Combination of terrestrial and GNSS observations for geodynamic research

The basic quantity of strain are determined vectors of velocity or displacement of de- formed body. Determination of displacements in geodetic practice is possible only with repeated survey of a geodetic net. Coordinates of points in geodetic net are estimated in each survey on a basis of observations. Thesis presents datum parameters of specific type of observation in projection plane and methods of datum assurance in geodetic nets. Velocity or displacement vectors are estimated from repeated surveys, where different survey techniques were used. Estimation is taking place in one step for all survey epochs in 4D space. Results are estimated coordinates of points in some reference epoch with corresponding velocity vectors. Velocity vectors are biased because of bad datum defi- nitions in separate surveys. These vectors are datum dependent, while strain tensor is invariant to transformation, but dependent on scale of a net. Vectors are analyzed on datum alterations presence and datum independent velocity vectors are obtained, which represent relative displacements of points in geodetic net. Main purpose of this thesis is to present a method of velocity vectors estimation from repeated surveys, that represent geometric displacements and are not biased because of datum alterations in separated surveys

Time dependent geodetic networks and coordinate systems

This thesis represents the theoretical and practical aspects of establishing a new coordinate\ud system on the basis of repeated GNSS observations, which is defined in five steps. First,\ud we determine the precise coordinates of geodetic stations that are in the second step\ud transformed to a global coordinate system. In the third step we determine the coordinates\ud of geodetic stations for the reference epoch with their corresponding velocity vectors on the\ud basis of repeated GNSS observations. The fourth step is establishing a proper coordinate\ud system performed using a time-dependent spatial transformation. On the basis of the\ud estimated velocity vectors in the newly established coordinate system, the geokinematic\ud model of the corresponding territory can be determined with the least-squares collocation\ud in the final, fifth step. The practical part of the thesis is based on repeated GNSS\ud observations in the territory of Slovenia and its surroundings over the last 20 years. The\ud GNSS observations were obtained for the geodetic stations of the passive GNSS network\ud as well as for permanent GNSS stations. Besides, our work included the establishment\ud of a new coordinate system, and an analysis of the precision and accuracy of the already\ud established coordinate system based on GNSS observations, which has been officially used\ud in Slovenia since 2008

PPP method for static GNSS survey

This paper presents Precise Point Positioning (PPP),\ud a method of GPS observation processing from a single\ud receiver that provides coordinates of the highest quality.\ud The requirements for high quality results are an exact\ud mathematical model, high quality GPS biases modelling,\ud and high quality IGS products. On the basis of monthly\ud GPS observations from a permanent station GRAZ in\ud Graz, Austria, we will demonstrate that PPP method is\ud able to determine stations position with the accuracy and\ud precision of a centimetre in the ITRF global coordinate\ud frame. Because of high precision transformation between\ud ITRF and ETRS89, the PPP method can also be used\ud in Slovenia to determine high precision positions in the\ud national coordinate reference system of Slovenia (D96/TM),\ud as it is based on ETRS89

Ionosperic refraction modeling for better autonomous GNSS code positioning: in preparation of solar cycle 24.\ud

This paper describes GNSS-processing optimisation\ud for better autonomous single-point positioning using\ud single frequency code receivers. GNSS processing\ud improvement is carried out in terms of near-real time\ud ionosphere delay modelling, which will be crucial\ud during the upcoming 24th maximum solar cycle. The\ud main scope of this article is to examine how sudden\ud changes in the ionosphere, caused by events on the\ud Sun, affect autonomous single-point positioning in\ud simple navigation tasks. Further, the specific method\ud of ionosphere delay modelling from actual twofrequency\ud receivers, acquiring carrier phase and code\ud observations, is shown. The modelled value of the\ud ionospheric refraction, which is given in GNSS path\ud delay, is further used in point positioning from singlefrequency\ud code instruments. In addition, we show\ud the advantage of GNSS permanent stations that can\ud supply a wide range of users with better ionosphere\ud data in near real time. From actual experiments, the\ud magnitude of the ionospheric impact on each specific\ud 3D position component is shown and further improved\ud using modelled ionosphere delay values. Finally, we\ud show how to improve GNSS position determination\ud from simple single- or two-frequency GNSS code or\ud carrier-phase receivers in differential GNSS method.\ud This study was conducted for preparations for the\ud upcoming solar cycle maximum, expected to be held\ud in May 2013

Statistical Properties of Strain and Rotation Tensors in Geodetic Network

This article deals with the characteristics of deformation of a body or a figure represented by discrete points of geodetic network. In each point of geodetic network kinematic quantities are considered normal strain, shear strain, and rotation. They are computed from strain and rotation tensors represented by displacement gradient matrix on the basis of known point displacement vector. Deformation analysis requires the appropriate treatment of kinematic quantities. Thus statistical properties of each quantity in a single point of geodetic network have to be known. Empirical results have shown that statistical properties are strongly related to the orientation in single point and local geometry of the geodetic network. Based on the known probability distribution of kinematic quantities the confidence areas for each quantity in a certain point can be defined. Based on this we can carry out appropriate statistical testing and decide whether the deformation of network in each point is statistically significant or not. On the other hand, we are able to ascertain the quality of the geometry of the geodetic network. The known characteristics of the probability distributions of two strain parameters and rotation in each point can serve as useful tools in the procedures of optimizing the geometry of the geodetic networks

Realisation of geodesy in geotechnics

This paper deals with surveying activities in order to define the displacement of the Earth's crust, local displacements of the Earth's surface, and the displacement and deformation of constructed buildings. The determinations of horizontal movements in the terrestrial network, in the terrestrial altitude network and in the GNSS network are dealt with at two levels of accuracy. Geotechnical surveying activities are explained in the paper and demonstrated in the table. The paper Geodesy in geotechnics, published in Geodetski vestnik 54(1), and this paper present an integral whole

Geodesy in Geotechnics\ud

Geodetic methods are one of the possible means of determining the stability of geotechnical objects. The determination of the displacements of the geotechnical objects is specific due to the size and the expected displacements. The expected size of the displacement determines the necessary precision of the displacement determination, whereas the size of the object determines the method of the geodetic measurement. We choose either the terrestrical or the GNSS methods. There is no relevant legal framework for geotechnical measurements. For this reason, we present the characteristics of the single methods and suggest general recommendations regarding the implementation of the geodetic procedures when monitoring the displacements of the geotechnical objects. The recommendations are intended for geotechnical engineers planning the geotechnical objects and the operators of geodetic measurements and investors. The recommendations the facilitate supervision of the geotechnical projects

Use of Terrestrial Laser Scanning Technology for Long Term High Precision Deformation Monitoring

The paper presents a new methodology for high precision monitoring of deformations with a long term perspective using terrestrial laser scanning technology. In order to solve the problem of a stable reference system and to assure the high quality of possible position changes of point clouds, scanning is integrated with two complementary surveying techniques, i.e., high quality static GNSS positioning and precise tacheometry. The case study object where the proposed methodology was tested is a high pressure underground pipeline situated in an area which is geologically unstable

Geodetic activities at the new tide gauge station Koper

Under the auspices of the Environmental Agency of\ud the Republic of Slovenia a new state-of-the-art tide\ud gauge station was set up in Koper. The paper presents\ud the geodetic works that were performed in order to\ud determine the position of the tide gauge station in the\ud terrestrial reference system. All measurements were\ud carried out during the testing period of the tide gauge,\ud that is, from the end of 2005 until the begining of\ud 200

Sturdy Positioning with High Sensitivity GPS Sensors Under Adverse Conditions

High sensitivity GPS receivers have extended the use of GNSS navigation to environments which were previously deemed unsuitable for satellite signal reception. Under adverse conditions the signals become attenuated and reflected. High sensitivity receivers achieve signal reception by using a large number of correlators and an extended integration time. Processing the observation data in dynamic and rapidly changing conditions requires a careful and consistent treatment. Code-based autonomous solutions can cause major errors in the estimated position, due primarily to multipath effects. A custom procedure of autonomous GPS positioning has been developed, boosting the positioning performance through appropriate processing of code and Doppler observations. Besides the common positioning procedures, robust estimation methods have been used to minimise the effects of gross observation errors. In normal conditions, differential GNSS yields good results, however, under adverse conditions, it fails to improve significantly the receiver’s position. Therefore, a so-called conditional DGPS has been developed which determines the position differentially by using data from the strong signals only. These custom-developed procedures have been tested in different conditions in static and kinematic cases and the results have been compared to those processed by the receiver