(IX-B4, 2012
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International Archives of the Photogrammetry, Remote Sensin
g and Spatial Information Sciences, Volume XXXIX-B4, 2012
XXII ISPRS Congress, 25 August — 01 September 2012, Melbourne, Australia
Figure 4. System II based on a Riegl solution (VMX 250).
The whole system was put on a truck and, together with the
flatcar, participated in the measurement.
3. TEST MEASUREMENTS
3.1 Selection of the Route
For the performance of tests measurement, 3 railway track
sections on the Warsaw-Cracow route were selected, each 10
km long, with different land features and elements so that to
take into account the following:
- selected clearance infrastructure elements, such as bridges,
viaducts, various type semaphores, traction poles, platforms,
platform umbrella roofs, and a tunnel,
- a relatively diversified track geometry, including circular arcs
and transition curves,
- à previously set geodetic control network with already
monumented points. The latter was of a high significance since
it considerably reduced project preparation time and costs.
A reference field geodetic measurement was performed to
verify the accuracy of selected methods.
On the basis of measured geodetic control network, a
measurement was conducted, which included the performing of
Profiles perpendicular to the rail direction and a tachymetric
measurement of selected clearance infrastructure elements. Fig.
5 shows an example of track reference measurement with the
use of the most recent LaserTEC device by GRAW.
Figure 5. Track reference measurement with the use of the most
recent LaserTEC device by GRAW
3.2 Examination of Acquired Data Quality
Following the data recording by means of the measuring flatcar
(System I and II) and geo-referential measurements, has been
proceeded with the examination of geometrical quality of
acquired data.
In the first turn, conformity of the cloud of points obtained with
the use of System II was examined based on control points. In
the course of the measuring flatcar's travel, there were posts put
along the track and their coordinates measured by GPS
technique (precisely the post starting points). 16 control points
were set along the travel route.
Next there were accuracy measurements on particular sections
performed on the basis of selected sections, which were
measured geodetically and with the use of a precision rail gauge
(LaserTEC), with a millimetre accuracy.
Comparisons were made with reference to about 30 sections
(involving geodetic measurements and in-house works in
relation to the cloud of points — see example, Fig. 6). Deviations
were measured in the section plane perpendicular to the track
axis. The width of the section was selected depending on
processed elements and ranged from 0.10 to 1.00 m.
First measurements were performed on the System II cloud of
points. Clearance was measured in 10 sections on the route near
the village of Podlesna Wola, and in 21 sections in the vicinity
of Slomniki station. 14 measurements were performed towards
track 2 axis, while 17 measurements were performed towards
track | axis. Deviations were measured in the section plane
under '2000' geodetic coordinate system, while vectors from the
cloud of points to reference points from geodetic measurements.
Deviations were within the acceptable limit assumed to
be 2 cm.
Additionally, a measurement was performed near the railway
station, of 32 points on the track and the already referenced 16
posts placed before the travel of the scanner. Measurement of
deviations of posts and points was performed only for
System II.
In addition to examining the geometric quality of the cloud of
points, also the quality of data was examined as regards their
preparation for further processing.
Within the framework of the task, an attempt at an automatic
classification of the whole of the cloud of points was made, and
additionally selected elements were classified manually in those
track sectors where geodetic measurements had been made, i.e.
in the tunnel, before the tunnel, and at the railway station.
With reference to selected places, a comparison of sections
obtained by means of both Systems was performed. Exemplary
comparison results are shown in Figs. 7 and 8.
Figure 6. Cross section through the railway station at Slomniki,
obtained with System II
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