Journal of Geomatics Science and Technology
http://jgst.issge.ir
Journal of Geomatics Science and Technology - Journal articles for year 2014, Volume 4, Number 1Yektaweb Collection - http://www.yektaweb.comen2014/8/10The Precision and Computation Time Analysis of Semi-Analytical and Numerical Methods for LEO Satellites Orbit Propagation
http://jgst.issge.ir/browse.php?a_id=173&sid=1&slc_lang=en
<p>The various methods are published for satellite orbit propagation and the numerical integration is one of the most common methods. The numerical integrators can be divided into two main methods, Single-Step and Multi-Step methods. In this paper, the results of Runge-Kutta method as the most common Single-Step method and prediction-estimation-correction-estimation method as the most common Multi-step method are compared. In this paper, it is proved that if the error-controlled integration methods are used, the difference between Single-step and Multi-step methods would be at sub-millimeter level. In this paper, the Lagrange method is introduced as a semi-analytical method too and the Lagrange coefficients are developed from central field to full gravitational field of Earth. By this development, the Lagrange method can be used in LEO satellite orbit determination. The results show that the accuracy of the Lagrange method for LEO satellite orbit determination is about 5 millimeter over one day.</p>
M. R. Seif Curvature Change of the Earth\'s Crust Surface in Iran by Analytical Deformation Theory
http://jgst.issge.ir/browse.php?a_id=174&sid=1&slc_lang=en
<p>In the context of shell theory in continuum mechanics, based on three-dimensional displacement fields and assuming height as a differentiable function of the geodetic surface coordinates analytical surface deformation theory provides a method for analyzing the contemporary state of surface deformation of the Earth's crust using differential geometry. In this method, based on finite elements representation of the Earth's crust (Delaunay triangulation) deformation analysis is based on a two-dimensional computational approach: Gaussian and mean curvatures are computed using metric tensor and the second fundamental form. Variations of the mean and Gaussian curvatures in Makran, 0.503×10-14/myr and 1.097×10-21/m2yr respectively, obtained from the Iran global GPS campaigns (epochs 2001 and 2005) are a signature for the subduction process in this area. Moreover, maximum change in the curvature are in accord with the main Zagros and Alborz (+1.574×10-21/m2yr and-9.992 ×10-21/m2yr ) folds in Iran. Frequently the subsidence paths in precise leveling network of Iran are in areas with reduction in curvature.</p>
M. R. JafariLeast-Squares Variance Component Estimation Applied to GPS Geometry-Based Observation Model
http://jgst.issge.ir/browse.php?a_id=175&sid=1&slc_lang=en
<p>Geodetic data processing usually is performed using the least-squares method. To achieve the best linear unbiased estimation, it is necessary to use the proper and realistic stochastic model of the observables. The estimation of the unknown (co)variance components of the observables is referred to as variance component estimation (VCE). In geodetic applications, VCE is also known as the observables weights estimation. In this paper, least-squares variance component estimation is applied in a straightforward manner to GPS observables for determination of the realistic stochastic model. For this purpose, the functional model used in the analysis is the GPS geometry-based observation model (GFOM). The numerical results for two receivers, namely Trimble 4000 SSi and Trimble R7, are presented. The results indicate that the correlation between observation types is significant. A positive correlation of 0.55 is observed between the code observations on CA and P2 for Trimble 4000 SSi. Also, a significant positive correlation of 0.64 is observed between the phase observations on L1 and L2 for Trimble R7.</p>
F. ZangenehnejadDeformation Analysis of the Lake Urmia Causeway Embankments in Northwest Iran Using Interferometry Synthetic Aperture Radar (Insar) Data
http://jgst.issge.ir/browse.php?a_id=176&sid=1&slc_lang=en
<p>In order to make a connection between West and East Azerbaijan embankments a bridge with the length of ~1300 m and width of ~30 m has been constructed in the late 2009s. This bridge has an important role in the development of tourism, transportation and trade in the area. The difference between the deformation rates of the embankments on both sides of the bridge may seriously damage the bridge itself, so it is very important to accurately monitor them in space and time in order to assess the state of the bridge concerning deformations. Interferometric Synthetic Aperture Radar (InSAR) is a powerful geodetic technique for precise deformation monitoring in space and time due to its extensive area coverage, high spatial (1-20 m) and temporal resolution (11-46 days) and acceptable accuracy (cm to mm level). Advanced interferometric time-series techniques such as Small BAseline Subset (SBAS) approach is a valuable tool for structural monitoring and provide deformation maps with millimeter accuracy. In this study, this technique has been applied on a dataset of 58 SAR images acquired by ENVISAT, ALOS and TerraSAR-X (TSX) satellites from 2003 to 2013 to monitor spatio-temporal evolution of ground deformation on the embankments. The InSAR results show deflation on both embankments of the bridge is occurred with peak amplitude of ~50 mm/year in the line of sight direction.</p>
R. ShamshiriEffect of Using Different Types of Threshold Schemes (in Wavelet Space) on Noise Reduction over GPS Times Series
http://jgst.issge.ir/browse.php?a_id=177&sid=1&slc_lang=en
<p>The goal of this study is the role of using different thresholding effects on types of noise reductions based on wavelet schemes. Assumed thresholding techniques are penalized threshold, Birgé-Masssart Strategy, SureShrink threshold, universal threshold, minimax threshold and Stein’s unbiased risk estimate. In order to compare the performance of them in denoising of types of noise components (white noise, flicker noise and random walk noise) we have constructed three kinds of stochastic models: the pure white noise model (I), the white plus random walk noise model (II) and the white plus flicker noise model (III). The numerical computations are performed through the analyzing 10 years (Jan 2001 to Jan 2011) of raw daily GPS solutions which are selected of 264 stations of SOPAC. According to results of computations, among the thresholding schemes in de-noising of the pure white noise model (I): minimax threshold and Stein’s unbiased risk estimate could reduce the distribution of low amplitude of white noise. However, minimax threshold and SureShrink threshold could reduce the distribution of high amplitude of white noise. Birgé-Masssart Strategy and universal threshold could reduce both low and high amplitudes of white noise. In model II (white noise plus random walk noise) and model III (white noise plus flicker noise), all of threshold schemes could reduce both high and low amplitudes of white noise in same level. Whereas for power-law noise (flicker noise and random walk noise) penalized threshold and Stein’s unbiased risk estimate led to reduction of low amplitudes and SureShrink threshold and minimax threshold led to reduction of colored noise with high amplitudes. Birgé-Masssart Strategy and universal threshold could reduce both low and high amplitudes of colored noise.</p>
Kh. Moghtased-AzarEvaluation of Scale Change Effect on Simulating Urban Expansion Using Continuous Cellular Automata
http://jgst.issge.ir/browse.php?a_id=178&sid=1&slc_lang=en
<p>Cellular Automata are common approach to simulate urban expansion and different implementations based on them have done for modeling urban growth in recent years. Scale of model is one of the important properties that are effective on the results of these models in urban expansion area. In this study, the effect of changing scale was considered based on results of modified continuous cellular automata. At the first step, fundamentals and basic components of proposed model were represented and uncertain effects of changing scale in cells were demonstrated. Furthermore, the proposed model was implemented on a real city. The study area is the Isfahan city and land cover data for modeling of this area were derived from satellite images using supervised classification methods. Scale change experiments were done based on two different strategies in this study. In the first strategy the growing factor of cells was constant in experiment but the value of this factor was changed according to cell size during the next experiment. The estimations of error were done by the Root Mean Square error. In the first strategy, the best simulation results were given at phase with the cell size of 68.5 meters and the maximum deviation between the upper and lower error based on this index was 0.0035 meters. In the later strategy, the best simulation results were given at phase with the cell size of 63.5 meters and the maximum deviation between the upper and lower error was 0.1055 meters.</p>
M. FarsaieModeling 3D Querying Based on Location and Orientation Information for Buildings
http://jgst.issge.ir/browse.php?a_id=179&sid=1&slc_lang=en
<p>One of the most important services in mobile environments is Location Based and orientation aware services. Mobile Geo Information System (MGIS) users by using of various ways can interact with physical objects. One of this ways is pointing. In this study, by similar manner we want to use mobile devices as a pointer for obtaining information from buildings. It has recently been studied by researchers for specific purposes, but in most of their researches making true target is not investigate or they use heavy process to do this. Elements of ambiguity in selecting true target, is one of the most important problems that ought to be monitored. To deal with mentioned problem, first we classified the ambiguity into two categories. The first type occurs when selected buildings in pointing line are more than one. In this regards, we consider some kind of contextual information. These contexts consist of: user interest land use, proximity of current user position to position of buildings, point in polygon concept. Besides, we develop a method so called space digitizing based on drawing simple geometry shape of buildings. The other kind of ambiguity occurs when the intersect position of pointing line and building’s edge, is on the boundary of those buildings. We proposed probabilistic method to overcome this kind of ambiguity.In order to implementing above objectives, an application for mobile devices with Android operating system has been developed. By implementing this in K.N.Toosi University of Technology faculty of Civil and Survey Engineering, the correctness of application functionalities has been confirmed.</p>
S. OjaghEvaluating the Role of Urban Spatial Structure in Functionality of Streets
http://jgst.issge.ir/browse.php?a_id=180&sid=1&slc_lang=en
<p>This paper is intended to determine whether there is a meaningful relationship between urban spatial structure and functionality of streets. Urban spatial structure refers to spatial configuration and arrangement of streets in an urban transportation network. Also, in this context, functionality of a street defines if the street is an arterial or local path. In order to evaluate the spatial structural properties of streets in an urban transportation network, this paper applies an indicator called “Shortest Path Frequency” (SPF). This indicator determines the frequency in which a given street participates in possible shortest paths throughout the network. Higher SPF indicates that the street is more structurally important. Moreover, in order to achieve the mentioned goal, the SPF indicator was adopted to assess the structural importance of streets in a case study network. Then, the assessed importance of each street is compared to its functionality in real network. The functionality of streets was categorized in four level including: main arterial, secondary arterial, main streets and local streets. The comparison between calculated and observed importance of streets was achieved by using a statistical test.The test revealed that there is restrict meaningful relationship between structural importance level of streets and functionality of streets. In other words, the streets which were identified as structurally important also are identified in the category of main or secondary arterials in real world. As a result, this procedure can help urban designers to predict structurally important streets in a network and provide required plans such as particular land-use policy or specific design to avoid from congestion in such streets.</p>
A. Sheikh MohammadzadehA Heuristic Evolutionary Algorithm for Planning Moving Agents According to the Equilibrium Instead of Multi-Objective Optimization
http://jgst.issge.ir/browse.php?a_id=181&sid=1&slc_lang=en
<p>Agent-based methodologies facilitate complicated hypotheses verification, modeling and dynamic simulation. Hence, there are many interests in the geospatial information science to model rational autonomous agents due to their closer-to-realism decision-making and influence on environment. In this study, we consider the planning and task distribution among vehicle entities in the geospatial domains based on an agent-based approach. We show at the beginning of the paper, the rational agents have tendency to change their strategies to reach the highest possible satisfaction/utility. To obtain such a utility in the group of collaborative agents, equilibrium, a key concept taken from the Game theory, appears more efficient than the common multi-objective optimization. We challenge this issue according to the dependency or contention of moving agents' payoffs. Because of high complexity of determining equilibrium, i.e. exponential, an efficient non-deterministic heuristic algorithm is proposed. We get our inspiration from evolutionary computations to introduce this novel algorithm. We have evaluated our approach with several datasets and received perfectly acceptable convergence, accuracy and speed. In comparison to a pure deterministic method, retrieving the equilibrium and the optimality of the best equilibrium solution were experimented at least as 80% and 92% respectively.</p>
M. H. VahidniaA Quasi-Rigorous Approach for the Solution of the Relative Orientation of the Linear Array Satellite Images with Similar Viewing Geometry
http://jgst.issge.ir/browse.php?a_id=182&sid=1&slc_lang=en
In this paper a quasi-rigorous approach for the solution of a two-dimensional relative orientation of two images, acquired during the satellite revisit, is proposed. Unlike the conventional relative orientation methods in frame photography, the proposed approach utilizes both x and y parallaxes for the solution of the relative orientation. Since the revisit images have similar viewing geometry, the ill-conditioning problem arising from the height undulations in the x-parallaxes, does not occur. The proposed algorithm is tested on two afterwards Cartosat IRS-P5 revisit images acquired over a highly mountainous terrain. The accuracy figures indicate a sub-pixel precision of 0.30 and 0.47 pixels for the residual x and y parallaxes respectively. The proposed algorithm is suitable for the landslide applications for which highly accurate image co-registration is required
A. AziziAn Evolutionary Strategy for Georeferencing and Blunder Detection of High Resolution Satellite Imagery
http://jgst.issge.ir/browse.php?a_id=183&sid=1&slc_lang=en
<p>The georeferencing of High Resolution Satellite Imagery (HRSI) is an important task for various remote sensing and photogrammetric applications. During the process of georeferencing, Ground Control Points (GCPs) in the image have an essential role to obtain the georeferencing parameters via the adjustment method. Therefore, the appearance undesirable blunders can cause the fundamental problem for image georeferencing and influence in adjustment results. There are traditional algorithms for detecting the presence of blunders in a set of points, such as data snooping and robust estimation. In case of blunders or systematic errors appearance either in the mathematical model or in the observations to be adjusted, both of these methods have considerable problems for isolating them and avoiding their influence. In this study, a novel method based on evolutionary algorithms is described for georeferencing and blunder detection simultaneously and is analyzed versus the traditional approaches. Based on the proposed method, through least square estimation, by maximizing the residual on each individual check point, the estimated values of parameters are computed and blunders in control points are found. The novel method is implemented on IKONOS and WorldView2 images with respect to the different number and propagation of blunders. The results show that the genetic algorithm based proposed method is a more efficient method for detecting blunders than data snooping and robust estimation even when the cluster of blunders exist in GCPs.</p>
F. AlidoostDesign and Development of a Simulator System for Star Trackers with the Aim of Aerial Vehicle Navigation
http://jgst.issge.ir/browse.php?a_id=184&sid=1&slc_lang=en
<p>According to importance of aerial vehicle automatic navigation and involved problems in GPS and IMU navigation systems there are always needs for other navigation or aided navigation systems. Navigation of aerial vehicles using image information is a proper option for these systems. In this regard, using image information of stars for navigation has led to development of star tracker systems. Simulators of these systems have important role in evaluating navigation algorithms before real flight tests. As all parameters of sensor and star positions are known this simulation can be used for assessment of accuracy and precession of all involved algorithms in star tracker data processing scheme, such as center detection, star identification, and attitude determination algorithms. In this research a star tracker simulator system have been presented. The presented simulator can does different pre-processing schemes on star catalogue. Tuning of sensor parameters and its carrier platform in inertial space also has been provided by presented simulator system. Assessment of different simulations considering different sensor parameters and in different attitudes with different rotational rates shows the high capability of the proposed system</p>
M. Hamidi