Uwe Bacher
namely the utilization of dark shadows in sun direction!, and the exploitation of vertical structures, i.e., especially the
trunks, which are projected to nadir pointing straight lines (Jaynes et al., 1994, Lin and Nevatia, 1998, Shufelt, 1996).
Additionally, we assume that the deciduous tree is rotational symmetric. Thus, its 3D outline can be derived from its
normalized and symmetric shadow projection. Please note that conifers would require a totally different modeling. The
main reason for this is that they never loose their needles resulting into a totally different appearance in the image.
disturbing objekt
mostly
rotational symmetric
medium-|| vertical] — 00055 0560 bus, HUE PEAT ITY
sized linear REA
volume object hierarchically »~ ~
connected ‘
with “uf
vertical " thick vertical extremely thin fhin MATERIAL
; 3D point ; ; wooden AND
cylinder wooden cylinder | | wooden cylinder cylinder GEOMETRY
point of intersection
A intersect in
. — Y
disturbs : —— : !
„Hm eam Or I LN
N : Y y f long, : | long,
dark : | dark, blurred | |. short, distinct distinct indistinct short, indistinct
blob edge datk line dark line in|: line in line IMAGE
light : nadir-
direction | : | direction
dark lines, dark and light lines,
: high contrast ; low contrast
DIRECT OR
SHADOW : SHADOW PROJECTION DIRECT PROJECTION
PROJECTION :
—® specialization relation concrete relation
part-of relation 2 generalrelation’ ^ ii meme properties of objects
Figure 1: Model of leafless deciduous tree and disturbing object
Figure 1 represents the deciduous tree from three different points of view, i.e., levels, which are connected by the so-called
concrete link (Tónjes, 1997, Mayer, 1998): In the real world, the nearly rotational symmetric tree consists of its trunk and
crown. The base of the trunk is a part of the trunk and determines the position of the tree on the ground. The tree crown
is connected to the trunk and consists of branches. The branches are connected hierarchically with decreasing thickness,
ending in twigs.
The material and geometry level describes the objects independently of the sensor. The trunk is represented as thick
vertical, the branch as thin and mostly curved, and the twig as extremely thin wooden cylinder with a bark surface. The
base of the trunk is a 3D point whose coordinates can be derived from two or more images or an existing digital terrain
model (DTM).
The objects at the material and geometry level are connected with the image primitives at the image level. On this level,
the deciduous tree is represented on one hand indirectly by its shadow projection and on the other hand by its direct
projection. In shadow projection, the more or less vertical trunk appears as long distinct dark line in sun direction. The
branches correspond to short dark lines of high contrast. The outermost thin twigs of the tree crown are not resolved at
this resolution as lines, but appear as a blurred edge. In direct projection, the branches are short lines and the trunk is a
long line in nadir direction. The lines are dark or light and mostly of low contrast.
I1.e., projection of a vertical line on the horizontal ground, where the sun is the projection center
52 International Archives of Photogrammetry and Remote Sensing. Vol. XXXIII, Part B3. Amsterdam 2000.
a A A
To mal
volumé
materi
distinc
mediui
the tre
shadov
3 ST
The st
high c:
are hy]
branch
The p
shado
structu
refinec
accura
recons
these :
their «
which
4 IN
Figure
image
image
Marct
trees €
