Recently launched satellites of BeiDou Phase 3 program have started broadcasting new signals. Javad GNSS announced successful tracking of these signals and provided the adjacent figures.
Interface control documents (ICDs) for B1C and B2A signals are available, while an ICD for the other signal, called B2B, has not yet been published. The company tracked the signal on the 1207.14 Mhz frequency on BeiDou’s satellites 32, 33 and 34, and subsequently saw that this signal is available on all recently launched BeiDou Phase 3 satellites, and tracked it successfully.
This B2B signal plus B2A signal together form an AltBOC(10,15) signal on 1191.795 MHz — JAVAD GNSS calls it BaltBOC. Assuming that BOC parameters of this signal are similar to Galileo’s, the company tracked this. Figures 1 and 2 show BeiDou andGalileo (BaltBOC and altBOC) discriminator curves; they appear identical.
Figure 1. BeiDou AltBoC signal. Red and blue: I of B2A(E5A) and B2B(E5b) sub-signals; purple and yellow: Q of B2A(E5A) and B2B(E5b) sub-signals (their sum is zero); green and aqua: I (early-minus-late) of B2A(E5A) and B2B(E5b) sub-signals.
Figure 2. Galileo AltBoC signal. Colors same as Figure 1.
According to another source, the signals are mentioned in some publications (Figure 3, 4 and 5 from an official Chinese government presentation at the International GNSS Service Workshop, Oct. 2018) and intended to be open signals, but an ICD is presently missing. However there appears to be some clarity now, that the modulation of B2a+b is an “ACE-BOC” modulation, which is similar to but formally different from “AltBOC.”
The launch and deployment of the 42nd and 43rd BeiDou satellites complete the basic BDS-3 constellation.
China has successfully sent twin BeiDou satellites into space by a Long March-3B launch vehicle (with an Expedition-1 upper stage) from the Xichang Satellite Launch Center, at 02:07 am, on Nov. 19. The twins, both medium Earth orbit (MEO) satellites, are the 42nd and 43rd of the BeiDou Navigation Satellite System (BDS), and the 18th and 19th of the BeiDou-3 family.
The satellites successfully entered their designated orbit after more than three hours of the launch, and will join the constellation with the 17 previously launched BDS-3 satellites, after completing in-orbit test.
The successful launch marks that the basic BDS-3 constellation has successfully been deployed. Networking of the constellation and assessment on its performances will be carried out in the near future.
Plans are for the BeiDou-3 constellation to be put into operation before the end of this year, to provide basic navigation services to countries and regions participating the Belt and Road initiative, which will be a key milestone for BDS in expanding service areas from regional to global.
The BDS-3 project was officially launched in 2009 with state approval, and a demonstration system was completed in 2016. Having verified the new-generation navigation signal system architecture, the BDS-3 development followed up with a three-step pattern, to construct its pilot, basic and nominal constellations respectively, according to the China Satellite Navigation Office,
On Nov. 5, 2017, the first pair of satellites for the BDS-3 constellation was launched from Xichang Satellite Launch Center. By the end of March 2018, a pilot constellation consisting of 8 BeiDou satellites was built.
At present, the project is progressing smoothly, and the basic constellation consisting of 19 BDS satellites will soon be operational. In the future, BDS with global coverage will be completed by the end of 2020.
Since November 2017, the past year has witnessed a highly intensive launch of the China’s BDS constellation. With the joint efforts of the whole team participating in this project, 11 launches have been completed within one year, while 19 BDS-3 satellites and 1 BDS-2 satellite have been successfully sent into space.
In particular, since July 2018, seven launches have been conducted to deliver 12 BDS satellites into orbit, with the shortest interval between launches being only 17 days. Both highly intensive and high success rate of launches set a new record in the history of the BDS constellation development.
The satellites and the launch vehicle (with an Expedition-upper stage) for this mission were developed by the China Academy of Space Technology and the China Academy of Launch Vehicle Technology respectively, both are affiliated to the China Aerospace Science and Technology Co., Ltd. The launch was the 291st mission of the Long March rocket series.
Currently, the BeiDou system comprises two families of operational navigation satellites; BeiDou-2, also known as Compass, presently consists of 15 operational satellites in Geostationary Orbit (GEO), Geosynchronous Orbit (GSO), Inclined Geosynchronous Orbit (IGSO) and Medium Earth Orbit (MEO).
The new BeiDou-3 series, on the other hand, only has operational MEO satellites at the moment, although China is testing the first BeiDou-3 GEO satellite (BeiDou-3G1) and plans to launch at least four GEO and GSO satellites in 2019.
http://www.GIM-INTERNATIONAL.com Jueves 22 de Noviembre del 2018
NovAtel’s GPS Anti-Jam Technology (GAJT) now rides into battle and military exercises aboard the Canadian Army’s Artillery Observation Post Vehicles (OPV) that have been fitted with the GAJT‑710ML antenna.
OPVs are highly mobile vehicles that perform observation, reconnaissance and patrolling missions, surveying and acquiring strategic targets and relaying instant, accurate target coordinates acquisition to artillery fire command systems. With their exposed position on the frontlines of the battlefield, OPVs can encounter severe GPS jamming aimed at crippling their capabilities. OPVs require reliable Position, Navigation and Timing (PNT) not only to safely and effectively navigate on the battlefield, but to provide reliable information to artillery in the rear.
GAJT provides protection for GPS navigation and precise timing receivers from intentional jamming in electronic attacks, ensuring that the satellite signals necessary to compute position and time are always available.
“GAJT allows us to have confidence that the position information from the GPS constellation is assured.” said Major Mike Moulton, the project manager in the Directorate of Land Communication Systems Program Management.
NovAtel’s GAJT is a retrofittable system. A military-off-the-shelf (MOTS) product, it comes in versions suitable for land or sea applications and smaller platforms such as unmanned aerial vehicles (UAVs). The antenna works with an array of military and civil receivers, including the Army’s handheld Defense Advanced GPS Receiver (DAGR), other military receivers using SAASM and M-Code, and with civil receivers.
“GAJT scrubs off unwanted signals. It differentiates between what we can recognize as a signal coming from a satellite and something anomalous, which could be interference or deliberate jamming,” explained Peter Soar, NovAtel’s Business Development Manager for defence. “GAJT does not contain a GPS receiver, but works with the receiver that’s already installed. So GAJT faithfully passes the good satellite signals to the receiver which then operates functions such as integrity monitoring in its normal way. GAJT is in use operationally and has been shipped to 16 allied nations around the globe.”
GAJT is a null-forming antenna system that ensures that satellite signals necessary to compute position and time remain available. There is no need to replace the GPS receiver that’s already installed, as GAJT works with both civil and military receivers operating in the GPS L1 and L2 bands. It is ready for M-Code, is a non-ITAR product and is readily available to authorized customers.
Trials with the Canadian Army’s testing unit validated the technology, maintaining access to the GPS signal in an adverse signal environment. It also gave NovAtel engineers a detailed unclassified report on the trial findings and recommendations. The feedback helped NovAtel modify GAJT into a stronger product. The GAJT-710ML antennas were delivered earlier this year, and the Army worked with General Dynamics Missions Systems Canada, the prime contractor for the mission systems on the OPV, to integrate the antenna aboard the vehicle.
“GAJT is a Canadian success story. It is 100 percent produced in Canada and sourced from Canadian components. I think that the Directorate of Land Communication Systems Program Management have shown there is excellent technology in Canada that can be leveraged to meet the Army’s requirements in a very rapid manner,” added Moulton.
This story uses some quotes that first appeared in “Out of a Jam,” an article by Chris Thatcher in Canadian Army Today.
http://www.GIM-INTERNATIONAL.com Jueves 22 de Noviembre del 2018
Forest management planning is a delicate process. Environmental, economic and social aspects need to be taken into account in order to achieve sustainable development. In Quebec, before a plan can be implemented, local communities have to be consulted for their feedback and concerns. Instead of just expecting citizens to decipher complex maps, this project is aimed at sharing a realistic view of the potential changes through a 3D virtual experience. This application is based on GIS data that consists of a shapefile with information derived from a Lidar survey, as well as a digital elevation model.
In the province of Quebec, Canada, the Ministry of Forests, Wildlife and Parks (MFFP) is in charge of the sustainable development of the forests. As part of its duties, the MFFP devises forest management plans. The initial plan has to be submitted for public consultation with the local population before any action can be taken. By holding such meetings, the ministry strives to keep the public informed, while taking into account citizens’ interests and opinions. In what is commonly known as the ‘harmonisation process’, the MFFP takes the feedback into consideration and, if possible, adjusts the forest management plan accordingly.
A communication problem
However commendable this process may be, it does not always make it easy for citizens to form an opinion. Using the current technology, it is hard to visualise the real impact of the forest harvesting plans. This presents a communication problem for the forestry experts who are responsible for conveying the information to the residents taking part in the consultations. For example, maps offering an aerial perspective of the territory are currently being used to illustrate the various forestry operations. These maps are difficult to understand for anyone who is not familiar with this field of expertise. As such, for the vast majority of the population, these documents are not particularly helpful when it comes to visualising the final result in a practical manner – and yet how the end result will look matters immensely to many attendees of the consultation meetings.
A virtual solution
In an attempt to provide an answer to this communication issue, FPInnovations and the Centre en Imagerie Numérique et Médias Interactifs (CIMMI) joined forces to develop a virtual reality application called the Virtual Forest. An immersive and concrete way of visualising the result of forestry operations on a territory was created in the space of just two months. The application depicts a precise representation of the forest: each tree is in the right place and is the right height. The generation of the forest tree-type (or ‘essence’) diversity follows a precise set of rules which has been configured to represent the forestry management plan presented to the public as accurately as possible.
Instead of relying entirely on confusing 2D maps and written documents, the residents can now explore an immersive and accurate three-dimensional (3D) environment in which they can navigate at will thanks to teleportation mechanics. From a user’s point of view, the app showcases two major features: 1) it shows the before and after state of the forest (allowing the user to switch from one state to the other), and 2) it can be experienced in either a first-person or a top-down perspective. Consequently, for the population of an area targeted for a forestry operation, the Virtual Forest app provides a great tool to observe how it will visually affect their region. The intention is for the application, along with the forestry management plans and documents, to be available to the public during the consultation process. Although the Virtual Forest app is still a prototype for now, ramping it up to an operational app is not an insurmountable challenge.
From GIS data to 3D models
Geospatial data is at the root of the Virtual Forest’s creation. In this case, the dataset available was:
a shapefile showing the height and location of each tree in the area extracted from a Lidar survey
a digital elevation model (DEM) of the terrain in Esri ASCII raster format with each cell value representing the elevation.
The main objective was to represent these geospatial datasets in a realistic way in virtual reality, using the game engine Unity.
Starting with the DEM, a point was created at the centre of each cell with an elevation attribute. Using Blender’s plugin BlenderGIS, those points were imported and a Delaunay triangulation process was applied to create faces between the points. Once that was done, the resulting surface was exported in the Unity-friendly FBX format.
As for the trees, the initial shapefile was converted into CSV format. Then, a Unity plugin was built to read the file and, for each line, instantiate a 3D model of a tree at the right location. Those 3D models could then be scaled according to the corresponding height in the CSV file. The Unity plugin can take into account many types of trees, as well as the percentage of each of them on the terrain. The information available for the area was that the tallest 70% of the trees were white pines and the remaining 30% were broadleaves. In this scene, a lake and a forest road were drawn manually for visual purposes, but the process could have been implemented to add them from geospatial data as well. Also, all the steps could be fully scripted and automated, providing that the input comes in a standardised format.
The main objective was for the app to be easily usable by anybody without extensive tutorials or prior gaming experience. Indeed, the application was showcased multiple times to diverse audiences and their feedback helped to provide an understanding of how people relate to their environment and how small details can make a huge difference. For example, when foresters tested the app, two users argued that the tree type depicted in the area was not a white pine as it was supposed to be, but some kind of oak. The 3D model used correctly showed the forest essence, but one user explained that the dead leaves on the ground did not correspond to what is commonly found in a pine forest. This misunderstanding arose from the fact that the ground texture used was completely unrelated to the type of forest. People’s perspectives are clearly affected by their personal background; the developers focused on trees and models, while the foresters looked at the forest as a whole. In light of this experience, one should also expect local citizens to look for familiar features to orient themselves, such as the right texture on the ground or landmarks such as a pier, a small cabin, some huge boulders, etc.
User feedback led to many improvements to the app. The texture on the ground was added, then the sun in the sky casting shadows accurately. People in general seemed to prefer a realistic approach and attention to small details. But even after some flowers and grass had been added to the environment, something still felt static and unrealistic. To bring things to life even more, the branches were made to sway softly as if in a breeze and an audio track reinforced the immersive feeling. In 3D applications such as this, it is important to keep enhancing the realism until it becomes almost the same as the real world. Everyone should be able to relate to the environment immediately in order to focus on discussing the main issue: the planned forestry operations.
Building a virtual forest puts geospatial data to use at a human scale. Replacing unclear 2D maps with an immersive and intuitive 3D virtual reality application might become an important part of the public consultation process in the future. The next step of this project could be to define the metrics to measure the efficiency of the virtual reality application compared to the current way of conducting public consultations. This would reveal the extent to which virtual reality can improve communication between the MFFP and the people using the forest.
Consultation on integrated forest management plans: