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International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Volume XXXIX-B7, 2012
XXII ISPRS Congress, 25 August — 01 September 2012, Melbourne, Australia
Figure 8. During construction only half of the highway will be
closed
Figure 10. Metro line aligned avoiding bridge foundations
| Design criteria taken into consideration during different
planning stages were the following:
The design speed is 80 km/h.
Metro lines were designed with minimum curve radius of
550 m and transient curve of P ^ 110 m (A value).
During the design work, the designers used values (for the
above mentioned) parameters as large as possible.
e During the design work, a maximum attention was paid to
the location of stations; the location of stations in essence
was determined by the Libyan contrasting partner
(RPEMB) in the original (previous) planning study.
e Planning the line alignments was a result of multi-step
iterative process:
* In the first step, the stations were placed, and then the
line alignment (trail) between stations was planned. In
many cases, it was not possible to align the lines with
the axis of the stations because of the constraints of
the minimal radii and transient curves. Additional
constraint meant that the stations might be only
imposition on straight line sections.
* In the second step, the line (trail) was drawn and led
as close as possible to the problematic station, if any,
and station location was slightly modified to have the
station fallen on the line and aligned with its
direction. This choice was in a way limited in densely
built-up areas because of retained buildings. In the
case of stations, additional constraining factor was the
location of exits; these had to be located in
advantageous locations regarding the pedestrian
movement patterns.
* The first and second steps were repeated until no
compromise or acceptable compromises were reached
and the lines and stations imposition into their final
locations.
e During planning the alignment lines, special criteria were
adopted for these line sections with special characteristics.
For example, for the inner city section of line (B) a curve
radius of R-400 m was adopted. Another exception was
between stations B 10 and B11, a curve radius of R-300 m
was adopted because these two stations were very near to
each other, and to avoid the foundations of a planned
future high-rise building. In these short sections of the line
it presumed that the speed will be decreased.
e During planning, existing and future development in the
traffic system were considered, attention was paid to road
crossings and nodes, and special caution was paid to the
foundations of bridges where the line sections were
planned as deep alignment.
e Remotely sensed images and photographs were of great
help in planning those sections of the line where
subsurface alignment construction was adopted. These
sections will be built by cut-and-cover construction.
During the construction phase, surface traffic will be
insured, and there will be no need for unjustified building
demolitions. Surface features, such as roads, buildings,
pedestrian pavements, and even young trees and utility
poles were easily distinguished and identified in remotely
sensed images and aerial photographs, a fact that eased
planning the alignment of Metro lines in a way where
vehicle and pedestrian traffic is ensured during the
construction phase, for example on the sections between
B04-B01 and A01-A08 stations (Paulini, 2008).
5. CONCLUSIONS
Remotely sensing imagery, whether these were satellite images
or aerial photographs, has a spatial accuracy equal or better that
50 cm. Both kinds of images have a high resolution of 60 cm
for satellite images 30 cm for aerial photographs. Satellite
imagery, after carrying out the necessary corrections,
transformations, and co-registration has satisfied the required
