scholarly journals Georeferencing of Multi-Channel GPR—Accuracy and Efficiency of Mapping of Underground Utility Networks

2020 ◽  
Vol 12 (18) ◽  
pp. 2945
Author(s):  
Marta Gabryś ◽  
Łukasz Ortyl
Keyword(s):  
Time Synchronization ◽  
Amplitude Distribution ◽  
Satellite System ◽  
Destructive Testing ◽  
High Rise ◽  
Wide Range ◽  
Urban Character ◽  
Global Navigation Satellite ◽  
Ground Penetrating ◽  
Urban Conditions

Due to the capabilities of non-destructive testing of inaccessible objects, GPR (Ground Penetrating Radar) is used in geology, archeology, forensics and increasingly also in engineering tasks. The wide range of applications of the GPR method has been provided by the use of advanced technological solutions by equipment manufacturers, including multi-channel units. The acquisition of data along several profiles simultaneously allows time to be saved and quasi-continuous information to be collected about the subsurface situation. One of the most important aspects of data acquisition systems, including GPR, is the appropriate methodology and accuracy of the geoposition. This publication aims to discuss the results of GPR measurements carried out using the multi-channel Leica Stream C GPR (IDS GeoRadar Srl, Pisa, Italy). The significant results of the test measurement were presented the idea of which was to determine the achievable accuracy depending on the georeferencing method using a GNSS (Global Navigation Satellite System) receiver, also supported by time synchronization PPS (Pulse Per Second) and a total station. Methodology optimization was also an important aspect of the discussed issue, i.e., the effect of dynamic changes in motion trajectory on the positioning accuracy of echograms and their vectorization products was also examined. The standard algorithms developed for the dedicated software were used for post-processing of the coordinates and filtration of echograms, while the vectorization was done manually. The obtained results provided the basis for the confrontation of the material collected in urban conditions with the available cartographic data in terms of the possibility of verifying the actual location of underground utilities. The urban character of the area limited the possibility of the movement of Leica Stream C due to the large size of the instrument, however, it created the opportunity for additional analyses, including the accuracy of different location variants around high-rise buildings or the agreement of the amplitude distribution at the intersection of perpendicular profiles.

scholarly journals Fast Time Synchronization on Tens of Picoseconds Level Using Uncombined GNSS Carrier Phase of Zero/Short Baseline

Sensors ◽  
2020 ◽  
Vol 20 (17) ◽  
pp. 4882
Author(s):  
Yinghao Zhao ◽  
Letao Zhou ◽  
Wei Feng ◽  
Shaoguang Xu
Keyword(s):  
Carrier Phase ◽  
Time Synchronization ◽  
Satellite System ◽  
Fast Time ◽  
Short Baseline ◽  
Variation Characteristics ◽  
Single Difference ◽  
Short Baselines ◽  
Transfer Method ◽  
Global Navigation Satellite

Since the observation precision of the Global Navigation Satellite System (GNSS) carrier phase is on the order of millimeters, if the phase ambiguity is correctly solved, while calibrating the receiver inter-frequency bias, time synchronization on the order of tens of picoseconds is expected. In this contribution, a method that considers the prior constraints of the between-receiver inter-frequency bias (IFB) and its random variation characteristics is proposed for the estimation of the between-receiver clock difference, based on the uncombined GNSS carrier phase and pseudorange observations of the zero and short baselines. The proposed method can rapidly achieve the single-difference ambiguity resolution of the zero and short baselines, and then obtain the high-precision relative clock offset, by using only the carrier phase observations, along with the between-receiver IFBs being simultaneously determined. Our numerical tests, carried out using GNSS observations sampled every 30 s by a dedicatedly selected set of zero and short baselines, show that the method can fix the between-receiver single-difference ambiguity successfully within an average of fewer than 2 epochs (interval 30 s). Then, a clock difference between two receivers with millimeter precision is obtained, achieving time synchronization on tens of picoseconds level, and deriving a frequency stability of 5 × 10−14 for averaging times of 30,000 s. Furthermore, the proposed approach is compared with the precise point positioning (PPP) time transfer method. The results show that, for different types of receivers, the agreement between the two methods is between −6.7 ns and 0.2 ns.

scholarly journals GNSS-ISE: Instruction Set Extension for GNSS Baseband Processing

Sensors ◽  
2020 ◽  
Vol 20 (2) ◽  
pp. 465 ◽  
Author(s):  
Krzysztof Marcinek ◽  
Witold A. Pleskacz
Keyword(s):  
Flash Memory ◽  
Low Cost ◽  
Satellite System ◽  
Microprocessor System ◽  
Instruction Set ◽  
Advantages And Disadvantages ◽  
Wide Range ◽  
Instruction Set Extension ◽  
Baseband Processing ◽  
Global Navigation Satellite

This work presents the results of research toward designing an instruction set extension dedicated to Global Navigation Satellite System (GNSS) baseband processing. The paper describes the state-of-the-art techniques of GNSS receiver implementation. Their advantages and disadvantages are discussed. Against this background, a new versatile instruction set extension for GNSS baseband processing is presented. The authors introduce improved mechanisms for instruction set generation focused on multi-channel processing. The analytical approach used by the authors leads to the introduction of a GNSS-instruction set extension (ISE) for GNSS baseband processing. The developed GNSS-ISE is simulated extensively using PC software and field-programmable gate array (FPGA) emulation. Finally, the developed GNSS-ISE is incorporated into the first-in-the-world, according to the authors’ best knowledge, integrated, multi-frequency, and multi-constellation microcontroller with embedded flash memory. Additionally, this microcontroller may serve as an application processor, which is a unique feature. The presented results show the feasibility of implementing the GNSS-ISE into an embedded microprocessor system and its capability of performing baseband processing. The developed GNSS-ISE can be implemented in a wide range of applications including smart IoT (internet of things) devices or remote sensors, fostering the adaptation of multi-frequency and multi-constellation GNSS receivers to the low-cost consumer mass-market.

scholarly journals Unsupervised Human Detection with an Embedded Vision System on a Fully Autonomous UAV for Search and Rescue Operations

Sensors ◽  
2019 ◽  
Vol 19 (16) ◽  
pp. 3542 ◽  
Author(s):  
Eleftherios Lygouras ◽  
Nicholas Santavas ◽  
Anastasios Taitzoglou ◽  
Konstantinos Tarchanidis ◽  
Athanasios Mitropoulos ◽  
...  
Keyword(s):  
Embedded System ◽  
Emergency Services ◽  
Vision System ◽  
Open Water ◽  
Satellite System ◽  
Search And Rescue ◽  
Human Detection ◽  
Primary Role ◽  
Wide Range ◽  
Global Navigation Satellite

Unmanned aerial vehicles (UAVs) play a primary role in a plethora of technical and scientific fields owing to their wide range of applications. In particular, the provision of emergency services during the occurrence of a crisis event is a vital application domain where such aerial robots can contribute, sending out valuable assistance to both distressed humans and rescue teams. Bearing in mind that time constraints constitute a crucial parameter in search and rescue (SAR) missions, the punctual and precise detection of humans in peril is of paramount importance. The paper in hand deals with real-time human detection onboard a fully autonomous rescue UAV. Using deep learning techniques, the implemented embedded system was capable of detecting open water swimmers. This allowed the UAV to provide assistance accurately in a fully unsupervised manner, thus enhancing first responder operational capabilities. The novelty of the proposed system is the combination of global navigation satellite system (GNSS) techniques and computer vision algorithms for both precise human detection and rescue apparatus release. Details about hardware configuration as well as the system’s performance evaluation are fully discussed.

The Research of Multipath and Linear Error for Pseudolites Applications

2011 ◽  
Vol 130-134 ◽  
pp. 2890-2893 ◽  
Author(s):  
Xiao Guang Wan ◽  
Xing Qun Zhan
Keyword(s):  
Carrier Phase ◽  
Indoor Environment ◽  
Phase Measurement ◽  
Satellite System ◽  
Independent System ◽  
Carrier Phase Measurement ◽  
Wide Range ◽  
Positioning Method ◽  
Global Navigation Satellite ◽  
Is Design

Pseudolites are ground-based transmitters that send global navigation satellite system like signals, such as GPS, GLONASS, or Galileo. As an independent system for indoor positioning, pseudolites technique can be explored for a wide range of positioning and navigation application where the signal of satellite GNSS can’t be received. However, with indoor environment, the positioning method of pseudolite navigation system is not entirely same as GNSS, and there are some challenging issues in research and system design. In this paper, a signal difference carrier phase measurement system with pseudolites is design. Furthermore, two major problems are studied that they are multipath error and linear errors.

scholarly journals SibNet — Siberian Global Navigation Satellite System Network: Current state

2018 ◽  
Vol 4 (4) ◽  
pp. 82-94 ◽  
Author(s):  
Юрий Ясюкевич ◽  
Yury Yasyukevich ◽  
Артем Веснин ◽  
Artem Vesnin ◽  
Наталья Перевалова ◽  
...  
Keyword(s):  
Global Navigation Satellite System ◽  
Satellite System ◽  
General Information ◽  
Navigation Satellite ◽  
Main Research ◽  
Current State ◽  
Wide Range ◽  
Global Navigation ◽  
Using Data ◽  
Global Navigation Satellite

In 2011, ISTP SB RAS began to deploy a routinely operating network of receivers of global navigation satellite system signals. To date, eight permanent and one temporal sites in the Siberian region are operating on a regular basis. These nine sites are equipped with 12 receivers. We use nine multi-frequency multi-system receivers of Javad manufacturer, and three specialized receivers NovAtel GPStation-6 designed to measure ionospheric phase and amplitude scintillations. The deployed network allows a wide range of ionospheric studies as well as studies of the navigation system positioning quality under various heliogeophysical conditions. This article presents general information about the network, its technical characteristics, and current state, as well as the main research problems that can be solved using data from the network.

Strategies for International Travel with “High-Tech” Archaeological Field Equipment

2017 ◽  
Vol 5 (4) ◽  
pp. 382-387 ◽  
Author(s):  
William F. Limp ◽  
Malcolm D. Williamson
Keyword(s):  
Value Added ◽  
Satellite System ◽  
International Travel ◽  
High Tech ◽  
X Ray Diffraction ◽  
Field Equipment ◽  
International Transport ◽  
Gnss Receivers ◽  
Global Navigation Satellite ◽  
Ground Penetrating

ABSTRACTConducting archaeological fieldwork increasingly relies on “high-tech” instruments. These include such technologies as portable X-ray diffraction; ground penetrating radar; high-precision global navigation satellite system (GNSS) receivers; laser scanners; multispectral, thermal, lidar, and hyperspectral instruments on Uncrewed Aerial Vehicles (UAVs); and many others. Using these devices internationally can present complex issues with export regulations and the potential for duties and value-added taxes. In short, there are many regulations affecting the movement of these devices across international borders. In the past, archaeologists had interactions with customs personnel and faced the complexities of import and export laws at the end of a project, as they dealt with the issues of taking samples or artifacts out of a country for study. Today's archaeologists must be prepared before they even begin their travel to ensure that their equipment and software can travel overseas. This article provides a practical overview of the laws, regulations, and practices affecting international transport of the archaeological high-tech tool kit.

scholarly journals Timing and Navigation in UAVs

2018 ◽  
Vol 5 (1) ◽  
pp. 17-25
Author(s):  
Karen Von Hünerbein ◽  
Werner R Lange
Keyword(s):  
Time Synchronization ◽  
Health And Safety ◽  
Test Methods ◽  
Global Navigation Satellite Systems ◽  
External Control ◽  
Satellite Systems ◽  
Environment And Health ◽  
Wide Range ◽  
Correct Function ◽  
Global Navigation Satellite

Precise timing and precise location information are provided by Global Navigation Satellite Systems (GNSS) and play a crucial role in the positioning, navigation and data acquisition of most Unmanned Aerial Vehicles (UAV). GNSS functions include the following applications in UAVs: time-stamping and geo-referencing of collected data and images, synchronization of swarm flying and follow-me flights, determination of position and attitude in-flight, flight trajectory by following a pre-defined number of waypoints, mission planning, return home automatically without external control, avoidance of obstacles and geo-fencing.  Some of these critical operations have implications for the safety of the UAV, the surrounding environment and health and safety of people, for example UAVs threatening to bring down aircrafts  at airports, which are no-fly zones for UAVs. The appropriate GNSS based function to avoid this is geo-fencing. Another example is obstacle avoidance to prevent collisions and damages both for the UAV and the obstacle, e.g. anything from a window pane, tree, human being, to a power line. In order to ensure health and safety it is thus important to ensure correct function of the navigation and the timing, under a wide variety of circumstances, and in different signal environments. There can be signal disturbances, such as obscurations by buildings or reflected GNSS signals, called multipath. The performance of timing and navigation based on GPS/GNSS can be tested and verified in a controlled and repeatable way in the laboratory with different types of test equipment. We will give an introduction to a wide range of potential threats to GNSS Positioning, navigation and timing and an overview of different test methods. In addition, we are presenting a method for time synchronization of drones to enable safe swarm and follow flights in UAVs.

Progress in Time Series Soil Moisture Retrievals Using the Cyclone Global Navigation Satellite System Mission

2021 ◽  
Author(s):  
Mohammad Al-Khaldi ◽  
Joel Johnson ◽  
Scott Gleason
Keyword(s):  
Time Series ◽  
Soil Moisture ◽  
Global Navigation Satellite System ◽  
Satellite System ◽  
Retrieval Algorithm ◽  
Navigation Satellite ◽  
Gps Satellites ◽  
Wide Range ◽  
Global Navigation ◽  
Global Navigation Satellite

<p>NASA's Cyclone Global Navigation Satellite System (CYGNSS) mission has continued to provide measurements of land surface specular scattering since its launch in December 2016. CYGNSS’s operates in a GNSS-R configuration in which  CYGNSS satellites together with GPS satellites form a bistatic radar geometry with GPS satellites acting as transmitters and CYGNSS satellites acting as receivers. The fundamental GNSS-R measurement obtained using the CYGNSS observatories is the delay-Doppler map (DDM), from which normalized radar cross section (NRCS) estimates are derived. The sensitivity of CYGNSS measurements to a wide range of surface properties has motivated their use for soil moisture retrievals.</p><p>This presentation reports an updated analysis of soil moisture retrieval errors using a previously reported time series soil moisture retrieval algorithm that considers a  multi-year CYGNSS dataset. The presentation also reports recent progress in which further simplifications to the proposed algorithm are introduced that limit its need for ancillary soil moisture data and promote use in an operational capacity. This is accomplished, in part, through the incorporation of a recently developed global Level-1 coherence detection methodology and the use of a soil moisture climatology.</p><p>Soil moisture is sensed using a time-series retrieval in which NRCS ratios derived from CYGNSS measurements are used to form a system of equations that can be solved for a times series of surface reflectivities. While the NRCS exhibits a dependence on a wide range of properties such as soil moisture, soil composition, vegetation cover, and surface roughness, NRCS ratios in consecutive acquisitions, at sufficiently low latency, exhibit a direct proportionality to reflectivity ratios that are a function of soil permittivity and therefore soil moisture. The dependence of NRCS ratios on reflectivity facilitates a location dependent inversion of reflectivity to soil moisture through a dielectric mixing model. The use of NRCS ratios however results in N-1 equations for the N soil moistures in the time series, thereby necessitating the incorporation of additional information typically expressed in terms of maximum and/or minimum soil moisture (or reflectivity) values over the time series when solving the system. These values can be obtained either from ancillary data from other systems or from a soil moisture climatology as incorporated in this presentation.</p><p>Retrieved moisture values from the updated algorithm are compared against observed values reported by the Soil Moisture Active Passive (SMAP) mission. The findings suggest that there exists potential for using GNSS-R systems for global soil moisture retrievals with an RMS error on the order of 0.06 cm<sup>3</sup>/cm<sup>3</sup> over varied terrain. The dependence of the algorithm’s retrieval error on land cover class, soil texture, and moisture variability trends will be reported in detail in this presentation.</p>

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