scholarly journals Estimation of GPS L2 Signal Observables Using Multilayer Perceptron Artificial Neural Networks for Positional Accuracy Improvement

2020 ◽  
Vol 24 (1) ◽  
pp. 97-103
Author(s):  
Cassio Vinícius Carletti Negri ◽  
Paulo Cesar Lima Segantine
Keyword(s):  
Multilayer Perceptron ◽  
Low Cost ◽  
Location Based Services ◽  
Global Navigation Satellite Systems ◽  
Dual Frequency ◽  
Positional Accuracy ◽  
Geospatial Information ◽  
Satellite Systems ◽  
Artificial Neural

In recent decades, due to the increasing mobility of people and goods, the rapid growth of users of mobile devices with location-based services has increased the need for geospatial information. In this context, positioning using data collected by the Global Navigation Satellite Systems (multi-GNSS) has gained more importance in the field of geomatics. The quality of the solutions is related, among other factors, to the receiver’s type used in the work. To improve the positioning with low-cost devices and to avoid additional user expenses, this work aims to propose the implementation of an Artificial Neural Network (ANN) to estimate the GPS L2 carrier observables. For this, a network model was selected through the cross-validation (CV) technique, the observations were estimated, and the accuracy of the solutions was analyzed. The CV technique demonstrated that a Multilayer Perceptron with four intermediate layers and one with one intermediate layer are the most appropriate configurations for this problem. The dual-frequency RINEX processing (with artificial data) revealed significant improvements. For some tests, it was possible to comply with the rural property georeferencing regulations of the Brazilian National Institute of Colonization and Agrarian Reform (INCRA). The results indicate, therefore, that the methodological proposal of the present investigation is very promising for approximating the quality of positioning reachable using a dual-frequency receiver.

scholarly journals UAV-Based GNSS-R for Water Detection as a Support to Flood Monitoring Operations: A Feasibility Study

2019 ◽  
Vol 10 (1) ◽  
pp. 210 ◽  
Author(s):  
Rayan Imam ◽  
Marco Pini ◽  
Gianluca Marucco ◽  
Fabrizio Dominici ◽  
Fabio Dovis
Keyword(s):  
Low Cost ◽  
Environmental Parameters ◽  
Global Navigation Satellite Systems ◽  
Passive Radar ◽  
Geospatial Information ◽  
Satellite Systems ◽  
Small Water ◽  
Water Detection ◽  
Sensing Applications ◽  
Flood Monitoring

Signals from global navigation satellite systems (GNSS) can be utilized as signals of opportunity in remote sensing applications. Geophysical properties of the earth surface can be detected and monitored by processing the back-scattered GNSS signals from the ground. In the literature, several airborne GNSS-based passive radar experiments have been successfully demonstrated. With the advancements in small unmanned aerial vehicles (UAVs) and their applications for environmental monitoring, we want to investigate whether GNSS-based passive radar can provide valuable geospatial information from such platforms. Low-cost GNSS reflectometry sensors, developed using commercial of the shelf components, can be mounted onboard UAVs and flown to sense environmental parameters. This paper presents the results of a preliminary study to investigate the feasibility of utilizing data collected by UAV-based GNSS-R sensors to detect surface water for a potential application in supporting flood monitoring operations. The study was conducted in the area surrounding the Avigliana lakes in Northern Italy. The results show the possibility of detecting small water surfaces with few tens of meters resolution, and estimating the area of the lake surface with 92% accuracy. Furthermore, it is proved through simulations that the use of multi-GNSS increases this accuracy to about 99%.

scholarly journals Evaluation of Low-Cost GNSS Receiver under Demanding Conditions in RTK Network Mode

Sensors ◽  
2021 ◽  
Vol 21 (16) ◽  
pp. 5552
Author(s):  
Daniel Janos ◽  
Przemysław Kuras
Keyword(s):  
High Precision ◽  
Patch Antenna ◽  
Low Cost ◽  
Satellite System ◽  
Dual Frequency ◽  
Satellite Systems ◽  
Satellite Positioning ◽  
Satellite Signal ◽  
Global Navigation Satellite

Positioning with low-cost GNSS (Global Navigation Satellite System) receivers is becoming increasingly popular in many engineering applications. In particular, dual-frequency receivers, which receive signals of all available satellite systems, offer great possibilities. The main objective of this research was to evaluate the accuracy of a position determination using low-cost receivers in different terrain conditions. The u-blox ZED-F9P receiver was used for testing, with the satellite signal supplied by both a dedicated u-blox ANN-MB-00 low-cost patch antenna and the Leica AS10 high-precision geodetic one. A professional Leica GS18T geodetic receiver was used to acquire reference satellite data. In addition, on the prepared test base, observations were made using the Leica MS50 precise total station, which provided higher accuracy and stability of measurement than satellite positioning. As a result, it was concluded that the ZED-F9P receiver equipped with a patch antenna is only suitable for precision measurements in conditions with high availability of open sky. However, the configuration of this receiver with a geodetic-grade antenna significantly improves the quality of results, beating even professional geodetic equipment. In most cases of the partially obscured horizon, a high precision positioning was obtained, making the ZED-F9P a valuable alternative to the high-end geodetic receivers in many applications.

scholarly journals Loosely Coupled GNSS and UWB with INS Integration for Indoor/Outdoor Pedestrian Navigation

Sensors ◽  
2020 ◽  
Vol 20 (21) ◽  
pp. 6292
Author(s):  
Vincenzo Di Pietra ◽  
Paolo Dabove ◽  
Marco Piras
Keyword(s):  
Data Fusion ◽  
Low Cost ◽  
Ground Truth ◽  
Location Based Services ◽  
Global Navigation Satellite Systems ◽  
Ultra Wideband ◽  
Portable Devices ◽  
Positioning System ◽  
Fusion Algorithm ◽  
Satellite Systems

The growth of location-based services (LBS) has increased rapidly in last years, mainly due to the possibility to exploit low-cost sensors installed in portable devices, such as smartphones and tablets. This work aims to show a low-cost multi-sensor platform developed by the authors in which an ultra-wideband (UWB) indoor positioning system is added to a classical global navigation satellite systems–inertial navigation system (GNSS-INS) integration, in order to acquire different synchronized data for further data fusion analysis in order to exploit seamless positioning. The data fusion is based on an extended Kalman filter (EKF) and on a geo-fencing approach which allows the navigation solution to be provided continuously. In particular, the proposed algorithm aims to solve a navigation task of a pedestrian user moving from an outdoor space to an indoor environment. The methodology and the system setup is presented with more details in the paper. The data acquired and the real-time positioning estimation are analysed in depth and compared with ground truth measurements. Particular attention is given to the UWB positioning system and its behaviour with respect to the environment. The proposed data fusion algorithm provides an overall horizontal and 3D accuracy of 35 cm and 45 cm, respectively, obtained considering 5 different measurement campaigns.

scholarly journals GEOSPATIAL DATA QUALITY OF THE SERVIR CORS NETWORK

2015 ◽  
Vol II-3/W5 ◽  
pp. 285-290 ◽  
Author(s):  
J. Santos ◽  
R. Teodoro ◽  
N. Mira ◽  
V. B. Mendes
Keyword(s):  
Quality Control ◽  
Geospatial Data ◽  
Global Navigation Satellite Systems ◽  
Positional Accuracy ◽  
Worst Case ◽  
Static Mode ◽  
Satellite Systems ◽  
Gnss Positioning ◽  
Global Navigation Satellite

The SERVIR Continuous Operation Reference Stations (CORS) network was implemented in 2006 to facilitate land surveying with Global Navigation Satellite Systems (GNSS) positioning techniques. Nowadays, the network covers all Portuguese mainland. The SERVIR data is provided to many users, such as surveyors, universities (for education and research purposes) and companies that deal with geographic information. By middle 2012, there was a significant change in the network accessing paradigm, the most important of all being the increase in the responsibility of managing the network to guarantee a permanent availability and the highest quality of the geospatial data. In addition, the software that is used to manage the network and to compute the differential corrections was replaced by a new software package. These facts were decisive to perform the quality control of the SERVIR network and evaluate positional accuracy. In order to perform such quality control, a significant number of geodetic monuments spread throughout the country were chosen. Some of these monuments are located in the worst location regarding the network geometry in order to evaluate the accuracy of positions for the worst case scenarios. Data collection was carried out using different GNSS positioning modes and were compared against the benchmark positions that were determined using data acquired in static mode in 3-hour sessions. We conclude the geospatial data calculated and provided to the users community by the network is, within the surveying purposes, accurate, precise and fits the needs of those users.

scholarly journals Relative Positioning in Remote Areas Using a GNSS Dual Frequency Smartphone

Sensors ◽  
2021 ◽  
Vol 21 (24) ◽  
pp. 8354
Author(s):  
Américo Magalhães ◽  
Luísa Bastos ◽  
Dalmiro Maia ◽  
José Alberto Gonçalves
Keyword(s):  
Low Cost ◽  
Global Navigation Satellite Systems ◽  
Reference Station ◽  
Dual Frequency ◽  
Phase Measurements ◽  
Satellite Systems ◽  
Remote Areas ◽  
Wide Range ◽  
Innovative Capabilities ◽  
Global Navigation Satellite

The use of GPS positioning and navigation capabilities in mobile phones is present in our daily lives for more than a decade, but never with the centimeter level of precision that can actually be reached with several of the most recent smartphones. The introduction of the new GNSS systems (Global Navigation Satellite Systems), the European system Galileo, is opening new horizons in a wide range of areas that rely on precise georeferencing, namely the mass market smartphones apps. The constant growth of this market has brought new devices with innovative capabilities in hardware and software. The introduction of the Android 7 by Google, allowing access to the GNSS raw code and phase measurements, and the arrival of the new chip from Broadcom BCM47755 providing dual frequency in some smartphones came to revolutionize the positioning performance of these devices as never seen before. The Xiaomi Mi8 was the first smartphone to combine those features, and it is the device used in this work. It is well known that it is possible to obtain centimeter accuracy with this kind of device in relative static positioning mode with distances to a reference station up to a few tens of kilometers, which we also confirm in this paper. However, the main purpose of this work is to show that we can also get good positioning accuracy using long baselines. We used the ability of the Xiaomi Mi8 to get dual frequency code and phase raw measurements from the Galileo and GPS systems, to do relative static positioning in post-processing mode using wide baselines, of more than 100 km, to perform precise surveys. The results obtained were quite interesting with RMSE below 30 cm, showing that this type of smartphone can be easily used as a low-cost device, for georeferencing and mapping applications. This can be quite useful in remote areas where the CORS networks are not dense or even not available.

Precise carrier phase altimetry over lakes using dual-frequency reflected signals of the Global Navigation Satellite Systems (GNSS)

2021 ◽  
Author(s):  
Estel Cardellach ◽  
Weiqiang Li ◽  
Dallas Masters ◽  
Takayuki Yuasa ◽  
Franck Borde ◽  
...  
Keyword(s):  
Sea Ice ◽  
Carrier Phase ◽  
Radio Occultation ◽  
Global Navigation Satellite Systems ◽  
Data Sets ◽  
Dual Frequency ◽  
Effective Wavelength ◽  
Raw Data ◽  
Satellite Systems ◽  
Global Navigation Satellite

<p>Recently, different studies have shown evidence of signals transmitted by the Global Navigation Satellite Systems (GNSS), coherently reflected over some parts of the ocean, and received from cubesats. In particular, strong coherent scattering has been reported in regions with low water surface roughness as those near continental masses and in atolls. Over open ocean, few coherent signals were reported to be found, although the data sets were somewhat limited and certainly not exhaustive. The level of coherence in reflected GNSS signals depends on the roughness of the  surface (i.e. significant wave height and small scale ripples and waves induced by the wind), the viewing geometry (i.e. incidence angle, or equivalently, elevation angle of the GNSS satellite as seen from the point of reflection), propagation effects (namely ionospheric disturbances) and on the frequency (i.e. particular GNSS band, like L1/E1, L2 or L5/E5). These coherent measurements over ocean follow earlier evidence of coherent GNSS reflections over sea ice which date back to 2005, the time of UK-DMC mission. More recently, Sea Ice Thickness (SIT) retrievals have also been carried out with this technique, at an accuracy comparable to that of SMOS.</p><p>All the observations referred so far were done at a single frequency, L1/E1. So, there is an interest to explore the coherence at the other main GNSS bands, i.e. L2 and L5/E5 as well as to the widelane combinations between them (linear combinations of carrier-phase measurements, of longer effective wavelength). Spire Global radio occultation cubesats work at L1 and L2 frequency bands, and therefore provide unique dual-frequency raw data sets of reflected signals over open ocean, sea ice and inland water bodies. With these, it is possible to study the coherence of these targets at each of the bands and at their widelane combination, as well as the performance of altimetric retrievals at grazing angles of observation (very slant geometries, which facilitate coherence properties of the scattering). The dual-frequency observations can correct the ionospheric effects, and their widelane combinations, of longer effective wavelength, might expand the conditions for coherence. The fact that this new approach is fully compatible with small GNSS radio occultation payloads and missions, might represent a low cost source of precise altimetry to complement larger dedicated missions.</p><p>An ESA research study involving Spire Global and IEEC aims at studying this new potential altimetric technique. Raw data acquisitions from limb-looking antennas of Spire’s cubesat constellation were selected to be geographically and time collocated with ESA Sentinel 3A and 3B passes in order to compare the results of coherence and altimetry. For this study, the raw data at two frequencies, acquired at 6.2 Mbps, are shifted to intermediate frequencies and downloaded to the ground without any further processing. In-house software receivers are then applied to generate the reflected echoes or waveforms, and to track the phase of the carrier signals. Precise altimetry (a few cm in 20 ms integration) is then possible from these observables. The results of this activity will be shown, focusing on altimetric retrievals over large lakes.</p>

scholarly journals Positioning Evaluation of Single and Dual-Frequency Low-Cost GNSS Receivers Signals Using PPP and Static Relative Methods in Urban Areas

2021 ◽  
Vol 11 (22) ◽  
pp. 10642
Author(s):  
Rosendo Romero-Andrade ◽  
Manuel E. Trejo-Soto ◽  
Alejandro Vega-Ayala ◽  
Daniel Hernández-Andrade ◽  
Jesús R. Vázquez-Ontiveros ◽  
...  
Keyword(s):  
Urban Areas ◽  
Precise Point Positioning ◽  
Low Cost ◽  
Observation Data ◽  
Dual Frequency ◽  
Positional Accuracy ◽  
Gnss Receivers ◽  
Point Positioning ◽  
Error Circle ◽  
Vertical Positioning

A positional accuracy obtained by the Precise Point Positioning and static relative methods was compared and analyzed. Test data was collected using low-cost GNSS receivers of single- and dual-frequency in urban areas. The data was analyzed for quality using the TEQC program to determine the degree of affectation of the signal in the urban area. Low-cost GNSS receivers were found to be sensitive to the multipath effect, which impacts positioning. The horizontal and vertical accuracy was evaluated with respect to Mexican regulations for the GNSS establishment criteria. Probable Error Circle (CEP) and Vertical Positioning Accuracy (EPV) were performed on low cost GNSS receiver observation data. The results show that low-cost dual-frequency GNSS receivers can be used in urban areas. The precision was obtained in the order of 0.013 m in the static relative method. The results obtained are comparable to a geodetic receiver in a geodetic baseline of <20 km. The study does not recommend using single and dual frequencies low cost GNSS receivers based on results obtained by the Precise Point Positioning (PPP) method in urban areas. The inclusion of the GGM10 model reduces the vertical precision obtained by using low cost GNSS receivers in both methods, conforming to the regulations only in the horizontal component.

scholarly journals EVALUATION AND TAILORING OF GLOBAL GEOPOTENTIAL MODELS IN THE DETERMINATION OF GRAVITY FIELD IN SERBIA

2020 ◽  
Vol 14 (1) ◽  
Author(s):  
Oleg Odalović ◽  
Danilo Joksimović ◽  
Dušan Petković ◽  
Marko Stanković ◽  
Sanja Grekulović
Keyword(s):  
Global Navigation Satellite Systems ◽  
Satellite Systems ◽  
Average Value ◽  
Free Air ◽  
Geopotential Models ◽  
Normal Heights ◽  
Discrete Values ◽  
Global Navigation Satellite

Within this paper, we evaluated the quality of three Global Geopotential Models entitled: EGM96,EGM2008, and GOCO05c. The models were evaluated by using 1001 terrestrial discrete values ofheight anomalies determined by Global Navigation Satellite Systems and normal heights, which weconsidered to be true values within this research. In addition to the quality evaluation, we tailoredthe models by using more than 80000 free air anomalies. The results obtained from the evaluationand tailoring indicate that by using the GOCO05c it is possible to determine a set of anomaly heightsacross Serbia, which are in agreement with terrestrial values with an average value of -7 cm, thestandard deviation of ±9 cm and with the range of 44 cm.

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