Using Mobile LiDAR To Efficiently Collect Roadway Asset and Condition Data. Pierre-Paul Grondin, B.Sc. Surveying

Transcription

1 Using Mobile LiDAR To Efficiently Collect Roadway Asset and Condition Data Pierre-Paul Grondin, B.Sc. Surveying

2 LIDAR (Light Detection and Ranging) The prevalent method to determine distance to an object or surface is to use laser pulses. Like the similar radar technology (Radio detection and Ranging), which uses radio waves instead of light, the range to an object is determined by measuring the time delay between transmission of a pulse and detection of the reflected signal.

3 Primary difference between LiDAR and radar: LiDAR uses much shorter wavelengths of the electromagnetic spectrum, typically in the ultraviolet, visible, or near infrared.

4 Why LiDAR and not RADAR At radar frequencies, a metallic object produces a significant reflection while non-metallic objects produce weak reflections; some materials may produce no detectable reflection at all. Lasers provide a solution to these problems because of the beam densities and coherency + wavelengths are much smaller and are therefore reflected very well from small objects.

5 LiDARs used in mapping are eye-safe. When not, they incorporate preprogrammed safety functions.

6 One Technology Same technology as that used for airborne applications

7 One Technology 2D (dynamic) or 3D (static) Range in mobile mapping Generally 30 m to 100 m Reigl Q-240 Terrestrial/Airborne 450 m App points/sec Accuracy Generally +/- 1 inch Final accuracy greatly enhanced due to nb of pts

8 Data acquisition One Technology, Multiple Applications Mobile Mapping and Inventory Vehicles

9 Mobile mapping + lidar Why? Inventory Method Feet on the Street Historical Records Ortho Photography Mobile Mapping + LiDAR Safety Efficiency Complete ness Accuracy Low-Med Low High Med-High High Low Low Low High High Low Med-High High High High High Cost $$$$ $ $$$ $

10 Mobile mapping + lidar Process Capture Convert Post Processing Optional for greater accuracy Analyst Office Analysis Manual/Automated Asset Extraction End Use GIS Asset Management Image Viewing Database/Tabular Data Acquisition Field Data Collection

11 DATA ACQUISITION 2D Laser Scanning

12 DATA ACQUISITION 2D Laser Scanning

13 DATA ACQUISITION 2D Laser Scanning

14 DATA ACQUISITION 2D Laser Scanning

15 OFFICE ANALYSIS Common issues in mobile mapping: Accuracy and Error Budget Raw GPS Errors Camera and Lens Errors Vehicle Lever Arm Errors Photogrammetric Errors Synchronization Errors Real time GPS and RTK corrections GPS post processing Precise lens calibration Precise measurement of lever arms On the fly QA & QC Integration of high resolution cameras Robust photogrammetric engine Precise synchronization of devices using PPS signal Multiplexer

16 Office Analysis Automated Asset Detection Key data returned by laser: Coordinates (position) Object reflectivity Automation of: Location Measurements Recognition

17 Office analysis Automated Asset Detection Assets distinguished from surrounding environment Achieved through the use of: Filters Spatial Analysis Dynamic Parameters Reflectivity Analysis

18 SOME APPLICATIONS

19 Applications Automation Automation Focus on infrastructure related to safety o Signs o Pavement Markings o Road Geometry o Poles o Guiderails

20 applications Automated Sign Detection Every point has a 3D coordinate and a reflectivity value They enable the calculation of the position and size Reflective value does not meet MUTCD standards but...

21 applications Automated Sign Recognition Sign recognition is analyzed through comparison to sign library Recognition requires editing at the moment v

22 applications Automation Results Study Verification 23.7 miles surveyed 16 false detections 416 signs detected, located, and measured 1 missed sign Processing time ~ 90 seconds Final production including QA/QC: 416 signs in 45 mins

23 Applications Trident 3D Solution Road Geometry o Road cross fall o Vertical / horizontal alignments o Road centerlines Corridor Assessments o Infrastructure offsets (encroachment) o Vertical clearances o Capital improvement studies o Historical records Pavement / Shoulder Imaging o Image rectification for general condition rating

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32 Applications Image Rectification

33 applications Utility Modeling

34 applications Utility Measurements Pole Heights Connection Heights Cable Clearances Cable Separations Clearance Measurements 8 m

35 Pole Detection

36 BENEFITS

37 TRIDent-3D Solution Benefits Safety Efficiency Simplicity Completeness Accuracy Scalable No workers on the roadside: does not hinder traffic Data processing at a desktop level Faster than conventional data collection methods Rapid access to data Reduced operational costs Generally user friendly interfaces Click of the button in most cases Real time QA/QC in field and office settings Field re-visits can be done from a desktop Data is available at all times Depending on equipment, location referencing provides good absolute accuracy and very good relative accuracy Open, modular, and portable solution Coupled closely to GIS and Asset Management Systems

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