FSO is free space optics provides point-point broadband communications using Laser Light as the transmission medium.
FSO is a state of art data communication method which is based on a very old communication solution. Ancient Chinese developed a protection system against the Mongol tribes, building watchtowers within the line of site to other towers. And as soon as the towers saw some hostile sign on the horizon they use they shield to reflect the sun to the remote towers. In this way the area could be prepared against the attack in a very short period of time.
In the ancient times for this communication use the mirror as a transmitter and the sunlight was the light source, and the receiver was the remote guard’s eye. This basic signaling method was developed later into up communication device which used „line coding”. This allowed the guards to tell the number of enemy, or the direction they are coming from.

Current FSO systems use a laser-diode as a light source, and a receptor diode (photo diode) to receive the signals coming from the laser diode from the transmitter side. But the basic elements are still the same: line of site between the communication nodes, and individual line coding. It is all about performance. Trimble FSO offers FSO systems with the highest power budget available on the market.

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Advanced substation automation applications such as wide area phasor monitoring with Phasor Measurement Units (PMU) and sampled value process buses require synchronising accuracy to be better than 1 μs, rather than the 1–2 ms that is generally required today. Substation automation systems are now using Ethernet to communicate between SCADA systems and protection relays.

Precision Time Protocol (PTP) is a time synchronisation system that uses the substation LAN, rather than a dedicated time distribution system, that can synchronise protection relays, merging units and other devices to better than 1 μs.

This white paper explains how PTP can be used in substation automation systems to overcome incompatibilities and shortcomings of existing time distribution systems. The operation of PTP using the “Power Profile” is explained and examples of how PTP can be used in new and existing substations are presented.

Tekron has over fifteen years’ experience in producing timing equipment for the power industry. Their latest substation timing products support PTP and this white paper explains how these can be used to meet the timing needs of modern substation automation applications, while retaining compatibility with existing substation protection and control designs. This allows utility and industrial substation operators to gradually gain experience with PTP.

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VELODYNE LIDAR : 16 channels Velodyne versus planar LiDARs based perception system for Large Scale 2D-SLAM

The ability of self-localization is a basic requirement for an autonomous vehicle, and a prior reconstruction of the environment is usually needed. This paper analyses the performances of two typical hardware architectures that we evaluate in our 2D Simultaneous Localization and Mapping (2D-SLAM) system for large scale scenarios. In particular, the selected configurations are supposed to guarantee the possibility of integrating at a later stage mobile objects tracking capabilities without modifying the hardware architecture. The choice of the perception system plays a vital role for building a reliable and simple architecture for SLAM.

Therefore we analyze two common configurations: one based on three planar LiDARs Sick LMS151 and the other based on a Velodyne 3D LiDAR VLP-16. For each of the architectures we identify advantages and drawbacks related to system installation, calibration complexity and robustness, quantifying their respective accuracy for localization purposes. The conclusions obtained tip the balance to the side of using a Velodyne-like sensor facilitating the process of hardware implementation, keeping a lower cost and without compromising the accuracy of the localization. From the point of view of perception, additional advantages arise from the fact of having 3D information available on the system for other purposes.

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POLYPHASER:  Coaxial Cable Protection

Skin effect is a physical phenomenon that relates to the limited penetration into a conductor of a RF signal, according to its frequency. This effect is present in coax cable, keeping the RF signal inside and any coupled outside interference on the shield’s outer surface. The effect begins to fall apart as the frequency is lowered and the penetration, which is a gradient, begins to mix the shield’s outside interference energy with the desired inside energy. A ground loop, which imparts 60 Hz onto a desired signal, is due to dissimilar ground potentials causing ac current flow between points on the coax shield and is low enough in frequency to couple energy through to the center conductor With lightning, the main frequency range is dc to about 1 MHz (-3dB). This is in the range that affects the coax transfer impedance.

The thicker the shield material, the less the effect to these low frequency currents. A test was performed on 51-feet (15.5 m) of 1/2-inch (13 mm) coax, where the center conductor to the shield on one end was shorted, simulating a shunt-fed antenna. (see catalog page 29) A fast rise time pulse was applied to the shorted end and the resulting voltage was viewed across the .001 ohm resistors at the far end. These current viewing resistors went to separate channels on a digital storage scope. The velocity factor / inductance of the shield caused its pulse to arrive first. The center conductor had more inductance, and a capacitive relationship through the dielectric to the shield, so the pulse was spread out in time. The total energy (area under the curves) was the same for both the shield and the center conductor.

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TRIMBLE : A New Integration Method for MEMS Based GNSS/INS Multi-sensor Systems

Trimble has developed its new multi-sensor GNSS-INS integrated system which is called BD935-INS. It employs the new Quasi-tightly-coupled (QTC) integration architecture [1-3] and Trimble’s centimeter-accuracy GNSS positioning technology to produce an accurate, robust and low-cost single-board integrated product for small and medium sized unmanned aerial vehicles(UAV), ground based and marine platforms.

The new system has the salient characteristics of a tightly-coupled integration with a much simplified design. It features INS seeding of the GNSS RTK engine to increase the availability and accuracy of RTK output in challenging GNSS signal environments. In addition an observable subspace constraint (OSC) is applied in the INS-GNSS position measurement to block the uncorrected a priori INS errors for entering the integration Kalman filter (KF). The new system has been extensively tested. Field test results from land-based mapping vehicle missions in urban areas verify the benefits of QTC integration architecture. For UAV missions, it satisfies the high accuracy demands for position and orientation as well.

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TRIMBLE : GALILEO/Modernized GPS – A New Challenge to Network RTK

Network RTK in local or regional reference networks has been proven as an efficient technology for high accuracy GPS positioning over the last few years. Comparing with single base RTK, the advantage of network RTK is that large portions of ionospheric and geometric errors are removed through network corrections. Hence network solutions increase the reliability and productivity of ambiguity resolution and the positioning accuracy of rovers working in the system.

Several preliminary studies have demonstrated that with the third/fourth frequency available from GALILEO and modernized GPS, the reliability and productivity of single base OTF (on the fly) initializations at the rover increase dramatically when comparing with a dual frequency RTK system. So, the question arises: will network RTK become obsolete when GALILEO and modernized GPS are operational because of the high performance of single base RTK? What can network RTK benefit from GALILEO and modernized GPS?

It is a well-known fact that the initialization performance of an RTK system decreases significantly with higher ionosphere activity. Furthermore, the geometric errors (including troposphere and orbit), which are not frequency-dependent, will not be removed by adding more frequencies. In other words, positioning accuracy will be improved only marginally by mitigating multipath due to the availability of more observables. This paper demonstrates two and three carrier RTK performance in various single-base and network scenarios. Simulation studies show that in the presence of a reference station network, RTK initialization and positioning accuracy are improved considerably.

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APPLANIX : Quasi-Tightly-Coupled GNSS-INS Integration with a GNSS Kalman Filter

Quasi-tightly-coupled (QTC) GNSS-INS integration is a method of loosely-coupled integration that has the salient characteristics of a tightly-coupled integration. This method is intended for the integration of an existing GNSS navigation engine into a GNSS-INS closed-loop configuration with little or no modification of the GNSS navigation engine. The method of integration uses the range measurement model matrix typically used to compute dilutions of precision (DOP) to identify the observable subspace in the time-space frame generated by the available satellites and project the loosely-coupled INS-GNSS Kalman filter position measurement into this subspace.

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POLYPHASER: AC & DC Power Protection at Communication Sites

The incidence of damage to equipment in general is higher from power line surges than by any other I/O port. This is not to say more energy comes through the power line, just that the damage is more visible there. Since the coax connection to the tower is the source of the largest surge current in the building, power line port damage is usually due to improper grounding techniques and lack of surge protection devices. There are two probable ways power line caused equipment damage occurs

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TRIMBLE : Portable GPS Devices Prove Central to Accurate Solutions

The casual use of satellite-based positioning has proliferated, with GPS now readily available in mobile phones and cars. Most GPS receiver chips in such devices can achieve an accuracy of just two to three meters, which is far less accurate than professional-grade devices. Consumergrade devices lack the ability to provide quality assurance details or metadata about position so that you can’t be sure with confidence that the positions that you collected are correct.

When lower-end accuracy is used for data collection, what also gets lost is the utility of high-accuracy position, and the kinds of insight that are revealed only at higher accuracies. Businesses increasingly understand that spatial awareness of workers, assets and processes can lead to much greater efficiencies. But the best enterprise-wide information system can be sabotaged by data that is not accurate enough. The bottom line of ‘garbage in, garbage out’ is as relevant today as it was when the first database was invented. Poor positional accuracy, and in some cases wrong positions, degrade the utility of your systems, and can even result in costly errors.

Given the benefit of greater accuracy, the trend across the GIS and mapping arena is toward higher accuracy data collection. This began with aerial and satellite imagery as pixels the size of a meter squared rapidly improved to the 50 cm range. Similarly, we have high-speed LiDAR collection tools that capture large areas at 5 to 10 cm accuracy. We’re now entering a realm where highly portable handheld devices can achieve accuracy that was once only possible with survey-grade tools.

The improved portable high-accuracy capability is potentially a game changer. It puts high precision into the hands of a greater percentage of the workforce, which can improve the quality of spatial information in an organization to unlock new efficiencies and insight.

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In recent years, mobile devices, such as smart phones and tablets, have become an essential part of how people communicate and get their information. The use of these devices has grown rapidly and they now serve as a way for businesses across many industries to work smarter. Location accuracy from these devices, however, has long prevented them from being a viable solution for GIS work in the field; after all, their GPS accuracy only had to be good enough for basic navigation and turn-by-turn directions. The introduction of new receiver devices that pair with smart phones or tablets has opened the doors to higher accuracy positioning that can be achieved with such a combination, resulting in a new, cost-effective solution for Mapping and GIS professionals.

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