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Sanborn's LiDAR Team Presentation regarding LiDAR QA/QC.
© 2007, The Sanborn Map Company, Inc. Privileged and confidential information.
Distribution or copying prohibited unless approved in writing.1
LiDAR Calibration Errors & QA/QC
September 16th, 2009
GIS in The RockiesPresented By: Brandon Tilley
© 2007, The Sanborn Map Company, Inc. Privileged and confidential information.
Distribution or copying prohibited unless approved in writing.2
What is Calibration?
• Calibration varies by
vendor
• Four different lines
collected
• 3 perpendicular
• 1 parallel
• All used to calibrate a
single mission
© 2007, The Sanborn Map Company, Inc. Privileged and confidential information.
Distribution or copying prohibited unless approved in writing.3
What is Calibration?
• This calibration is flown before
and after the flight/mission
• Flown over a flat surface
• Enables user to account for the
attitude of the aircraft
• Yaw, pitch, and roll are primarily
adjusted using opposing lines
• Calibration settings apply to entire
mission
© 2007, The Sanborn Map Company, Inc. Privileged and confidential information.
Distribution or copying prohibited unless approved in writing.4
What is Calibration?
• Roll accounted
• Pitch accounted
• Settings applied throughout
mission strips
• Similar calibration settings
for each flight
• Accurate calibration =
Accurate Dataset
Roll Error
Corrected Roll
Pitch Error
Corrected Pitch
© 2007, The Sanborn Map Company, Inc. Privileged and confidential information.
Distribution or copying prohibited unless approved in writing.5
Calibration Errors
Roll
• Can potentially be seen in
entire project
• Can greatly effect the
horizontal and vertical
accuracy of your data
• Create sharp elevation shifts
between each swath
• Cutting overlap usually helps
with roll errors
Pitch
• Can decrease the quality of the
building and structure by shape
• Decreases accuracy of
classifications, i.e. ground and
building classes
• Greatly reduces the accuracy of
the horizontal and vertical planes
• If widespread throughout project,
will create inaccurate geo-
referenced data
© 2007, The Sanborn Map Company, Inc. Privileged and confidential information.
Distribution or copying prohibited unless approved in writing.6
Relative Accuracy - CalibrationErrors – Roll
© 2007, The Sanborn Map Company, Inc. Privileged and confidential information.
Distribution or copying prohibited unless approved in writing.7
Relative Accuracy - CalibrationRoll Error Corrected
© 2007, The Sanborn Map Company, Inc. Privileged and confidential information.
Distribution or copying prohibited unless approved in writing.8
Relative Accuracy - CalibrationRoll Error- Example 2
© 2007, The Sanborn Map Company, Inc. Privileged and confidential information.
Distribution or copying prohibited unless approved in writing.9
Relative Accuracy - Calibration
Pitch Error
© 2007, The Sanborn Map Company, Inc. Privileged and confidential information.
Distribution or copying prohibited unless approved in writing.10
Relative Accuracy - CalibrationPitch Error Corrected
© 2007, The Sanborn Map Company, Inc. Privileged and confidential information.
Distribution or copying prohibited unless approved in writing.11
Filtering
• Cutting over edge or overlap?
• No? Increases chances for less accurate data (off nadir) but provides more
bare earth points per sq. m.
• Yes? Eliminates chances for less accurate data, less ground
• Removing (classifying) outliers?
• Ground filter: Does it classify too much? Not enough?
• All filter steps are necessary for an accurate BE model
© 2007, The Sanborn Map Company, Inc. Privileged and confidential information.
Distribution or copying prohibited unless approved in writing.12
Filtering- Under Filtering
© 2007, The Sanborn Map Company, Inc. Privileged and confidential information.
Distribution or copying prohibited unless approved in writing.13
Filtering- Over Filtering
© 2007, The Sanborn Map Company, Inc. Privileged and confidential information.
Distribution or copying prohibited unless approved in writing.14
Filtering- Ground
• Under Filtering
• Produces an inaccurate bare earth model
• Within the BE surface, can be vegetation, swath noise, buildings and bridges
• Increases manual QC TPT
• Over Filtering
• Also creates inaccurate bare earth model
• Cuts off mountains, hills, and other terrain features
• Increases manual QC TPT
© 2007, The Sanborn Map Company, Inc. Privileged and confidential information.
Distribution or copying prohibited unless approved in writing.15
Final QC Techniques
• What should your bare earth
surface contain?
• Structures removed
• Artifacts/Vegetation removed
• Noise removed
• Very minimal calibration
errors (if any)
• Common Sense• Anything not man made
© 2007, The Sanborn Map Company, Inc. Privileged and confidential information.
Distribution or copying prohibited unless approved in writing.16
Artifact Removal – Bridges/Overpasses
© 2007, The Sanborn Map Company, Inc. Privileged and confidential information.
Distribution or copying prohibited unless approved in writing.17
Artifact Removal – Buildings/Structures
© 2007, The Sanborn Map Company, Inc. Privileged and confidential information.
Distribution or copying prohibited unless approved in writing.18
Artifact Removal – Vegetation
© 2007, The Sanborn Map Company, Inc. Privileged and confidential information.
Distribution or copying prohibited unless approved in writing.19
Clients’ Specifications
Standard LIDAR 1.4m
• Automated process yields 89% of Artifacts removed
• Automated process yields 90% of all outliers removed
• Automated process yields 90% of all vegetation removed
• Automated process yields 93% of all Building removed
FEMA Compliant LIDAR• Automated process yields 90% of Artifacts or as required by FEMA lead
• Outliers removed per the FEMA lead provisions for a limited percentage of outliers
• Automated process yields 95% of all vegetation removed and as per FEMA lead provisions
• Automated process yields 98% of all Building removed and as per FEMA lead provisions
High Density LIDAR 0.7m
• Automated and manual processes yields 95% of Artifacts removed
• Automated process yields 98% of all outliers removed
• Automated process yields 97% of all vegetation removed
• Automated process yields 99% of all Building removed
© 2007, The Sanborn Map Company, Inc. Privileged and confidential information.
Distribution or copying prohibited unless approved in writing.20
Efficiency
• Tiled datasets
• Fast read/write
• Multitasking
• Data tracking
• Easy to use tools for
classifying points
© 2007, The Sanborn Map Company, Inc. Privileged and confidential information.
Distribution or copying prohibited unless approved in writing.
Thank You!
Graphics provided by Leica