Transcript Using LIDAR to Assess the Development of William B

Lidar Point Clouds for
Developing Canopy Height
Models (CHM) for Bankhead
National Forest Plots
By: Soraya Jean-Pierre
REU Program at Alabama A & M University
Oakwood University
07/25/08
Background Information
The state of Alabama is 71% forest and is
this nation’s second largest commercial forest.
There is nearly 23 million acres of forested
land in Alabama.
Different tools have been developed to assist
in studies of the forest and LIDAR has proven
to be very useful.
What is Light Detection and
Ranging (LIDAR)?
Remote sensing tool used to measure certain
physical characteristics of the forest.
Beneficial to foresters that utilize data such as
tree heights, wood volume and biomass.
Components of a Lidar system include
laser scanner, receiver, Airborne GPS
and an Inertial Measurement Unit (IMU).
Uses of the Components
of LIDAR Systems
Scanners are vital because they copy the
images into the LIDAR system.
Receivers are important for capturing
reflections produced by objects.
GPS and an IMU are needed to determine the
location and orientation of the LIDAR sensor.
How Does a LIDAR System
Work?
IMU, GPS, and laser scanner are placed on
the bottom of an airplane.
Lidar system uses pulses of multiple laser
light that collide with the target surface.
Ground vegetation along with the canopy
reflect the laser light, which then returns to
the sensor’s receiver.
LIDAR
The time it takes for the reflected emitted pulse
to return to the receiver is then measured.
The ground vegetation, and the canopy
produce different time delayed measurements.
Accurate measurements of the physical
characteristics of forests can be made.
What is CIR?
Color infrared imagery is a relatively new tool
that provides photos of vegetation.
It presents foresters with images that can
differentiate between healthy vegetation and
stressed vegetation.
The accuracy of CIR imagery can also be
used to distinguish between various tree
species.
Objectives
Examine the capabilities of Lidar
data in conjunction with CIR imagery
to develop Canopy Height Models
(CHM) using ArcGis Applications .
Treated Plot Areas
Nine treatment combinations
Four block study areas
Each treatment applied to an area 22 ac
Block 1 (of 4)
Trt 1
Trt 5
Trt 3
Trt 2
Trt 8
Trt 6
Trt 4
Trt 7
Trt 9
created by Dr.
Schweitzwer
Study Area and Data William B.
Bankhead National Forest (BNF)
Aerial photo of B2T6 with
specified boundary
Study Area and Data William B.
Bankhead National Forest (BNF)
Aerial photo of B2T6 with
specified boundary
A Model of Procedures
Lidar Data Points
Clip Data
Extract points within
Specific boundary
Interpolation
First Returns
Vegetation heights
Model Builder
Bare Earth Returns
Subtracted OK BER
Data from OK FR
Ground topography
CANOPY HEIGHT
MODEL
Block 2 Treatment 6
Using Model Builder To
Create CHM (B2T6)
First Return – Bare Earth Return = Canopy Height Measurement
B2T7
Using Model Builder To
Create CHM
First Return – Bare Earth Return = Canopy Height Measurement
Conclusion
Lidar data along with CIR imagery
proved to be capable of developing
canopy height models.
ArcGIS applications also worked in
conjunction with the Lidar data in
developing the canopy height model.
Further research to be done includes
calculating individual tree heights and
locations.
Tree Variable Window (TreeVaW ©)
Author: Sorin C. Popescu - Texas A&M University
CHM are processed
using IDL software.
Input is a LIDARderived CHM into ENVI
image format.
The output consists of
individual tree
positions, crown radius,
and tree height. Trees
can be identified and
located based on local
maximum filtering
technique using
continuously varying
windows of circular
shape.
Acknowledgements

Dr. Wubishet Tadessee and Dawn Lemke

Joe Gardinski and Rick Fields

Dr. Moss and Dr. Wang

Co-PIs Dr. Luben Dimov, and Dr. Callie Schweitzer

REU Colleagues
References
M.D. Behera and P.S. Roy. 2 December 2002. Lidar Remote
Sensing for Forestry Applications. 10 December 2002
Yungshen Wang, Holger Weinacker and Barbara Koch. 6
June 2008. A Lidar Point Cloud Based Procedure for Vertical
Canopy Structure Analysis and 3D Single Tree Modelling in
Forest. 12 June 2008