Comparison of Inertial Profiler Measurements with Leveling and 3D Laser Scanning

Abby Chin and Michael J. OlsenOregon State University

Road Profile Users Group28 September 2011

Outline

• Research Objectives & Plan

• 3D Laser Scanning

• Field Data

• Observations & Future Work

1

Research Objectives

• Establish certification test site

• Determine repeatability and accuracy of reference profiler (inclinometer)

• Develop procedures and guidelines for certification of inertial profilers

2

Background

• ODOT is implementing IRI-based incentive/disincentive program

• Certification on site proved difficult

• Inertial profilers were showing great repeatability, but did not meet AASHTO criteria

3

Research Plan

• Compare Methods• Inertial Profiler• Terrestrial LiDAR• Rod and Level• Inclinometer Profilers

• Develop Certification Procedure Guidelines• Pavement Texture Analysis

• Study Roughness and Aggregate Size

4

What is LiDAR?

Original Slide by: Evon Silvia - Oregon State University

D = 0.5c∆t• c = speed of light• ∆t = travel time

D

∆t

LiDAR = Light Detection and Ranging

Terrestrial LiDAR

• Time of Flight System• Produces 3D Point Cloud• ~5 mm Accuracy at 50 m• Data are Geo-referenced

• Targets• GPS

6

Equipment

7

Camera

Power Source

Scanner

GPS

Computer

Data

• Point Cloud• X Y Z coordinates• R G B color mapped• Intensity value (return signal strength)• 3D model

8

Point Cloud Example

9

Point Cloud Example

10

Laser Scanning Advantages• Multiple Profiles• Redundant Data

• Dense Point Cloud (1-5 cm Spacing)• Quick Data Acquisition• Improved Safety• Road Open to Traffic• Identify Localized Depressions• Continual Evaluation• As Built Survey Data

11

Laser Scanning Disadvantages• Individual measurements accurate to +/- 5mm

• Objects can block line of sight

• Field setup time

• Data processing requires training and time

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Mobile Laser Scan System

13

Laser scanner

Camera

GPS receiver

Mobile Laser Scan Example

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Test Site – Albany, Oregon

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Field Testing

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Field Test Setup

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• 528 ft Section• 6 Scan Positions

• Every 50 m• GPS used to

determine position• 5 Targets

• Every 50 m• Total station used to

determine position

Point Cloud

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Point Cloud – Colored from Photos

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Field Data - Workflow

• Obtain 3D point cloud• Prune data to roadway

• Statistically filter data to specified spacing

• Obtain profile using GIS

• Input data in ProVAL20

Editing Point Clouds

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Statistical FilteringProcess

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http://www.lidarnews.com/content/view/8378/136/

• Inclinometer Profiler

• Left – 66 in/mi

• Right – 84 in/mi

IRI Comparisons

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• Laser Scanner

• Left – 73 in/mi

• Right – 88 in/mi

ProVAL Data – Left Wheel Path

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Inclinometer

Scanner

ProVAL Data – Right Wheel Path

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Inclinometer

Scanner

Observations

• Data between inclinometer profiler and laser scanner is offset• Offset gets larger

• Laser scan data filtered to 1 ft intervals• Visible noise in the data

• Starting points may not be exactly the same

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Laser Scan Data Comparison - Worst

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1 ft Spacing

0.5 ft Spacing

0.25 ft Spacing

Grid Cell Dimensions2” V x 20’ H

Laser Scan Data Comparison - Best

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1 ft Spacing

0.5 ft Spacing

0.25 ft Spacing

Grid Cell Dimensions2” V x 20’ H

Localized Depressions

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Right End

Middle Section

Questions to Investigate

• Laser Scanning• Can the noise be smoothed out while taking

advantage of the dense data?• i.e. close point spacing

• Compare the profiles in ProVAL• Are IRI values consistent?• Do the distance vs. elevation plots agree?• What are the reasons for any discrepancies?

30

Future Work

• Obtain and compare additional profiles from test site• Laser Scanning• Inertial Profiler• Rod & Level

• Create procedures and guidelines for certification

31

Questions?

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Comparison of Inertial Profiler Measurements with Leveling and 3D Laser ScanningOutlineResearch ObjectivesBackgroundResearch PlanWhat is LiDAR?�Terrestrial LiDAREquipmentDataPoint Cloud ExamplePoint Cloud ExampleLaser Scanning AdvantagesLaser Scanning DisadvantagesMobile Laser Scan SystemMobile Laser Scan ExampleTest Site – Albany, OregonField TestingField Test SetupPoint CloudPoint Cloud – Colored from PhotosField Data - WorkflowEditing Point CloudsStatistical Filtering�ProcessIRI ComparisonsProVAL Data – Left Wheel PathProVAL Data – Right Wheel PathObservationsLaser Scan Data Comparison - Worst�Laser Scan Data Comparison - BestLocalized DepressionsQuestions to Investigate Future Work Questions?