Creating Value …

… Delivering Solutions

Aerial and Mobile LiDAR Data Fusion

Dr. Srini Dharmapuri, CP, PMP

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

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

Mobile and Aerial LiDAR

Aerial LiDAR

Optech Gemini

Mobile LiDAR

Optech Lynx

LiDAR Project Life Cycle

Phase Mobile LiDAR Aerial LiDAR

Scope Development

LiDAR Data Collection

LiDAR Data Pre-processing

LiDAR Data Processing

Product Generation

• Mission Plan to Cover the Project Area • Access & Logistics • Geodetic Control Validation

• System Calibration • Data Collection

• Filtering/Classification • Planimetric Data Capture

• Filtering/Classification • Intensity Images • LiDARgrammetry

• Geocoding of LiDAR data • Geometric Correction of LiDAR data • Projection Transformation

• Elevation: Grid generation / TIN / Contours

• Supplemental & Derived

LiDAR Vertical Products

Aerial LiDAR Bare Earth /

Digital Elevation Models

TIN/Contours

Cross-Sections/Profiles

Intensity Images

Volume Calculations

Breaklines for hydro

flattening.

Mobile 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

Mobile LiDAR Supplemental Products

- Color gradation denotes elevation - Dashed lines depict Track corridor

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.

Mobile LiDAR

Mobile LiDAR Components & Parameters

Parameters Elevation Accuracy Around 5cm

Field of View 360°

Pulse Repetition Frequency

50, 100 or 200 KHz

Area Coverage Limited. For Corridor Applications

Returns per Shot 4 (1st, 2nd, 3rd, Last)

Range 200m (corridor varies)

Components Laser Sensor Range Information

GPS Precise Position Information

Inertial Measurement Unit

(IMU)

Attitude Information

Distance Measurement

Instrument (DMI)

To Assist IMU incase of GPS Outage

Mobile LiDAR “Instrument”

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

Mobile LiDAR: Mission Planning Key Terms

DEM Post

Spacing

Pulse Repetition

Frequency

Scan Frequency

Drive Speed

Range

Expected

Vertical

Accuracy

Control Points

Check Points

Control Points

Data Collection Path

Mobile LiDAR Products

Standard point-cloud with elevation/intensity display

"Colorized" point-cloud

Mobile LiDAR Products

Mobile LiDAR Products

Mobile LiDAR Products

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

Aerial LiDAR

Aerial LiDAR Components and Parameters

Parameters Elevation Accuracy Variable. 12cm or above is

Standard Field of View 0-50°

Pulse Repetition Frequency

150 or above

Area Coverage Broad

Returns per Shot 4 (1st, 2nd, 3rd, Last)

Operational Altitude 1500m – 6500m

Components Laser Sensor Range Information

Airborne GPS Precise Position Information

Inertial Measurement Unit

(IMU)

Attitude Information

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°

Aerial LiDAR Sample

Clipped to area of interest

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.

LiDAR Fusion

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

Sensor 1 Sensor 2 Fusion

Signal Level

Pixel Level

Signal Fusion - Pixel

Transformation - Feature Extraction - Decision Making

Signal Level

Pixel Level Pixel Level Fusion- Feature Extraction -

Decision Making

Feature Level

Decision Level

Feature Fusion - Decision Making

Feature Level

Decision Level

Decision Fusion

LiDAR Fusion: Remote Sensing Perspective

LiDAR Fusion: Issues and Challenges

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

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

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 Aerial LiDAR Data

Conflate Aerial LiDAR with Mobile LiDAR

Fuse into a Single Dataset

Geocode & Geometric Correction of Mobile LiDAR Data

LiDAR Fusion Sample

Fusion: Mobile LiDAR Collection

Fusion: Clipped Area

Fusion: Mobile with Aerial Supplement

Fusion: Combined Mobile and Aerial Points

Fusion: Contours with Ortho Image

Keystone Corridor

LiDAR Sensor

IMU

GPS

Camera

Mobile LiDAR

Mobile LiDAR

Project Area – LiDAR Scanning

105 Miles

Captured over 4-day Period

Collection Swath

Custom Mounting

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

Data Fusion

Merging of Data

Aerial LiDAR

Mobile LiDAR

Value:

Single Dataset

Scene Comprehension

Common Accuracy

Minimizes Shadowing

Spatial Extent

LiDAR Fusion Benefits

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

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

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

Mobile LiDAR

Void

Aerial LiDAR Supplement

Benefits of LiDAR Fusion

Integrated data set with

complete and extended coverage

Complete data coverage including the areas of

underpass, bridges, under canopy etc.

Dr.Srini Dharmapuri LiDAR Scientist

Michael Baker Jr., Inc.

Beaver, PA

sdharmapuri@mbakercorp.com

724-495-4154

Merging of Aerial and Mobile data