Drones are making construction projects vastly more efficient and more safe, according to a media release from Diversified Communications.
“While the benefits of UAV technology are clear, knowing what information to capture isn’t always obvious. Then there are the legislative challenges. This report addresses these topics, and also provides insight into:
How drones have changed the approach construction professionals can take in terms of gathering data.
The many ways UAVs are making projects safer.
What sort of new opportunities will be opened up by the technology.”
Jeremiah Karpowicz, executive editor of Commercial UAV News, interviewed construction professionals from The Beck Group, Hensel Phelps and IMCO General Construction for the report, which is available via download.
Mayflower Communications Company Inc. will develop a small security-certifiable GPS module for the United States Air Force’s Modernized GPS User Equipment (MGUE) Program.
The Mayflower NavAssure 125a GPS receiver.
Mayflower was awarded a Phase III SGUE (Small GPS User Equipment) contract with the U.S. Air Force Research Laboratory sponsored by the Space and Missile Systems Center/GPS Directorate (SMC/GPSD).
Under the contract, the company will develop a small SWaP (Size, Weight, and Power) security certifiable Common GPS Module (CGM).
Mayflowers’ small SWaP GPS receiver technology will allow the Department of Defense (DoD) and its agencies to benefit from increased competition, enhanced capability and reduction in overall program costs to DoD program managers and prime contractors in upgrading their navigation systems to the modernized M-code receiver.
Mayflower’s SGUE program is aimed at the development of advanced GPS receiver technology to support future military GPS requirements. The goal of the program is to develop a NAVWAR (Navigation Warfare) compatible CGM form factor that will support SWaP-constrained military users.
The SGUE CGM development effort will expand Mayflower’s military GPS receiver product line to include modernized NavAssure-M product offerings so that current customers will have a form-fit-function upgrade path from SAASM to MGUE.
“Mayflower is a leader in small SWaP and miniaturized military GPS receiver and anti-jam products,” said Triveni Upadhyay, Mayflower founder and CEO. “I am confident in the quality and innovation expertise of our GPS engineering team to successfully develop the SGUE CGM. The development of small SWaP MGUE form factors, enabled by SGUE CGM, will have a significant impact in the M-Code market, providing secure modernized GPS signals to the warfighters and lowering total ownership costs on many military programs.”
“The Air Force is very pleased to see innovative GPS technology developed under its SBIR Program to find commercialization opportunity in the MGUE market. Mayflower has performed well and we are confident of the SGUE program success,” said Dana Howell, Air Force Research Laboratory (AFRL) program manager.
“The AFRL/GPSD objective in the SGUE Program is to advance MGUE technology and make it affordable to the warfighter,” said Eddy Emile, chief of the Advanced Technology and International Branch, GPS Directorate. ”
The SGUE Program fits the need and will lower the cost to the user by increased competition enabled by the SGUE Program.”
According to Mayflower, the NavAssure-M MGUE receiver form factors, focused toward small SWaP GPS receiver applications, will be backward compatible to SAASM, therefore, lowering the platform integration cost and total life-cycle cost.
In the Himalayas, MAVinci GmbH has operated a Sirius Pro unmanned aircraft system (UAS) at an altitude of 4,800 meters above sea level (ASL).
“Take-off altitude was 4,150 meters ASL. The flight was performed at BaSu County, ChangDu, Tibet,” the company shared in an email. “This is a new altitude record for us! Thank you to everyone who supported this mission!”
MAVinci manufactures UAS for surveying professionals, designed to enable easy and quick surveying and documentation.
The MAVinci Surveying Sirius Pro is manufactured in Germany. It is a fixed wing UAV with a 1.6-meter wingspan and less than 3-kilogram take-off weight.
The Siruis Pro guarantees high precision without setting control points on the ground, according to MAVinci.
Using a Topcon receiver and navigation system, it precisely measures the camera position for each image, making it equivalent to a control point. With the control points virtually set from the air during the flight, their coordinates calculated in real time.
By Aidan F. Browne and David Vutetakis, The University of North Carolina at Charlotte. Presented at IEEE/ION PLANS 2016 in Savannah, Georgia.
A novel laser-beacon localization system has been developed that has applications in positioning and navigation of mobile ground or aerial vehicles where other forms of localization are absent (such as GPS). The system allows for accurate position determination within an area of interest with reasonable accuracy.
The overall operation of the system is accomplished using only two external co-located beacons and a single on-board detector to perform pseudo-triangulation. The two beacons are spaced two meters apart, and continuously scan the area of interest in a sweeping fashion. As a beacon sweeps across the area of interest, its instantaneous angle is encoded in the pulse frequency of its emitted laser beam using a unique range of frequencies. A rotating detector on the vehicle is continually scanning over a 360-degree arc; it captures and decodes received beacon information in combination with its own relative angle at time of receipt.
The system has been successfully modeled in MATLAB to evaluate its effectiveness in terms of spatial localization accuracy under thousands of scenarios as well as to analyze the effects of the error parameter variations.
A prototype of the system has been realized using stepper motors, TTL-modulated 4.5 milliwatt line-generating lasers and a transimpedance amplified photodetector. Initial system testing has been promising with consistent results, indicating that the assumed error levels for the model were reasonable. Testing is underway to validate the results of the model and demonstrate the feasibility of the system.
UAS Sense and Avoid Integrity
By Michael B. Jamoom, Mathieu Joerger, and Boris Pervan, Illinois Institute of Technology Presented at IEEE/ION PLANS 2016 in Savannah, Georgia.
Sense and avoid (SAA) concepts and methods can be tools for certification authorities to set potential requirements for integrating unmanned aircraft systems (UAS) into the National Airspace System.
One new method seeks to ensure the safety of SAA functions for UAS in the presence of multiple intruders. Integrity and continuity are used as quantifiable safety performance metrics, and are addressed though determination of the probability of data mis-associations for multiple intruders. A miss-association occurs when the system incorrectly associates one intruder’s measurement with another intruder’s trajectory. Incorrect intruder associations are hazardously misleading information, impacting integrity. Likewise, a detected mis-association can result in a break in the continuity of the SAA operation.
A sensitivity analysis is performed based on two two-intruder encounters. The resulting impact of mis-associations between multiple intruders on integrity and continuity is quantified for a nominal composite SAA sensor.
A fourth speaker has joined the line-up of experts in unmanned aerial vehicles (UAVs) who will share their know-how in UAV design and applications in a freeGPS World webinar May 19.
Chris Miser, CEO and owner of Falcon Unmanned, will discuss a topic important to all of our readers: the practical considerations to integrate a professional GNSS receiver on a drone.
The free webinar will take place Thursday, May 19, at 1 p.m. U.S. Eastern / 7 p.m. Central European Time. Register here for “UAV Design and Applications: Autonomous Relative Navigation and GNSS Robustness for UAV Systems.”
Constantly evolving, it’s no wonder keeping up on the latest in UAV design and applications can be challenging. In the webinar, speakers will engage you in discussions involving:
Self-generated radio-frequency interference aboard UAVs. (Presented by Dennis Akos, Professor, University of Colorado at Boulder, and Joshua Stubbs, Ph.D. candidate)
An autonomous relative navigation tool for in-air UAV refueling. (Presented by Jeff Fayman, CTO, Geodetics)
GNSS integration aboard small UAVs (Presented by Chris Miser, CEO, Falcon Unmanned)
Considerations for multi-GNSS integration onto UAV platforms. (Presented by Jan Leyssens, Product Manager, Septentrio)
About Falcon Unmanned. Falcon Unmanned provides professional tactical unmanned aircraft systems for public safety agencies and commercial sector customers, as well as anti-poaching / conservation activities.
Falcon has several modular payload options providing multi-mission capability including live video missions (day or night), photogrammetry, high-resolution aerial photography and multispectral sensing.
In April, Falcon Unmanned delivered the first round of Falcon (fixed-wing) and Falcon Hover (quadcopter) aircraft to the U.S. Department of Interior (DOI) as part of a four-year IDIQ vendor contract. Falcon Unmanned is tasked with providing a complete array of aircraft, payloads, ground control stations, training and support services.
Falcon Unmanned successfully completed DOI/NASA airworthiness testing for its Falcon and Hover models, becoming one of only a handful of UAVs with a U.S. federal agency airworthiness evaluation.
Falcon and Hover meet or exceed a number of key DOI target requirements including:
Communications/video range of 5 miles
Fixed-wing/multicopter interoperability, with interoperable batteries, ground-control stations (GCS) and payloads
Easily swappable modular electro-optical/infrared (EO/IR) gimbal and mapping payloads
Open-source GCS
Secure 256-bit encrypted communications link(s)
Miser will be joined by three other experts, who will share their in-depth knowledge and practical tips, as well as take audience questions.
Click here to learn about the other four speakers, and register quickly and easily for this free webinar, sponsored by Septentrio.
CHC has launched its new N72 GNSS series, a high-end sensor designed for GNSS applications including offshore surveys and machine control, national geodetic networks, crustal deformation monitoring and bathymetry
CHC N72 GNSS series.
The N72 GNSS series is designed to offer all necessary technical features, making it one of the most complete and reliable GNSS receivers for scientific and surveying industries professionals.
“To meet the market requirements from geodetic survey and demanding applications such as CORS, on-board machine control and disaster monitoring, CHC research and development has designed one of the most feature-rich GNSS receivers available on the market. The N72 GNSS went through extensive validation and stringent quality process to achieve high performance and reliability,” said George Zhao, CEO of CHC. “This new-generation GNSS sensor reinforces our commitment to provide complete solutions to GNSS professionals.”
N72 features top level specifications:
Embedded battery supporting 15 working hours without external power supply
32GB internal memory integrated and 1TB+ external memory supported
8 threads of logging with circulating storage and FTP push functions
Wi-Fi, LAN, Bluetooth and serial ports for data communications
LCD display and function buttons for direct configuration
In the most critical phase of the landing maneuver, the UAV flight control system must compensate for the accelerated air flow above the ground vehicle. (Photo: DLR)
Moving at 75 kilometers an hour (47 mph) an unmanned, electric, autonomous aircraft settled gently on the roof of a moving car.
Scientists from the German Aerospace Center (DLR) Institute of Robotics and Mechatronics combined robotics and unmanned aerial vehicles (UAVs) to develop a system where a fixed-wing aircraft automatically lands on a moving ground vehicle.
The DLR system is designed for commercial applications such as remote sensing and communication. It could be applied to ultra-lightweight solar aircraft that complement traditional satellite systems in the stratosphere. Or, it could support crisis management, such as aiding disaster-communications networks or providing data on climate change.
Losing weight
Ultralight solar aircraft can reach more than 20 kilometers in altitude. The weight factor is crucial to how long the ultralight can stay in the air.
The Demonstrator Platform Penguin BE UAV is equipped with redundnant landing hardware. (Photo: DLR)
By omitting the traditional landing gear, the dead weight of these UAVs can be significantly reduced. This allows more load capacity, greater range and better performance. A lighter craft also increases payload capacity, creating more space for scientific instruments.
In flight tests on an airfield in Swabia Mindelheim-Mattsies, the DLR system was successfully tested with a 3-meter, 20-kilogram, electric fixed-wing UAV. A net was provided on the roof of a car, along with optical markers. The UAV can position itself up to half a meter over the 4 x 5 meter landing platform. The optical multi-marker tracking system detects the landing apparatus and determines the relative position of the ground vehicle with high accuracy. The computer-controlled landing is then carried out.
Movement of UAV and the vehicle are adjusted with the help of special algorithms. With the car and the UAV moving at the same speed, the landing is more like a settling, making the landing safer and easier. Though designed for both autonomous car and UAV, a driver remained in the car for safety during the tests. A robotic vehicle without a driver will be tested next.
The work was supported by the EU project EC-Safe Mobile Support and complement the activities of the Flight Robotics Group.
In the semi-autonomous landing vehicle, the driver receives control commands via a graphical display. The crosshairs indicate the location of the UAV. (Photo: DLR)
A: Similar to airplanes with an autopilot feature, the key issues that must be addressed in autonomous vehicles are redundancy and reliability of systems and appropriate, timely signals to the operator. One key area where this is required is the location of the vehicle. Autonomous location systems have to take into account areas where GPS works fine — but may suffer from an outage — and where GPS does not work, such as in urban canyons.
Jane Macfarlane Chief Scientist, Head of Research HERE
A: Autonomous vehicles face two key challenges. The first is enabling the vehicle to see beyond its sensors. Autonomous vehicles are composed of two functions: sensing the local environment and controlling the vehicle to operate in the sensed environment. This model must be extended to include the larger environment using cloud-delivered map information informed by a connected vehicle fleet. The second is building intelligence that allows autonomous vehicles to share the road safely with human drivers.
A: The development of autonomous vehicle sensors, artificial intelligence and software is advancing rapidly. Technology is being tested in open-road environments — and in bad weather. Component costs are falling as technology companies and automakers eye specific rollout dates. What could slow this developing industry is bad press, and the resulting government regulation, from a high-profile cyber security breach or an incident like a partially autonomous car getting into a fatal crash.
Recent progress with Dedicated Short Range Communications (DSRC) Notice of Proposed Rule Making (NPRM) brings connected cars or V2X — connectivity between vehicles, infrastructure and all road users — closer to reality than ever before. If all goes well, an NHTSA mandate on DSRC in new light vehicles is expected to start around 2020 as a phase-in plan, with completion around 2025.
Regulations for aftermarket devices are expected to come soon after. The mandate is expected to leave auto OEMs to choose the applications and human-machine interface (HMI). This will be the culmination of more than a decade of technology development and standardization by U.S. Department of Transportation (USDOT), automotive OEMs and other industry partners.
Significance of V2X. According to USDOT, V2X technology can positively impact more than 80% of non-impaired vehicle crash types that result in over 30,000 deaths in the U.S. alone. A report by the Federal Highway Administration to Congress states that V2X technology is ready to be deployed in the near future and is expected to yield significant safety and efficiency benefits.
From a consumer’s perspective, V2X will be a part of a vehicle ADAS (Active Safety Driver Assistance System). Initial systems will provide information only, and these systems are expected to evolve into warning and control capabilities. In a future vehicle, information from multiple sensors including V2X will be combined/fused to generate a view of the surrounding environment. Figure 1 gives an example of such sensors including long- and short-range radar, lidar, cameras and V2X. V2X offers unique advantages over other sensors that depend on direct line-of-sight. Information can be received from vehicles not visible to other sensors, giving a much larger field of view. V2X can transmit information directly from traffic control devices, instead of inferring information from camera observations.
Figure 1. Example of a vehicle sensor configuration.
Figure 2 depicts the sensor fusion screen from an ADAS development platform by Renesas Electronics America. Such a platform offers the flexibility to implement an ADAS using all available sensors, for example blind-spot warning from radar, forward collision warnings from combined radar, camera and V2X, surround object detection from combined radar, lidar, vision and V2X, with information presented via an OEM-specific HMI.
Figure 2. Renesas ADAS development platform.
GNSS role and challenges
V2X is built on the assumption that vehicles, infrastructure elements, and other road users are location-aware and can communicate critical information to others around them. As seen in Figure 3, the system will position all communicating V2X entities with respect to the host vehicle and security interface, which validates all relevant DSRC messages. A control area network (CAN) or a similar interface will be needed for direct access to vehicle information such as brake and turn-light status and odometer. Interfaces to long-range connectivity such as cellular networks and other data sources such as maps may also be included. The system will connect to an HMI to display information, and future systems will likely evolve to vehicle control functions.
Figure 3. Components of a V2X system.
Looking at the components of an over-the-air (OTA) V2X basic safety message (BSM), this includes a UTC-based time marker, WGS84-based position, and an estimated position error — all critical data that primarily depend on GNSS. RTCM-formatted data may also be sent as optional attachments. A BSM-like personal safety message (PSM) is also defined for pedestrians with V2X-enabled devices.
As per current Minimum Performance Requirements (MPR), a UTC time source with better than 1 millisecond accuracy is required in a V2X device. While almost all current prototypes use GNSS as source of time, others, such as NTP, may also be used. Accurate time reference is a critical prerequisite for basic DSRC functionality. MPR requires time-marked position estimates with 2D and elevation accuracy of 1.5 and 3 meters or better (1 sigma) under open-sky conditions. The automotive industry has opted to define open sky as unobstructed sky view above 5-degree elevation with seven or more satellites visible with HDOP and VDOP limits. The industry expectation is to use this criteria to select GNSS devices that could eventually support lane-level applications (better than 1.5-meter accuracy).
MPR does not put any requirements on the accuracy of the position error estimate in the BSM. It does require that a vehicle stop transmitting BSM whenever the aforementioned time and position accuracy requirements are not met. This implies that a V2X-enabled vehicle may disappear from the V2X view of others in a dense urban canyon or similar environments, leaving at least two questions for system designers from a GNSS perspective alone. First, how to reliably declare that the system cannot meet time and position accuracy requirements, and second, how to deal with the vehicle itself and other V2X entities that may cease to function or broadcast due to GNSS or other limitations. V2X systems are assumed to include inertial and vehicle sensor integration.
Road Ahead. Starting in 2017, connected vehicle pilots (CVP) in New York, Tampa, Florida, and Wyoming will be the next major milestone for V2X. These deployments will be limited to commercial fleets (taxis, public transit, city/road crews and delivery trucks) and some limited road-user categories.
Among the automotive OEMs, Toyota was the first to offer V2X-based driver-assistance technology as ITS Connect in Japan in 2015. General Motors is the first to announce a V2X technology offering in a passenger vehicle in the U.S. with an initial rollout in select 2017 models. The first phase of V2X deployments will only provide driver assistance information while subsequent iterations are expected to bring in safety-focused functions leading to control capabilities.
There is a growing interest in the cellular industry to support V2X-like communication in an upcoming release of the 3GPP standards commonly referenced as 5G. This would enable low latency, peer-to-peer communication with the advantage of an existing device provisioning/authentication infrastructure, something that needs to be built up for DSRC. However, 5G is still a concept, and judging by the lifecycle of LTE, a 5G deployment will take several years to start and several more years to fully deploy while still leaving some rural areas with legacy technology. A framework to manage commercial traffic vs. likely free safety traffic will also be required. These raise the question as to how 5G alone can support vehicle safety applications nationwide.
The FCC has recently proposed a rule to potentially open up the DSRC band for unlicensed Wi-Fi devices, provided Wi-Fi users do not interfere with the primary safety use. Automotive and wireless industry and other stakeholders are investigating the feasibility of possible co-existence in the future. Among the proposed solutions are the rechannelization of DSRC to use a smaller bandwidth and a mechanism for Wi-Fi devices to Detect-and-Vacate the DSRC band when a safety user is detected.
From a technology point of view, V2X has reached a significant milestone with R&D in various technology areas converging and critical standards being adopted recently. With Toyota V2X offering in Japan and GM V2X commitment in the U.S., customers will have V2X as an option this year, further proof that V2X will be on the roads soon. However, significant further work is needed to address the GNSS accuracy and reliability needed for next-generation systems and to address GNSS-specific vulnerabilities such as jamming or spoofing. The New York CVP, which includes deep urban canyons, will probably be a great opportunity for GNSS and V2X communicates to work together on some of these limitations.
Preparations for Arianespace’s upcoming mission have moved into the fueling phase for the next two Galileo navigation satellites, Galileo 13 and 14. The satellites will be sent into orbit by a medium-lift Soyuz on May 24 from the Spaceport in French Guiana.
Galileo 13 is fueled at the Spaceport for Arianespace’s May 24 mission with Soyuz.
As part of the process, the 13th in the series of Full Operational Capability (FOC) Galileo platforms (Galileo-FOC FM10) has been “topped off” in the Spaceport’s S3B payload preparation facility.
Galileo 13 is named for Lithuanian student Danielė — continuing the practice of designating Galileo spacecraft after youngsters who created space and aeronautics-related drawings that were selected by national juries in European Union member states.
Galileo’s FOC phase is funded and managed by the European Commission, which has designated the European Space Agency as the system’s design and procurement agent. Prime contractor OHB System in Bremen, Germany, produces the Galileo FOC satellites.
This month’s dual Galileo payload mission is designated Flight VS15 in Arianespace’s launcher family numbering system. It will be the 15th liftoff of the workhorse launcher from French Guiana since Soyuz’ introduction at the Spaceport in 2011.
Flight VS15 is one of up to 12 Arianespace missions targeted for 2016 with the company’s launcher family of the medium-lift Soyuz, heavy-lift Ariane 5 and lightweight Vega. So far this year, Arianespace has performed three launches: two with Ariane 5, and one utilizing Soyuz.
The Federal Aviation Administration (FAA) is expanding the part of its Pathfinder Program that focuses on detecting and identifying unmanned aircraft systems (UAS) flying too close to airports.
On Monday, the FAA signed Cooperative Research and Development Agreements (CRDAs) with Gryphon Sensors, Liteye Systems Inc. and Sensofusion. The FAA will evaluate procedures and technologies designed to identify unauthorized UAS operations in and around airports. This research effort, part of the FAA’s Pathfinder Initiative, addresses one of the significant challenges to safe integration of UAS into the nation’s airspace.
“Sometimes people fly drones in an unsafe manner,” said Marke “Hoot” Gibson, FAA Senior Advisor on UAS Integration. “Government and industry share responsibility for keeping the skies safe, and we’re pleased these three companies have taken on this important challenge.”
“Gryphon Sensors, LLC is excited to collaborate with the FAA on utilizing technologies that detect, track and identify errant or hostile UAS in and around our nation’s airports and sensitive areas. Detecting these threats is challenging because most of them are very small, fly low to the ground and can be pre-programed to fly autonomously,” said Gryphon Sensors President Tony Albanese.
“Our AUDS team is very excited to join the FAA’s efforts to counter rogue UAVs,” stated Thomas Scott, President of Liteye Systems. He added, “As the legitimate use of unmanned vehicles becomes more prevalent in many industries, unfortunately this large number of aircraft also makes them readily available for illicit use. With the right technologies we can assist the UAV operator to conduct his mission, while protecting against those who wish us harm.”
“We first developed the technology to detect, locate, track and gain control over UAS three years ago as a military project and operated it with three European armies under NATO,” said Sensofusion CEO Tuomas Rasila. “Fast forward to the present time, and AIRFENCE is now protecting various customer sites in Europe, including prisons, high profile government buildings, police, and military sites. Since the technology is software based, it improves with over-the-air updates, ensuring that we are always ahead of the commercial UAS market.”
The companies’ prototype UAS sensor detection systems will be evaluated at airports selected by the FAA. The agency and its federal government partners — particularly the Department of Homeland Security (DHS) — will work with the companies to study how effective their respective technologies are, while ensuring they do not interfere with the safety and security of normal airport operations.
The CRDAs with Gryphon, Liteye and Sensofusion expand upon collaborative efforts with industry to develop system standards to identify unauthorized UAS flights near airports, which could pose a hazard to manned aircraft. The agency has seen a steep increase in reports of small UAS close to airports over the last two years.
The FAA has also partnered with DHS and CACI International on similar research to explore how that company’s prototype detection technology may help detect UAS.
The FAA supports DHS in an inter-agency effort to meet the threat of unauthorized UAS from a “whole of government” perspective. Other participating federal agencies include: the Department of Defense, Department of Energy, U.S. Secret Service and the Federal Bureau of Investigation.
CORS station tracks China’s constellation over three frequencies.
Headquarters for the National Bank of Kuwait, a new 300-meter-tall building under construction, combines concrete, steel, glazing and glass-reinforced concrete in a unique shellfish shape. The engineering challenges behind this building led the engineers of Ahmadiah Company, the contractor, to use GNSS technology to install the core wall structure with millimeter accuracy.
They adopted the core wall control survey method developed by Joël van Cranenbroeck during construction projects in Dubai. To guarantee the precise vertical thrust of a tower during construction, complete control must be maintained of the position of each new element erected on top of the existing core walls. Such new elements, and their formwork structures, must be precisely positioned with respect to the main axis of the design reference frame, defined as the vertical positioned in the tower center. This means that the position of the formwork structures at the top of the tower must be continuously measured during erection of the building.
Core walls are constructed bit by bit, one on top of the other. Each core wall element consists of several concrete pours. The placement of the formwork structure on top of existing core walls must be done precisely, determined from the position of previously placed elements. For this purpose, control points (nails in this instance) are set in the top of the concrete. The basic task of the surveyor is to determine the coordinates of these control points and to compute and stake out the position of the formwork structure in a design reference system based on the main axis of the tower. Dual-axis inclinometers, precise leveling observations and vertical laser plummets complete the method, which is based on a sensor fusion approach.
Active Control Points
A small network of three to four GNSS receivers and antennas are installed on top of the formwork to provide control points to total station operators. As the construction stages rise, surveyor sightings of ground-based control points decrease.
An active GNSS control point consists of a 360° reflector with a GNSS antenna screwed on its top. The coordinates obtained by post-processing the GNSS observations are transformed in the local datum and are available for any total-station “free station” calculation operating on the building top.
The technique has proven to be successful in several other projects worldwide. Comparisons with resection on ground control points, when made possible by tower height, indicated differences of less than a few millimeters.
GNSS CORS Station
As GNSS can only deliver such performances in differential mode, this requires setup of a local GNSS base station.
The local GNSS CORS station receiver and a geodetic-grade GNSS antenna were placed near the construction site and connected to an Internet router to provide easy access whenever the data had to be downloaded for post-processing the GNSS receivers placed on top of the building.
To confirm that the GNSS observations by the selected reference receiver match with those of GNSS receivers used in previous similar projects, a zero baseline test was performed by connecting both sets of equipment to the same GNSS antenna. Simultaneously, a temporary GNSS base station was set up using another geodetic receiver.
All the RINEX data collected over an hour was processed using open-source RTK-LIB software. The results showed less than a millimeter variation between the receiver selected for the project and those used on previous projects.
The baseline components between the temporary base station and both receivers showed respectively 1 millimeter in X and Y (WGS-84) and 2 millimeters in Z difference.
BeiDou Role
Up to 11 BeiDou satellites are now visible in the sky over Kuwait. By setting up the selected BeiDou-capable receiver as a local CORS station — processing signals over the three constellation frequencies (B1, B2 and B3) — project operators benefit from additional GNSS signals that aid positioning where obstructions make GNSS use challenging.
The National Bank of Kuwait construction is the first GNSS CORS station tracking Beidou satellite signals deployed in the Middle East area. Surveyors on this job can access remotely via the on-board web server all the information (satellites in view, quality indicators, memory, RINEX files and so on), and can evaluate the impact of new signals and new frequencies within the context of an exceptional architectural project.
Manufacturers
The GNSS M300 Pro from ComNav Technology (Shanghai, China), a multi-purpose GNSS receiver for a range of applications, has 256 channels tracking GPS, GLONASS and BeiDou, with Galileo capability.
Joël Van Cranenbroeck established Creative Geosensing Belgium as an engineering geodesy consultancy company specialized in high-definition positioning, positioning infrastructures (CORS network) and monitoring.
Diversified Communications has published a free report, “Putting UAVs to Work in Construction.”
