The first overseas center for China’s BeiDou Navigation Satellite System (BDS) was inaugurated in Tunis, Tunisia, on April 10, according to the Xinhua News Agency.
The China-Arab States BDS/GNSS Center was established as a pilot project between China and the Tunisia-based Arab Information and Communication Technology Organization (AICTO), an Arab governmental organization under the Arab League, to promote the global application of BeiDou, said Ran Chengqi, director of the China Satellite Navigation Office.
“The center could serve as both a window to showcase the BDS, and a platform for promoting international exchanges and cooperation,” Ran said.
Mohamed Ben Amor, secretary general of AICTO, hailed the center as a unique technology project for the Arab region and the entire world. AICTO will “intensify its cooperation with China in the field of satellite navigation to boost technological advance and economic development in the region,” Amor said.
The BeiDou pilot project will help train satellite navigation scientists and develop digital economy in Arab countries, according to Khalil Amiri, Tunisia’s secretary of state for scientific research. “We are working closely with China to effectively access and develop win-win database services via BeiDou and other satellites for various uses,” Amiri said.
Ran (left front) and Amor shake hands during the inauguration ceremony of the China-Arab States BDS/GNSS Center in Tunis. (Photo: Xinhua)
Airgain Inc., a provider of advanced antenna technologies used to enable high-performance wireless networking, has released its Ultramax MIMO 9-in-1 antenna, which can receive multiple GNSS signals.
Designed for public safety fleet management, it provides high rejection GNSS technology with coverage for multiple satellite systems including GPS, GLONASS, Galileo and BeiDou.
The new Ultramax MIMO 9-in-1 antenna will help improve public safety and fleet solutions with enhanced Wi-Fi capability, the company said. It includes 6 x 6 MIMO Wi-Fi, dual LTE and multi-GNSS technology antennas in a single enclosure.
MIMO — multiple input multiple output — is used within LTE to provide better signal performance and higher data rates. With integrated 6×6 Wi-Fi antennas, the antenna provides support for full high-definition (HD) streaming video and other high bandwidth applications.
The antenna is the first in an Airgain series designed to support state-of-the-art communications technology in fleet routers, including the Cradlepoint IBR1700.
The Ultramax MIMO 9-in-1 antenna is equipped with nine ports, supporting tri-band Wi-Fi, LTE/MIMO (including Band 14 for FirstNet) and GNSS. With a single compact footprint, the antenna avoids multiple mounting and cable entry points.
“Technology advances in routers, including enhanced Wi-Fi and expanded MIMO LTE, require enabling antenna technology to deliver an optimized end user experience,” said Reed Pangborn, vice president of channel sales for North America. “We designed a new antenna to support the fleet management applications required in today’s evolving mobile environment. The Ultramax MIMO 9-in-1 antenna demonstrates our commitment to providing leading antenna solutions for our mobility customers covering a wide range of vehicles, including police, fire, ambulance and other fleet assets.”
The Ultramax MIMO 9-in-1 antenna complements Cradlepoint’s IBR1700 and supports all six of its Wi-Fi ports.
Airgain will unveil the new antenna at the Cradlepoint Global Partner Summit in Scottsdale, Arizona, April 11-12. The Ultramax MIMO 9-in-1 antenna will be available to order starting in June.
Another navigation satellite is scheduled to join India’s NavIC constellation this week. IRNSS-1I is on the launchpad, with launch set for Thursday, April 12, at 04:04 (IST), according to the India Space Research Organization (ISRO).
All three rubidium atomic clocks on IRNSS-1A have failed. A replacement satellite, IRNSS-1H, was launched on Aug. 31, 2017, but was not successfully deployed. This satellite, IRNSS-1I, is also a replacement satellite for IRNSS-1A.
Satellite IRNSS-1I will be the eighth satellite to join the NavIC constellation (formerly IRNSS). The satellite will be launched from First Launch Pad (FLP) of SDSC SHAR, Sriharikota, using India’s Polar Satellite Launch Vehicle (PSLV), in its 43rd flight (PSLV-C41) in XL configuration. The XL configuration is being used for the 20th time.
IRNSS-1I undergoes testing at the Compact Antenna Test Facility. (Photo: ISRO)
IRNSS-1I’s predecessors — IRNSS-1A, 1B, 1C, 1D, 1E, 1F and 1G — were launched by PSLV-C22, PSLV-C24, PSLV-C26, PSLV-C27, PSLV-C31, PSLV-C32 and PSLV-C33 in July 2013, April 2014, October 2014, March 2015, January 2016, March 2016 and April 2016 respectively. See the GPS World Almanac for details on the constellation.
Like all other IRNSS satellites, IRNSS-1I also has a lift-off mass of 1425 kilograms. The configuration of IRNSS-1I is similar to IRNSS-1A, 1B, 1C, 1D, 1E, 1F and 1G.
Like its IRNSS predecessors, IRNSS-1I also carries two types of payloads — navigation and ranging. The navigation payload of IRNSS-1I transmits signals for the determination of position, velocity and time. This payload is operating in L5-band and S-band. Rubidium atomic clocks are part of the navigation payload of the satellite.
The ranging payload of IRNSS-1I consists of a C-band transponder, which facilitates accurate determination of the range of the satellite. It also carries Corner Cube Retro Reflectors for LASER Ranging.
The miniature UAV, smaller than a human palm, zips right to its human target — identified through facial recognition technology — and pierces the forehead with a projectile, for an instant kill.
That harrowing scene takes place in a seven-minute viral video issued by autonomousweapons.org, a non-profit sounding warning bells over potential automation of weapons. Its Campaign to Stop Killer Robots (#BANKILLEROBOTS) seeks a preemptive international ban on “fully autonomous weapons which enable strikes to be carried out without human intervention.”
“Allowing machines to choose to kill humans will be devastating our security and freedom,” warns Stuart Russel, professor of computer science at the University of California at Berkeley, on the video.
What feels like science fiction to those of us raised on the Terminator franchise could be closer than we think. Because of this, a new U.S. Army report emphasizes the need to develop countermeasures against swarming drones and other unmanned weapons.
The Army and U.S. Department of Defense have invested significantly in technologies in response to these threats, often focusing on detecting radio frequency transmissions of the UAVs or their operators.
However, as the report points out, today’s consumer and customized UAS increasingly can operate without radio frequency command-and-control links by using automated target recognition and tracking, obstacle avoidance, and other capabilities enabled by software.
The U.S. Army discusses the pros and cons of autonomous weapons in a June 2017 article in Military Review, saying an international ban should be considered on “fully autonomous weapons with missions that cannot be aborted and that cannot be recalled once they are launched. If they malfunction and target civilian centers, there is no way to stop them.”
Sobering thoughts about a future that may not be too distant.
A roundup of recent products in the GNSS and inertial positioning industry from the April 2018 issue of GPS World magazine.
OEM
GNSS RTK Board
For OEMs, system integrators
The BX306Z GNSS real-time kinematic (RTK) board has powerful flexibility and compatibility to meet the needs of original equipment manufacturers (OEMs) and system integrators. The BX306Z is a cost-efficient board for positioning and raw measurement output. The board is a compact, multi-GNSS (GPS L1/L2, GLONASS G1/G2, BeiDou B1/B2) RTK module with centimeter-level accurate positioning capability. It is able to integrate with autopilots and inertial navigation units. Log and command is compatible with major GNSS boards.
The Taoglas Terrablast antenna line is designed for UAVs and transportation. (Photo: Taoglas)
Rugged antennas
For automotive, drone markets
Terrablast polymer-based patch antennas are 30 percent lighter than their ceramic counterparts and extremely resistant to fracture upon impact. They are designed for the automotive and unmanned aerial vehicle (UAV) markets, where impacts are possible but antenna performance cannot be compromised. The 35-mm GPS/GLONASS/BeiDou patch antenna has high efficiency of more than 70 percent across all bands, improving time to first fix. All Terrablast antennas undergo rigorous temperature, vibration and impact tests, exceed ISO 16750 standards, and are manufactured in Taoglas’ purpose-built facilities in Taiwan and the United States.
The S1216F8-GI2 is a NavIC + GPS/GAGAN receiver module for emerging intelligent transport systems (ITS) applications requiring NavIC/GPS capability in India. It integrates an L1/L5 RF front-end and baseband processor capable of receiving up to 14 L5 NavIC signals and up to 20 L1 GPS/GAGAN signals simultaneously. With six NavIC signals and three GAGAN signals, it offers 18–23 usable signals, providing improved accuracy in urban canyons. The S1216F8-GI2 is form-factor and pin-out compatible with 12 x 16-millimeter modules, enabling drop-in replacement. NavIC sub-frame data outputs broadcast warning messages for weather alerts and natural disasters. The S1216F8-GI2 is manufactured with ISO/TS 16949 automotive certification.
To meet stringent requirements in harsh environments
The automotive-grade MAX‑M8Q‑01A GNSS module measures 9.7 x 10.1 x 2.5 millimeters and has an operating temperature range from –40° C to 105° C. It is designed to meet the stringent requirements of the automotive market, providing superior positioning accuracy even in challenging environments such as urban canyons. Its temperature range ensures reliable performance in harsh environments, such as when mounted in a car‑roof antenna.
The Teseo APP receiver enables safer autonomous driving. The multi-frequency GNSS receiver chipset is suitable for safety-critical automotive applications and high-accuracy positioning at the decimeter and centimeter levels for precise point positioning (PPP) and RTK applications. By tracking satellites of all GNSS constellations simultaneously on at least two of the frequencies used by each system, ST’s automotive-quality Teseo APP (automotive precise positioning) receiver provides high-quality raw GNSS data for PPP and RTK algorithms, which allows accurate positioning and rapid convergence time worldwide. The receiver monitors the integrity of the satellite data to alert the system if accuracy is degraded for any reason. This permits Tier-1 manufacturers to certify safety-critical systems in accordance with ISO 26262.
Qinertia post-processing kinematic software has been designed to help surveyors get the most of their surveys. After the mission, Qinertia gives access to offline real-time kinematic (RTK) up-to-date corrections from more than 7,000 base stations in 164 countries. By creating a virtual base station near a project, the software delivers the highest level of accuracy without having to set up a base station. An advanced tight coupling algorithm delivers high accuracy and maximizes RTK availability. Trajectory and orientation are greatly improved by processing inertial data and raw GNSS observables in forward and backward directions, especially in challenging environments. With Qinertia, surveyors can quickly identify and solve issues such as mechanical installations or sensor alignment.
The T300 Plus GNSS receiver is designed for demanding surveying tasks, with full-constellation tracking capability, tilt compensation, 4G/Wi-Fi connection, 8-GB internal memory and an easy survey workflow with Android-based Survey Master Software. It is designed to make collecting accurate data easy and fast, whether done by a beginner or experienced professional surveyor. As an upgrade of the T300, SinoGNSS T300 Plus combines a GNSS board, Bluetooth and adjustable TX&RX UHF, Wi-Fi and 4G modem into one rugged device. Its built-in 4G modem ensures the T300 Plus works with all kinds of continuously operating reference stations (CORS) worldwide. A built-in tilt sensor supports maximum 30° pole tilt and keeps the compensation accuracy within 3 centimeters; the user can check the electronic bubble on the controller for fast surveys in the field.
Atlas-capable GNSS receiver for precision 3D applications
The Vector V1000 GNSS receiver is designed for precision marine applications, such as hydrographic and bathymetric surveys, dredging, oil platform positioning, buoys and other applications that demand the highest level 3D positioning accuracies. It provides high-accuracy heading, position, pitch, roll and heave data. The V1000 supports multi-frequency GPS, GLONASS, BeiDou, Galileo, QZSS and IRNSS (with future firmware upgrade and activation) for simultaneous satellite tracking. The receiver is powered by Hemisphere’s Athena real-time kinematic (RTK) engine and is Atlas L-band capable. Based on Hemisphere’s Eclipse Vector technology, the V1000 uses the most accurate differential corrections including RTK and Atlas L-band. It has an integrated display that can be conveniently installed near the operator. The V1000 has heading accuracy of better than 0.01 degree when using a 10-meter antenna separation.
Machine-to-machine (M2M) and internet of things (IoT) device
The SmartOne Solar M2M/IoT device is solar-powered and offers Bluetooth Low Energy connectivity while addressing the growing global demand for reliable and affordable remote monitoring and automated data collection of assets located both within and beyond terrestrial networks. The SmartOne expands the market for remote connectivity to include assets that are otherwise difficult or expensive to reach for power replacement, and lowers the operating cost of monitoring assets being served by legacy SmartOne products. SmartOne Solar’s rechargeable batteries can deliver more than eight years of serviceable life. Without exposure to the sun, a fully charged unit can operate for many months while reporting twice daily. The product’s Bluetooth connectivity allows wireless device configuration and firmware upgrades in the field.
Designed for large-scale surveying and mapping projects
The WingtraOne post-processed kinematic (PPK) drone is the result of collaboration with Pix4D and Septentrio. It is able to deliver orthomosaic maps and 3D models with an absolute accuracy down to 1 centimeter (cm), offering broad coverage and high resolution with ultra-precise accuracy. The WingtraOne can cover 130 hectares (320 acres), equivalent to 240 football fields, in a one-hour flight, and deliver maps at ground sample distances below 1 cm/pixel. Vertical take-off and landing (VTOL) offers hands-free operation and a smoother ride for onboard sensors as well as greater coverage than comparable multi-rotor UAVs. PPK computes ultra-precise geolocations for each image by combining the GNSS data with correction data from a nearby reference receiver. It offers a root-mean-square (RMS) error of 1.3-cm horizontally and 2.3-cm vertically without any ground control points.
DroneHunter is a fully autonomous UAS airspace defense solution. The intelligent robotic aircraft is enabled with TrueView radar designed and engineered for physical remediation of intruder or threatening drones. DroneHunter is an autonomous UAS perimeter detection and protection solution designed to quickly detect, classify and secure against drones and other UAS. When an intruder drone is discovered, DroneHunter can engage autonomously via artificial intelligence (AI)-directed detection, tracking and guidance. Once the rogue drone is identified and the threat level analyzed, DroneHunter safely remediates the threat day or night, at a safe stand-off distance, with no collateral damage. DroneHunter supports multiple drone platforms based on use-case requirements.
By Simon Batzdorfer, Markus Bobbe, Martin Becker and Ulf Bestmann, Technische Universitaet Braunschweig
All images courtesy of the authors.
Autonomous vehicles equipped with different environmental sensors, such as optical or thermal camera or a lidar, performed a team survey controlled by a central ground station. The ground station serves as a user interface to define missions and tasks and also to visualize exploration task results online. 2D stitched orthophoto or lidar point clouds are transmitted for display and processing into 3D photogrammetry. Georeferencing data is gathered by an integrated GNSS/IMU positioning system.
In disaster scenarios such as fires, floods or search-and-rescue tasks, good situational awareness is indispensable for responders coping with a complex and often chaotic environment. In most cases, a prior known map data are outdated, and an efficient situational proceeding such as path planning or creation of a search pattern cannot be performed. This information can often only be gathered by manned exploration using ground or airborne systems, with limits on availability.
The research project Automated Navigation and Communication for Exploration (ANKommEn) seeks to create an automated unmanned system to close this gap by providing up-to-date scenario information while increasing the safety of human resources, using unmanned aerial (UAV) and ground-based (UGV) vehicles.
To provide up-to-date information of the desired destination area, all vehicles are equipped with identical positioning and communication hardware complemented by diverse sensors (RGB camera, infrared [IR] camera, lidar) for visual exploration. The visual sensor information is transmitted to a central ground station for visualization and/or analysis. To increase the advantages of the system, the unmanned systems should have a high grade of automation to reduce the workload of the operator so that only basic inputs have to be done by the operator. For example, just by marking a destination area and choosing a predefined task, the mission will be planned automatically, and after the corresponding waypoint-list has been transmitted to the vehicles, the mission will start.
Automated procedures of a UAV in particular require valid position information related to accuracy, availability and continuity. In exploration areas where the UAV operates in low altitude or using a UGV, the reception of the GNSS signal can be degraded by the topology (buildings and such). Using more than one GNSS can increase the availability of position information. Vehicle control, georeferencing environmental sensor data and exploration results all require high-frequency absolute position and attitude and heading information. This data is gathered by fusing GNSS and inertial measurment unit (IMU) data.
OVERALL SYSTEM DESIGN
The overall system consists of three UAVs, two UGVs (Opening photo) and a central ground control station. The latter serves as a central human-machine interface to monitor and manage cooperative operation of the UAVs/UGVs by an operator. Based on a priori known map data, exploration areas and tasks are defined and assigned to the UAVs/UGVs and will be updated with actual information of the visual sensors while performing a mission.
Figure 1 shows the interaction and information exchange between the different vehicles and sensors.
Figure 1. Diagram of interaction and information exchange.
All UAVs/UGVs are equipped with a navigation and communication unit (NAV/COM) and an environmental sensor payload (ENV) unit, including an RGB camera, thermal camera or a lidar respectively.
UAV/UGV and Sensor Hardware. The UAVs carry a payload of 2.7 kg (NAV/COM unit, mounted in the upper compartment, and ENV unit mounted under the UAV) and a flight time of up to 30 minutes (Figure 2, left). The payload sensors are carried and stabilized by a two-axis-gimbal. The environmental sensor payload unit is based on three different types of sensors, which are interchangeable between the different UAVs: RGB camera, lidar and IR camera.
For ground-based exploration, two four-wheel-drive UGVs carry a pan-tilt-zoom (PTZ) camera at the top of front chassis (Figure 2, right), and are equipped with a lidar and a thermal camera, or a stereo RGB camera, respectively.
Figure 2. UAV carrying a lidar (left) and UGV carrying lidar and IR camera (right).
The navigation and communication unit mounted as a stack includes a network processor board for communication and data exchange between the UAV/UGV and the central ground and control station. An embedded processing board provides position calculation and GNSS-NTP-based time server. Data for the position calculation is provided by a custom-designed break-out-board (Figure 3).
Figure 3. Navigation and communication unit.
Data traced by these sensors cannot be sent directly to the ground station because of the huge data amount and the limited bandwidth of the communication link. Therefore, data from the sensors are preprocessed or compressed on a small form-factor personal computer and then transmitted to the ground station.
Ground Station. The ground station is the central device for command, control and visualization of the total system. It provides several options to display the data from the sensors and vehicles and a combination of them, and also provides automated path planning and calculation of the 3D reconstruction (photogrammetry) and online 2D stitched orthophoto.
Software Frameworks. The basic software for determining the vehicle’s state in 3D position, velocity, attitude and heading is established within a modular navigation software framework, with the option to process data of different sensors in real time as well as post-processing for data evaluation and development purposes. Several algorithms for sensor data fusion are implemented. The algorithm for IMU/GNSS fusion is based on an extended Kalman filter and also provides an IMU data-based state vector, stabilized by GNSS information, for the visual sensors. This state vector is published by using the robot operating system (ROS), a framework for inter-process communication based on a TCP or UDP publisher/subscriber concept. The visual sensors and embedded PCs subscribe to different ROS messages, for example, the state-vector-message or information of other sensors.
Figure 4 shows examples of the actual camera view from the UGV, and point cloulds and map generated by the UAV. The software layout can be customized by the user.
Figure 4. From left to right: the actual view by the PTZ camera onboard the UGV, the point cloud gathered by the UAV’s lidar, and the mission parameters and map of an aerial view.
POSITIONING OF UAV AND UGV
Automated operation of UGVs and UAVs requires valid position as well as attitude and heading information. In the case of using only one GNSS, signal quality and availability can be degraded by the environment (buildings) and can result in less precise or even a lack of position information.
GNSS Multi-Constellation. To overcome the risk of poor availability of GNSS-based position information, parallel usage of different GNSS can raise the number of received satellite signals: GPS, GLONASS, the evolving Galileo and BeiDou. When using a multi-constellation approach for positioning, one has to take care of several differing aspects between the GNSS. Each system uses a different geodetic reference frame and time basis. Measurements gathered from another GNSS system must be transformed into the reference frame of the desired system. The geometric distribution of the satellites is improved by using more than one GNSS constellation, indicated by a lower dilution-of-precision value.
The navigation software framework is designed for real-time computation and also for post-processing. In post-processing, the recorded sensor data is streamed to the software framework with the option of changing several parameters and settings for calculation. One option is to exclude satellites at low elevation from position calculation by changing the cut-off elevation for these satellites. This parameter will be changed to simulate environmental conditions that block receiving GNSS signals, like buildings within urban scenarios, to compare the availability of received GNSS signals for single- and multi-constellation-based position calculation.
Recorded data of a real-world test serves as the database for the post-processing with different cut-off elevation parameters. At the beginning of the field test, there was a short initialization period to boot the OS and to start basic processes for positioning. After that, a predefined mission was flown and the GNSS measurements have been saved for the described post-processing.
Post-processing has been performed with different cut-off elevation parameters of 5° up to 35°. In the case of 35°, the number of GPS satellites is reduced to the minimum for position calculation of four, in contrast to 5–7 available satellites for a multi-constellation based solution.
GNSS/IMU Fusion. Using the GNSS multi-constellation approach can increase availability of position information. For attitude and heading determination, an IMU is nevertheless indispensable. Additionally, the frequency of the pure GNSS-based positioning information is usually between 1 Hz to 5 Hz within the described hardware setup. Meaningful georeferencing of the environmental sensors requires much higher frequency position and attitude information.
The IMU provides high-frequency 3D measurements of accelerations and angular rates. Using common strapdown algorithm processing, high-frequency position, velocity, attitude and heading information is provided in real time. Due to the short time stability of pure inertial navigation, the GNSS positioning results are used for aiding purposes within the Kalman filter’s update step. To overcome the absence of GNSS aiding information even when using multi-constellations, there are mainly two options. First, a short coasting period is possible after the data fusion has reached a steady state.
Second, due to the highly modularly design of the navigation software framework, it is possible to use position or attitude increments from environmental sensor data processing for aiding the IMU.
The vehicle’s state vector is then distributed with high frequency within the system for georeferencing measurements of the environmental sensors, especially the RGB camera and the lidar for photogrammetry and simultaneous location and mapping (SLAM) applications.
PHOTOGRAMMETRY AND SLAM
In major fire scenarios, maps can be out of date. Therefore, techniques have been developed to gather a 2D overview based on several single RGB pictures taken and processed on board a UAV and transmitted to the ground station via data links. Additional processing of a 3D reconstruction of the scenario is an integrated feature within the ground station. Both approaches were implemented to get an automated rapid aerial mapping solution.
In the case of the 2D overview, SLAM algorithms, often used in robotic research, are adapted for this specific use case. These algorithms provide good results for a rapid aerial mapping solution to get an overview of the scenario, because the map is updated incrementally with every new image, but they are less precise, which can be compensated for by using the photogrammetric 3D reconstruction. The live mapping (SLAM) approach is based on the ORB-SLAM algorithm, and the photogrammetry-based approach uses commercially available photogrammetry software.
The systems, on the UAV for 2D and for 3D on the ground station, use the ROS framework for processing the visual sensor data and the described techniques for positioning, georeferencing and attitude determination. For data exchange between these frameworks, several software interfaces have been implemented. Figure 5 displays a flowchart of the implemented workflow.
The sensor/input data is received by corresponding nodes on the aerial vehicle. After adding the camera pose information to the image in the geo-image flight node, the image is sent to the geo-image ground node on the ground station. The SLAM process is separated into two parts. The SLAM tracker node calculates the transformation between images, and the SLAM stitcher node applies the transformations. The transformed images are displayed by the visualization node. The photogrammetry node receives the georeferenced images, stores the data, and initiates the photogrammetric processing once the survey is finished. The results can also be displayed by the visualization node and exported in a desired format.
Visual SLAM. Computer vision-based algorithms have developed rapidly over the last few years. One method estimates a pose by using monocular image processing, known as parallel tracking and mapping (PTAM). This integrates a bundle adjustment and separates the tracking and the mapping procedure into different threads, leading to a real-time capable framework. These basic PTAM principles have been integrated into a robust loop-closing and another method of relocalization, known as Oriented FAST and Rotated BRIEF (ORB SLAM), shown in Figure 6. Here, tracking, local mapping and loop closing are separated into different threads (gray boxes), with the main map and place recognition in the middle.
Figure 6. ORB SLAM system overview [Mur-Artal, 2015].The tracking thread predicts the current pose from the last known position and movement by using a constant velocity model and performs a guided search of map points. If these points are found near the estimated position, the velocity model is valid and the tracking procedure continues. Otherwise, the tracking is lost and a relocalization in the global map starts by using a subset of features, which are increased after detection of corresponding features in other keyframes to optimize the camera pose and, finally, the tracking procedure continues. The last step of this procedure is to decide whether the current frame contains enough information to be inserted as a new keyframe for further calculations.
To mark a frame as a new keyframe, the frame must fulfill all of the following conditions:
More than minimum number of frames has passed.
Local mapping is on idle or condition 1 fulfilled.
A minimum number of 50 points is observed.
A maximum of 90% of the features is already observed by the other frames.
When a new keyframe is passed to the local mapping procedure and inserted as a node into a co-visibility graph structure, new correspondences are searched in the connected keyframes to triangulate new points. Based on the information accumulated during the tracking, a point culling keeps only high-quality points in the map as well as a culling of redundant keyframes.
Then a loop closing is performed. This is one of the main improvements compared to PTAM. If a loop is detected, the drift accumulated in the loop is computed, and both sides of the loop are aligned and visible points are fused. In a final step, a pose graph optimization is done to achieve global consistency.
This information of the 3D camera pose is used to generate a 2D orthophoto in real time while the vehicle is flying. To create a 2D orthophoto, a common reference frame is approximated, which is orthogonal to all camera measurements. The projection is performed by using a projection model based on a pinhole camera.
After the compensation and distortion, the whole image can be stitched to the current global map.
Photogrammetry. This approach uses off-the-shelf photogrammetric processing software. The processing is triggered automatically when the survey is completed and all images are transferred to the ground station via data link. For georeferencing of the images, the camera location and the inner camera geometry were written to the EXIF file of each image by the geo-image ground node (Figure 5). To ensure an acceptable compromise between orthophoto quality and the required processing time, an analysis regarding the impact of the most relevant processing parameters has been performed.
Figure 5. ROS node layout with SLAM (green) and photogrammetry workflow (red).
The photogrammetry process consists of four steps:
camera alignment (optimizing the homographic equation)
mesh creation by generated tie points
orthophoto creation (dense cloud or digital elevation model)
export.
Analyses and Evaluation. To evaluate the correct workflow of both approaches of 2D live-stitching and the 3D photogrammetry, a real-world flight test above agricultural cropland has been performed. The results of both approaches are shown in Figure 7 and Figure 8. Generally, agricultural cropland and its mean textured surface pose a challenge for mapping processes because of the limited number of trackable features.
Figure 7. Orthophotos created with the profiles high and lowest (including ground reference points).Figure 8. Orthophotos created with 2D live stitching approach of cropland.
Four predefined profiles were used to cover the requirement of compromise between processing duration and quality of the generated orthophoto. Each profile level generates a corresponding level of alignment accuracy and mesh face count: lowest, low, medium and high.
To estimate the accuracy of the created maps by the different profiles, five ground reference points (GRPs) were distributed over the mission area. The location of the GRPs was determined using a RTK-GNSS system leading to a horizontal RMSE below 2 cm. To enable robust processing for this scenario, the overlap and the sidelap was chosen to be 70%. A ground-sampling distance (GSD) of 2 cm was needed to identify the GRPs. This resulted in a mission consisting of six times 100-meter (m) lines with a distance of 25 m in an altitude of 60 m over ground. During the flight time of 4.5 minutes, 271 images were taken.
To compare the profiles, they were triggered one after another with the same set of images. The created results are shown in Figure 7. All profiles resulted in consistent solutions and were successfully georeferenced. The map based on the lowest profile could not recreate the complete area (Figure 7, right). The remaining profiles led to similar results without notable differences to visual inspection. The processing time varied between 1.2 and 3.6 minutes. A comparison of this and other criteria is given in Figure 9.
Figure 9. Evaluation and comparison of defined software profiles and visual SLAM.
The created final image of the SLAM pipeline is shown in Figure 8. The image was updated with every new image and was therefore finished before the UAV landed. The mean location error measured using the reference points was about 8 m, significantly larger than the errors observed in the photogrammetry results. In Figure 9 the results are contrasted to the results of the photogrammetry approach.
While the mean error in the low profile is half as high as in the lowest profile, the calculated errors using the medium and high profiles are not enhanced significantly. The number of tie points created by the lowest profile is an order a magnitude lower compared to the other three profiles.
We conducted flight tests on Langeoog island in the North Sea, to gather information on efforts to protect the island’s coastline from water erosion. For this reason, sand was selectively washed up to the coastline by dredgers at the beginning of October 2017. Between Oct. 26 and 31, due to severe weather with a storm flood, a huge erosion of the washed up sand occurred, and the result is shown in Figure 10. The level of erosion was determined by comparison of the orthophoto of the same area. The dislocation averaged out to 9.9 m with some peaks up to 17.6 m.
Figure 10. Evaluation of erosion.
The 3D photogrammetry provides a more detailed image compared to the image of the 2D-live-stitching approach (Figure 11), but both approaches can provide the desired information of the area.
Figure 11. Result of the SLAM approach with camera poses and tracked features.
Both implemented approaches were successfully integrated to get the desired fully automated rapid aerial mapping solution. This also includes the basic tasks of the automated mission planning, camera control, image transport to ground station, automated processing and the visualization of the results.
CONCLUSION
The benefits of multi-constellation GNSS positioning have been demonstrated with a focus on UAVs and UGVs operating in catastrophic scenarios, especially where GNSS signal reception might be blocked. This position information is also used for georeferencing of images and visual reconstruction of the area. The overall system has demonstrated the capability of an automated orthophoto generation. Both implemented mapping methods — a 2D live stitching and a 3D photogrammetry — provided results that fulfill the requirements to get an instantaneous 2D overview and a contemporary 3D reconstruction of the area.
ACKNOWLEDGMENTS
This work was done within the joint research project ANKommEn, funded by the German Federal Ministry of Economic Affairs and Energy, administered by the Space Administration of the DLR (funding code: 50NA1518). Project partners are the Institute of Flight Guidance (IFF), the Institute of Mobile Machines and Commercial Vehicles (IMN) — both part of Technische Universität Braunschweig — and AirRobot GmbH & Co. KG, a German manufacturer of multirotor UAVs. The professional fire brigade of Braunschweig and the Lower Saxony Water Management, Coastal Defense and Nature Conservation Agency also participate as associated project partners.
SIMON BATZDORFER holds a Dipl.-Ing. in mechanical engineering and is a research engineer at the Technische Universitaet Braunschweig, Institute of Flight Guidance (IFF).
MARKUS BOBBE holds a M.Sc. in aerospace engineering and is a research engineer at the Braunschweig IFF.
MARTIN BECKER holds a Dipl.-Ing. in aerospace engineering and is a research engineer at the Braunschweig IFF.
ULF BESTMANN received his Dr.-Ing. in mechanical engineering from TU Braunschweig. He is head of the navigation department of the IFF. He co-founded the company messWERK GmbH, a service provider in flight testing and certification.
Orolia, a resilient positioning, navigation and timing (PNT) company, has entered into a definitive agreement to acquire Talen-X.
Talen-X is a U.S. technology innovator with the ability to characterize, enhance and implement advanced techniques and products to solve real-world GNSS vulnerability problems. It has expertise in GPS/GNSS performance, requirements, testing, integration and threat mitigation.
Orolia has completed 10 acquisitions since 2007, including Spectracom, Spectratime and McMurdo brands. The transaction is subject to customary closing conditions and approvals required by the U.S. Defense Security Service (DSS) and the Committee on Foreign Investment in the United States (CFIUS).
Through this acquisition, Orolia said it will significantly enhance Assured PNT capabilities across the global company’s portfolio to support mission-critical applications. The additional resources also strengthen Orolia’s commitment to serving the U.S. government, with further expansion of domestic capabilities and a greater U.S. footprint. Toward that end, the companies will reinforce their commercial cooperation to maximize market awareness and access.
“Military personnel know that accurate and trusted time and position information is a critical enabler for almost all warfighting functions and systems,” said Orolia CEO Jean-Yves Courtois. “Reliable PNT data are critical for communications, sensors, network synchronization, situational awareness, command and control or search and rescue missions. This acquisition reinforces Orolia’s position as a major supplier of Assured PNT technology and enhances our ability to offer unique end-to-end solutions.”
Talen-X has extensive technology integration and PNT engineering resources that will enable Orolia to rapidly develop and offer new, superior products and services to the U.S. market.
“Our culture of innovation, together with our demonstrated testing capabilities, will complement Orolia’s global technology expertise and significantly enhance the reliability, performance and safety of military operations,” said Tim Erbes, CTO of Talen-X.
The MPS865 GNSS receiver is designed for marine positioning.
Trimble has debuted the MPS865 marine positioning system multi-frequency and multi-application GNSS receiver.
The Trimble MPS865 is a versatile, rugged and reliable GNSS positioning and heading solution for a wide variety of real-time and post-processing applications for marine survey and construction.
It features integrated communications options such as Wi-Fi, UHF radio, cellular modem for internet connectivity, Bluetooth and MSS satellite-based correction channels.
The patented GNSS-centric technology uses all available GNSS signals to deliver reliable positions in real time. The GNSS receiver provides for the connection of two GNSS antennas for precise heading.
With a modular form factor, the MPS865 is flexible and can be used as an integrated on-board rover receiver, a base station or a continuously operating reference station. According to Trimble, the built-in precise heading feature ensures the receiver is of minimal size, consumes less power and has less cabling, which are all benefits when on-board space it at a premium.
The MPS865 adds new features to improve usability in a congested marine construction site – multi constellations, cellular connectivity and beacon support. The multi-constellation option maintains productivity in marine sites or when antennas or satellites are partly obstructed.
At many sites, the receiver can use the free-to-air beacon support. When coupled with GA830 antennas, the MPS865 will receive the free-to-air beacon signals to deliver sub-meter accurate horizontal positioning in many parts of the world. It always delivers precise heading even when no GNSS corrections are received.
The marine receiver also has cellular, making it easier to use Internet Base Station Service (IBSS) and VRS corrections over the internet as well as communicate with the receiver via the internet and SMS messages. The receiver also can be used as a data access point on the vessel to download design files or for immediate remote support.
The MPS865’s design enables a broad range of mounting capabilities and built-in communication options. Features include an internal removable battery, internal memory and optional accessory kits for specific applications.
The receiver is also compatible with a variety of software solutions including the new Trimble Marine Construction software.
The weatherproof, high-impact-resistant moulded aluminium housing protects it in extreme marine conditions or base-station applications.
“With the addition of the MPS865 receiver to our portfolio, Trimble has introduced a new generation of rugged, compact and feature-rich GNSS, a solution the marine industry has been needing for some time,” said Scott Crozier, general manager of Trimble’s Civil Engineering & Construction Division. “This highly flexible and capable receiver can be combined with our marine construction software providing contractors with a market-leading solution for any marine survey or construction application.”
YellowScan has launched a new lidar system, the Surveyor Ultra. It integrates the Velodyne VLP-32C scanner and the Applanix APX-15 GNSS/inertial measurement unit (IMU).
With high density (600,000 shots per second), the system is suitable for high-speed UAVs and long-range needs (maximum range: 100 meters). Its light weight (1.7 kg) makes it easy to mount on any drone, including vertical takeoff and landing (VTOL) UAVs.
As for all YellowScan lidar systems, the Surveyor Ultra is a turn-key system fitted for under vegetation 3D modeling and fast data processing, the company said.
Applications such as forestry, archeology and environmental research will benefit from Surveyor Ultra, as they require long-endurance flights high above trees or over rocky mountains and rugged terrain.
“The Surveyor Ultra shows great potential to safely and efficiently operate lidar on lightweight fixed-wing UAVs,” said Tristan Allouis, YellowScan CTO. “The Surveyor Ultra completes our product line, including the successful Surveyor Lidar System (integration of the VLP-16 scanner from Velodyne).”
The NovAtel OEM6 GNSS receiver card used in the CEESCOPE echo sounder has been replaced with NovAtel’s latest low-power, high-performance OEM729 receiver.
With 555 channels, the new GNSS option brings a vast increase in available channels for future-proofing, improved interference rejection and better performance in challenging environments, the company said.
The TerraStar L-Band support remains.
The OEM729-equipped CEESCOPE is available with a built-in UHF radio modem and direct Ethernet connectivity to the GNSS receiver for NTRIP cell-phone real-time kinematic corrections.
Pix4D has announced Pix4Dfields, its first fully dedicated product for agriculture. A beta program to test the software is now open.
Pix4Dfields is designed to give users fast and accurate maps while in the field, with a simple yet powerful interface fully dedicated to agriculture.
“When we decided to create a fully dedicated product for agriculture, we wanted to go beyond the research and development and create a product that actually understands agriculture,” the company said in a press release. “So in July 2017, we opened a new office in Berlin fully dedicated to do exactly that: Understand the agriculture industry, listen to our users, and create a product that caters to all the main agricultural practices.”
Pix4Dfields is equipped with fast processing that provides accurate and instant results and an easy-to-use interface with tools tailored to agricultural workflows.
Pix4Dfields is currently available as a closed beta, which we are opening to select users to test it and provide feedback. The product will evolve at a fast pace with new and updated features being added with every new iteration, the company said
Pix4Dfields is currently available for macOS only; the next iterations will include Windows support as well.
Topcon Positioning Group has added a new laser series to its RL-H line of self-leveling rotating lasers.
The RL-H5 series is designed for high-accuracy and long working range in laser applications for grading, excavating and general construction projects. The new offering includes instruments to support diverse jobsite demands.
Lasers in the series include options in working range of up to 800 meters and up to 100 hours of battery life. The RL-H5A with ±1.5 mm at 30 m horizontal accuracy will be available in the Americas, Europe and Oceania. An additional option, the RL-H5B, with ±3 mm at 30-m horizontal accuracy, will be available in the United States and Oceania.
“The RL-H5 builds on what Topcon has been bringing to the market for years and pushes the contractor’s productivity capabilities to the next level. It is another example of our commitment to The Intersection of Infrastructure and Technology, the point at which construction productivity can be improved by applying advanced positioning technology,” he said.
The series is covered by the five-year guarantee on Topcon manufactured lasers.
