LiDAR 101

Joanne White

Canadian Forest Service, Natural Resources Canada

Pacific Forestry Centre

Victoria, BC

Active remote sensing technology

SOA: emit ~500,000 pulses of laser light per second

Typical: emit ~150,000 pulses/sec

Range (m) = (Speed of Light x Time) / 2

What is LiDAR?

Light Detection And Ranging LiDAR

TARGET

Range (m)

Platforms:

• Spaceborne

• Airborne

• Terrestrial

1. Aircraft - Forward motion of the aircraft provides coverage

Source: McGaughey, USDA Forest Service

Airborne Laser Scanning

4. On-board GPS receiver - Logs trajectory of the aircraft

2. Scanning laser emitter-receiver unit - Emits laser pulses at controlled rates (pulses/second)

- Scanning mechanism directs laser beam on either side

of the flight path within an operator-specified angle

3. Time Interval Meter (TIM) - Records pulse travel time

5. Inertial measurement unit (IMU) - Records aircraft heading, pitch, roll

3 key data streams:

1. GPS (aircraft trajectory)

2. POS (aircraft heading, pitch, roll)

3. LiDAR (range, scan angle)

Post-flight processing

XYZ points Point Cloud

Source: Forest Inventory Research Group, UBM-INA, Norway

Discrete return For each pulse emitted, the

lidar can record information

for multiple returns

SOA: 8 returns/pulse

Typical: 4 returns/pulse

First return

Second return

Last return

Small footprint

Lidar footprint is the effective area that

the laser light encompasses on the

ground

• “small”: ≤ 90 cm in diameter

• typical: ≤ 50 cm

Source: Woods et al. (2008) TFC

Point spacing/Hit density

Ground

Non-Ground

Classifying the point cloud

Special considerations for coastal forests:

• Complex terrain

• Dense vegetation cover

Source: Steve Platt, Strategic Group

Basic products:

Digital Surface Model

(DSM)

Digital Elevation Model

(DEM)

Canopy Height Model (CHM)

Source: Clark et al. (2004) RSE

www.botany.hawaii.edu/GISlab.htm

www. Saminc.biz

Ambercore.com

• Hazard mapping

• Floodplain/risk mapping

• Landform Classification-ELC

• Corridor/Right-of-way Mapping

• Woodlot Extraction

• Agricultural mapping

• Geological Mapping

• Urban Modeling

• Predictive Hydrology

• Transmission Line corridors

• Wetlands/Riparian areas

• Open pit mining

• Coastal/Shoreline Mapping

• Habitat modeling

• Forest Engineering

• Forest Inventory

Opportunities for cost-sharing!

Unlimited applications:

• TRIM2

– 25m resolution

– 10m vertical accuracy

LiDAR

– 1m resolution

– 10–30 cm vertical accuracy

Source: Miura and Jones (2010) RSE

• Mean, minimum, maximum height

• Percentiles of height

• Coefficient of variation of height

• Percentage of first returns above specified

height (estimate of canopy cover)

• Etcetera…

• FUSION, version 3.3, Feb. 2013;Bob

McGaughey, USFS; ~ 90 different metrics http://forsys.cfr.washington.edu/fusion/fusionlatest.html

LiDAR metrics

LiDAR 300 …

Using the point clouds for

area-based estimates…

LiDAR Point Cloud P 0

hei

ght

1

D(%)

Cloud Statistics LiDAR Data by elevation

Using the point clouds for

area-based estimates…

LiDAR 300…

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Actual

Pre

dic

ted

tvol

1:1

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sta

nd

vo

lum

e -

tota

l (m

3/h

a)

Actual stand volume - total (m3/ha)

Sb GTV (m3/ha) = 31.46 + 1.78(mean · p90)Sb GTV (m3/ha) = 31.46 + 1.78(mean · p90)

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Actual

Pre

dic

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tvol

1:1

Pre

dic

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sta

nd

vo

lum

e -

tota

l (m

3/h

a)

Actual stand volume - total (m3/ha)

Sb GTV (m3/ha) = 31.46 + 1.78(mean · p90)Sb GTV (m3/ha) = 31.46 + 1.78(mean · p90)

Top and Dom/codominant

Height

QMDBH

Volume (GTV, GMV)

Basal area

Biomass

Density

Mean tree volume

Sawlog volume

Diameter/volume

Distributions

LiDAR predictive models

Murray WoodsMurray Woods

Proper calibration is essential!

LiDAR 300…

Using the point clouds for

area-based estimates…

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Actual Tree Diameter (cm)

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Tre

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iam

ete

r (c

m)

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Actual Tree Diameter (cm)

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Actual mean tree diameter (cm)

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Actual Tree Diameter (cm)

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Tre

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r (c

m)

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0 5 10 15 20 25 30 35 40 45

Actual Tree Diameter (cm)

Pre

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Tre

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Actual mean tree diameter (cm)

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me

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r (c

m)

y

• Height

•

Volume (GTV, GMV)

•

Basal area

•

Density

•

Quadratic mean DBH •

Biomass

• Mean tree volume

Size distribution •

20 m

20 m

Now, we have “spatial” data!

LiDAR 300…

Both tactical AND strategic!

LiDAR 300…