scholarly journals Applicability of a Recreational-Grade Interferometric Sonar for the Bathymetric Survey and Monitoring of the Drava River

2020 ◽  
Vol 9 (3) ◽  
pp. 149 ◽  
Author(s):  
Ákos Halmai ◽  
Alexandra Gradwohl–Valkay ◽  
Szabolcs Czigány ◽  
Johanna Ficsor ◽  
Zoltán Árpád Liptay ◽  
...  
Keyword(s):  
Satellite System ◽  
Water Levels ◽  
Cross Sectional ◽  
Bathymetric Survey ◽  
Sonar System ◽  
Recent Developments ◽  
Long Time ◽  
Drava River ◽  
Water Courses ◽  
Global Navigation Satellite

Sonar survey of shallow water bodies has challenged scientists for a long time. Although these water courses are small, still they have an increasing ecological, touristic and economical role. As maritime sonars are non-ideal tools for shallow waters, the bathymetric survey of these rivers has been taken with cross-sectional methods. Due to recent developments, interferometric surveying technology have also burst into the market of recreational-grade fish-finders. The objective of the current study was the development of a novel, complex and integrated surveying technique which is affordable, robust and applicable even at low water levels. A recreational-grade sonar system was assembled and mounted on a double-hull vessel and connected with a geodetic Global Navigation Satellite System (GNSS) device. We have developed a novel software which enables the bridging between a closed sonar file format and the commonly used Geographic Information System (GIS) datasets. As a result, the several month-long conventional bathymetric survey of the 146 km-long reach of the Drava River was reduced to 20 days and provided channel bathymetry of many orders of magnitude higher than the classical methods. Additionally, a large number of spatial derivatives were generated which enables the analysis of channel morphology, textural variation of channel sediments and the accurate delineation of navigational routes.

scholarly journals ICESat-2 Marine Bathymetry: Extraction, Refraction Adjustment and Vertical Accuracy as a Function of Depth in Mid-Latitude Temperate Contexts

2021 ◽  
Vol 13 (21) ◽  
pp. 4352
Author(s):  
Seamus Coveney ◽  
Xavier Monteys ◽  
John D. Hedley ◽  
Yeray Castillo-Campo ◽  
Brian Kelleher
Keyword(s):  
Satellite System ◽  
Coastal Monitoring ◽  
Temperate Latitude ◽  
Bathymetric Survey ◽  
Bathymetric Data ◽  
Monitoring Applications ◽  
Vertical Accuracy ◽  
Global Navigation Satellite ◽  
Maximum Photon ◽  
Manual Extraction

Nearshore bathymetric data are used in many coastal monitoring applications, but acquisition conditions can be challenging. Shipborne surveys are prone to the risk of grounding in shallow waters, and scheduled airborne surveys often fail to coincide with optimal atmospheric and water conditions. As an alternative, since its launch in 2018, ICESat-2 satellite laser profile altimetry data provide free and readily available data on a 91-day repeat cycle, which may contain incidental bathymetric returns when suitable environmental conditions prevail. In this paper, the vertical accuracy of extracted, refraction-adjusted ICESat-2 nearshore marine bathymetric data is evaluated at four test sites in a Northern hemisphere, temperate latitude location. Multiple ICEsat-2 bathymetric values that occurred in close horizontal proximity to one another were averaged at a spatial scale of 1 m and compared with Multibeam Echosounder bathymetric survey data and Global Navigation Satellite System reference data. Mean absolute errors of less than 0.15 m were observed up to depths of 5 m, with errors of less than 0.24 m (to 6 m), 0.39 m (to 7 m) and 0.52 m (to 10 m). The occurrence of larger bathymetric errors with depth, which increase to 0.54 m at maximum photon depths of 11 m, appears to be primarily related to reduced numbers of geolocated photons with depth. The accuracies achieved up to 6 m suggest that the manual extraction, refraction adjustment and bathymetric filtering steps were effective. Overall, the results suggest that ICESat-2 bathymetric data accuracy may be sufficient to be considered for use in nearshore coastal monitoring applications where shipborne and airborne bathymetric data might otherwise be applied.

scholarly journals Synergistic Use of UAV and USV Data and Petrographic Analyses for the Investigation of Beachrock Formations: A Case Study from Syros Island, Aegean Sea, Greece

Minerals ◽  
2018 ◽  
Vol 8 (11) ◽  
pp. 534 ◽  
Author(s):  
Konstantinos Nikolakopoulos ◽  
Paraskevi Lampropoulou ◽  
Elias Fakiris ◽  
Dimitris Sardelianos ◽  
George Papatheodorou
Keyword(s):  
Low Cost ◽  
Remote Sensing Data ◽  
Aegean Sea ◽  
Mineralogical Composition ◽  
Satellite System ◽  
Side Scan Sonar ◽  
Sonar System ◽  
Petrographic Analyses ◽  
Global Navigation Satellite ◽  
Area Monitoring

Up until the last ten years, remote sensing data and especially high-resolution satellite data and airphotos were mainly used in shallow water mapping. The evolution and low cost of unmanned aerial vehicles (UAVs) provides a new tool for coastal area monitoring. This paper presents the synergistic use of a small commercial UAV and an unmanned surface vehicle (USV) for beachrock mapping in Syros Island, Greece. RGB images collected with a quadcopter were processed using Structure from Motion (SFM) photogrammetry in order to create digital surface models (DSMs) and orthophotos of the coastline. A beachrock lying in shallow waters was detected and mapped using the UAV derived products. At the same time, a USV equipped with a compact side scan sonar (SSS) and bathymetric sonar system, provided the shape of the beachrock by mosaicking the backscatter strength of the SSS. In order to evaluate the results of the UAV and USV data derivatives, the beachrock perimeter and its depth were also mapped using a differential global navigation satellite system (GNSS) receiver. During the fieldwork, samples from the beachrock were collected and analyzed in the laboratory. The mineralogical composition of the bulk samples was determined by powder X-ray diffraction (XRD). Further petrographic study was also performed by petrographic polarizing microscope, macroscope, and scanning electron microscopy (SEM). Beachrock samples are classified as fine to medium grain sandstones and conglomerates. The mineral compositions of their grains and lithoclasts reflect the bedrocks of Syros Island (mainly metamorphic rocks) while a micritic high-Mg calcite constitutes the cement of these rocks.

scholarly journals Sparse GLONASS Signal Acquisition Based on Compressive Sensing and Multiple Measurement Vectors

2020 ◽  
Vol 2020 ◽  
pp. 1-11
Author(s):  
Guodong He ◽  
Maozhong Song ◽  
Shanshan Zhang ◽  
Peng Song ◽  
Xinwen Shu
Keyword(s):  
Compressive Sensing ◽  
Satellite System ◽  
New Method ◽  
Signal Acquisition ◽  
Multiple Measurement ◽  
Multiple Measurement Vectors ◽  
Navigation Data ◽  
Long Time ◽  
Global Navigation Satellite ◽  
Sparse Features

A sparse global navigation satellite system (GLONASS) signal acquisition method based on compressive sensing and multiple measurement vectors is proposed. The nonsparse GLONASS signal can be represented sparsely on our proposed dictionary which is designed based on the signal feature. Then, the GLONASS signal is sensed by a normalized orthogonal random matrix and acquired by the improved multiple measurement vectors acquisition algorithm. There are 10 cycles of pseudorandom codes in a navigation message, and these 10 pseudorandom codes have the same row sparse structure. So, the acquisition probability can be raised by row sparse features theoretically. A large number of simulated GLONASS signal experiments show that the acquisition probability increases with the increase in the measurement vector column dimension. Finally, the practical availability of the new method is verified by acquisition experiments with the real record GLONASS signal. The new method can reduce the storage space and energy loss of data transmission. We hope that the new method can be applied to field receivers that need to record and transmit navigation data for a long time.

scholarly journals Riverbed Mapping with the Usage of Deterministic and Geo-Statistical Interpolation Methods: The Odra River Case Study

2021 ◽  
Vol 13 (21) ◽  
pp. 4236
Author(s):  
Anna Uciechowska-Grakowicz ◽  
Oscar Herrera-Granados
Keyword(s):  
Interpolation Method ◽  
Absolute Error ◽  
Satellite System ◽  
Cross Sectional Survey ◽  
Cross Sectional ◽  
Interpolation Methods ◽  
River Bed ◽  
Odra River ◽  
Global Navigation Satellite

In this contribution, interpolation methods were assessed to build the bathymetry of 200 km of the Odra River in South Poland. The River Bed Mapping (RBM) was carried out surveying the depth of several reaches of the canalized part of the river using an Global Navigation Satellite System (GNSS) with an echo sounder as well as two navigation schemes. The values from the interpolation were compared with the data from a classical cross-sectional survey as part of the ISOK (Polish acronym for Information System of Country Protection Against Extraordinary Hazards) project. Two statistical errors between the interpolation values and the ISOK information were estimated, namely, the Mean Absolute Error (MAE) and the Root Mean Square Error (RMSE). Thanks to the presented analysis, it was possible to compare and analyze which interpolation method fits the best for the batymetric surveying of a shallow river. For this specific case study, the TIN (Triangular Irregular Network) and the NN (Natural Neighbor) methods generates the most accurate RBM.

scholarly journals Case study on complex sporadic E layers observed by GPS radio occultations

2014 ◽  
Vol 7 (9) ◽  
pp. 9203-9236 ◽  
Author(s):  
X. Yue ◽  
W. S. Schreiner ◽  
Z. Zeng ◽  
Y.-H. Kuo ◽  
X. Xue
Keyword(s):  
Satellite System ◽  
Time Interval ◽  
Long Distance ◽  
Shear Theory ◽  
Long Time ◽  
Distance Communication ◽  
Statistical Studies ◽  
Sporadic E ◽  
Global Navigation Satellite ◽  
Event Based

Abstract. The occurrence of sporadic E (Es) layer has been a hot scientific topic for a long time. Global Navigation Satellite System (GNSS) based Radio Occultation (RO) has been proven a powerful technique on detecting the global Es layers. In this paper, we focus on some cases of complex Es layers based on the RO data from multiple missions processed in UCAR/CDAAC. We first show some examples of multiple Es layers occurred in one RO event. Based on the evaluations between co-located simultaneous RO events and between RO and Lidar observations, it could be concluded that some of these do manifest the multiple Es layered structures. We then show a case of the occurrence of Es in a broad region during a certain time interval. The result is then validated by the independent ionosondes observations. These complex Es structures could be understood well by the popular wind shear theory. We could map the global Es occurrence routinely in the near future given that more RO data will be available. Further statistical studies will enhance our understanding on the Es mechanism. The specification on Es should benefit both the Es based long distance communication and accurate neutral RO retrievals.

scholarly journals A Navel Analysis of GNSS for Monitoring the Position of Trains

2018 ◽  
Vol 7 (3.27) ◽  
pp. 24
Author(s):  
P Yakaiah ◽  
K Nishanth Rao ◽  
S V.S. Prasad ◽  
G Ramesh Reddy ◽  
B Raveendranadh ◽  
...  
Keyword(s):  
Global Navigation Satellite System ◽  
Navigation System ◽  
Satellite System ◽  
Water Levels ◽  
Railway Track ◽  
Navigation Satellite ◽  
Global Navigation ◽  
Global Navigation Satellite ◽  
System 1

This Proposed paper using the technique of Navigation system that is Global navigation satellite system[1-2], which are usable to reach the trains in accurate time. The performance of these system is able analyze the based on reliability and maintainability. In this paper presented the operation of receiver navigation system, and also analyze the water levels on the railway track, and also identifying the accidents, and the information will be sent to respective registered mobiles.  

scholarly journals Uncertainty of Drone-Derived DEMs and Significance of Detected Morphodynamics in Artificially Scraped Dunes

2021 ◽  
Vol 13 (9) ◽  
pp. 1823
Author(s):  
Enrico Duo ◽  
Stefano Fabbri ◽  
Edoardo Grottoli ◽  
Paolo Ciavola
Keyword(s):  
Volume Change ◽  
Mean Squared Error ◽  
Morphological Changes ◽  
Winter Season ◽  
Satellite System ◽  
Water Levels ◽  
Data Uncertainty ◽  
Morphological Variations ◽  
Elevation Data ◽  
Global Navigation Satellite

This work capitalises on the morphodynamic study of a scraped artificial dune built on the sandy beach of Porto Garibaldi (Comacchio, Italy) as a barrier to protect the touristic facilities from sea storms during the winter season and contributes to understanding of the role of elevation data uncertainty and uniform thresholds for change detection (TCDs) on the interpretation of volume change estimations. This application relies on products derived from unmanned aerial vehicle (UAV) surveys and on the evaluation of the uncertainty associated with volume change estimations to interpret the case study morphodynamics under non-extreme sea and wind conditions. The analysis was performed by comparing UAV-derived digital elevation models (DEMs)—root mean squared error (RMSE) vs. global navigation satellite system (GNSS) < 0.05 m—and orthophotos, considering the significance of the identified changes by applying a set of TCDs. In this case, a threshold of ~0.15 m was able to detect most of the morphological variations. The set of TCD ≤ 0.15 m was considered to discuss the significance of minor changes and the uncertainty of volume change calculations. During the analysed period (21 December 2016–20 January 2017), water levels and waves affected the front of the artificial dune by eroding the berm area; winds remodelled the entire dune, moving the loose sand around the dune and further inland; sediment volumes mobilised by sea and wind forcing were comparable. This work suggests that UAV-derived coastal morphological variations should be interpreted by integrating: (i) a set of uniform thresholds to detect significant changes; (ii) the uncertainty generated by the propagation of the original uncertainty of the elevation products; (iii) the characteristics of the morphodynamic drivers evaluated by adopting uncertainty-aware approaches. Thus, the contribution of subtle morphological changes—magnitudes comparable with the instrumental accuracy and/or the assessed propagated uncertainty—can be properly accounted for.

scholarly journals Investigation of method of elimination of interference situation effect on GPS navigation receiver operation by smoothing of pseudorange measurements by pseudophase increment

2020 ◽  
pp. 46-53
Author(s):  
V. Y. Vovasov ◽  
D. A. Sukharev
Keyword(s):  
High Precision ◽  
Experimental Studies ◽  
Satellite System ◽  
Mobile Object ◽  
Time Interval ◽  
Urgent Task ◽  
Long Time ◽  
The Difference ◽  
Navigation Signals ◽  
Global Navigation Satellite

The wide application of high-precision GNSS (global navigation satellite system) positioning technologies for unmanned mobile object management requires the acquisition of solutions with subdecimeter accuracy and the reduction of the convergence period to such accuracy from the beginning of measurements to 20–25 minutes. Unfortunately, the accuracy of the obtained navigation solutions and the time of convergence to high-precision solutions are influenced by re-reflection of GNSS signals from the ground, buildings and structures, as well as interference from different sources of radio emissions of the urban environment. Therefore, it is an urgent task to implement methods of eliminating the influence of the interference situation on the operation of the navigation receiver of GNSS signals and investigating their effectiveness. The paper considers the results of investigation of the method of elimination of interference situation effect on GPS signal navigation receiver operation using smoothing of raw pseudorange measurements by pseudophase increment. Justification of the difference of measurement of pseudo-range by carrier phase and pseudo-range by code is given as a criterion of efficiency of estimation of interference situation influence in the area of navigation signals reception. As a result of the analysis of experimental studies, it has been shown that using the described method, starting from 900 seconds, the values of the smoothed parameter do not deviate from the averaged measurements over a long time interval by more than 0.1 meters, which indicates the efficiency of the method of smoothing by phase increments and is potentially promising for highly accurate measurements.

scholarly journals 2-D Coherent Integration Processing and Detecting of Aircrafts Using GNSS-Based Passive Radar

2018 ◽  
Vol 10 (7) ◽  
pp. 1164 ◽  
Author(s):  
Hong-Cheng Zeng ◽  
Jie Chen ◽  
Peng-Bo Wang ◽  
Wei Yang ◽  
Wei Liu
Keyword(s):  
Matched Filter ◽  
Power Level ◽  
Doppler Frequency ◽  
Satellite System ◽  
Passive Radar ◽  
Match Filter ◽  
Coherent Integration ◽  
Long Time ◽  
Global Navigation Satellite ◽  
Aircraft Detection

Long time coherent integration is a vital method for improving the detection ability of global navigation satellite system (GNSS)-based passive radar, because the GNSS signal is not radar-designed and its power level is very low. For aircraft detection, the large range cell migration (RCM) and Doppler frequency migration (DFM) will seriously affect the coherent processing of azimuth signals, and the traditional range match filter will also be mismatched due to the Doppler-intolerant characteristic of GNSS signals. Accordingly, the energy loss of 2-dimensional (2-D) coherent processing is inevitable in traditional methods. In this paper, a novel 2-D coherent integration processing and algorithm for aircraft target detection is proposed. For azimuth processing, a modified Radon Fourier Transform (RFT) with range-walk removal and Doppler rate estimation is performed. In respect to range compression, a modified matched filter with a shifting Doppler is applied. As a result, the signal will be accurately focused in the range-Doppler domain, and a sufficiently high SNR can be obtained for aircraft detection with a moving target detector. Numerical simulations demonstrate that the range-Doppler parameters of an aircraft target can be obtained, and the position and velocity of the aircraft can be estimated accurately by multiple observation geometries due to abundant GNSS resources. The experimental results also illustrate that the blind Doppler sidelobe is suppressed effectively and the proposed algorithm has a good performance even in the presence of Doppler ambiguity.

scholarly journals Case study on complex sporadic E layers observed by GPS radio occultations

2015 ◽  
Vol 8 (1) ◽  
pp. 225-236 ◽  
Author(s):  
X. Yue ◽  
W. S. Schreiner ◽  
Z. Zeng ◽  
Y.-H. Kuo ◽  
X. Xue
Keyword(s):  
Satellite System ◽  
Time Interval ◽  
Long Distance ◽  
Shear Theory ◽  
Layer Structures ◽  
Long Time ◽  
Distance Communication ◽  
Sporadic E ◽  
Global Navigation Satellite ◽  
Event Based

Abstract. The occurrence of sporadic E (Es) layers has been a hot scientific topic for a long time. The GNSS (global navigation satellite system)-based radio occultation (RO) has proven to be a powerful technique for detecting the global Es layers. In this paper, we focus on some cases of complex Es layers based on the RO data from multiple missions processed in UCAR/CDAAC (University Corporation for Atmospheric Research (UCAR) the Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) Data Analysis and Archive Center (CDAAC)). We first show some examples of multiple Es layers occurred in one RO event. Based on the evaluations between colocated simultaneous RO events and between RO and lidar observations, it could be concluded that some of these do manifest the multiple Es layer structures. We then show a case of the occurrence of Es in a broad region during a certain time interval. The result is then validated by independent ionosondes observations. It is possible to explain these complex Es structures using the popular wind shear theory. We could map the global Es occurrence routinely in the near future, given that more RO data will be available. Further statistical studies will enhance our understanding of the Es mechanism. The understanding of Es should benefit both Es-based long-distance communication and accurate neutral RO retrievals.

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