INTRODUCTION AND BACKGROUND
Rail Overhead and Top of Rail elevation
data was required to support the high speed rail corridor. In addition
to the top of rail and wire information, designers needed additional
information at each catenary pole including the elevation of the guy
wires at the catenary pole, the cross members between the catenary poles
& the top of the catenary pole foundation. AXIS was contracted to
provide supplemental survey data along a high speed passenger corridor,
to include the location of catenary wires, towers and other features
used to power passenger trains.
PROBLEM
Due to the narrow high speed rail
corridor AXIS recognized from the outset the limited instrument set up
locations. Through careful planning and execution, difficulties with
control geometry were avoided. The remaining challenge was related to
the narrow incidence angle of the laser scanner beam with some of the
wires, this was mitigated by placing control to cover shorter spans of
wires, and gathering both overlapping and redundant data from adjacent
control points.
SOLUTION
To fulfill the client’s needs, AXIS
deployed its Leica MS-50 robotic total station, which also has a
high-definition (HD) laser scanner capability built into the instrument.
After orientation to the work area and
railroad safety requirements, AXIS first located existing control points
on each end of the area of interest. A control traverse was run through
the work area as needed to connect to existing control points, and to
establish control for the laser scanner data collection. AXIS used a
combined workflow for the project, which meant that while the instrument
was in place to set control, a second workflow for the laser scanner
was initiated, eliminating the complicated logistics and multiple setups
required if both a surveying instrument and a laser scanner were
deployed on the project. The single occupation work flow also served to
minimize errors in the dataset, which are introduced every time an
instrument is setup or removed from a control point.
During the data collection workflow,
separate conventional laser measurements were observed to selected
features in the work area that were visible from adjacent control
points. Positions of these features from all control points were
compared and used to verify the integrity of the control points and
laser scanner.
The full dataset was analyzed prior to
delivery to the point cloud modeling team, ensuring the terrestrial data
was fully valid, complete and geometrically sound before it was
integrated into the airborne dataset. The fit of the terrestrial data
into the airborne data without any adjustment proved the validity of
both datasets, which were collected by radically different platforms and
technologies, tied together by a common, high precision control
network.
LESSONS LEARNED
When the terrestrial data was compared
to airborne laser data, the redundantly collected data matched closely
to the aerial data, independently confirming the quality of the entire
dataset, while densifying and clarifying catenary and guy wire locations
thus yielding a highly precise and accurate map of the entire work
area. The use of a high precision control network and careful planning
allowed a seamless point cloud to be developed for the client.
BENEFITS
The final deliverable was a high density
point cloud showing the location of a large number of wires following
different paths along a narrow corridor enabling the design team to
analyze the paths of the wires as they crossed and re-crossed each other
in different planes. Additionally, wires connecting the catenary wires
to a transformer field, as well as unrelated power and transmission
lines were located and modeled as they ran along the rail corridor or
crossed it.
The project was completed ahead of schedule and on budget.
SERVICES
- Using a high speed, high precision terrestrial laser scanner, AXIS surveyed catenary wire locations and elevation data of the designated area
- Aerial and Terrestrial LiDAR Processing to classify and digitize catenary wires in the designated area
- Aerial and Terrestrial LiDAR Compilation for compiling individual catenary wires in the designated area
- Map Production / Final Edits of the catenary wires
- Project Management
- QA/QC
DELIVERABLES
- 2D & 3D Planimetric MicroStation Files
