The territory of Slovenia sits in the NE corner of the active collisional boundary between the Eurasian plate and the Adriatic microplate, which at this location near its Euler pole, indents north-northeastward at a velocity of 2-4 mm/yr. Using velocities from more than 40 permanent GNSS stations located within Slovenia and immediate surroundings we analyzed the regional distribution and structural style of active tectonic deformation and assessed activity along and across the main fault systems. (Stations are in the SIGNAL network and the national zero-order geodetic network.) From 2010-2025 GNSS observations, we determined daily coordinates in a Eurasian reference frame, used these to establish coordinate time series, and derived horizontal velocity vectors at each site. Data from more than 70 campaign GNSS stations surveyed between 1994 and 2016 were also similarly analyzed. By interpolating between the obtained point velocity vectors, we calculated a continuous strain-rate field. Velocity profiles were then constructed and analyzed for elastic strain accumulation across major fault systems. Relocated earthquake hypocenters from 2004-2024 and the new high-quality ARSO focal mechanism database were used to enhance our analysis.Based on the distribution of strain-rates and seismicity, we divide Slovenia into three distinct active deformation domains: 1) The coastal zone, which is on the Adriatic microplate, exhibits minor (< 1 mm/yr) internal deformation and shows a pronounced counterclockwise rotation; 2) A central transpressive zone, which is approximately 70 km wide and extends from NW Slovenia eastward and southeastward into the Sava Folds, accommodates the highest rates of deformation in Slovenia and exhibits the highest shear strain rates, which is reflected by the abundance of strike-slip and oblique-reverse focal mechanisms there. In its western segment, approximately 40% of the deformation occurs along the Periadriatic fault system; the remainder is accommodated by Dinaric faults; 3) NE Slovenia, located east and north of the Periadriatic fault system, behaves as a rigid block translating (extruding) slowly (< 1 mm/yr) toward the NE with negligible internal deformation; this domain probably belongs to the slowly extruding ALCAPA/Pannonian block that has been suggested in earlier studies.

Low-cost (LC) Global Navigation Satellite System (GNSS) receivers are argued as an alternative solution to geodetic GNSS counterparts for different applications. Single-frequency low-cost (SF-LC) GNSS receivers have been in the market for many years while their inability to acquire GNSS observations in second frequency limited their use. A few years ago, dual-frequency low-cost (DF-LC) GNSS receivers with enhanced capabilities entered the mass market, considering the advancements they have been tested and evaluated by many researchers. Lastly, multi-frequency low-cost (MF-LC) GNSS receivers become available. With the ability to track more satellite signals, these GNSS receivers are expected to obtain better overall performance. This review article aims to analyze recent advances and applications of LC GNSS receivers. To provide answers to the research question relevant articles were selected and analyzed. From the reviewed articles, it was concluded that the performance of SF-LC and DF-LC GNSS receivers is comparable to that of geodetic counterparts only in open-sky conditions. However, in adverse conditions, the differences become more highlighted. In such environments, SF and DF-LC GNSS receivers face challenges not only with positioning quality but also with their proper work. Limited studies on MF-LC receivers have reported comparable observations and positioning performance to geodetic GNSS receivers. Despite drawbacks, LC GNSS receivers have been successfully applied in surveying, mapping, geodetic monitoring, precision agriculture, navigation, atmosphere monitoring, Earth surface monitoring, and other fields.

This paper examines mathematical models for processing classical horizontal geodetic (triangulation and trilateration) networks. Two rigorous parametric adjustment models are discussed. The first one is a well-known model of adjustment in the geodetic coordinate system. This model is completely rigorous (functional and stochastic parts) and uses unreduced distance and direction observations. The proposed alternative is a model of planar network adjustment with observations rigorously reduced directly to the mapping plane. These ground-to-grid reductions are simple and universal, regardless of which map projection is used. Slightly different results of the planar network adjustment are obtained. The differences are attributed to a non-rigorous stochastic model. In theory, the stochastic properties of the reduced observations should also be adapted. However, these differences are very small and can always be neglected in geodetic and surveying practice.

The article presents the use of photogrammetric traverses for image orientation and the acquisition of mass spatial data in environments where GNSS (Global Navigation Satellite Systems) or tachymetric surveys are not available or not reliable, such as inside buildings. The photogrammetric traverses were tested indoors. The basic idea of a photogrammetric traverse is to start from an area where the positions of the ground control points are surveyed and then use a still camera to develop a traverse of overlapping images. The images are then processed with SfM (Structure from Motion) to calculate their orientation and accuracy of points along the traverse. The study tested the accuracy and reliability of linked, looped and open photogrammetric traverses. The positional accuracy of the check points was better than 10 cm, even when adjusting several hundred images in the least accurate open traverse.

Over the past two decades, low-cost single-frequency Global Navigation Satellite System (GNSS) receivers have been used in numerous engineering fields and applications due to their affordability and practicality. However, their main drawback has been the inability to track satellite signals in multiple frequencies, limiting their usage to short baselines only. In recent years, low-cost dual-frequency GNSS receivers equipped with Real-Time-Kinematic (RTK) engines entered the mass market, addressing many of the limitations of single-frequency GNSS receivers. This review article aimed to analyze the observations and positioning quality of low-cost GNSS receivers in different positioning methods. To provide answers to defined research questions, relevant studies on the topic were selected and investigated. From the analyzed studies, it was found that GNSS observations obtained from low-cost GNSS receivers have lower quality compared to geodetic counterparts, however, they can still provide positioning solutions with comparable accuracy in static and kinematic positioning modes, particularly for short baselines. Challenges persist in achieving high positioning accuracy over longer baselines and in adverse conditions, even with dual-frequency GNSS receivers. In the upcoming years, low-cost GNSS technology is expected to become increasingly accessible and widely utilized, effectively meeting the growing demand for positioning and navigation.

Low-cost dual-frequency global navigation satellite system (GNSS) receivers have recently been tested in various positioning applications. Considering that these sensors can now provide high positioning accuracy at a lower cost, they can be considered an alternative to high-quality geodetic GNSS devices. The main objectives of this work were to analyze the differences between geodetic and low-cost calibrated antennas on the quality of observations from low-cost GNSS receivers and to evaluate the performance of low-cost GNSS devices in urban areas. In this study, a simple RTK2B V1 board u-blox ZED-F9P (Thalwil, Switzerland) was tested in combination with a low-cost calibrated and geodetic antenna in open-sky and adverse conditions in urban areas, while a high-quality geodetic GNSS device was used as a reference for comparison. The results of the observation quality check show that low-cost GNSS instruments have a lower carrier-to-noise ratio (C/N-0) than geodetic instruments, especially in the urban areas where the difference is larger and in favor of the geodetic GNSS instruments. The root-mean-square error (RMSE) of the multipath error in the open sky is twice as high for low-cost as for geodetic instruments, while this difference is up to four times greater in urban areas. The use of a geodetic GNSS antenna does not show a significant improvement in the C/N-0 and multipath of low-cost GNSS receivers. However, the ambiguity fix ratio is larger when geodetic antennas are used, with a difference of 1.5% and 18.4% for the open-sky and urban conditions, respectively. It should be noted that float solutions may become more evident when low-cost equipment is used, especially for short sessions and in urban areas with more multipath. In relative positioning mode, low-cost GNSS devices were able to provide horizontal accuracy lower than 10 mm in urban areas in 85% of sessions, while the vertical and spatial accuracy was lower than 15 mm in 82.5% and 77.5% of the sessions, respectively. In the open sky, low-cost GNSS receivers achieve a horizontal, vertical, and spatial accuracy of 5 mm for all sessions considered. In RTK mode, positioning accuracy varies between 10-30 mm in the open-sky and urban areas, while better performance is demonstrated for the former.

The development of low-cost dual-frequency global navigation satellite system (GNSS) receivers in recent years has enabled the use of these devices in numerous applications. In the monitoring of natural hazards, such as landslides, these devices can be considered suitable sensors. In this work, dual-frequency GNSS receivers and antennas were used for setting up near-real-time continuous low-cost GNSS monitoring systems (LGMSs) under field conditions. The SimpleRTK2B board, which integrates the u-blox ZED-F9P dual-frequency GNSS chip and the survey-calibrated GNSS antenna are the main components of the GNSS system. The LGMS was installed and tested for six months in the Laze landslide located in the northwestern part of Slovenia. A total of four GNSS systems were deployed, three of which were located in pillars in the landslide itself and one in a stable area. Open-source software was used to postprocess the acquired data, providing daily coordinates in static relative and precise point positioning (PPP) positioning modes. The results of six months of near-real-time monitoring showed that the Laze landslide was stable during this period, with only minor changes in the vertical component. The trend of decreasing ellipsoid height was evident at all stations, although it was in the range of a few millimeters. To validate the results in static relative positioning mode, the coordinate differences between low-cost and high-end geodetic GNSS instruments were estimated and found to be in the range of 5 mm or less, while the difference between horizontal and spatial positions was less than 7 mm for all stations. The same data were processed in PPP, vertical displacements were not detected as in the static relative positioning mode due to the lower accuracy of the method itself. Considering the six-month performance of a low-cost GNSS system under field conditions, it can be emphasized that these devices are capable of performing near real-time continuous monitoring of slow movements with high accuracy and decreased costs. In addition, an experimental test was performed to identify the size of detected displacements in real-time kinematic (RTK). Based on the achieved results, it was concluded that 20 mm spatial displacements are detectable with LGMSs in RTK considering only 15 s of observations.

An analysis of the present-day geodetic marks representing trigonometric points of the 2nd and 3rd order was carried out in the area of Slovenia that was part of the Kingdom of Italy between 1920 and 1947. By reviewing topographies, photographs on hribi.net and sample field surveys, we identified, among the 52 2nd order points, 16 points that had the Italian type of geodetic marks and 6 points with even older types of geodetic marks, dating back to the Austro-Hungarian Monarchy. Among the 407 3rd order points, we identified 68 Italian geodetic marks and 15 even older ones. The so-called Italian type of geodetic mark can be recognised as a concrete pillar with a square or octagonal shape, about 1 m high, with a diameter of 40 to 70 cm. The even older geodetic marks are carved from natural stone. These often have the dual function of being a trigonometric point mark and a land cadastral mark, indicating the boundary of cadastral municipalities. We also investigated the eccentric metal target signals erected in 1996, and those between 1995 and 1997, which were an additional post -consolidation of the existing granite trigonometric marks installed after the Second World War. Finally, we highlight the potential of these old geodetic marks in the design and planning of new measurements in the future.

Global Navigation Satellite System (GNSS) low-cost multi-frequency receivers are argued as an alternative to geodetic receivers for many applications. Calibrated low-cost antennas recently became available on the market making low-cost instruments more comparable with geodetic ones. The main goal of this research was to evaluate the noise of low-cost GNSS receivers, to compare the positioning quality from different types of low-cost antennas, and to analyze the positioning differences between low-cost and geodetic instruments. The results from a zero baseline test indicated that the u-blox multi-frequency receiver, namely, ZED-F9P, had low noise that was at the sub-millimeter level. To analyze the impact of the antennas in the obtained coordinates, a short baseline test was applied. Both tested uncalibrated antennas (Tallysman TW3882 and Survey) demonstrated satisfactory positioning performance. The Tallysman antenna was more accurate in the horizontal position determination, and the difference from the true value was only 0.1 mm; while, for the Survey antenna, the difference was 1.0 mm. For the ellipsoid height, the differences were 0.3 and 0.6 mm for the Survey and Tallysman antennas, respectively. The comparison of low-cost receivers with calibrated low-cost antennas (Survey Calibrated) and geodetic instruments proved better performance for the latter. The geodetic GNSS instruments were more accurate than the low-cost instruments, and the precision of the estimated coordinates from the geodetic network was also greater. Low-cost GNSS instruments were not at the same level as the geodetic ones; however, considering their cost, they demonstrated excellent performance that is sufficiently appropriate for various geodetic applications.

Recently, a new national height reference system was implemented: the Slovenian Height System 2010 (SVS2010). This new system replaced the Slovenian Height System 2000 (SVS2000). It is a new realisation of a national height system, which is based on new levelling and gravity surveys and recent tide gauge data. Its implementation changes the height datum (from Trieste to Koper) as well as the type of heights (from normal-orthometric to normal). Consequently, differences between the old and new height reference systems from 1.4 cm to 30.8 cm were detected. Unfortunately, there is no simple transformation between the two height reference systems. The surveyor must choose an appropriate method of local transformation or recalculation based on the given data and the required accuracy. To provide all necessary information for the users, the Surveying and Mapping Authority of the Republic of Slovenia has, in cooperation with the Faculty of Civil and Geodetic Engineering at the University of Ljubljana, prepared a new Technical instruction for the use of the new national height system. Online software called SiVis is also available for converting GNSS-based heights into both height reference systems (SVS2000 and SVS2010). Due to some problems with the (old) AMG2000/Trst geoid model near the national boundary, this model was extrapolated to a buffer covering parts of neighbouring countries. EPSG codes for both national height reference systems of Slovenia were also created.

The horizontal component of the national spatial reference system of Slovenia is based on EUREF GPS campaigns at the passive GNSS-network of EUREF sites in the years 1994-1996. Both active GNSS networks (the SIGNAL and Zero-Order Combined Geodetic Networks) were established afterwards, which caused inconsistencies in coordinates based on GNSS surveys. Furthermore, the lifetime of the national coordinate reference system (D96) might be expired after two decades from its realization due to relatively active tectonics. A new GNSS campaign was carried out in 2016 in order to validate and improve the quality of coordinates of GNSS sites in Slovenia. The result is a new realization of ETRS89 referred to as D17. However, it was not implemented directly due to substantial coordinate differences when compared to the previous realization. A pragmatic approach was chosen that attempted to keep changes of coordinates as small as possible. It eliminated inconsistencies but also distortions in GNSS networks caused by the changes in physical space. The new coordinates are based on both the old (D96) and new (D17) realizations of ETRS89 and are denoted by D96-17. According to the requirements for the quality of coordinates in the land cadastre surveys, all the previously determined coordinates of cadastral points remain unchanged. The main benefit of the update of coordinates in the core GNSS networks in the country is more precise and accurate positioning in the future.

In this paper, the theoretical background of the Caspary method of geodetic deformation analysis is described and implemented in a simulated geodetic network in which two epochs of measurements are used. The Caspary approach foresees congruence testing of the geodetic network, the determination of the stable points between two analysed epochs, the transformation of the geodetic network using S-transformation, the calculation of displacements, and, in the last step, the graphical presentation of displacement vectors. Results obtained from the presented example are similar to those presented in the Hannover, Karlsruhe, Delft, Fredericton, Munchen, and robust methods.

The horizontal component of the national spatial reference system of Slovenia is based on EUREF GPS campaigns at the passive GNSS-network of EUREF sites in the years 1994–1996. Both active GNSS networks (the SIGNAL and Zero-Order Combined Geodetic Networks) were established afterwards, which caused inconsistencies in coordinates based on GNSS surveys. Furthermore, the national coordinate reference system (D96) was supposed to expire after two decades from its realization due to relatively active tectonics. A new GNSS campaign was carried out in 2016 in order to validate and improve the quality of coordinates of GNSS sites in Slovenia. The result is a new realization of ETRS89 referred to as D17. However, it was not implemented directly due to substantial coordinate differences when compared to the previous realization. A pragmatic approach was chosen that attempted to keep changes of coordinates as much small as possible. It eliminated inconsistencies but also distortions in GNSS networks caused by the changes in physical space. The new coordinates are based on both the old (D96) and new (D17) realizations of ETRS89 and are denoted by D96-17. According to the requirements for the quality of coordinates in the land cadastre surveys, all the previously determined coordinates of cadastral points remain unchanged. The main benefit of the update of coordinates in the core GNSS networks in the country is more precise and accurate positioning in the future.

Global Navigation Satellite System (GNSS) technology is widely used for geodetic monitoring purposes. However, in cases where a higher risk of receiver damage is expected, geodetic GNSS receivers may be considered too expensive to be used. As an alternative, low-cost GNSS receivers that are cheap, light, and prove to be of adequate quality over short baselines, are considered. The main goal of this research is to evaluate the positional precision of a multi-frequency low-cost instrument, namely, ZED-F9P with u-blox ANN-MB-00 antenna, and to investigate its potential for displacement detection. We determined the positional precision within static survey, and the displacement detection within dynamic survey. In both cases, two baselines were set, with the same rover point equipped with a low-cost GNSS instrument. The base point of the first baseline was observed with a geodetic GNSS instrument, whereas the second baseline was observed with a low-cost GNSS instrument. The results from static survey for both baselines showed comparable results for horizontal components; the precision was on a level of 2 mm or better. For the height component, the results show a better performance of low-cost instruments. This may be a consequence of unknown antenna calibration parameters for low-cost GNSS antenna, while statistically significant coordinates of rover points were obtained from both baselines. The difference was again more significant in the height component. For the displacement detection, a device was used that imposes controlled movements with sub-millimeter accuracy. Results, obtained on a basis of 30-min sessions, show that low-cost GNSS instruments can detect displacements from 10 mm upwards with a high level of reliability. On the other hand, low-cost instruments performed slightly worse as far as accuracy is concerned.

Recently, a new national height reference system was implemented: the Slovenian Height System 2010 (SVS2010). This new system replaced the Slovenian Height System 2000 (SVS2000). It is a new realisation of a national height system, which is based on new levelling and gravity surveys and recent tide gauge data. Its implementation changes the height datum (from Trieste to Koper) as well as the type of heights (from normal-orthometric to normal). Consequently, differences between the old and new height reference systems from 1.4 cm to 30.8 cm were detected. Unfortunately, there is no simple transformation between the two height reference systems. The surveyor must choose an appropriate method of local transformation or recalculation based on the given data and the required accuracy. To provide all necessary information for the users, the Surveying and Mapping Authority of the Republic of Slovenia has, in cooperation with the Faculty of Civil and Geodetic Engineering at the University of Ljubljana, prepared a new Technical instruction for the use of the new national height system. Online software called SiVis is also available for converting GNSS-based heights into both height reference systems (SVS2000 and SVS2010). Due to some problems with the (old) AMG2000/Trst geoid model near the national boundary, this model was extrapolated to a buffer covering parts of neighbouring countries. EPSG codes for both national height reference systems of Slovenia were also created.

For more than a decade, the GNSS Service at the Geodetic Institute of Slovenia has been managing the national GNSS CORS network SIGNAL, and since 2016 also the GNSS part of the national Zero-Order Geodetic Network. During this period, different problems in the operation of CORS networks have been encountered, and much experience in the field of management and quality control of CORS networks has been gained. In cooperation with the Chair of Mathematical and Physical Geodesy and Navigation at the UL FGG and the Surveying and Mapping Authority of the Republic of Slovenia, a research project named The increase of reliability of public GNSS network SIGNAL and combined zero-order geodetic network was carried out in 2018 and 2019. Based on all the experience gained, a methodology for upgrading and improving the current procedures for management of both national CORS networks, with an emphasis on improving operational reliability and the quality control of both networks, was developed. In this article, the results of that project are presented.

In December 2018, a new national height system called the Slovenian Height System 2010' was introduced (denoted as :WS:2010 It is based on a new levelling network of the first onder, which has been measured over the previous decade. For geopotential number computation with simultaneous levelling measurements, gravimetric measurements were carried out an the benchmark; of the first order levelling network &sedan geopotential numbers, normal heights were computed, as they were chosen as the new official type of heights Anew height datum has also been introduced determined . from 18.6 years of sea level observations on the tide gauge station in Koper, Slovenia with the mean epoch 10. 10. 2010. The new height reference surface (quasi geoid), named 'SLO _VRP2016/Koper' was determined All levelling lines of lower orders are recalculated in the new vertical datum, so all benchtmark; kept in the dataset of geodetic points have a newly determined height. The differences in heights between the old and the new height systems range from 1.4 cm to 30.8 cm.