generatinggy lidar data in laboratory: lidar...

Generating LiDAR data in laboratory: g yLiDAR Simulator

Bharat Lohani, R K MishraDepartment of Civil EngineeringDepartment of Civil EngineeringIndian Institute of Technology Kanpur Kanpur INDIA

M i iMotivation…

Are LiDAR data available ?

LiDAR data NOT available in majority ofLiDAR data NOT available in majority of countries

Lack of awarenessLack of awarenessSecurity issuesCost

Bharat Lohani, IIT Kanpur India


LiDAR data NOT available for teachingLiDAR data NOT available for teaching purposes

Readily available dataReadily available data Data with as-desired specificationsData with ground truthg



LiDAR data NOT available for researchLiDAR data NOT available for researchData with a wide range of desired specificationsData with complete and 100% accurate groundData with complete and 100% accurate ground truth


Solution lies in LiDAR simulator…

User creates a terrainUser creates a terrainUser chooses the flight parametersLiDAR data are generated for createdLiDAR data are generated for created terrain as if the actual LiDAR sensor had flown the terrainflown the terrain


Design consideration forDesign consideration for simulator

Should be . . .

User friendlyUser friendly

Wider distribution

Help or tutorial


Can simulate . . .

Generic sensor

Specific sensorsSpecific sensorsALTMALSAnd others…


Should simulate trajectory as in a normal flight

6 degrees of freedom6 degrees of freedom


Should simulate earthlike surfaces

Source: Optech Inc.Bharat Lohani, IIT Kanpur India

Also…

Possibility of error introductionPossibility of error introduction

Output data available in common formats


Development of simulatorDevelopment of simulator

System components

IntegrationSensor component

T i

Trajectory

Terrain component Out

putInputTrajectory component


T j t p tTrajectory component

Flight directionLocation Attitude

Location

Location: coordinates of laser head at each firing of pulse

Location depends on Instantaneous accelerationsaccelerations

Instantaneous accelerations should be simulated as in a normal flight: pseudo-random simulation


Acceleration simulation

2 2sin ( ( )) cos ( ( )) ( )J K

iX j j t k k t ta A B id C D id m id

T Tπ π⎛ ⎞ ⎛ ⎞= + +⎜ ⎟ ⎜ ⎟

⎝ ⎠ ⎝ ⎠∑ ∑

1 1X j j t k k t t

j kT T= =⎜ ⎟ ⎜ ⎟⎝ ⎠ ⎝ ⎠

∑ ∑

F = Firing frequencyJ,K,A,B,C,D and m governing parametersparameters


Location simulation1 21

2i i i i

x t x tX X u d a d+ = + +2

X

V l it i di ti fli ht i X iux = Velocity in direction flight i.e. X axis


Attitude (Roll, Pitch, Yaw) simulation

2 2sin ( ( )) cos ( ( )) ( )J K

ij j t k k t tR A B id C D id m id

T Tπ π⎛ ⎞ ⎛ ⎞= + +⎜ ⎟ ⎜ ⎟

⎝ ⎠ ⎝ ⎠∑ ∑

1 1j j t k k t t

j kT T= =⎜ ⎟ ⎜ ⎟⎝ ⎠ ⎝ ⎠

∑ ∑


Sensor componentsSensor components

Sinusoidal scan patternpZig-zag scan pattern

Sinusoidal scan patternpLet time taken to complete 1/4th of a scan is T.

P is the numbers of points in 1/4th of a scan.

( )

p

The maximum scan angle is өmax.

1

( )max 2sin

where

i iT

Ti i

t

t

πθ θ=

0

0.5

Z (m

)

where, i iPt =

160140160

-1

-0.5

6080

100120

140160

80100

120140

X (m)Y (m)Bharat Lohani, IIT Kanpur India

Zig-zag scan patterng g p

θ max iPiθθ =

1

0

0.5

Z (m

)

140160

-1

-0.5

6080

100120

140

80100

120140

X (m)Y (m)Bharat Lohani, IIT Kanpur India

Terrain componentTerrain component

Modeling surfaces: earthlikeVector approach: mathematical surfacesRaster approach with over ground objectsFractal terrain

Vector approach: Mathematical surfacespp

Simple SurfaceSimple Surface•AX+BY+CZ+D=0

Example of a simple surface: 2X+5Y+10Z-100=0 (displayed in surfer)Bharat Lohani, IIT Kanpur India

Vector approach: Mathematical surfacespp

Complex Surfacep•Z=A[sin(X/B)+sin(XY/BC)]+D

Example of a complex surface: z=10[sin(X/25)+sin(XY/(25*50)]-300 (displayed in surfer)Bharat Lohani, IIT Kanpur India

Raster surfaces


Fractal surfaces


Integration of componentsIntegration of components

Integration of components

i i iX X Y Y Z Zi i i

i i i

X X Y Y Z Za b c− − −

= =


Error introduction in simulated data

2( )i iX X N μ σ= + ( , )T t X XX X N μ σ= +


Concept implementationConcept implementation

Optimal flight lines given by systemp g g y y


User defined flight lines g


Simulated data and resultsSimulated data and results

3D raster terrain (displayed in f )

Altitude=210m Overlap=4%Velocity=60m/s

surfer) Sensor-ALS-50Firing frequency=20KHz Scan frequency=48HzScan angle=40°Flight area=430m 430m


LiDAR data plot in plan

A-A

B-B


Profile A-A without error

Profile A-A with error


Profile B-B w. r. t. flight lines g


LiDAR data without error


LiDAR data with error


Data with no attitude variation


Data with attitude variation


Fractal data displayed in surfer


Terrain with objects


LiDAR data of terrain with objects Altitude=490m Overlap=2%Velocity=60m/sSensor-ALS-50Firing frequency=20KHz Scan frequency=48HzScan angle=50°Flight area=640m×460m


Altitude=400m Overlap=2%Velocity=60m/sSensor-ALS-50

Effect of data density Firing frequency=20KHz Scan frequency=48HzScan angle=50°


Altitude=400m Overlap=2%Velocity=60m/sSensor-ALS-50Firing frequency=5 KHz Scan frequency=48HzScan angle=50°


1

2Profile view of buildings

2

Profile view-1

Profile view-2


Effect of different altitude Altitude=200m Overlap=2%Velocity=60m/sSensor-ALS-50Sensor-ALS-50Firing frequency=5 KHz Scan frequency=48HzScan angle=50°


Altitude=100m Overlap=2%Velocity=60m/sSensor-ALS-50Sensor-ALS-50Firing frequency=5 KHz Scan frequency=48HzScan angle=50°


Effect of different scan angle Altitude=200m Overlap=2%Velocity=60m/sSensor-ALS-50Sensor-ALS-50Firing frequency=5 KHz Scan frequency=48HzScan angle=50°


Altitude=200m Altitude=200m Overlap=2%Velocity=60m/sSensor-ALS-50Firing frequency=5

Scan angle=32

Firing frequency 5 KHz Scan frequency=48HzScan angle=32°


Effect of different flight direction


Applications of simulatorApplications of simulator

Education

To understand:

Process of data generationEffect of change in various parameters on dataEffect of errors on data


Laboratory exercises

Data with varied specificationsData with varied specifications

Full and accurate ground truth knownFull and accurate ground truth known


Research projects

Evaluation of Information extraction algorithmsg

Assessing effect of error on performance of galgorithms

Finding optimal data specifications for an application


Application in building identification research


Variation of accuracy indices


Final touches…in next three months

Multiple return implementationMultiple return implementation

Error introduction in individual parametersError introduction in individual parameters


)())(2(cos))(2(sin ttk

K

ktj

J

jiX idmidDCidBAa +⎟

⎞⎜⎛ ∏

+⎟⎞

⎜⎛ ∏

= ∑∑

j=2, k=2

)())((cos))((sin11

ttkk

ktjj

jX idmidT

DCidT

BAa +⎟⎠

⎜⎝

+⎟⎠

⎜⎝

∑∑==

0.38B1

1.65A2

3.54A1

0.51C1

2.45B2

1

0.88D2

2.77D1

3.77C2

1000T

0.001dt

0.0m

1000T



K

ktj

J


⎞⎜⎛ ∏

+⎟⎞

⎜⎛ ∏

= ∑∑

j=2, k=2

)())((cos))((sin11

ttkk

ktjj

jX idmidT

DCidT

BAa +⎟⎠

⎜⎝

+⎟⎠

⎜⎝

∑∑==

3.38B1

3.25A2

0.68A1

0.89C1

4.45B2

1

1.34D2

5.23D1

2.54C2

1000T

0.001dt

0.0m

1000T



K

ktj

J


⎞⎜⎛ ∏

+⎟⎞

⎜⎛ ∏

= ∑∑

j=2, k=2

)())((cos))((sin11

ttkk

ktjj

jX idmidT

DCidT

BAa +⎟⎠

⎜⎝

+⎟⎠

⎜⎝

∑∑==

4.38B1

0.25A2

1.78A1

1.78C1

2.45B2

1

2.34D2

3.23D1

1.24C2

1000T

0.001dt

0.003m

1000T



K

ktj

J


⎞⎜⎛ ∏

+⎟⎞

⎜⎛ ∏

= ∑∑

j=2, k=2

)())((cos))((sin11

ttkk

ktjj

jX idmidT

DCidT

BAa +⎟⎠

⎜⎝

+⎟⎠

⎜⎝

∑∑==

4.38B1

0.25A2

1.0A1

0.78C1

5.45B2

1

4.34D2

7.23D1

1.24C2

1000T

0.001dt

0.004m

1000T


j=3, k=3)())(2(cos))(2(sin ttk

K

ktj

J


⎞⎜⎛ ∏

+⎟⎞

⎜⎛ ∏

= ∑∑

0.65A2

2.75A1

)())((cos))((sin11

ttkk

ktjj

jX idmidT

DCidT

BAa +⎟⎠

⎜⎝

+⎟⎠

⎜⎝

∑∑==

B2 4.45

B1 2.38

A3 0.6

C 1 77

C1

B3

1.51

80

D1

C3

2.77

C2 1.77

0.35

m

D3

D2

0.0

3.38

100

T

dt

1000

0.006


Comparison of data sets without RPY and with Roll only.Equation of the surface: Z=sin(X/10)-sin(XY/90)-60.Flight velocity: 60 m/s.Flight height: 60 m.Distance: 30 m.Firing frequency: 5000 Hz.Scan frequency: 48 Hz

a d t o o y

Scan frequency: 48 Hz.Scan angle: 50 deg.


Comparison of data sets without RPY and with Pitch only

Equation of the surface: Z=sin(X/10)-sin(XY/90)-60.Flight velocity: 60 m/s.Flight height: 60 m.Distance: 30 m.Firing frequency: 5000 Hz.Scan frequency: 48 Hz.Scan angle: 50 deg.


Comparison of data sets without RPY and with Yaw onlyEquation of the surface: Z=sin(X/10)-sin(XY/90)-60.Flight velocity: 60 m/s.Flight height: 60 m.Distance: 30 m.Firing frequency: 5000 Hz.Scan frequency: 48 Hz.Scan angle: 50 deg.


Comparison of data sets with and without RPYEquation of the surface: Z=sin(X/10)-sin(XY/90)-60.Flight velocity: 60 m/s.Flight height: 60 m.Distance: 30 m.Firing frequency: 5000 Hz.Scan frequency: 48 Hz.Scan angle: 50 degScan angle: 50 deg.


Comparison of data sets with lower and higher ax

Eq ation of the s rface AX+B +CZ+D 0Equation of the surface: AX+By+CZ+D=0.(A=0, B=0, C=0, D= -65)Flight velocity: 60 m/s.Flight height: 65 m.Distance: 60 m.Firing frequency: 5000 Hz.Scan frequency: 48 Hz.Scan frequency: 48 Hz.Scan angle: 50 deg.


LiDAR data of fractal terrain Altitude=500m Overlap=2%Velocity=60m/sSensor-ALS-50Firing frequency=20KHz Scan frequency=48HzScan angle=50°Flight area=550×550km

A-A


Profile A-A

P fil B BProfile B-B


generatinggy lidar data in laboratory: lidar...

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