Oskar Sterle

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.

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.

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.

Determination of tropospheric GNSS impacts from a radiosonde data series in Ljubljana: case study from october to december 2017

GNSS observations, tropospheric impacts, standard atmosphere, radiosonde measurements opazovanja GNSS, vpliv troposfere, standardna atmosfera, radiosondažne meritve UDK: 528.28:551.510.52(497.451.1) Klasifikacija prispevka po COBISS.SI: 1.01 Prispelo: 5. 3. 2018 Sprejeto: 26. 8. 2018 DOI: https://doi.org/10.15292/geodetski-vestnik.2018.03.415-429 SCIENTIFIC ARTICLE Received: 5. 3. 2018 Accepted: 26. 8. 2018 Alenka Senica, Oskar Sterle, Polona Pavlovčič Prešeren DOLOČITEV VPLIVA TROPOSfERE NA OPAZOVANJA GNSS IZ NIZA RADIOSONDAžNIH MERITEV V LJUBLJANI OD OKTOBRA DO DECEMBRA 2017 DETERMINATION Of TROPOSPHERIC GNSS IMPACTS fROM A RADIOSONDE DATA SERIES IN LJUBLJANA: CASE STUDY fROM OCTOBER TO DECEMBER 2017

The employment of a radial basis function network for 3D surface modelling

IZVLEČEK SI | E N Polona Pavlovčič Prešeren, Bojan Stopar, Oskar Sterle | MODELIRANJE 3D-PLOSKEV Z NEVRONSKIMI MREŽAMI Z RADIALNIMI BAZNIMI AKTIVACIJSKIMI FUNKCIJAMI | THE EMPLOYMENT OF A RADIAL BASIS FUNCTION NETWORK FOR 3D SURFACE MODELLING | 241-255 | | 242 | | 60/2 | GEODETSKI VESTNIK RE CE NZ IRA NI ČL AN KI | P EE RRE VIE W ED AR TIC LE S

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

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

Positioning under Adverse Conditions Using High Sensitivity GPS

Positioning is a key component of location-based services (LBS). An LBS user wants to acquire the current location in any possible environment. GNSS positioning, the fundamental component of a positioning system, is limited to open areas with unobstructed reception of GNSS satellites signals. In order to assure a ubiquitous positioning, other sensors have to be included in the positioning system. Inertial sensors are the most commonly used to compliment the GNSS sensors. However, the inertial sensors are very susceptible to drifts and other errors. Recently, other sensors have been considered for use in the positioning systems, e.g. UWB, Wi-Fi, pseudolites and high sensitivity GPS. High sensitivity GPS receivers have extended the use of GNSS navigation to environments which were previously believed unsuitable for satellite signal reception. However, extra care has to be considered when using high sensitivity GPS because autonomous solutions can cause major errors in the estimated position in the challenging environments. A careful and consistent treatment of the observation data can yield adequate results even under adverse conditions for signal reception.

Geodesy in Geotechnics

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.