GNSS-Condition Impacts on Land Boundary Coordinates and Land Area Determination

Background: Determining the location, boundaries and areas of land properties accurately in the land cadastre is essential. The named data are provided using coordinates, acquired from field measurements. Since 2008, the Slovenian land cadastre claims positioning in the national realization of the ETRS89, so the GNSS use is practically indispensable. Objectives: Contrary to real-time, we can change parameters in GNSS post-processing. The aim of this paper is to simulate different measurement conditions for GNSS in order to determine how to acquire the best possible coordinates for further use in land area calculation. Methods/Approach: Simulations of obstacles near points followed the increasing of the cut-off angle. Furthermore, shortening the observation interval resulted in different occupation duration. The final condition evaluation for coordinate quality acquisition followed from fuzzy logic. Results: The results show that for short baselines, occupation duration is the most important factor in acquiring high quality coordinates and avoiding the multipath. Differences in coordinates from specific strategies can sometimes exceed the tolerance and evidently affect the area calculation. Conclusions: The findings confirm that only good measurement conditions lead to high quality coordinates and well-defined areas of land properties, which are the fundamental factor in relation to the issues of property valuation and assessing land taxes or rents

Analiysis of GNSS-RTK instruments testing on the ISO 17123-8

GNSS-instruments (Global Navigation Satellite System) are the standard field surveying equipment (in addition to tachymeter and levels) for geodetic network establishment and detail surveying. As in the case of other geodetic instruments, it is essential to pre-analyse GNSS-receiver quality parameters, obtained from laboratory calibration and/or field testing of the specific instrument and/or measuring method. Thus, the relevance of the results, as indicated by manufacturer, is obtained that may explain the suitability of a specific GNSS-instrument for field measurements. In 2007, the International Organization of Standardization (ISO), Technical Committee 172, Subcommittee 6 (ISO/TC 172/SC6), presented a comprehensive GNSS field testing procedures for real time measurements, based on statistical evaluation and verification of the manufacturer's hardware and firmware. The test can be performed anywhere on the field assuming that the test area includes minimal potential influences to GNSS measurements. At the same time, a test does not require any additional processing software, because the test data evaluation is based on elementary statistics. This paper presents the theoretical basis of GNSS instrument testing in accordance with the ISO 17123-8 guidelines and further examination of specific measurements on the selected site

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

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

Analiza preizkusa instrumentarija GNSS-RTK po navodilih standarda ISO 17123-8 : Analysis of GNSS-RTK instruments testing on the ISO 17123-8 instructions

GNSS-instrumente (angl. Global Navigation Satellite System) uvrščamo med standardno terensko geodetsko mersko opremo (poleg elektronskih tahimetrov in nivelirjev), ki jo lahko uporabljamo za vzpostavitevgeodetskih mrež in za detajlno izmero. Podobno kot pri drugih geodetskih instrumentih moramo tudi pri GNSS-instrumentih pred izmero ovrednotiti parametre kakovosti instrumentarija oziroma metodeizmere, ki jih pridobimo s postopki laboratorijske kalibracije in/ali s terenskim preizkušanjem. Tako pridobimo podatek o ustreznosti navedenih tehničnih značilnostih proizvajalca in ovrednotimo primernost uporabe GNSS-instrumentov za konkretne potrebe.Mednarodna organizacija za standarde ISO (angl. International Organization of Standardization) je v okviru tehnične skupine 172 in podskupine 6 (ISO/ TC 172/SC 6) v letu 2007 predstavila postopkepreizkušanja GNSS-merskega instrumentarija za določanje položaja v realnem času, ki temeljijo na oceni kakovosti delovanja strojne in programske opreme posameznega instrumenta. Preizkus lahko opravimo kjerkoli na terenu, kjer so zagotovljeni primerni pogoji za izvedbo GNSS-opazovanj predvsem s stališča čim manjših vplivov na opazovanja zizvorom v okolici. Preizkus tudi ne zahteva dodatnega programskega orodja za obdelavo podatkov meritev, saj je statistično vrednotenje rezultatov opazovanj dokaj enostavno. V prispevku opisujemo teoretične podlage preizkusa GNSS-instrumentov po navodilih standardaISO 17123-8, ki jih uporabimo za praktični preizkus GNSS-instrumenta. ; GNSS-instruments (Global Navigation Satellite System) are the standard field surveying equipment (in addition to tachymeter and levels) for geodetic network establishment and detail surveying. As inthe case of other geodetic instruments, it is essential to pre-analyse GNSS-receiver quality parameters, obtained from laboratory calibration and/or field testing of the specific nstrument and/or measuring method. Thus, the relevance of the results, as indicated by manufacturer, is obtained that may explain the suitability of a specific GNSS-instrument for field measurements. In 2007, the International Organization of Standardization (ISO), Technical Committee 172, Subcommittee 6 (ISO/TC 172/ SC6), presented a comprehensive GNSS field testing procedures for real time measurements, based on statistical evaluation and verification of themanufacturer’s hardware and firmware. The test can be performed anywhere on the field assuming that the test area includes minimal potential influences to GNSS measurements. At the same time, a test does not require any additional processing software, because the test data evaluation is based on elementary statistics. This paper presents the theoretical basis of GNSS instrument testing in accordance with the ISO 17123-8 guidelines and further examination of specific measurements on the selected site

Izračun položaja GPS-satelita iz podatkov oddanih efemerid : GPS-Orbit Computation from Broadcast Ephemeris Data

The article describes the theoretical point of view of the GPS-broadcast ephemerides application. Beside the raw GPS observations, any kind of GPS ephemerides represents indispensable data in the GPS processing engine. Broadcast ephemerides have been produced in the central Control Station in Colorado Springs and interposed from GPS satellites to the users as part of the GPS navigation message. The article focuses on the theoretical broadcast-ephemeris-data treatment for computing the position of a GPS satellite. The reason for the orbit-problem explanation is that anyone who uses any GPS measurement methods should be aware of the advantages and disadvantages of the ephemeris data. Thus, numerical examples of GPS-satellite position computation for 4-hour time span from broadcast ephemerides and deviations of the results regarding the IGS ultra-rapid and IGS final precise ephemerides are presented in the article

Evaluating the vulnerability of several geodetic GNSS receivers under chirp signal L1/E1 jamming

Understanding the factors that might intentionally influence the reception of global navigation satellite system (GNSS) signals can be a challenging topic today. The focus of this research is to evaluate the vulnerability of geodetic GNSS receivers under the use of a low-cost L1 GPS band and E1 Galileo frequency band (L1/E1) frequency jammer. A suitable area for testing was established in Slovenia. Nine receivers from different manufacturers were under consideration in this study. While positioning, intentional 3-minute jammings were performed by a jammer that was located statically at different distances from receivers. Furthermore, kinematic disturbances were performed using a jammer placed in a vehicle that passed the testing area at various speeds. An analysis of different scenarios indicated that despite the use of an L1/E1 jammer, the GLONASS (Russian: Globalnaya Navigatsionnaya Sputnikovaya Sistema) and Galileo signals were also affected, either due to the increased carrier-to-noise-ratio (C/N$_0$) or, in the worst cases, by a loss-of-signal. A jammer could substantially affect the position, either with a lack of any practical solution or even with a wrong position. Maximal errors in the carrier-phase positions, which should be considered a concern for geodesy, differed by a few metres from the exact solution. The factor that completely disabled the signal reception was the proximity of a jammer, regardless of its static or kinematic mode

Robustness against chirp signal interference of on-board vehicle geodetic and low-cost GNSS receivers

Robust autonomous driving, as long as it relies on satellite-based positioning, requires carrier-phase-based algorithms, among other types of data sources, to obtain precise and true positions, which is also primarily true for the use of GNSS geodetic receivers, but also increasingly true for mass-market devices. The experiment was conducted under line-of-sight conditions on a straight road during a period of no traffic. The receivers were positioned on the roof of a car travelling at low speed in the presence of a static jammer, while kinematic relative positioning was performed with the static reference base receiver. Interference mitigation techniques in the GNSS receivers used, which were unknown to the authors, were compared using (a) the observed carrier-to-noise power spectral density ratio as an indication of the receivers ability to improve signal quality, and (b) the post-processed position solutions based on RINEX-formatted data. The observed carrier-to-noise density generally exerts the expected dependencies and leaves space for comparisons of applied processing abilities in the receivers, while conclusions on the output data results comparison are limited due to the non-synchronized clocks of the receivers. According to our current and previous results, none of the GNSS receivers used in the experiments employs an effective type of complete mitigation technique adapted to the chirp jammer

GPS-Derived Motion of the Adriatic Microplate from Istria Peninsula and Po Plain Sites, and Geodynamic Implications

We studied the motion of the Adriatic microplate using Eurasian-referenced GPS-derived velocities from Istria Peninsula (Slovenia, Croatia) and Po Plain (Italy) sites and earthquake slip vectors around its edges from a Regional Centroid Moment Tensor catalogue. We explored kinematic parameters by inverting GPS velocities using a variety of site combinations and comparing results. Our best-fitting GPS Adria–Eurasia angular velocity vector (Euler pole) comes from 7 Istria Peninsula (Slovenia, Croatia) and 10 Po Plain (Italy) sites; it locates at 45.03°N, 6.52°E, with a 0.297 ± 0.116°/Myr counterclockwise rotation rate. This new GPS-derived pole locates and overlaps with our earthquake slip-vector-derived pole. An Adriatic microplate interpretation is at odds with Neogene geologic features that indicate recent convergence across the Apennines and Alps. The neotectonics–geology mismatch probably signals the recent birth of the Adria microplate upon termination of the Nubia–Eurasia Alpine collison and Adria slab break-off beneath the Apennines