LiDAR Calibration Errors & QA/QC
September 16th, 2009
GIS in The Rockies
Presented By: Brandon Tilley
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Distribution or copying prohibited unless approved in writing.
1

What is Calibration?
• Calibration varies by
vendor
• Four different lines
collected
• 3 perpendicular
• 1 parallel
• All used to calibrate a
single mission
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Distribution or copying prohibited unless approved in writing.
2

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
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Distribution or copying prohibited unless approved in writing.
3

What is Calibration?
Roll Error
• Roll accounted
• Pitch accounted
• Settings applied throughout Corrected Roll
mission strips
• Similar calibration settings
for each flight Pitch Error
• Accurate calibration =
Accurate Dataset
Corrected Pitch
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Distribution or copying prohibited unless approved in writing.
4

Calibration Errors
Roll Pitch
• Can potentially be seen in • Can decrease the quality of the
entire project building and structure by shape
• Can greatly effect the
• Decreases accuracy of
horizontal and vertical
classifications, i.e. ground and
accuracy of your data
building classes
• Create sharp elevation shifts
between each swath • Greatly reduces the accuracy of
the horizontal and vertical planes
• Cutting overlap usually helps
with roll errors • If widespread throughout project,
will create inaccurate geo-
referenced data
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Distribution or copying prohibited unless approved in writing.
5

Relative Accuracy - Calibration
Errors – Roll
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Distribution or copying prohibited unless approved in writing.
6

Relative Accuracy - Calibration
Roll Error Corrected
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Distribution or copying prohibited unless approved in writing.
7

Relative Accuracy - Calibration
Roll Error- Example 2
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Distribution or copying prohibited unless approved in writing.
8

Relative Accuracy - Calibration
Pitch Error
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Distribution or copying prohibited unless approved in writing.
9

Relative Accuracy - Calibration
Pitch Error Corrected
© 2007, The Sanborn Map Company, Inc. Privileged and confidential information.
Distribution or copying prohibited unless approved in writing.
10

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.
11

Filtering- Under Filtering
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Distribution or copying prohibited unless approved in writing.
12

Filtering- Over Filtering
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Distribution or copying prohibited unless approved in writing.
13

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
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Distribution or copying prohibited unless approved in writing.
14

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
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Distribution or copying prohibited unless approved in writing.
15

Artifact Removal – Bridges/Overpasses
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Distribution or copying prohibited unless approved in writing.
16

Artifact Removal – Buildings/Structures
© 2007, The Sanborn Map Company, Inc. Privileged and confidential information.
Distribution or copying prohibited unless approved in writing.
17

Artifact Removal – Vegetation
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Distribution or copying prohibited unless approved in writing.
18

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
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Distribution or copying prohibited unless approved in writing.
19

Efficiency
• Tiled datasets
• Fast read/write
• Multitasking
• Data tracking
• Easy to use tools for
classifying points
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Distribution or copying prohibited unless approved in writing.
20

Thank You!
Graphics provided by Leica
© 2007, The Sanborn Map Company, Inc. Privileged and confidential information.
Distribution or copying prohibited unless approved in writing.