Land Based Laser Scanning Applications for Transportation Construction Projects Edward Jaselskis, Ph.D., P.E. Iowa State University

Agenda n Overview of Laser Scanning Technology n Pilot Study of Applications for Transportation Projects n Video Demonstration

An Overview of 3D Laser Scanning Technology

Overview n Why Laser Scanning? n Cyra System n Basic Concept n Major Procedures n Advantages n Applications

Why Laser Scanning? Poor As-built Info => Poor Retrofit Design  Higher project costs n Construction Industry Study: >5% – 15%  Missed schedules  Operations & maintenance inefficiencies and problems  Safety problems

Laser Scanner Electronics & Power Supply Laptop Computer Cyrax System

> 2000 points/sec 40ºx40º Field-of-view Cyclone 4.0 Scan Cloud Processing Software Cyrax mm Accuracy m Scanning range Basic Concept of Laser Scanning

Up to 150m range (50m recommended) Eye-safe Class 2 Basic Concept of Laser Scanning

Scan Step 1: Target the Structure

Scan Step 2: Scan the Scene => Create a Point Cloud

Scan Step 3: Color the Points

Scan Step 4: Complex-Meshing Surfaces

Register Scans Together & Create Visual Database

Create Detailed 3D Model

2D Plan, Elevation, Section Views

Accurate, complete, fast measuring, safe… Integrated modeling 2D / 3D CAD Advantages “point clouds” Export to CAD or use Virtual Surveyor

Applications n As-built drawings of Bridges, Industrial Plants, and Monuments n Rock Quantity Surveys n Freeway Redesign n Movie Animations

A Pilot Study on 3D Laser Scanning for Transportation Projects

outline n Objectives n Methodology n Field Operation n Data Processing n Project Results n Benefits and Conclusions

Objectives of Pilot Study n Determine Safety & Efficiency of Laser Scanning Technology for Iowa DOT n Determine Cost Saving and Accuracy of various applications

Methodology Identify Possible Projects Establish Goals Software Training Scan Objects in Field 3D Image Processing Comparison to other Technologies Benefits and Recommendations

Intersection (Lincoln Way & Grand Ave, Ames) Railway Bridge (Grand Ave, Ames) I-235 (500m) (Des Moines) Broadway Bridge (Des Moines) New Pavement (HW 5, Des Moines) Bridge Camber (HW520, Hardin) Stockpile (Hardin) Borrow Pit (I-235&80) Pilot Projects Training Elevation Smoothness Beam Camber Volume As Built DWG

Field Operations Surveying Scanning

Lesson Learned in the Field n Scanner Resolution n Battery Management n Sun Glare n Cabling n Target Overlap n Acquiring Targets n Vibration

Data Processing n Importing Coordinates n Registration n Fitting and Editing n Meshing n Contouring n Virtual Surveying

Analysis and Facts Pilot Projects Section of Highway Pair of Bridges New Concrete Pavement Bridge Beams StockpileBorrow Pit Importing coordinatesXXXX*XX RegistrationXXXXXX Fitting and editingXXXXX Mesh editingXXXXX ContouringXXX Using virtual surveyorXXXX ExportingXXXX 2D drawingX No. of Scans No. of Valid Scans Coordinate control problems Many NoneFewNoneMany Amount of cleanup required Substantial LessAverage Less Extra proceduresYes

Coordinates System n Coordinate File must be Imported into the Scan Database Before any Registration was Started n The Coordinate Unit, Three Coordinates Values and Coordinate File Format must be determined

Registration n Understand the Scanning Process n Match Images Together n Three Step Process:  Target Registration  Registration to Survey Data  Object Registration (Scanworlds)

Fitting & Editing n Images Scanned from Field May Contain Some Unnecessary Data n The noise needs to be removed n Major Steps Involved:  Segmenting  Region Growing  Editing

Fitting & Editing n Example of Region Growing

Fitting & Editing n Example of Fitted Point Clouds

Meshing n Creating a mesh can make point cloud more manageable n Different types of mesh available (TIN, Complex, etc.) n Major Steps  Mesh creation  Mesh editing  Mesh decimation

Contours and Lines Drawing n Reference Plane n Cut Plane n Contours n Export to Micro Station n Measure the volume

Measuring

Virtual Surveyor n Easy to obtain information w/o physically being on site n Pick coordinates, assign notes, and export data n Major Steps:  Create a file  Select points  Export data

Concerns and Special Features n Targets with acquisition problems  Larger errors happened beyond 50 meter  Different targets with same ID number n Checking and measuring target locations and distances in control space  Most of target errors ranged from 0 to 7 mm n New coordinate system needed to measure non- typical shape elevation n Multiple meshes needed to measure the volume

Concerns and Special Features n Example of poor registration

Project Results n Technical Results I-235 Elevation Stockpile Volume Beam Camber Result Limitations n Time Requirements n Cost Comparison

Major Technical Results n I-235 Elevation Measurement  Laser scanning is more accurate than Helicopter Photogrammetry

Major Technical Results n Stockpile Volume  cubic meters by laser scanning  cubic meters by GEOPAK with traditional surveying  Only 1.2% difference

Major Technical Results n Bridge Beam Camber  Rapid Calculation and reasonable accuracy

Result Limitations n Pavement Smoothness  Smoothness Measurement within instrument accuracy limits n Borrow Pit  Targeting Error

Time Requirements n Time Per Scan  Field time = 3.5~4.0 hrs (average 3.7 hrs)/8 = 28 minutes  Lab analysis = 1.3 ~ 10.5 hrs (average 2.5 hrs)/1 person = 2.5 hrs  Final Lab Trial = 0.3 ~ 1.6 hrs (average 0.8 hrs)/1 person = 48 minutes Note: Field time assumes an 8 person crew (2 scanner and 6 surveyors)

Cost Comparison for I-235

Benefits n Safer: No surveyors required on roadway n Less Disruption  No road closures required  Survey can occur with traffic n Collect design data quickly and accurately n Provides accurate assessment of soil and rock quantities n Cost comparable to slightly higher than other methods

Conclusion n Laser Scanning has application for Transportation Design and Construction n On-going hardware/software modifications will make this approach even competitive

A Video Demonstration on 3D Laser Scanning