Global Navigation Satellite Systems (GNSS) have revolutionized land surveying, by determining position coordinates with centimeter-level accuracy in real-time or up to sub-millimeter accuracy in post-processing solutions. Although low-cost single-frequency receivers do not meet the accuracy requirements of many surveying applications, multi-frequency hardware is expected to overcome the major issues. Therefore, this paper is aimed at investigating the performance of a u-blox ZED-F9P receiver, connected to a u-blox ANN-MB-00-00 antenna, during multiple field experiments. Satisfactory signal acquisition was noticed but it resulted as >7 dB Hz weaker than with a geodetic-grade receiver, especially for low-elevation mask signals. In the static mode, the ambiguity fixing rate reaches 80%, and a horizontal accuracy of few centimeters was achieved during an hour-long session. Similar accuracy was achieved with the Precise Point Positioning (PPP) if a session is extended to at least 2.5 h. Real-Time Kinematic (RTK) and Network RTK measurements achieved a horizontal accuracy better than 5 cm and a sub-decimeter vertical accuracy. If a base station constituted by a low-cost receiver is used, the horizontal accuracy degrades by a factor of two and such a setup may lead to an inaccurate height determination under dynamic surveying conditions, e.g., rotating antenna of the mobile receiver.
No abstract
EPOS-PL+ is the Polish national realization of the European Plate Observing System (EPOS) project that aims to build a multidisciplinary infrastructure. It allows integration of a variety of geoscience expertise and techniques to better understand the geohazard related to the underground mining of coal in the Upper Silesian Coal Basin (USCB) in Poland. The study case in this project is the Marcel Mine, located within USCB, where the detected subsidence for the analyzed period of four months reaches 91 cm. Various interferometric processing techniques demonstrated some advantages and also some limitations in the context of mining deformation measurement, including accuracy, spatial resolution, detectable deformation rate, atmospheric delay, and ability to detect the maximal deformation gradients. This is especially important from a mining perspective. Therefore, we investigated three different interferometric processing techniques to monitor fast mining deformation in the Marcel hard coal mine area. More specifically, we used conventional DInSAR, Small Baseline Subsets (SBAS), and Persistent Scattered Interferometry (PSInSAR). The result confirmed that none of these methods can be considered as the best. The DInSAR approach allows capturing the maximal deformation gradient, which was not possible with the PSInSAR and SBAS approaches. On the contrary, PSInSAR and SBAS allow us to provide less noisy and reliable results in the area of safety pillars.
Abstract. Mining-induced deformations are characterized by high deformation rates. These deformations consist of both vertical and horizontal components, which should not be neglected during the monitoring of such areas. Unfortunately, Differential Satellite Synthetic Aperture Radar Interferometry (DInSAR) can only measure deformations in the line of sight (LOS) direction towards the satellite. Combining data from ascending and descending geometry allows reconstruction of the vertical and east-west deformation components. Theoretically, at least information from one ascending and one descending geometry is enough to reconstruct the vertical and east-west deformation components; however, for the area of interest three various Sentinel-1 datasets (one ascending and two descending) are available and have been used in the study. Furthermore, considering the availability of other SAR missions with slightly different geometries, the objective of this study was to evaluate the effect of ALOS-2 use on the accuracy of estimating the east-west and vertical cumulative deformation component estimated for a time span of approximately one year. Unfortunately, we have access to only five ALOS-2 scenes within the area of interest. However, the comparison of the decomposed results with GNSS measurements shows that the application of additional ALOS-2 data, even five scenes, allows the root mean square error (RMSE) to be decreased for the vertical and horizontal deformation component from 0.038m to 0.032m and from 0.031m to 0.018m, respectively. This means that the application of ALOS-2 data has a positive value on the accuracy of decomposed vertical and horizontal deformation components.
<p>The EPOS-PL project is the Polish realization of the European Plate Observing System (EPOS) initiative, which aims at the integration of existing and newly created research infrastructures to facilitate the use of multidisciplinary data and products in the field of Earth sciences in Europe. Within the EPOS, one of the tasks aims at SAR data utilization for deformation monitoring in the area of Rydu&#322;towy mine. The Rydu&#322;towy mine is the oldest active mining in the Upper Silesia Coal Basin in Poland. In the area of this mine, five Corner Reflectors (CRs) have been deployed in the framework of the EPOS- PL. Additionally, in the area of interest one high-frequency GNSS receiver working permanently has been placed. This GNSS permanent station (RES100POL) enables estimating of deformation time-series based on multi-GNSS observation in post-processing.</p><p>In this study, we use Sentinel-1A/B TOPSAR images acquired between 25 June 2018 and 14 July 2019 in one ascending and two descending geometries with revisiting time of 6-days. Additionally, we use ground truths of two leveling and GNSS measurement campaigns carried out to precisely estimate deformations on five CRs (2<sup>nd</sup>-4<sup>th</sup> of July 2018 and 28<sup>th</sup>-30<sup>th</sup> of June 2019). GNSS static measurements were carried out via three independent measurement sessions. Coordinates of the station RES100POL and static GNSS and leveling measurements ware were used for validation of SAR measurements.</p><p>SAR data has been processed by means of classical consecutive Differential Interferometry (DInSAR) as well as Persistent Scattering (PSInSAR) approach. During SAR data processing, snow coverage accumulated on the CRs caused that some Sentinel-1 images from the winter season have been removed from DInSAR as well as PSInSAR processing. Results from ascending and descending orbits allow the estimation of vertical as well as east-west deformation components. Root Mean Square Error (RMSE) between CRs measured by conventional geodetic techniques and DInSAR was estimated as 31mm and 38mm for east-west and vertical deformation components, respectively. RMSE measured between PSInSAR and GNSS was estimated as 5mm and 7mm for east-west and vertical components, respectively. RMSE of 15mm and 3mm was estimated for DInSAR with respect to GNSS from RES100POL station for east-west and vertical components, respectively. Subsequently, RMSE of 4mm and 5mm was estimated as deformation time variations between PSInSAR and GNSS from RES1 station for east-west and vertical components, respectively. These measures indicate clearly the advantage of the PSInSAR method. However, &#160;the PSInSAR approach was able to estimate deformations only for three CRs due to the fast and non-linear deformation pattern observed on other two CRs.</p>
<p>Monitoring the deformation of the mining ground surface is crucial to ensuring the safety of residents, workers and the protection of all infrastructure in mining areas.The Polish realization of the European Plate Observing System project (EPOS-PL and its continuation EPOS-PL+) aims to build an infrastructure to monitor the deformation of the ground surface caused by extensive underground mining activities in the area of Upper Silesian Coal Basin in Southern Poland.&#160; Among many geodetic and geophysical approaches for monitoring, two different Interferometric Synthetic Aperture Radar (InSAR) techniques have been applied, also taking the advantage of the big set of freely available and with shorter revisiting time (6 days) Sentinel-1 satellite data. In the current study the Differential InSAR (DInSAR) and the Persistent Scattered Interferometry (PSInSAR) approaches are compared, evaluated and integrated. Various processing strategies are tested aiming to increase the quality of the produced integrated deformation maps. The optimal processing strategy should accurately detect stable areas, estimate the small deformation, as well as the maximum deformation gradient occurring in the center of the subsidence bowl directly in the excavation area.&#160;</p><p>One of the main error contributors to the Sentinel-1 data is the water vapor in the atmosphere that might slower the radar signal and modulate the results. Thus, the atmospheric artefacts have to be minimized since they are one of the main effects that limits the accuracy of interferometric products. In the PSInSAR approach high-pass and low-pass filtering has been used, while in the DInSAR approach &#8211; estimation of the Atmospheric Phase Screen has been made based on polynomial surface estimation using stable coherent points. Comparison of the one-year cumulated deformation for the area of Rydu&#322;towy mine in Poland with ground truth data such as static GNSS measurement on reference points shows that PSInSAR results are more accurate. However, due to the linear deformation model required in the PSInSAR processing the areas in the center of the subsidence bowls were not estimated. Therefore, the difference between PSInSAR and DInSAR results was used for the refinement of the DInSAR deformation map. This refinement was made based on various statistical approaches (e.g. polynomial interpolation, kriging, inverse distance weighted-IDW). The results of IDW and kriging shows the best performance and allowed to minimize errors associated with DInSAR approach and provide a more accurate deformation map in the area of mining as well as provided the opportunity to capture maximal deformation gradient.&#160;</p>
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