assumptions for a measuring system responding to the questions
about selection and configuration of measuring equipment
(photogrammetric cameras, laser scanners, GPS/INS equipment,
etc.).
2. ASSUMPTIONS OF A MEASURING SYSTEM
2.1 Assumptions of a Measuring System
When developing the assumptions, a rule was established that
the system would be installed on a flatcar, hauled by a railway
engine with the maximum speed of 100 km/h.
Due to the nature of equipment tested, it was decided that
measuring systems should be placed in the back part of the
railway engine. Such solution offers the following advantages:
- it is possible to utilize a standard railway flatcar,
- data control and recording systems, a scanner system, a geo-
referential system and a photogrammetric system can be
installed on the flatcar, applying variant modes of their mutual
arrangement,
- scanning made diagonally in relation to the rail track axis can
be performed in almost full 360° profiles (in the event that the
scanning-photogrammetric system is installed before the
railway engine, diagonal scanning is performed in 0-180°
profiles).
Once the detailed review of existing systems had been
completed, the authors decided that the system should include
the following components:
- a set of 2D scanners profiling in three directions:
perpendicularly to the rail track axis and in two diagonal
directions,
- a set of four cameras to colorize the cloud of points
originating from laser scanning,
- a GNSS/IMU geo-referential module integrated with scanners
and cameras,
- a photogrammetric module composed of two stereovision
systems of canonical or convergent geometry.
Figure 1. Schematic diagram of flatcar with a single profiling
scanner
Figure 2. Schematic diagram of flatcar with two diagonal
scanners
International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Volume XXXIX-B4, 2012
XXII ISPRS Congress, 25 August — 01 September 2012, Melbourne, Australia
In order to compare potential and measuring accuracy offered
by various systems, the authors decided to carry out separate
measurements using two independent methods:
System I (based on a phase scanner):
- a scanner profiling perpendicularly to the direction of travel,
System II (based on pulse scanners):
- scanners profiling in two diagonal directions and integrated
with photogrammetric cameras.
Schematic diagrams of both systems are shown in Figs. | and 2.
Fig. 1 shows flatcar with System I, whereas Fig. 2 depicts the
idea of System II (installation of two diagonal scanners).
2.2 Description of used measurement systems
System I was to test the technology of measurement by means
of the so-called "railway dedicated" device. A Z+F PROFILER
9000 profiling scanner, coupled with an odometer, was applied.
That system (Z+F PROFILER 9000 with an odometer) operates
in the mode of data acquisition being performed
perpendicularly to the train travel direction and conducts
measurement of data within the track axis system. To acquire
data, Z+F PROFILER 9000 utilizes only a single scanner,
which is capable of acquiring them in 360° profiles, as opposed
to the earlier model - PROFILER 6007 DUO - which employed
two scanners.
R088ND3 odometer by Wenglor was installed for the period of
measurements. For safety reasons, Z+F PROFILER 9000 was
put on a flatcar (car type RES), on a previously prepared
supporting structure (Fig . 3).
Figure 3. System I — Profiler 9000 scanner during installation
The Z+F PROFILER 9000 measuring system is the fastest
scanner that provides data in the form of two-dimensional
profiles. This is a phase scanner, allowing to record more than 1
million of points per second, with the maximum recording
speed of 200 profiles per second. Thanks to those parameters, it
is possible to obtain very small distances between sections,
even at high speeds. The second measuring system (System II -
Fig. 4) was based on a RIEGL solution, namely VMX-250.
During research, the equipment configuration has been
modified and extended by additional NIKON 7000 cameras.
The mobile RIEGL VMX - 250 system is a set of two Riegl
VQ-250 scanners with a GPS unit, installed under an
aerodynamic cover. The whole measuring system includes four
digital cameras, whose viewing ranges can be determined
individually for each camera, depending on project needs.
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