Differential Global Positioning Research Articles

Monitoring of large-scale deformation in mining areas using sub-band InSAR and the probability integral fusion method

ABSTRACTThe large-scale and rapid land subsidence that occurs in mining areas often leads to problems, such as densely spaced interference fringes and the temporal decorrelation of interferometric synthetic aperture radar (InSAR) interferograms. To solve these problems, sub-band InSAR is applied to monitor the large-scale deformation that occurs in mining areas. First of all, four different bandwidth images with three sub-band bandwidth parameters are used to extract simulated mining-induced subsidence with seven different deformation magnitudes. The results of the simulation experiment suggest the following conclusions. In monitoring subsidence with different deformation magnitudes using images with different bandwidths, an optimal monitoring value exists; wider image bandwidths lead to smaller optimal monitoring values and higher monitoring accuracies. Therefore, an appropriate sub-band bandwidth should be selected that depends upon the image bandwidth and the subsidence level to achieve optimal monitoring. The optimal sub-band bandwidth for monitoring subsidence of different magnitudes in mining areas is determined through simulation experiments, and these conclusions can provide a technical basis for selecting the appropriate sub-band bandwidth for the monitoring of subsidence in mining areas. Although sub-band InSAR can reduce the number of interference fringes and the difficulty of unwrapping, the simultaneous introduction of large amounts of noise leads to reduced monitoring precision, and the application of the probability integral method in the prediction of mine subsidence is more mature. Therefore, the combined use of sub-band InSAR and the probability integral fusion method to monitor mining-induced deformation is proposed in this paper. The probability integral method is used to perform noise peeling on the interferometric phases of the sub-bands to improve the monitoring accuracy of sub-band interferometry. Then, according to the results of the simulation experiment, the fusion method with the appropriate sub-band bandwidth parameters is applied to monitor the surface deformation associated with working face 52,304 from 2 December 2012 to 13 December 2012. Finally, the monitoring results are compared with the results of monitoring using conventional differential interferometric synthetic aperture radar (D-InSAR) and global positioning system (GPS) field survey data. The results show that the reliability and accuracy of the fusion method are much better than those of conventional D-InSAR in monitoring the large-scale deformation that occurs at the edges of subsidence basins.

Performance evaluation of the Ordinary Least Square (OLS) and Total Least Square (TLS) in adjusting field data: an empirical study on a DGPS data

Survey measurements have become the traditional means of obtaining point positions by most surveyors over the centuries. The assertion that a post processed DGPS field data is precise, accurate and can be used to execute any engineering works due to its minimum human errors need to be reviewed; this is because the post processed field data still contains errors and needs to be adjust. Adjustments and computations is one of the main research field in mathematical and satellite geodesy to assess the magnitude of errors and to study their distributions whether they are within or not within the acceptable tolerance. In order to achieve the objective of this study, a DGPS field data was adjusted using the Ordinary Least Square (OLS) and Total Least Square (TLS) techniques. The OLS considers errors only in the observation matrix, and adjusts observations in order to make the sum of its residuals minimum. The TLS considers errors in both the observation matrix and the data matrix, thereby minimizing the errors in both matrices. The limited availability of information on OLS and TLS in adjusting DGPS field data and the uncertainty of which method is optimal, whether the OLS and TLS is the most appropriate technique has called for the need to undertake this study. This study aimed at comparing the working efficiency of the OLS and TLS, assessing their individual accuracy and selecting the most effective method in adjusting DGPS field data. Each model was assessed based on statistical indicators of mean horizontal error (MHE), mean bias error (MBE), mean absolute error (MAE), root mean square error (RMSE), and standard deviation (SD). After applying the OLS and TLS methods independently for the same datasets, it was ascertained that, the OLS method was better in adjusting DGPS field data than the TLS with a MHE and SD of +1.203079 m and +1.663134 m as compared to TLS with MHE and SD of +7.0985507 m and +2.594045 m respectively. This study will therefore create opportunity for geospatial professionals to know the efficiency of OLS and TLS in solving some of the problems in mathematical and satellite geodesy.Keywords: Differential Global Positioning, System, Total Least Square, Ordinary Least Square, Survey Adjustments, Horizontal Position Displacement

안전주행을 위한 DGPS/GIS 기반의 차량제어 연구

In recent days, vehicles have become equipped with electric systems that assist and help drivers driving safe by reducing possible accidents. LDWS(Lane Departure Warning System) and LKAS(Lane Keeping Assistant System) are involved in assist systems, especially for lateral motion of vehicles. Sudden and inattentive lateral motion of vehicles due to drivers' fatigue, illness, inattention, and drowsiness are major causes of accidents in highway. LDWS and LKAS provide drivers with warnings or assisting power to reduce any possibilities of accidents. In order to prevent or minimize the possibilities of accidents, lateral motion control of vehicles has been introduced in this research. DGPS/RTK(Differential Global Positioning System/Real Time Kinematics) and GIS(Geographic Information System) have been used to obtain the current position of vehicles and decide when activate controlling lateral motion of vehicles. The presented lateral motion control has been validated with actual vehicle tests.

Mapping simulated scenes with skeletal remains using differential GPS in open environments: An assessment of accuracy and practicality

Scene mapping is an integral aspect of processing a scene with scattered human remains. By utilizing the appropriate mapping technique, investigators can accurately document the location of human remains and maintain a precise geospatial record of evidence. One option that has not received much attention for mapping forensic evidence is the differential global positioning (DGPS) unit, as this technology now provides decreased positional error suitable for mapping scenes. Because of the lack of knowledge concerning this utility in mapping a scene, controlled research is necessary to determine the practicality of using newer and enhanced DGPS units in mapping scattered human remains. The purpose of this research was to quantify the accuracy of a DGPS unit for mapping skeletal dispersals and to determine the applicability of this utility in mapping a scene with dispersed remains. First, the accuracy of the DGPS unit in open environments was determined using known survey markers in open areas. Secondly, three simulated scenes exhibiting different types of dispersals were constructed and mapped in an open environment using the DGPS. Variables considered during data collection included the extent of the dispersal, data collection time, data collected on different days, and different postprocessing techniques. Data were differentially postprocessed and compared in a geographic information system (GIS) to evaluate the most efficient recordation methods. Results of this study demonstrate that the DGPS is a viable option for mapping dispersed human remains in open areas. The accuracy of collected point data was 11.52 and 9.55cm for 50- and 100-s collection times, respectfully, and the orientation and maximum length of long bones was maintained. Also, the use of error buffers for point data of bones in maps demonstrated the error of the DGPS unit, while showing that the context of the dispersed skeleton was accurately maintained. Furthermore, the application of a DGPS for accurate scene mapping is discussed and guidelines concerning the implementation of this technology for mapping human scattered skeletal remains in open environments are provided.

항공기에 탑재된 DGPS/INS 복합항법 장치의 비행 시험 성능 평가를 위한 기준궤적의 Lever Arm 보정

항공 산업의 발전에 따라 정밀하고 신뢰성 높은 항법 정확도를 제공하기 위하여 DGPS/INS 복합항법 장치에 대한 많은 연구가 수행되고 있다. 이러한 항법 시스템의 항법 정확도는 항공기의 안전성과 신뢰성에 직접적인 영향을 끼치기 때문에 항법 시스템의 비행시험 검증은 매우 중요하다. 특히 DGPS/INS 복합항법 장치와 같은 높은 수준의 위치 정확도를 가지는 항법시스템을 검증하기 위해서는 보다 정확한 비행 항법 성능 평가기법이 필요하다. 항법 성능 검증은 DGPS/INS보다 정밀한 항법 정확도를 가지는 기준 궤적과의 비교 분석을 통해 이루어지며 기준 수신기는 수 cm수준의 CDGPS 후처리 기법이 가능한 GPS 수신기를 사용해야 한다. 일반적으로 DGPS/INS 복합항법 장치의 출력 점은 항공기의 무게중심점으로 GPS 안테나의 위치를 출력하는 GPS 수신기와 다르기 때문에 출력데이터의 가공없이 성능 평가를 진행할 경우 추정 오차에 안테나 위치와 항공기의 무게중심점간 거리 오차가 포함된다. 따라서 보다 정확한 항법 성능 평가를 위하여 기준 궤적 생성을 위한 GPS 수신기의 Lever Arm 보정이 필요하다. 본 논문에서는 DGPS/INS 복합항법장치의 비행항법 성능 검증을 위하여 기준궤적의 Lever Arm 보정을 포함한 비행시험 성능평가 절차 및 비행 시험 결과를 제시한다. It has been studied for DGPS/INS(Differential Global Positioning System/Inertial Navigation System) to offer the more precise and reliable navigation data with the aviation industry development. The flight performance evaluation of navigation system is very significant because the reliability of navigation data directly affect the safety of aircraft. Especially, the high-level navigation system, as DGPS/INS, need more precise flight performance evaluation method. The performance analysis is performed by comparing between the DGPS/INS navigation data and reference trajectory which is more precise than DGPS/INS. The GPS receiver, which is capable of post-processed CDGPS(Carrier-phase DGPS) method, can be used as reference system. Generally, the DGPS/INS is estimated the CG(Center of Gravity) point of aircraft while the reference system is output the position of GPS antenna which is mounted on the outside of aircraft. For this reason, estimated error between DGPS/INS and reference system will include the error due to lever arm. In order to more precise performance evaluation, it is needed to compensate the lever arm. This paper presents procedure and result of flight test which includes lever arm compensation in order to verify reliability and performance of DGPS/INS more precisely.

Automated Road Sign Inventory System Based on Stereo Vision and Tracking

Detection, recognition, and positioning of road signs are critical components of a roadway asset management system. In this research, a stereo vision- based system is developed to conduct automated road sign inventory. The system in real time integrates and synchronizes the data streams from multiple sensors of high-resolution cameras, Differential Global Position- ing System receivers, Distance Measurement Instrument, and Inertial Measurement Unit. Algorithms are devel- oped based on data sets from the multiple positioning sensors to determine the positions of the moving vehi- cle and the orientation of the cameras. The key findings from the research include feature extraction and analysis that are applied for automated sign detection and recog- nition in the Right-of-Way (ROW) images, implementing a tracking algorithm of the candidate sign region among the image frames so the same signs are not counted more than once in an image sequence, and implementing stereo vision technique to compute the world coordinates of the road sign from the stereo-paired ROW images. Particu- lar techniques are employed to conduct all data acquisi- tion and analysis in real time onboard the vehicle. This system is an advanced alternative to traditional inventory methods in terms of safety and efficiency.

Integrating advanced technologies for optimization of aerial herbicide applications

Aerial application of herbicides continues to be a dominant method of vegetation control in Canadian forest management. In this paper, we describe a suite of relatively modern technologies and emphasize their potential for integrated use in optimization of aerial herbicide treatments. The potential is illustrated using several case studies involving fixed-wing applications of glyphosate-based herbicide in the boreal forest region of Ontario, Canada. Results indicate that integration of geographic information systems, differential global positioning, electronic-guidance, on-site meteorological monitoring and remote sensing can be used to effectively plan, enhance application control and provide detailed post-treatment assessment and archival data for herbicide spray programs. SprayAdvisor, a GIS-based decision support system with the capacity to directly integrate all of these elements is briefly described.

Multi-Unmanned Aerial Vehicle (UAV) Cooperative Fault Detection Employing Differential Global Positioning (DGPS), Inertial and Vision Sensors

This paper presents a method to increase the reliability of Unmanned Aerial Vehicle (UAV) sensor Fault Detection and Identification (FDI) in a multi-UAV context. Differential Global Positioning System (DGPS) and inertial sensors are used for sensor FDI in each UAV. The method uses additional position estimations that augment individual UAV FDI system. These additional estimations are obtained using images from the same planar scene taken from two different UAVs. Since accuracy and noise level of the estimation depends on several factors, dynamic replanning of the multi-UAV team can be used to obtain a better estimation in case of faults caused by slow growing errors of absolute position estimation that cannot be detected by using local FDI in the UAVs. Experimental results with data from two real UAVs are also presented.

The long-term stability of survey monuments in permafrost

Monitoring the geological movements in areas of continuous permafrost requires that the surface movement due to the seasonal variation in the permafrost active layer be isolated from the underlying trend. Two potential ways of achieving this is to model the heave/settlement of the surface due to seasonal thaw/refreeze so that surface measurements can be utilised, or to place survey monuments that do not respond to the active layer and make point observations. This paper describes the requirements for monitoring natural trend and subsidence due to gas extraction in areas of the Mackenzie Delta/Beaufort Sea region of Canada, an area of continuous permafrost. Different solutions based on Differential Interferometric SAR and Differential Global Positioning are proposed to the monitoring problem based on the two methods of isolating the effects of permafrost movement described above. This paper reports on research undertaken to discover the long-term stability of survey monuments established in a test-bed in the area of the proposed gas extraction. Seven types of monument are present, with records of height variation available between 1987 and 1995. Two further epochs of measurement were made in 2003 and 2004, allowing analysis of a 17-year period to be made. Analysis of the data showed that only one type of monument displayed the required stability to model natural trend and subsequently to predict this trend in the analysis of subsidence caused by gas extraction.

TOPEX orbit determination and gravity recovery using global positioning system data from repeat orbits

A covariance analysis is presented for satellite tracking and gravity recovery with a differential Global Positioning System‐based technique to be demonstrated on TOPEX in the early 1990s. The technique employs data from an ensemble of repeat ground tracks to recover a unique satellite epoch state for each track and a set of invariant positional parameters common to all tracks. The positional parameters represent the effect of mismodeled gravitational field on the satellite orbit. At an altitude of 1336 km, where gravity modeling is the dominant systematic error, averaging of random error over many arcs and adjustment of the gravity model reduce the final satellite position error. The positional parameters can then be used to produce a refined global gravity model. The analysis indicates that errors ranging from 5 to 8 cm in TOPEX altitude and 0.05 to 0.2 mGal for the gravity field can be achieved, depending on the number of repeat arcs used.