B3. Istanbul 2004
nt in a project in
analysis of study
1g, as bare earth,
% of laser points
.310 points, what
ea.
ly to laser pulse
small height in
ccentuated slope,
arth (bridges).
it not beloging to
ation aided in
iltering process.
s building, while
and transmission
s have separated
und mainly with
points that they
ch, while other
ere defined for
(most with roofs
were correctly
R point filtering,
study area. The
in orange color,
ferring points to
in purple color
or.
its as bare earth
dition.
International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Vol XXXV, Part B3. Istanbul 2004
Layer Points Points Number | Percentual
before after points difference
manual manual difference | between 1
edition (1) | edition (2) (1-2) ea
Rare 137.701 143.470 | -5769 - 420
earth
Buildings 8.423 5840 2583 30,67
een 434887 | 430518 ] "4372 1.00
(
Other - 1186 - -
Total 581.011 581.011 E s
Table 2. Comparision between points defined as bare earth
and layers befor and after manual edition.
4.2 Land use surveying
Land use surveiyng made in this study is referred to February of
2002, period of aerial photographies taking.
Through the orthophotos mosaic analysis it was possible to
define the land use for influence direct and directly affected
area for the highway construction. It was possible the
identification of improvements as buildings. The LIDAR sensor
coming served as complement to orthophotos mosaic for
surveying of land use. Shade areas in orthophotos mosaic could
be analyzed in LIDAR intensity image and in traverse cuts in
3D points file. In areas with vegetation where was doubts with
relationship to class definition, it can differ thin vegetation and
dense vegetation with base in observation and measurement of
laser point height and density.
4.3 generation of DTM and DSM of study area
The model of Figure 4, where a TIN was generated from
contour lines with spacing of 5 m obtained by
aerophotogrammetry restitution left to want with relationship to
plasticity, but it presents natural breaklines (as streams) very
defined.
Figure 4. Part of DTM generated from aerophotogrammetric
restitution.
Figure 5 show part of a DTM obtained in same area of figure 4,
derived from LIDAR points. Due to high points density of
commercial systems available today, it presents as
characteristic the high plasticity. On the other hand, it presents
artificial depressions (due to points filtered and/or classified
erroneously by the algorithms as bare earth) and " natural
breaklines " don't appear.
Figure 5. Part of DTM generated from LIDAR points.
DTM generated from integration of LIDAR points and
aerophotogrammetric restitution elements (figure 6) it had for
objective to join characteristics of two previously produced
models: the high plasticity and density of dtm obtained from
LIDAR points and the morphologic quality of DTM obtained
from aerophotogrammetric restitution. Areas in DTM borders
should not be considered, therefore they present inherent
mistakes to TIN structure construction. To avoid this, is always
due to cut out a larger area than the one that will be analyzed
and to accomplish the cut after TIN structure construction.
DTM generated from integration of LIDAR points and
aerophotogrammetric retitution elements it was chosen to be
used in the subsequent stages of study.
Figure 6. Part of DTM generated from integration of
LIDAR points and aerophotogrammetric restitution
elements.
Comparison among altitude measures obtained with LIDAR
sensor and for aerophotogrammetry: With the objective of doing
a comparison among altitude measures of bare earth LIDAR
points with the coming contour lines in aerophotogrammetric
restitution, altitudes of two models were measured at several
places in study area. It was determined LIDAR located in
classes that it composes the land use map and exactly where
passed the 5 in Sm contour lines presents in
aerophotogrammetric restitution to avoid of contour lines values
interpolation. In ArcView GIS, were put on the themes " mosaic
" restitution " and " DTM LIDAR points".
