GPS World

Tag: DTM

  • Trimble Applanix: Unmanned aerial vehicles aid survey efforts

    Trimble Applanix: Unmanned aerial vehicles aid survey efforts

    L’avion jaune, a French UAV and aerial photogrammetry company, uses the Trimble Applanix APX-20 UAV GNSS-inertial OEM solution and a YellowScan VX-20 lidar on its M600 multirotor UAV. (Image: L’Avion Jaune)
    L’avion jaune, a French UAV and aerial photogrammetry company, uses the Trimble Applanix APX-20 UAV GNSS-inertial OEM solution and a YellowScan VX-20 lidar on its M600 multirotor UAV. (Image: L’Avion Jaune)

    The breakdown of limestone cliffs generates landslides and loose debris that threatens the environment, people and wildlife below. These conditions make it impossible to safely operate traditional survey equipment from the ground for landslide detection. Using UAVs for direct georeferencing is an efficient way to take traditional survey efforts to the sky and enables users to accurately assess land formations while mitigating risk.

    One way to implement direct georeferencing on UAV platforms is with the Trimble APX-20 UAV, which is a GNSS-inertial OEM solution that increases the mapping efficiency of small UAVs. It consists of small, low power, precision GNSS and inertial hardware components and POSPac UAV post-mission differential GNSS-inertial office software. The APX-20 UAV eliminates the need for ground control points and reduces the sidelap required to be flown per flight.

    The APX-20 UAV contains a precision, survey-grade GNSS receiver and dual inertial measurement units (IMU), so it automatically supports integration on gimballed platforms without requiring an external interface to an autopilot or on a mount. It computes at 100 hz using the embedded IMU while simultaneously logging the raw IMU data from both the internal and external IMU at 200 hz for post-processing in POSPac UAV. The postprocessed position and orientation solutions are suitable for direct georeferencing of cameras, lidars and other sensors.

    Trimble Applanix UAV Put to the Test

    For fast and safe landslide detection, the Trimble Applanix APX-20 UAV for direct georeferencing was put to the test using a Multirotor M600 manufactured by French company L’Avion Jaune equipped with a VX-20 lidar sensor made by YellowScan, also a French company. This combination produces cost-effective and reliable high-resolution UAV lidar-derived DTMs and 3D models for hazard mitigation and planning.
    L’Avion Jaune has performed more than 600 successful mapping missions globally. After pursuing mapping activities with mainly crewed aircraft, it began developing UAVs for long-distance applications for marine, tropical forest and polar regions such as the Multirotor M600/YellowScan VX-20, which offers high-precision, cost-effective and efficient aerial mapping.

    The APX-20 UAV and the M600/YellowScan VX-20 were combined and deployed to evaluate landslide activities in France. The mission parameters for this configuration included: high point density; x, y, z precision of 5 cm; access to dangerous zones; map generation under dense vegetation area, and fast deployment. The goal of this project was to enable the implementation of safety and prevention plans for the protection of pedestrians, infrastructure, wildlife and more.

    During the six-hour duration of the project, the APX-20 UAV and M600/YellowScan VX-20 configuration was flown four times for 15 minutes each during sunrise. It flew more than 75 ha in surface area with a flight speed of 5 m/s at 60 m in the air, following the topography. Checkpoints were surveyed with differential GPS following the conclusion of the flights. Data processing included computation of the georeferenced trajectory, matching flight lines and point cloud classification, which took two days.

    The Results

    The flexible UAV deployment of resources enabled the acquisition of dense point clouds and the generation of DTM in less than three days. During this project L’Avion Jaune was able to optimize the choice of material and discover the best practices to collect and process lidar data for mapping in dense vegetation.

  • Trimble: Grading smooth as butter

    Trimble: Grading smooth as butter

    On a project on the Butterfield Landfill — about 45 miles south of Phoenix, Arizona — Buesing Corp. needed to excavate and haul 1,850,000 cubic yards of dirt from a landfill more than 60 feet deep while grading the slope, basin and stockpile; inserting storm drains; and making an operations layer.

    Buesing, founded in 1965, specializes in modeling and building complex underground systems in challenging conditions. It had four months to complete the initial mass grading, with another month for shaping the stockpile and a final month for the operations layer and piping. The mass grading of the site required an accuracy of plus or minus one tenth of a foot in a landfill with 4:1 slopes and a slope length of 300 linear feet, and the operations layer had to be two feet thick. The project also required installing storm drain inlets, flow lines, and outlets to grade.

    To remain on schedule, the project required moving large quantities of soil quickly and efficiently, as well as adjusting grading models to incorporate design updates and changes while in production. “We used DTMs and orthophotos collected with our UAV to track progress quantities and adjust the stockpile model to minimize haul distances and slope rework as well as maintain proper drainage and control of stormwater,” said Rio Byman, Buesing’s GPS manager, who is responsible for building 3D models and managing the maintenance, calibration and updates for the company’s machine control (MC) solutions.

    Photo: Trimble
    A caterpillar CAT14M3 motorgrader is guided by Trimble’s dual-mast Earthworks system. (Photo: Trimble)

    For this project, the company used heavy equipment both with and without MC, including blades, excavators and dozers with MC, along with GNSS-based grade checkers to control the earthmoving operations. Specifically, Buesing, which started converting its equipment to Trimble around 2018, used the Trimble Earthworks Grade Control Platform and the Trimble GCS900 Grade Control System on the site and Trimble Business Center at its office.

    Buesing works in a variety of market segments for public and private entities in seven states, though it performs most of its work in the Phoenix metropolitan area. Key to its success has been an emphasis on skilled crews, continuous training and technology. In fact, Buesing was one of the early adopters of machine control in 2006. “A decade ago, the technology was pretty rudimentary, which limited adoption,” Byman said. “That’s changed a lot in recent years, particularly in the ease of use and flexibility. Today, grade control is an integral part of the company’s ability to build ever-more-complex solutions in even more challenging site and soil conditions.”

    The company started with the Trimble GCS900 on single-mast and dual-mast blades, excavators and dozers. It has since moved to the Trimble Earthworks Grade Control Platform along with Trimble Business Center for managing 3D models. Working closely with SITECH Southwest, Buesing has gone from six machines with grade control to more than 20 in just five years. The company relies on grade-control solutions on its excavators, dozers, motor graders and scrapers, and has used them on projects of every scope and scale, though their value is most evident on urban high-rise excavation.

    “It takes time for operators to gain faith in the data, and know that the machine will excavate efficiently and accurately, whether building pads or cutting basements,” Byman said. He believes that improved productivity in the field comes with trust in the technology.

    Using Trimble Earthworks’ Autos mode, the software controls the implements while the operator controls the machine’s direction and speed for consistent, high-accuracy finished grade in much less time than it would take without automation. “On any jobsite, the operators have to be aware of everything around them, as well as what’s going on with the blades or scrapers,” Byman said.

    “With Autos, they’re able to focus on what’s going on around the job and plan for watering and other environmental conditions with confidence that the machine is digging to grade. This makes our jobsites more productive, safer and more efficient. We have happier operators who are excited to come to work with newer equipment.”

  • Bluesky 3D building models aid designs for London residences

    Bluesky 3D building models aid designs for London residences

    Image: Bluesky
    Image: Bluesky

    London building-design agency DCSK is using 3D building models from Bluesky to inform the design of high-profile urban residential developments.

    Derived from the most up-to-date and accurate aerial photography, the Bluesky 3D models allow DCSK to place a design within its real-world context, consider sensitive view and vantage points, and communicate ideas to clients, planning authorities and the public.

    DCSK has used a number of models from Bluesky, including a detailed representation of central Birmingham for the design of a 24-storey student accommodation on Lancaster Street.

    “We have always had to consider how a design sits within the existing cityscape and how it will interact with the buildings and infrastructure that surround it,” said James Khamsi, Director of DCSK. “Before geographically accurate computer representations, such as the Bluesky 3D models, were available and affordable, we relied on a combination of site photographs and traditional 2D maps. This was a crude workflow that raised potential concerns about the currency and accuracy of information that was informing both the design and resulting planning permissions.”

    DCSK is using 3D models from Bluesky for projects such as Curzon Circle Student Accommodation and others.Photogrammetrically derived from stereoscopic aerial photography, the Bluesky models are fully rendered and are provided as either wireframe or block models in a format suitable for use in both CAD and GIS software.

    All Bluesky 3D models are supplied with a digital terrain model (DTM) depicting the topography of the underlying surface.

    DCSK imports the Bluesky data into its 3D modelling software Rhino, where it is used to create a background layer for the design. The development site is isolated, and this data removed from the background layer, allowing for the detailed design to be dropped in. The proposed development can then be viewed and analyzed in its real-world context with detailed assessments of access ways and viewpoints, for example.

    “The Bluesky models allow us to inhabit the site and experience the design as if we were there,” said Khamsi. “We can explore potential sensitivities, and, as the models are agile, we can massage the design exploring different options without leaving the office. The Bluesky models are also intuitive and therefore easy to interpret allowing us to communicate complex design ideas.”

  • 3 keys to successful canopy penetration

    3 keys to successful canopy penetration

    Sunlight through a tree canopy. (Photo: RedTail)
    Sunlight through a tree canopy. (Photo: RedTail)

    RedTail Lidar System’s RTL-400 delivers the trifecta

    Summer is here, and with it comes the challenge of creating accurate topographic maps under tree canopies. The adoption of drone-based, 3D light detection and ranging — or lidar — is emerging as the go-to sensing technique to meet this challenge consistently, safely and cost effectively.

    Designed specifically for use on small drones, the RTL-400 from RedTail Lidar Systems was developed with technology licensed from the U.S. Army Research Laboratory (ARL). The RTL-400 is designed to provide high-resolution 3D images of objects on the ground, flying at an altitude of up to 400 feet.

    The RedTail team recently partnered with the West Virginia Department of Environmental Protection (WVDEP) Division of Mining and Reclamation to demonstrate the RTL-400’s ability to generate an accurate digital terrain model (DTM) under “leaf on” conditions. This can be challenging, because pulsed laser light needs to reach the ground to generate laser light ground returns.

    RTL-400 flight specifications: speed -18 mph, flight time -12 minutes, acreage -20. (Image: RedTail)
    RTL-400 flight specifications: speed -18 mph, flight time -12 minutes, acreage -20. (Image: RedTail)

    One mission of the WVDEP Division of Mining and Reclamation is to assure compliance with the West Virginia Surface Mining and Reclamation Act and other applicable state laws. This task requires ongoing monitoring, mapping and assessment of sites across the state that are actively being reclaimed.

    Originally utilizing photogrammetry to generate point clouds, the WVDEP was unable to create the accurate, under-canopy DTMs that they desired. Looking for an alternate method, they began to consider lidar.

    The RedTail lidar team met with WVDEP representatives at a mine reclamation site in a remote area of south-central West Virginia. The terrain was a mixture of rolling hillside covered with grasses, brush and tree stands.

    The RTL-400 demonstration flight mapped approximately 20 acres of the reclamation site in 12 minutes, flying at an altitude of 196 feet and a speed of 18 mph.

    Once the data was collected, a digital terrain model (DTM) was created, revealing the RTL-400’s ability to generate the high-resolution, high-density point cloud needed to accurately map the terrain beneath the tree. 

    Digital terrain model (DTM) generated from RTL-400 point cloud. (Image: RedTail)
    Digital terrain model (DTM) generated from RTL-400 point cloud. (Image: RedTail)

    The RTL-400 delivered all three key elements needed to provide DTMs in foliated areas:

    • a small beam divergence of 0.5 milliradians (.03 degrees) with a spot size of just 2 inches diameter at the canopy cover
    • the ability to analyze up to five returns from every transmitted pulse so that returns from the ground can be received and processed
    • a pulse density of 800 pulses in every square meter of the canopy (for the WVDEP flight).  
    RTL-400 generated digital terrain model (DTM) overlaid with contour map. (Image: RedTail)
    RTL-400 generated digital terrain model (DTM) overlaid with contour map. (Image: RedTail)

    RedTail Lidar Systems is a division of 4D Tech Solutions Inc., a company focused on providing innovative technology-based solutions to address government and commercial customer needs. RedTail’s in-house technical expertise — coupled with a full suite of software and hardware design and manufacturing tools — allows the company to develop custom lidar solutions for manned and unmanned vehicle applications.

  • SimActive launches free data-processing service using Correlator3D

    SimActive Inc., a developer of photogrammetry software, is offering a new free data-processing service using Correlator3D.

    New users can upload their first UAV, satellite or aerial image project to obtain digital surface model (DSM), digital terrain model (DTM), point cloud and orthomosaic outputs.

    Along with optimal results, users also receive tailored feedback, recommendations and training from SimActive experts.

    The service requires no obligation, and is based on Correlator3D software, building on more than a decade of innovation on computer vision algorithms, a subfield of artificial intelligence. Quick turnaround is also possible due to the speed of the software and extensive use of GPU.

    “Our new offer is unique to get the best possible results from the very first project onward,” said Philippe Simard, president of SimActive. “Following this, users are trained with industry-leading technology, custom advice and necessary knowledge for successful mapping.”