Object 1 global shift only

46 CPT Absolute Adjustment

47 Absolute Adjustment 50 cm CPT

48 Absolute Adjustemnt CPT 43 cm

49 Absolute Adjustemnt before RiPRECISION after RiPRECISION 50 5 cm CPT

50 Absolute Adjustemnt before RiPRECISION CPT 43 cm after RiPRECISION

51 Railroad Mapping before RiPRECISION 4 scans (2 passes) 20 cm after RiPRECISION

52 Railroad Mapping before RiPRECISION 4 scans (2 passes) 20 cm after RiPRECISION

53 Tunnel Mapping 6 scans (3 passes) before RiPRECISION after RiPRECISION

54 Tunnel Mapping 6 scans (3 passes)

55 Multi Scanner Mobile Application VMX-450 VZ Scanner

56 Three Scanner Application before RiPRECISION 3 cm

57 Three Scanner Application after RiPRECISION 3 cm

58 Conclusions rigorous trajectory adjustment yields significantly better point cloud quality realistic modeling very precise and consistent rigorous statistics highly accurate and reliable time savings automatic processing almost no labor time efficient processor very short processing times control objects less time for reference field

59 Conclusion rigorous adjustment applicable for: City Highways Railways short Tunnels multi-scanner Applications...

60 Thank You for Your Attention!

GNSS/INS for High Accuracy Mobile Mapping. Olaf Gross 11 th Terrasolid European User Event Kittilä, Finland

GNSS/INS for High Accuracy Mobile Mapping Olaf Gross 11 th Terrasolid European User Event 15.02.2012 Kittilä, Finland IGI mbh Founded 1978 25 staff about half in R&D More than 380 customers in 60 different