Aerial and Mobile LiDAR Data Fusion

Transcription

1 Creating Value Delivering Solutions Aerial and Mobile LiDAR Data Fusion Dr. Srini Dharmapuri, CP, PMP

2 What You Will Learn About LiDAR Fusion Mobile and Aerial LiDAR Technology Components & Parameters Project Lifecycle Vertical Products Fusion of Mobile and Aerial LiDAR Data Compatibility and Challenges Fusion Workflow Fusion Sample Benefits of Data Fusion

3 Light Detection and Ranging (LiDAR) Proven technology in deriving elevation information Elevation is one of the FGDC Core Framework data layers as a foundation for GIS solutions Two general types of LiDAR collection: Aerial Fixed wing platform (aircraft) and Rotary platform (helicopter) Terrestrial Road vehicle, all terrain vehicle, Boat, barge and Stationary tripod

4 Mobile and Aerial LiDAR Mobile LiDAR Aerial LiDAR Optech Lynx Optech Gemini

5 LiDAR Project Life Cycle Phase Mobile LiDAR Aerial LiDAR Scope Development LiDAR Data Collection LiDAR Data Pre-processing Mission Plan to Cover the Project Area Access & Logistics Geodetic Control Validation System Calibration Data Collection Geocoding of LiDAR data Geometric Correction of LiDAR data Projection Transformation LiDAR Data Processing Filtering/Classification Planimetric Data Capture Filtering/Classification Intensity Images LiDARgrammetry Product Generation Elevation: Grid generation / TIN / Contours Supplemental & Derived

6 LiDAR Vertical Products Mobile LiDAR Bare Earth/ Digital Elevation Models TIN/Contours Cross-Sections/Profiles Intensity Images Volume Calculations Aerial LiDAR Bare Earth / Digital Elevation Models TIN/Contours Cross-Sections/Profiles Intensity Images Volume Calculations Planimetrics Centerline Shoulders Edge of Pavement Median barrier Pavement Striping Breaklines for hydro flattening.

7 Mobile LiDAR Supplemental Products Assets Pavement marking, Roadside obstacles, signs, street lighting Roadway Inventory Bridges, Approaches, Drive away, Lane, Median, Rail crossings Railway Applications Right of way, Vegetation encroachment. First Floor Elevation Geo-referenced Side-view images for verification and potentially QA/QC. - Color gradation denotes elevation - Dashed lines depict Track corridor

8 Mobile LiDAR

9 Mobile LiDAR Components & Parameters Components Laser Sensor Range Information GPS Inertial Measurement Unit (IMU) Distance Measurement Instrument (DMI) Precise Position Information Attitude Information To Assist IMU incase of GPS Outage Parameters Elevation Accuracy Around 5cm Field of View 360 Pulse Repetition Frequency Area Coverage Returns per Shot 50, 100 or 200 KHz Limited. For Corridor Applications 4 (1st, 2nd, 3rd, Last) Range 200m (corridor varies)

10 Mobile LiDAR Instrument

11 Mobile LiDAR: Dual Sensor System Minimize Laser Shadowing Optimize Field of View (FOV) Sensor will see everything behind the vehicle Sensor will see ~35º in front of vehicle Full 360º area coverage All sides captured Sensor arrangement facilitates effective corridor mapping

12 Mobile LiDAR: Mission Planning Key Terms DEM Post Spacing Pulse Repetition Frequency Scan Frequency Drive Speed Range Expected Vertical Accuracy Control Points Control Points Check Points Data Collection Path

13 Mobile LiDAR Products Standard point-cloud with elevation/intensity display "Colorized" point-cloud

14 Mobile LiDAR Products

15 Mobile LiDAR Products

16 Mobile LiDAR Products

17 Advantages of Mobile LiDAR Everything is Captured Inundate the site with high-density scan information Operational Efficiencies Collect day or night and around localized weather events Large project areas collected faster than traditional surveys Minimize or Eliminate notices for Right of Entry Quality Deliverables Complete scenes, not just lines and points Ability to look at from many angles and aspects High-precision promotes Change Detection Repeatable results allow for seamless integration with past surveys Cost Effective

18 Aerial LiDAR

19 Aerial LiDAR Components and Parameters Components Laser Sensor Range Information Airborne GPS Inertial Measurement Unit (IMU) Precise Position Information Attitude Information Parameters Elevation Accuracy Variable. 12cm or above is Standard Field of View 0-50 Pulse Repetition Frequency Area Coverage 150 or above Broad Returns per Shot Operational Altitude 4 (1st, 2nd, 3rd, Last) 1500m 6500m

20 Aerial LiDAR: Flight Planning Parameters Scanner System (relates to beam pattern) Flight Altitude (if flight limitations exist) Pulse Repetition Frequency (PRF) Scan Frequencies Scan Angle (FOV) - possible max FEMA 40, USGS suggests 34

21 Aerial LiDAR Sample Clipped to area of interest

22 Advantages of Aerial LiDAR Day or night operation. Efficient acquisition of millions of points per minute. Capture multiple returns per pulse including intensity information. Fast data processing providing rapid turnaround. Large data sets with many possible products. Accuracy.

23 LiDAR Fusion

24 LiDAR Fusion Mobile and Aerial LiDAR technologies have been deployed independently towards generating elevation information. The technologies are complimentary. The accuracies are comparable (in the big picture perspective) Similar products derived from both the technologies. The data storage format is the same: ASPRS.las format

25 LiDAR Fusion: Remote Sensing Perspective Sensor 1 Sensor 2 Fusion Signal Level Signal Level Signal Fusion - Pixel Transformation - Feature Extraction - Decision Making Pixel Level Pixel Level Pixel Level Fusion- Feature Extraction - Decision Making Feature Level Feature Level Feature Fusion - Decision Making Decision Level Decision Level Decision Fusion

26 LiDAR Fusion: Issues and Challenges Technology Accuracy Resolution Volume Point Density Area Coverage Primary Aerial Variable 15 cm 1 m 167,000 pts/sec 1-10 / Sq meter Variable Topo Products Mobile 5 cm 1-4 cm 400,000 pts/sec +200 / Sq meter 400 miles/day Survey Grade The Aerial LiDAR is Nadir; Vertical Down and Mobile LiDAR is Side Looking The project life cycle is nearly same for both Aerial and Mobile LiDAR data By fusing Aerial LiDAR data with Mobile LiDAR (base layer), we get more information than can be obtained from a single dataset

27 LiDAR Fusion: Work Flow Use the Same Base Station to Process Aerial and Mobile LiDAR Data The Same Control will be used to Constrain Aerial and Mobile LiDAR Data Geocode & Geometric Correction of Mobile LiDAR Data Geocode & Geometric Correction of Aerial LiDAR Data Conflate Aerial LiDAR with Mobile LiDAR Fuse into a Single Dataset

28 LiDAR Fusion Sample

29 Fusion: Mobile LiDAR Collection

30 Fusion: Clipped Area

31 Fusion: Mobile with Aerial Supplement

32 Fusion: Combined Mobile and Aerial Points

33 Fusion: Contours with Ortho Image

34 Keystone Corridor

35 Mobile LiDAR LiDAR Sensor Mobile LiDAR IMU GPS Camera

36 Project Area LiDAR Scanning 105 Miles Captured over 4-day Period

37 Collection Swath

38 Custom Mounting

39 Ground Control Utilized to Constrain LiDAR Data Enhances Overall Accuracy Established via GPS RTK / Total Station Captured at LiDAR Identifiable Objects: Top-of-Rail Station Platform Corners Base of Catenary Structures

40 Data Fusion Merging of Data Aerial LiDAR Mobile LiDAR Value: Single Dataset Scene Comprehension Common Accuracy Minimizes Shadowing Spatial Extent

41 LiDAR Fusion Benefits

42 The Best of Each Capture Technique Mobile LiDAR (Side-look) Provides high density micro-level data Data acquisition efforts are minimal compared to Aerial LiDAR Captures underpass and under canopy Low cloud will be not hinder data collection Everything is captured and so data is useful in Assets mapping, roadway inventory, pavement condition, intersection studies. Tall hard breaks (ie. retaining wall) obscure what is beyond

43 The Best of Each Capture Technique Aerial LiDAR (Nadir; Vertical down) Provides low density macro-level data extending coverage Areas like behind buildings, private property etc will be collected Building roof tops etc can be captured as it is vertical down Coverage of data at underpass not available Coverage of data under canopy potentially limited Low cloud severely impacts LiDAR collection

44 Benefits of LiDAR Fusion When used in tandem, the resulting dataset(s) provides a comprehensive insight that is greater than the sum of the parts. Cross sections from ROW limit to ROW limit Aerial LiDAR Supplement Mobile LiDAR Void

45 Benefits of LiDAR Fusion Integrated data set with complete and extended coverage Complete data coverage including the areas of underpass, bridges, under canopy etc.

46 Merging of Aerial and Mobile data Dr.Srini Dharmapuri LiDAR Scientist Michael Baker Jr., Inc. Beaver, PA