IX-B8, 2012
The other way is
rat.
eflectance derived
; wave propagation
lls were generated
ze of each cell had
the sampling rate.
' corresponding to
d by using initial
sections. And the
; both the intensity
ie echo signal was
cells.
petween sub laser
ator implemented
rticle with highest
| understand the
ts.
LOGY
llowing two steps:
the generation of
iput variables were
tion angle (degree
of the forest object
tion vector of laser
illumination angle
aser beams. The Z
"wpoint, in order to
;veral illumination
cedure were the
sub laser beam,
and the target, the
f target type. Next,
variables were the
based on the flag.
a csv file of echo
lowing steps. The
ect as the ground.
in 3DCG software.
, illumination angle
st object, as initial
beams with in the
ial point based on
1g the illumination
bject.
r the forest object.
International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Volume XXXIX-B8, 2012
XXII ISPRS Congress, 25 August — 01 September 2012, Melbourne, Australia
(8) Adjustment of the position of the forest and the ground
object to fix viewpoint.
(9) Execution of a ray tracing between the objects and the initial
points.
(10) Output of the position of initial points, intersections, the
intensity and the flag of object type.
- Generation of echo signal-
(1) Read of the output file.
(2) Input of the reflectance of each object, the sapling rate and
the illumination angle.
(3) Generation of cells using the sampling rate and the
illumination angle.
(4) Calculation of intensity of each particle using its intensity
and the reflectance of target type.
(5) Decision of the start position of particle of a sub laser beam
using the distance between initial positions of each laser
beam and the intersection.
(6) Summation of the intensity at cells.
(7) Output of the echo signal as csv format and display of the
graph of the echo signal.
6. SIMULATION SCENARIOS
Several simulation cases were tested in order to examine a
performance of the developed simulator. Table 2 shows lists of
simulation cases. The footprint size and the reflectance of target
types used common values in all simulation cases. The footprint
size was 10m. The reflectance of the forest and the ground were
0.5% and 0.3%, respectively.
No. Species Tree Phenology Illumination The
density angle ground
(degree) slope
angle
(degree)
1 Japanese low summer 0 0
cedar
2 Japanese low summer 6 0
cedar
3 Japanese low summer 0 30
cedar
4 Japanese low summer 0 -30
cedar
5 Japanese low summer 6 30
cedar
6 Japanese low summer 6 -30
cedar
7 Japanese high summer 0 0
cedar
8 Japanese high summer 6 0
cedar
9 Japanese high summer 0 30
cedar
10 Japanese high summer 0 -30
cedar
ll Japanese high summer 6 30
cedar
l2 Japanese high summer 6 -30
cedar
l3 Zelkova isolated summer 0 0
serrata
l4 Zelkova isolated winter 0 0
serrata
Table 2. The list of simulation cases
Figure 1 shows several samples of initial conditions of the
simulated scenarios. Figure 1 (a), (b), (c) and (d) stands for
corresponding to scenario no.l, no.3, no.13 and no.l4,
respectively. The discus object above the forest or the tree
object stands for an irradiated area of a laser beam. The plane
object under the forest and the tree object stands for the ground.
In case of these simulations, the ground plane was generated
automatically.
(c) (d)
Figure 1. Overview of several samples of initial conditions of
the simulated scenarios. (a), (b), (c) and (d) stands for
corresponding to scenario number 1, 3, 13 and 14, respectively.
7. RESULTS AND DISCUSSIONS
7.1 The difference of echo signals between conical shaped
and bowl shaped canopy.
Figure 2 is the echo signals of scenario no.l and no.13,
respectively. As a result of analysis of the echo signals, the first
peak corresponded to surface of object and the second peak
corresponded to the ground.
4 pres ne Vries
f
| ^
st à
| i epo
A | =
Ios ge
ur i 3
m
a
(b)
Figure 2. The simulated echo signals of scenario no.1 (a) and
no.13 (b)
