REMOTE SENSING LiDAR & PHOTOGRAMMETRY 19 May 2017 SERVICES - - PowerPoint PPT Presentation

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REMOTE SENSING LiDAR & PHOTOGRAMMETRY 19 May 2017 SERVICES - - PowerPoint PPT Presentation

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REMOTE SENSING LiDAR & PHOTOGRAMMETRY 19 May 2017 SERVICES Visual Inspections Digital Terrain Models Volume Computations Aerial Imagery Thermal Inspections Photo maps Aerial Video Training & Consultancy SYSTEMS Zenith (2 x)

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REMOTE SENSING LiDAR & PHOTOGRAMMETRY

19 May 2017

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SERVICES Visual Inspections Photo maps Digital Terrain Models Thermal Inspections Aerial Imagery Volume Computations Aerial Video Training & Consultancy

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SYSTEMS

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MD4-1000 HEF-30 (2x) Zenith (2 x) DJI Inspire I (2x) Asctec Falcon V8 (3x) Trimble UX 5 HP Cessna Balloon (5x) SkeyeBat

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CLIENTS

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UAV LiDAR vs PHOTOGRAMMETRY

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฀ ฀

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LiDAR PRINCIPLE

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Distance = Time of travel / 2 Speed of light Transmitter Receiver Reflector

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BATHYMETRIC LiDAR

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LiDAR PRINCIPLE ACTIVE LIGHT

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POSITIONING LIDAR

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POSITIONING LIDAR

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POSITIONING LIDAR

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POSITIONING LIDAR

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POSITIONING LIDAR POSITION AND ORIENTATION ERRORS ARE NOT THE SAME FOR ALL RETURNS PER SCAN => NOT CORRELATED

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LiDAR ERROR SOURCES

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  • Sensor Position
  • GPS error
  • INS/IMU error
  • GPS-IMU Integration error
  • Angular Errors
  • Misalignment between LiDAR scanner and IMU (Boresight

calibration)

  • Lever arm Error
  • Incorrect positioning between GPS antenna and LiDAR sensor
  • LiDAR Range Error
  • Precision of LiDAR scanner
  • Divergence of Laser beam
  • Multipath error
  • Reflection on a sloping surface
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LiDAR ERROR SOURCES

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  • Range
  • Between 5 mm to 20 mm
  • Position
  • With RTK or PPP Positioning between 15 mm and 50 mm
  • Orientation
  • Between 0.025 degrees and 0.15 degrees
  • Example Sum of all errors
  • Velodyne HDL 32E Scanner
  • Flying Height 60 meters AGL (Above Ground Level)
  • Range error:

<= 20 mm

  • GNSS Positioning
  • Horizontal:

1 cm + 1ppm, assume 11mm

  • Vertical :

1.5 times horizontal = 16.5 mm

  • Total =

√(11 mm2 + 16.5 mm2) = 19.83 mm

  • Range and Positioning error:

20 mm + 19.83 mm = 39.83 mm

  • IMU accuracy Pitch and roll:

0.15° ⟹ 60 meters Range = 60 * tan(0.15°) = 15.7 cm

  • IMU accuracy Pitch and roll:

0.025° ⟹ 60 meters Range = 60 * tan(0.015°) = 2.62 cm

  • Total Error = √(15.72 + 3.92) = 16.18 cm / Total Error = √(2.622 + 3.92) = 4.7 cm
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LiDAR PROJECT SCHEVENINGEN BREAKWATER

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PHOTOGRAMMETRY

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PHOTOGRAMMETRY

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PHOTOGRAMMETRY

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PHOTOGRAMMETRY

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POSITION AND ORIENTATION ERRORS ARE THE SAME FOR ALL PIXELS PER PHOTOGRAPH  CORRELATED NOT WITH ROLLING SHUTTER !!

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Rolling Shutter and Photogrammetry

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STEREO VIEWING

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PHOTOGRAMMETRY

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PHOTOGRAMMETRY

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PHOTOGRAMMETRY ALLIGNMENT

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PHOTOGRAMMETRY

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PHOTOGRAMMETRY

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PHOTOGRAMMETRY ACCURACIES General ‘rules of thumb’ for photogrammetry with dense matching techniques

  • Relative accuracy is influenced by resolution (GSD, Ground Sampling Distance)
  • Absolute accuracy is influenced by quality of the geodetic network (i.e. ground control points)
  • Absolute accuracy is influenced by the data processing methodology
  • If all of the above are favorable:
  • X,Y accuracy is 1 to 1.5 times the GSD
  • Z accuracy is 1.5 to 2 times the GSD
  • Absolute accuracy is the quality of the network + relative accuracy

Sample project Scheveningen breakwater

  • Flight altitude 40 meters with Sony A7r (36 Mp and 35mm lens) => GSD = 0.7 cm
  • Quality of the Ground control points assumed at 2cm X,Y and 3 cm Z
  • A priori estimated error = √((1.5 ∗ 0.7)2 + 32) = 3.18 cm
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PHOTOGRAMMETRY SAMPLE PROJECT

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PHOTOGRAMMETRY SAMPLE PROJECT

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PHOTOGRAMMETRY SAMPLE PROJECT

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PHOTOGRAMMETRY ACCURACIES BREAKWATER SCHEVENINGEN

X Y Height Level GPS DEM Dz-1 Dz-2 Absolute Dz-1 Absolute Dz-2

GCP01 77542.555 457425.012 5.676 5.681 5.686 0.005 0.010 0.005 0.010 GCP02 77519.250 457437.892 5.117 5.117 5.118 0.000 0.001 0.000 0.001 GCP03 77524.464 457471.887 4.607 4.623 4.62 0.016 0.013 0.016 0.013 GCP04 77534.839 457515.828 5.557 5.564 5.564 0.007 0.007 0.007 0.007 GCP07 77482.622 457470.247 4.542 4.544 4.541 0.002

  • 0.001

0.002 0.001 GCP08 77455.233 457499.366 4.525 4.533 4.523 0.008

  • 0.002

0.008 0.002 GCP14 77326.597 457699.824 4.519 4.521 4.516 0.002

  • 0.003

0.002 0.003 GCP20 77285.905 457852.778 4.511 4.509 4.511

  • 0.002

0.000 0.002 0.000 GCP23 77283.584 457876.050 4.496 4.502 4.494 0.006

  • 0.002

0.006 0.002

Average 0.005 0.003 0.005 0.004 STDEV 0.005 0.006 0.005 0.005

Dz-1 = Difference Level - GPS Dz-2 = Difference Level - DEM

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LiDAR vs PHOTOGRAMMETRY (UAV ONLY!) LiDAR ✔ Vegetation Penetration ✔ Detect smaller features (i.e. power line) ✔ Quicker data processing ✔ No (or little) Ground control ✔ Active light (better in dark/shadow areas) ✖ No Picture ✖ Accuracy ✖ Cost ✖ Weight (i.e. safety) Photogrammetry ✔ Accuracy ✔ Costs ✔ Weight ✔ Picture ✖ Only map what you see ✖ Longer Processing times ✖ Cannot detect small features ✖ Ground Control (even with RTK or PPK!) ✖ Less accurate in shadow areas CONCLUSION: One sensor is not ’better’ than the other. Depends very much on the type of project.

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