Mobile LiDAR Specifications:
Q. What are the measurement frequencies of Michael Baker
International’s Mobile LiDAR systems?
A. Each system utilizes 2 lasers that can each measure up to
600,000 points per second. The total
maximum measurement frequency on each system is 1,200,000 points per
second. The frequency is configurable
based upon the collection requirements and can be set to capture at 75, 150,
300 or 600 kHz.
Q. How many measurements can each system receive for every
laser pulse?
A. Each system can measure up to 4 returns (1st, 2nd,
3rd, and last) for each laser pulse. Theoretically, this
yields the ability to measure up to 4.8 million returns per second.
Q. What is the range of the lasers?
A. Each laser can accurately measure a target up to 200m
(656’) from the sensor-head, in all directions.
Q. What is the laser precision?
A. The stated, repeatable precision of each laser is ≤5mm.
Q. How wide is the Field of View?
A. The system has a complete 360° Field of View.
Q. What are the onboard camera specifications and capture
rates?
A. Michael Baker International’s Lynx systems includes four
5 mega-pixel cameras capturing up to 2 frames per second each, that can be
positioned at various locations and angles on the vehicle. In addition, each system includes a PointGrey
Ladybug 5 spherical camera – six 5 mega-pixel camera array. The Ladybug camera provides panoramic,
spherical and rectified formats of imagery.
Q. How often does the IMU (Inertial Measurement Unit)
measure?
A. Our systems have IMU’s that measure the attitude (pitch,
yaw, and roll) and acceleration 200 times per second (200Hz). One system includes an ITAR-free FMU P301 that
provides more flexibility to service clients outside the United States.
Q. Can you see the laser, and is it safe to look at?
A. The laser sensors produce an IEC/CDRH Class 1 light beam.
The light beam is invisible to the naked eye, and the Class 1 designation means
that it is “eye-safe”. Therefore, the lasers can be operating while drivers and
pedestrians are present without presenting any safety hazard or distraction.
Mobile LiDAR Applications:
Q. Can Baker’s Mobile LiDAR systems be mounted on other
platforms?
A. The entire survey platform, is removable and fully
capable of being mounted on an off-road vehicle, boat, hi-rail, or speeder car.
With this flexibility, Michael Baker is able to perform railroad assessments,
beach erosion surveys, mine surveys, other coastal environment surveys, and
many more where surveying with a conventional automobile is not feasible.
A. Yes, data from all three LiDAR categories (aerial,
mobile, static) can be integrated to completely saturate a project area from
the sky to the ground and within buildings. Traditional survey data can be
integrated as well; after all, each methodology is simply generating survey information.
How it Works:
Q. What is the vehicle’s primary method of positioning?
A. The system utilizes an onboard dual-antenna high-accuracy
GNSS receiver to provide accurate vehicle positioning.
Q. What are the other means for positioning?
A. Our Mobile LiDAR systems are also equipped with an
inertial measurement unit (IMU) and distance measurement instrument (DMI). The
IMU measures the attitude (roll, pitch and yaw) of the vehicle by measuring
changes in direction around the X, Y and Z axis 200 times per second. The DMI is used to calculate the distance
traveled by the vehicle by measuring the revolutions of the wheel 1,024 times
per second. The DMI is also used to supplement GPS and IMU drift by
communicating to the system that the vehicle is stationary.
Q. What is the primary function of the on-board cameras?
A. The onboard cameras are utilized to perform three primary
functions: 1) by pairing the cameras with the lasers, we are able to
georeference the images to the LiDAR data, and colorize the resulting point
cloud with the RGB values from the image pixels; 2) the camera images also
serve as a validation tool, by enabling our processing staff to rapidly
identify features and objects within the point cloud with the referenced
photos; and 3) certain software tools utilize the calibrated imagery for
additional feature extraction and attribution capabilities.
Q. Can data be accurately collected in a tunnel without GPS?
A. Even with the loss of GPS signals within a tunnel, our Mobile
LiDAR systems will produce accurate results.
During a GPS outage, the DMI and IMU automatically take over
primary positioning duties. Working in
unison, the DMI provides the distance traveled, while the IMU supplies the
measured rate of turn; enabling the system to accurately calculate the
vehicle’s trajectory. The need for
ground control still exists and our team can help identify control
requirements.
Collection Specifications:
Q. Can the Mobile LiDAR system operate at night?
A. Yes, because the system utilizes an active laser, we can
operate at night. Night surveys are very favorable, especially for road
corridor projects, due to lower traffic volumes and decreased number of
obstructions (such as cars) that could block the laser from striking the
desired target. Keep in mind that the cameras are not used at night, so
simultaneous collection of images with the point cloud is not possible. If photography
is desired, collection would also occur during daylight hours, or where
permissible, at night with onboard high-intensity lighting.
Q. Can the Mobile LiDAR system operate in rain or snow?
A. Yes. However, Baker makes all attempts not to operate the
system in poor weather conditions in an effort to preserve the operational
integrity of the equipment and ensure the data collected is of the highest
quality. Because the system is able to collect a large amount of data in a
short period of time, our team is usually able to work around adverse weather
conditions through careful project planning and execution. With the ownership of two systems, we can
deploy both systems on larger projects to take full advantage of more favorable
conditions.
Q. Can the lasers penetrate or produce returns off of a
water surface?
A. The system will not capture returns through water that has ponded on a surface. Additionally, no usable data is captured on the surface of ponded water. The area appears as a void in the LiDAR point cloud.
Q. Can the lasers penetrate a building to collect data
within the building?
A. No. The laser will not penetrate any hard surfaced
building material beyond its external face.
Q. How are the lasers positioned to capture all features in
a single pass?
A. The lasers are oriented to produce an “X” pattern. This
configuration enables a full 360° Field of View, as Sensor 1 will capture the
front face of an object during the approach, and Sensor 2 will capture the back
face during the departure. See figure below.
Q. How much area can be surveyed in one day?
A. Depending upon project requirements and local conditions,
our system can capture tens to hundreds of miles per day.
Post-Processing Specifications:
Q. What software can you use to view LiDAR data?
A. There are a number of commercially available software
packages that can be used to view and manipulate LiDAR data, including many GIS
applications, as well as several free-ware applications that enable viewing-only
capabilities. Our team can providefurther assistance upon request.
Q. What is the time frame for post-processing raw LiDAR
data?
A. There are a myriad of variables that can directly affect
the amount of processing required for a particular project (size of area,
amount of ground control, number and type of deliverables, etc.), but a general
rule of thumb to consider is a 2:1 ratio; whereas it will take approximately
twice as long to generate a LAS file (standard format for LiDAR data), as it
did to capture the data in the field. For more detailed and strictly controlled
deliverables including colorized point clouds, animations, planimetrics,
contours, etc., the post-processing time will be much greater.
Product Deliverables:
Q. What types of end
products can be derived from LiDAR point clouds?
A. Products that can be developed from a LiDAR point cloud
include, but not limited to: bare-earth digital elevation models, triangulated
irregular networks, high profile contours, 3D animations, 3D renderings,
complete planimetrics (2D or 3D drawings), and colorized point clouds, among
others.
Q. In what formats can LiDAR data be delivered?
A. LiDAR data can be delivered in many formats including:
point clouds in the form of LAS files or ASCII files (colorized point cloud);
vector data in the form of a DGN, DWG, KML/KMZ, TIN, shapefile, or geodatabase;
and raster data in the form of DTM’s.
Q. How does LiDAR data differ from traditional surveying
data in terms of end products?
A. With Mobile LiDAR scanning, complete scenes (in 3D) are
captured and blanketed with high-density scan information in fine detail
because the system is literally able to capture millions of points during each
collection. An added bonus is the simultaneous collection of photography that depicts
the objects within the point cloud. Time is saved by capturing the entire
project the first time and preventing costly go-backs. With traditional
surveying, there are substantially less points captured, causing the need to
“connect the dots” to obtain linear features during post-processing, and
significantly reduced overall scene comprehension
Additional Information and Contacts:
Q. Who can I contact for further information regarding
project scope, project deliverables and project pricing?
A. Baker has a team of Mobile LiDAR professionals that are ready
to assist you with any questions you may have. Please feel free to contact any
of our Team listed on the "About Us" page.