Using the very latest laser scanning technology coupled with TERRAcontrol, a high precision INS (Inertial Navigation System), we offer the service of a novel 3D mapping system to scan roads, buildings and trees from a moving vehicle.
The “StreetMapper” uses well-proven laser scanning technology to capture the position of up to 600,000 3D points per second whilst in motion. The typical positional accuracy is better than 20mm and the point-to-point accuracy within the data is 10mm.
An inherent feature of LiDAR data is that it is acquired, processed and delivered in a digital format, making it very easy to work with and to create data products that meet a wide range of needs. The system is easy to mobilise and immediately after the survey the data is processed to provide point data with XYZ position and reflective intensity. Depending upon the customer’s requirements, the data can be processed and analysed further:
• Classification of laser data (for example ground, vegetation, buildings, wires)
• Vectorisation of laser data
• Measurement of features
• 3D modelling and texturing
A combination of LiDAR, mobile and terrestrial scan
technologies provides valuable information for industrial plant management.
When an industrial plant in Africa
needed to develop 3D site models for information management and future
construction, the plant turned to African Consulting Surveyors. The scope of
work called for 3D terrestrial scans of approximately 70 percent of all the
process structures along with the capture of high-resolution imagery and LiDAR
data for topographical purposes. The site covered about 1,730 acres (700
hectares), 494 acres (200 hectares) of which were built up with process plants
and associated structures. Some structures reached heights of up to 328 feet
(100 meters). It was considered the largest as-built documentation project in
primary objective was to create accurate models and drawings of the plant with
2D to 3D environment migration. “Our goal for the project was to create a 3D
virtual plant that was accurate enough to create as-built data and engineering
drawings, yet can be a versatile tool to track personnel, manage assets and
essentially become a plant information and management system,” explains Willie
Timmerman, project manager and African Consulting Surveyors' director of
technology. “This, in turn, would facilitate an increase in productivity and
Three methods of data collection were used for the
project: a LiDAR system, a mobile mapping system and a terrestrial scanner. The
generated data layers were combined to form the point cloud for the entire
plant. “The LiDAR data formed an important part of the whole plant layout from
an external viewpoint, whereas the terrestrial scanner focused on the internal
structures of the buildings and the plant processes inside,” Timmerman explains.
|(This picture and the next) African
Consulting Surveyors' mobile platform with the StreetMapper 360.
post-processed GPS control was used to correlate the various sources of data.
Conventional survey methods were incorporated to control and quality check the
point clouds generated by the terrestrial scanner inside the various buildings.
The GPS control points on the tar roads were demarcated with white paint so that
they could easily be identified on the LiDAR and mobile mapper scans.
surveyors began by establishing 10 permanent pillar beacons and 50 ground
control aerial marks across the plant. The horizontal coordinates of the beacons
were fixed by post processing, with 30 minutes of data collected at 0.5 second
epoch intervals. The verticals were fixed by implementing a precise
double-leveling circuit. The ground control points were used by both the LiDAR
and mobile mapping teams to apply the necessary network adjustments.
control beacons were then used to transfer control (reflective target stickers)
into the various plants by using total stations with reflectorless capabilities.
These targets were used to fix the scan targets, which averaged +/-5 targets per
floor. Closed traverses were then introduced to effect quality
Once ground control was established, five LiDAR passes were flown
over the plant to increase the point resolution from 15 to 75 points per square
meter. This allowed for a higher density on structures and high-lying features
such as overhead cables and pipes as well as other lower-priority detail such as
slime dams and open fields. The LiDAR data acquisition was completed in a single
|A high-resolution aerial image on a
section of the plant.
To capture the
next level of detail, the crew used a StreetMapper 360 mobile mapping
system--the first commercial deployment of such a system in the region. The
vehicle-mounted mobile scanner was driven between buildings to gather data that
was omitted by the LiDAR scanner. The point cloud density of this scanner was
8,000 points per square meter, and two runs of the plant were driven to get the
accuracy of the point cloud within the required tolerances. The relative
accuracy between points was less than 0.01 meter and the positional accuracy
less than 0.03 meter using the real-time GPS and IMU as part of the mobile
scanning system. The surveyed road markings were used for the final reductions
of the mobile scanning and LiDAR scanning point clouds to correlate and increase
the positional accuracy of the data. The mobile mapping was also completed in a
A Leica HDS6100 terrestrial scanner was used for all the
building interiors and continues to be used to capture plant-specific detail.
The scanner is of a higher order with positional accuracies of 5 millimeters up
to 25 meters and a decimated unified point cloud resolution of 4 millimeters
across the plant. resulting data will be used for future design work, reverse
engineering and retrofitting.
|A rendered plant model.
A scan of such
a large area produced a point cloud containing billions of data points--2
terabytes in all. The data were broken into manageable sections, and each plant
structure was allocated its own dedicated file. The coordinate system had large
constants that had to be removed and brought as close to zero as possible to
avoid creating rendering issues. The team used Cyclone software to process the data.
different technologies used to gather the data, the point clouds of the three
orders of scanning all agreed well with each other. According to Timmerman,
combining the technologies proved a highly efficient way to meet the client’s
needs. “The fact that the LiDAR scan and mobile scan each took one day to
complete in the field meant that the client saved a lot of time and money for
such a large volume of data,” he says, noting that the terrestrial scanning
continues due to internal and external modifications and extensions to the
The scans provide information of sufficient detail, accuracy and
density to populate a comprehensive plant information management system. With
applications including asset and plant management, design and engineering
support, and safety and security, the laser scanned data will support decision
making, reduce costs and improve safety. Integration with other systems and
data, such as wireless sensors, vehicle and/or personnel tracking and onsite
access control systems, will further assist with the day-to-day management of
the plant. Says Timmerman: “The accuracies and benefits of laser scanning have
the payback effect of increasing productivity and can save companies money over
the long term.”
Sidebar: Technology Overview
Leica ALS50 (Phase II) and Leica RCD Camera
measurement systems use aircraft-mounted laser technology to determine accurate
heights of land and buildings. As the plane flies over a site, the laser is
beamed to the surface, and the time it takes for the beam to bounce back is
recorded. Using the position of the aircraft from the onboard satellite
positioning equipment along with the return time for the laser beam and the
known value of the speed of light, the distance between the aircraft and ground
can be calculated. In order to increase the detail of the height model, mirrors
can be used to deflect the laser beam and create multiple measurements from a
single pass of the aircraft. The Leica ALS50-II allows data capture at pulse
rates up to 150 kHz and accuracy of 11 centimeters (including GPS errors) at all
pulse rates. Combined with Leica’s integrated 39-megapixel RCD medium-format
digital aerial camera system, the technology allows users to provide digital
aerial photography along with the LiDAR data.Mobile Mapping
System: StreetMapper 360
Mobile mapping systems (MMS) use laser
scanning technology combined with a navigation system to scan highways,
waterways and buildings from a moving vehicle. MMS can be mounted on various
types of vehicles, including automobiles, boats and trains, to allow for
numerous applications including highway mapping, coastal, river and canal
surveying, city modeling and flood mapping, to name just a few. By employing the
latest laser scanning technology for improved field performance and accuracy
along with precision navigation--including a solution for reduced GPS coverage
in urban areas--the StreetMapper 360 can achieve high-precision mapping to a
range of 984 feet (300 meters), a capacity of 300,000 measurements per second
per sensor and recorded accuracies in independent real-world projects of better
than 1 centimeter.Terrestrial Scanning: Leica
3D laser scanning captures 3D images by performing a
number of independent laser distance measurements in different but well-defined
angular directions. This distance data together with the associated angles form
the basis of the 3D images, also commonly referred to as a point cloud. When
combined with a high-resolution digital camera, every scan point can be assigned
a color using the image data. The Leica HDS6100 is a high-speed phase-based 3D
laser scanner that scans up to 508,000 points per second and has a full
field-of-view (360 x 310 degrees).
By Johan Spangenberg - CEO of African Consulting
Surveyors . He can be
reached at firstname.lastname@example.org.