Global Positioning System Techniques Research Articles

Sustainable Surface Deformation Related with 2006 Augustine Volcano Eruption in Alaska Measured Using GPS and InSAR Techniques

Augustine volcano, located along the Aleutian Arc, is one of the most active volcanoes in Alaska and nearby islands, with seven eruptions occurring between 1812 and 2006. This study monitored the surface displacement before and after the most recent 2006 eruption. For analysis, we conducted a time-series analysis on data observed at the permanent GPS(Global Positioning System) observation stations in Augustine Island between 2005 and 2011. According to the surface displacement analysis results based on GPS data, the movement of the surface inflation at the average speed of 2.3 cm/year three months prior to the eruption has been clearly observed, with the post-eruption surface deflation at the speed of 1.6 cm/year. To compare surface displacements measurement by GPS observation, ENVISAT(Environmental satellite) radar satellite data were collected between 2003 and 2010 and processed the SBAS(Small Baseline Subset) method, one of the time-series analysis techniques using multiple InSAR(Interferometric Synthetic Aperture Radar) data sets. This result represents 0.97 correlation value between GPS and InSAR time-series surface displacements. This research has been completed precise surface deformation using GPS and time-series InSAR methods for a detection of precursor symptom on Augustine volcano.

Positional Accuracy Assessment for Effective Shoreline Change Analyses

The usefulness of any geographic data depends on its fitness for a particular purpose. The critical measure of that fitness is referred to as data quality. Data quality may be expressed in terms of several indicators such as attributes, temporal or positional accuracies. In this research, positional accuracy assessment was carried out on two datasets using Root Mean Square Error (RMSE) technique. Coordinates of nineteen ground controls points were measured in the field using Differential Global Positioning System technique which served as a reference base. The coordinates of these points were compared with their corresponding positions extracted from the two datasets, Town Sheet (1: 2500) and orthophoto (1: 5000). The Town Sheet was scanned, rescaled (1:5000) and georeferenced in Ghana Meter Grid coordinate system to conform to the orthophoto. The digitised Town Sheet and the reference base were superimposed with the orthophoto serving as backdrop in GIS environment. Positional error of 1.23 m was obtained for points extracted from the Town Sheet, while an error of 2.79 m was registered for points from the orthophoto. Shoreline features extracted from these two datasets and appended for shoreline change analysis recorded a total positional error of 3.98 m. The study has shown that the original scale (large) of the Town Sheet may have contributed significantly to the quality of data extracted. In the orthophoto, though geometrically rectified, the scale representation of a unit measure on the photo explains the uncertainties in the dataset. The integrated dataset obviously bore the cumulative effect of the input datasets. It is concluded that for the purpose of shoreline change analysis, such as shoreline change trends, large scale data sources should be used where possible for accurate decision-making. It is recommended that the positional accuracy of any spatial data be ascertained before using it to support decision. Keywords : Positional Accuracy, Shoreline Change, Differential GPS, Root Mean Squared Error, Orthophoto

Positional Accuracy Assessment for Effective Shoreline Change Analyses

The usefulness of any geographic data depends on its fitness for a particular purpose. The critical measure of that fitness is referred to as data quality. Data quality may be expressed in terms of several indicators such as attributes, temporal or positional accuracies. In this research, positional accuracy assessment was carried out on two datasets using Root Mean Square Error (RMSE) technique. Coordinates of nineteen ground controls points were measured in the field using Differential Global Positioning System technique which served as a reference base. The coordinates of these points were compared with their corresponding positions extracted from the two datasets, Town Sheet (1: 2500) and orthophoto (1: 5000). The Town Sheet was scanned, rescaled (1:5000) and georeferenced in Ghana Meter Grid coordinate system to conform to the orthophoto. The digitised Town Sheet and the reference base were superimposed with the orthophoto serving as backdrop in GIS environment. Positional error of 1.23 m was obtained for points extracted from the Town Sheet, while an error of 2.79 m was registered for points from the orthophoto. Shoreline features extracted from these two datasets and appended for shoreline change analysis recorded a total positional error of 3.98 m. The study has shown that the original scale (large) of the Town Sheet may have contributed significantly to the quality of data extracted. In the orthophoto, though geometrically rectified, the scale representation of a unit measure on the photo explains the uncertainties in the dataset. The integrated dataset obviously bore the cumulative effect of the input datasets. It is concluded that for the purpose of shoreline change analysis, such as shoreline change trends, large scale data sources should be used where possible for accurate decision-making. It is recommended that the positional accuracy of any spatial data be ascertained before using it to support decision. Keywords: Positional Accuracy, Shoreline Change, Differential GPS, Root Mean Squared Error, Orthophoto

Analysis of meteorological variables in the Australasian region using ground- and space-based GPS techniques

Results of analysis of meteorological variables (temperature and moisture) in the Australasian region using the global positioning system (GPS) radio occultation (RO) and GPS ground-based observations verified with in situ radiosonde (RS) data are presented. The potential of using ground-based GPS observations for retrieving column integrated precipitable water vapour (PWV) over the Australian continent has been demonstrated using the Australian ground-based GPS reference stations network. Using data from the 15 ground-based GPS stations, the state of the atmosphere over Victoria during a significant weather event, the March 2010 Melbourne storm, has been investigated, and it has been shown that the GPS observations has potential for monitoring the movement of a weather front that has sharp moisture contrast. Temperature and moisture variability in the atmosphere over various climatic regions (the Indian and the Pacific Oceans, the Antarctic and Australia) has been examined using satellite-based GPS RO and in situ RS observations. Investigating recent atmospheric temperature trends over Antarctica, the time series of the collocated GPS RO and RS data were examined, and strong cooling in the lower stratosphere and warming through the troposphere over Antarctica has been identified, in agreement with outputs of climate models. With further expansion of the Global Navigation Satellite Systems (GNSS) system, it is expected that GNSS satellite- and ground-based measurements would be able to provide an order of magnitude larger amount of data which in turn could significantly advance weather forecasting services, climate monitoring and analysis in the Australasian region.

Flight-Test Evaluation of Kinematic Precise Point Positioning of Small UAVs

An experimental analysis of Global Positioning System (GPS) flight data collected onboard a Small Unmanned Aerial Vehicle (SUAV) is conducted in order to demonstrate that postprocessed kinematic Precise Point Positioning (PPP) solutions with precisions approximately 6 cm 3D Residual Sum of Squares (RSOS) can be obtained on SUAVs that have short duration flights with limited observational periods (i.e., only ~≤5 minutes of data). This is a significant result for the UAV flight testing community because an important and relevant benefit of the PPP technique over traditional Differential GPS (DGPS) techniques, such as Real-Time Kinematic (RTK), is that there is no requirement for maintaining a short baseline separation to a differential GNSS reference station. Because SUAVs are an attractive platform for applications such as aerial surveying, precision agriculture, and remote sensing, this paper offers an experimental evaluation of kinematic PPP estimation strategies using SUAV platform data. In particular, an analysis is presented in which the position solutions that are obtained from postprocessing recorded UAV flight data with various PPP software and strategies are compared to solutions that were obtained using traditional double-differenced ambiguity fixed carrier-phase Differential GPS (CP-DGPS). This offers valuable insight to assist designers of SUAV navigation systems whose applications require precise positioning.

Comparisons of Ground-Based and Building-Based CORS: A Case Study in the Region of Puerto Rico and the Virgin Islands

AbstractThis study investigated long-term observations from three pairs of closely spaced, continuously operating reference stations (CORS): STVI and VITH (2008–2014, 0.6 km apart), BYSP and PRHL (2008–2014, 3.2 km apart), and CRO1 and VIKH (1995–2014, 23 km apart), in the region of Puerto Rico and Virgin Islands. The Global Positioning System (GPS) antennas of STVI, BYSP, and CRO1 are mounted on ground-based monuments. The GPS antennas of VITH, PRHL, and VIKH are mounted on building-based monuments. This study indicated that there is no considerable difference between building-based and ground-based CORS with regard to the precision of daily positions and the reliability of long-term site velocities. The amplitude of thermal movements associated with daily temperature changes and the wind drift associated with air pressure change from a 2-story concrete building fell below the detectable levels of the present high-precision GPS technique determined by Precise Point Positioning (PPP) processing. Further a...

Bridge Performance Assessment Based on an Adaptive Neuro-Fuzzy Inference System with Wavelet Filter for the GPS Measurements

This study describes the performance assessment of the Huangpu Bridge in Guangzhou, China based on long-term monitoring in real-time by the kinematic global positioning system (RTK-GPS) technique. Wavelet transformde-noising is applied to filter the GPS measurements, while the adaptive neuro-fuzzy inference system (ANFIS) time series output-only model is used to predict the deformations of GPS-bridge monitoring points. In addition, GPS and accelerometer monitoring systems are used to evaluate the bridge oscillation performance. The conclusions drawn from investigating the numerical results show that: (1)the wavelet de-noising of the GPS measurements of the different recording points on the bridge is a suitable tool to efficiently eliminate the signal noise and extract the different deformation components such as: semi-static and dynamic displacements; (2) the ANFIS method with two multi-input single output model is revealed to powerfully predict GPS movement measurements and assess the bridge deformations; and (3) The installed structural health monitoring system and the applied ANFIS movement prediction performance model are solely sufficient to assure bridge safety based on the analyses of the different filtered movement components.

Optimal Location Determination of Some Public Facilities within Minna Metropolis: A Geospatial Technique Approach

Theoretical frameworks used to explain the location of services include central place theory, aspects of industrial location theory and spatial diffusion theory. They are all described as normative theories which optimize with respect to defined criteria operating in prescribed environmental conditions (Rushton, 1979). However, recent advancement in geospatial technologies has led to several applications in geographically orientated challenges, hence, the adoption of an effective decision tool like Geographic Information System (GIS), high resolution products of satellite remote sensing as well as the Global Positioning System (GPS) in solving the rather challenging task of optimal location for facilities with respect to necessary criteria. Minna metropolis is being affected adversely by the problem of appropriate location of public facilities. These facilities are either too far from their market zone or they are too congested in a particular location and in some cases, political consideration to the siting of these facilities dominate without given considerations to the necessary criteria for demands and public interest. The study is an investigation into the “optimal determination of the locations of some public facilities in Minna metropolis of Niger State, using geospatial techniques”. The fusion of remote sensing, geographic information system (GIS) and GPS techniques was explored. Geodata base of existing facilities was created and Euclidean-distance geometry used to spatially analyze the appropriate locations with regards to the set of standard criteria. The results showed the haphazard and uncontrolled pattern of development of schools location. However, petrol stations met the evaluated criteria and optimal location indexes.

Alternative Solutions for RTK-GPS Applications in Building and Road Constructions

Currently, Global Positioning System (GPS) techniques are becoming a much larger part of the surveying industry. Many companies are now using GPS in their everyday work activities. The Real Time Kinematic (RTK) positioning is an integral part of topographic surveys, road surveying, constructions and most civil engineering applications. Normally, RTK can be used to collect the positioning data successfully and quickly. The civil and construction projects are designed in ground distances while RTK measurements are done in grid coordinate system, in which the distances between points are different from ground. The RTK measurements should be converted to ground for compatibility with the designed. In this paper, the accuracy of three alternatives for converting RTK measurements to ground was studied. These alternatives are, using scale factor, using two ground reference points and using Low Distortion Projection (LDP) surface. For the accuracy investigation purpose, a traverse of 14 points elongated for a distance of about 1400 m was constructed. Its coordinates were measured using total station, then the misclosure error was computed and the coordinates were adjusted. The traverse points coordinates were measured again using RTK_GPS considering one of them as base point. The three studied alternatives were applied and the results were compared. The results show that the accuracy of the three alternatives is ranging from 2.1 to 2.9 cm in the relative position of points to the base point. For absolute position accuracy, the two ground reference points alternative is the most accurate alternative with an average error of 3.8 cm while the other two alternatives are almost the same with an average error of 12.3 cm.

Application of Low-Cost GPS Tools and Techniques for Landslide Monitoring: A Review

The main goal of our ongoing research is to design a low-cost continuous monitoring system for landslide investigation using the Reverse RTK (RRTK) technique. The main objectives of this paper are to review the existing Global Positioning System (GPS) tools and techniques used for landslide monitoring, and to propose a novel low-cost landslide monitoring technique using Reverse RTK GPS. A general overview of GPS application in landslide monitoring is presented, followed by a review of GPS deformation monitoring systems and some of the factors used for their categorization. Finally, the concept, principles and advantages of the proposed new landslide monitoring system are discussed.

Land subsidence in Konya Closed Basin and its spatio-temporal detection by GPS and DInSAR

Konya Closed Basin that includes two depression blocks, Konya and Tuz Golu, is the biggest endorheic basin in Turkey. A lowering in the ground levels of the depositional areas has been shown with respect to the surrounding mountains. In the past, this process was controlled by geological and hydrogeological phenomena; nowadays, it has gained a new dimension due to the excessive pumping of groundwater to the Earth’s surface. The geodetic techniques such as Global Positioning System (GPS) and Interferometric Synthetic Aperture Radar (InSAR) reveal a considerable land subsidence resulting in the rate of 1–4 cm/year in Konya sub-basin. It seems that the calculated amounts are responsible for changing environmental conditions like seasonality. Both GPS and differential InSAR techniques verify these relatively small fluctuations in the subsidence development. Target districts that should be observed primarily are agricultural zones where groundwater is overused for irrigation and regions where human population density is high. The geocoded interferogram and vegetation index map verify the spatial relation between the subsidence and green areas. In this study, a project dealing with the investigation of the land subsidence occurrences and of their possible causes and consequences within a specific part of Konya Closed Basin is introduced.

Study on real-time construction quality monitoring of storehouse surfaces for RCC dams

Abstract Construction quality control of storehouse surfaces is a major concern in the construction management of roller-compacted concrete (RCC) dams. The construction quality of the special dam-filling material RCC is affected by many factors, including the rolling compaction, concrete temperature and construction climate of storehouse surfaces. Timely collection and comprehensive analysis of construction data from the entire construction process of storehouse surfaces and subsequent feedback to construction operations on site are key issues in the control of construction quality and thus obtain greater attention. Traditional methods of construction quality monitoring, including manual inspections or sampling tests, are labor-intensive and easily lead to indiscoverable and irreparable quality defects. In the present study, a real-time construction quality monitoring method for storehouse surfaces of RCC dams is proposed. The auto-identification of compacted layers is realized. Based on the integration of global positioning system (GPS) and global navigation satellite system (GLONASS) techniques, sensor technology and network transmission technology, a real-time construction quality monitoring system is developed and applied to the LDL dam as a case study. The application results realize the whole process, all-weather and timely monitoring of rolling compaction quality, concrete temperature and construction climate in each compacted layer of storehouse surfaces and guarantees satisfactory construction quality and high efficiency, which demonstrates the effectiveness of this system. Moreover, construction data are used to establish predictive models for compactness and the loss of vibrating-compacted (VC) value by applying a multiple regression analysis method.

Relations between the GNSS, InSAR, and the other techniques for prediction of earthquakes

It is a well-known fact that the earthquakes have a lot of different parameters. Modern technology allows us to observe an important part of these settings. For example, when an earthquake occurs, its location, time, and depth, etc., values are measured by a seismometer. Recently, using the modern technologies, Global Positioning System (GPS) and Interferometric Synthetic Aperture Radar (InSAR) give us a chance to predict earthquakes in the short or long term. For avoiding the destruction the force of an earthquake can bring to human beings, it is inevitable to use the newer techniques. To predict out about the expected main shock, someone must begin to study firstly earthquakes which have already occurred. In this research, the seismometer and acceleration-meter data have been evaluated and compared by the geodetic measuring data of the InSAR and GPS data for Van earthquake on 23 October 2011. The area of research made out by the InSAR technique and the deformations produced by the GPS technique are being tested under centimeter precision. Additionally, the ionospheric total electron content values obtained by the GPS method have been considered, and the ionospheric distortions acquired from the closest Continuously Operating Reference Stations-Turkey stations, particularly Muradiye station, have been observed. Also, they have been interpreted geophysically.

Direction-of-Arrival Estimation for Stratospheric Platforms Mobile Stations

This paper presents a new approach for localizing mobile phone users using the promising technique of stratospheric platform (SP) flying at altitudes 17-22 km high and a suitable Direction-of- Arrival technique (DOA). The proposed technique provides information about accurate locations for mobile stations - through high resolution DOA technique - which is very important for traffic control and rescue operations at emergency situations. The DOA estimation in this technique defines the user location using MUSIC algorithm which provides good accuracy comparable to the Global Positioning System (GPS) techniques but without the need for GPS receivers. Several scenarios for users' locations determination are tested and examined to define the robustness of the proposed technique.

Deformation Monitoring of Offshore Platform Using the Persistent Scatterer Interferometry Technique

One of the problems that occur during the exploitation of oil and gas is offshore platform deformation. It could occur due to the environments load as well as the extraction of oil and gas itself under the seabed that caused reservoir compaction. Offshore platform deformation may affect the platform structural integrity and cause loss of production, thus it is very important to monitor its occurrences. Offshore platform deformation monitoring has been carried out using the satellite-based Global Positioning System (GPS) technique until recently. Even though the technique has proven its worth for the job, it has however some limitations, the most prominent is it could only monitor selected portion of the offshore platform. Thus, this study presents an attempt of detecting and monitoring the deformation phenomenon of an offshore platform using the Persistent Scatterer Interferometry (PSI) technique. This technique would overcome some of the limitations of the previous (GPS) deformation monitoring technique. A total of 11 high resolution TerraSAR-X images (i.e., 3 m in StripMap mode) were acquired from Aug, 2012 to Apr, 2013 for this purpose, while one of the offshore platforms in South China Sea is being used as monitored platform. Preliminary results showed that detail and sensitive deformations could be detected by this technique. In addition, analysis results in the form of mean deformation velocity map and displacement time series would allow us to further understand the behaviour of offshore platform deformation.

Comparison of Site Velocities Derived from Collocated GPS, VLBI and SLR Techniques at The Hartebeesthoek Radio Astronomy Observatory (Comparison of Site Velocities)

Abstract Space geodetic techniques provide highly accurate methods for estimating bedrock stability at subcentimetre level. We utilize data derived from Satellite Laser Ranging (SLR), Very Long Baseline Interferometry (VLBI) and Global Positioning Systems (GPS) techniques, collocated at the Hartebeesthoek Radio Astronomy Observatory, to characterise local plate motion and compare the solutions from the three techniques. Data from the GNSS station were processed using the GAMIT/GLOBK (version 10.4) software, data from the SLR station (MOBLAS-6)were processed using the Satellite Laser Ranging Data Analysis Software (SDAS) and the VLBI data sets were processed using the Vienna VLBI Software (VieVS) software. Results show that there is a good agreement between horizontal and vertical velocity components with a maximum deviation of 1.7 mm/yr, 0.7 mm/yr and 1.3 mm/yr between the North, East and Up velocity components respectively for the different techniques. At HartRAO there is no significant trend in the vertical component and all the techniques used are consistent with the a-priori velocities when compared with each other. This information is crucial in monitoring the local motion variations since geodetic instruments require a very stable base to minimise measurement errors. These findings demonstrate that station coordinate time-series derived with different techniques and analysis strategies provide comparable results.

Accuracy assessment of topographic mapping using UAV image integrated with satellite images

Unmanned Aerial Vehicle or UAV is extensively applied in various fields such as military applications, archaeology, agriculture and scientific research. This study focuses on topographic mapping and map updating. UAV is one of the alternative ways to ease the process of acquiring data with lower operating costs, low manufacturing and operational costs, plus it is easy to operate. Furthermore, UAV images will be integrated with QuickBird images that are used as base maps. The objective of this study is to make accuracy assessment and comparison between topographic mapping using UAV images integrated with aerial photograph and satellite image. The main purpose of using UAV image is as a replacement for cloud covered area which normally exists in aerial photograph and satellite image, and for updating topographic map. Meanwhile, spatial resolution, pixel size, scale, geometric accuracy and correction, image quality and information contents are important requirements needed for the generation of topographic map using these kinds of data. In this study, ground control points (GCPs) and check points (CPs) were established using real time kinematic Global Positioning System (RTK-GPS) technique. There are two types of analysis that are carried out in this study which are quantitative and qualitative assessments. Quantitative assessment is carried out by calculating root mean square error (RMSE). The outputs of this study include topographic map and orthophoto. From this study, the accuracy of UAV image is ± 0.460 m. As conclusion, UAV image has the potential to be used for updating of topographic maps.

Study of ground subsidence in northwest Harris county using GPS, LiDAR, and InSAR techniques

Subsidence has been affecting many cities around the world, such as Nagoya (Japan), Venice (Italy), San Joaquin Valley and Long Beach (California), and Houston (Texas). This phenomenon can be caused by natural processes and/or human activities, including but not limited to carbonate dissolution, extraction of material from mines, soil compaction, and fluid withdrawal. Surface deformation has been an ongoing problem in the Houston Metropolitan area because of the city’s location in a passive margin where faulting and subsidence are common. Most of the previous studies attributed the causes of the surface deformation to four major mechanisms: faulting, soil compaction, salt tectonics, and fluid withdrawal (groundwater withdrawal and hydrocarbon extraction). This work assessed the surface deformation in the greater Houston area and their possible relationship with fluid withdrawal. To achieve this goal, data from three complimentary remote sensing techniques Global Positioning System (GPS), Light Detection and Ranging (LiDAR), and Interferometric Synthetic Aperture Radar were used. GPS rates for the last 17 years show a change in surface deformation patterns. High rates of subsidence in the northwestern areas (up to ~4 cm/year) and signs of uplift in the southeast are observed (up to 2 mm\year). High rates of subsidence appear to be decreasing. Contrary to previous studies in which the location of subsidence appeared to be expanding toward the northwest, current results show that the area of subsidence is shrinking and migrating toward the northeast. Digital elevation model generated from airborne LiDAR, revealed changes between salt domes and their surrounding areas. The persistent scatterer interferometry was performed using twenty-five (25) European remote sensing-1/2 scenes. Rates of change in groundwater level and hydrocarbon production were calculated using data from 261 observation wells and 658 hydrocarbon wells. A water level decline of 4 m/year was found in area of highest subsidence, this area also show ~70 million m3/year of hydrocarbon extraction. This study found strong correlation between fluid withdrawals and subsidence. Therefore, both groundwater and hydrocarbon withdrawal in northwest Harris County are considered to be the major drivers of the surface deformation.

PERFORMANCE OF 2-D DOA ESTIMATION FOR STRATOSPHERIC PLATFORMS COMMUNICATIONS

This paper presents a new approach for localizing mobile phone users using the promising technique of stratospheric platform (SP) ∞ying at altitudes 17{22km high and a suitable Direction-of- Arrival technique (DOA). The proposed technique provides information about accurate locations for mobile stations | through high resolution DOA technique | which is very important for tra-c control and rescue operations at emergency situations. The DOA estimation in this technique deflnes the user location using MUSIC algorithm which provides good accuracy comparable to the Global Positioning System (GPS) techniques but without the need for GPS receivers. Several scenarios for users' locations determination are tested and examined to deflne the robustness of the proposed technique.

Optimal data processing strategy in precise GPS leveling networks

GPS (Global Positioning System) technique has become a major tool in contemporary surveying and geodesy. This concerns mostly measurements of horizontal point coordinates, where centimeter-level accuracies are usually required and easily achievable. For the height component, however, these requirements are higher and millimeter-level accuracy is necessary. On the other hand, the intrinsic precision of GPS-derived heights is clearly lower comparing to the horizontal components. This is due to unfavorable satellite geometry, adverse effects of the troposphere or GPS antenna phase center offset and variations. In order to overcome these effects one has to carefully model all the error sources and rigorously process the GPS data. This paper presents studies on the optimal GPS data processing strategy suitable for precise leveling. This was done through the extensive testing and selection of the most appropriate observational session duration, ambiguity resolution strategy, network geometry, troposphere and ionospheric delay reduction methods, signal linear combination, elevation angle cut-off, etc. The analyzed processing strategies were evaluated through the processing of a test network. The test network consisted of 19 monitored points and 5 control points, and covered the area of 20 km x 60 km. The obtained results show that the precise GPS leveling with the selected optimal processing strategy allows for about 3 mm repeatability of height measurements when processing 4-hour long sessions. In our opinion GPS leveling may serve as fast and cost-effective replacement of classic geometric leveling, especially in applications where the heights in orthometric or normal height systems are not necessary. This is the case in, e.g., ground deformation studies.