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Traditional measurement methods are still widely used for recording cultural heritage objects. On the other hand, geodetic surveying and modern technologies such as 3D laser scanning can provide more accurate, geometrically consistent and extremely detailed data that can be used as a basis for detailed vector maps or 3D models. The main aim of our research was to investigate the complementary approach, using both traditional and modern methods, in order to produce detailed vector maps of the Romanesque church of St. Martin in Chapaize, France, which are essential for further unveiling its historic development. Geometrically, this church is rather extensive and has many irregularities in its shape. Our approach to the documentation process is presented and evaluated in this paper. We applied the Procrustes analysis for the ground floor map, which gave us an objective accuracy assessment. Point clouds of the bell tower acquired by two different laser instruments have also been compared.

This article describes the geodetic network of the Urbas landslide. It is the largest landslide in the Koroška Bela region, which, if triggered, can endanger human lives and damage infrastructure. In order to monitor the landslide, a geodetic network was established in the area of the Urbas landslide, on the basis of which the movements of control points can be calculated. After various analyses, only two small areas near the Urbas landslide proved to be stable, so we established four reference points there. In this research we defined the geodetic datum of the geodetic network of the Urbas landslide. The geodetic datum was defined on the basis of four measurement epochs processed with our own software.

In this work, we analyzed the quality of height transformation between the old height system SVS2000 (vertical datum Trieste) and the new height system SVS2010 (vertical datum Koper). Based on the height differences of the benchmarks between the old and the new height systems stabilised in the area of eastern Slovenia, we determined the height transformation surface for two areas of different sizes. For both areas we analyzed the influence of different interpolation methods and the influence of using height differences of benchmarks of different orders of the levelling net. We found that the quality of height transformation is satisfactory for most surveying services. We have also analyzed the quality of the height transformation based on the average height difference of the benchmarks by using the SiVis software, which is intended for the transformation of ellipsoidal heights obtained by GNSS measurements, between the old and the new height systems.

In December 2018, a new national height system called the ‘Slovenian Height System 2010’ was introduced (denoted as ‘SVS2010’). It is based on a new levelling network of the first order, which has been measured over the previous decade. For geopotential number computation with simultaneous levelling measurements, gravimetric measurements were carried out on the benchmarks of the first order levelling network. Based on geopotential numbers, normal heights were computed, as they were chosen as the new official type of heights. A new 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 benchmarks 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.

In Ribčev Laz near Lake Bohinj there is a model of Triglav, the highest mountain in Slovenia. Made of stones, it is the work of the painter Valentin Hodnik from Bohinj. Although it is a work of art, we wanted to evaluate the correctness of its shape compared to the actual mountain. We photographed it and created a point cloud model using the Structure from Motion process (SfM). By transforming the point cloud to actual size, we were able to compare it with the actual shape of the Triglav mountain range obtained from Laser Scanning of Slovenia (LSS). As expected, the shape of the model varied considerably from the actual shape of the mountain, and the scale of the individual slopes and ridges was not the same. For a qualitative evaluation of the model, we calculated the distances between the transformed model and actual surface. The average absolute distance between the nearest points in both point clouds was 41.8 m (6 cm at a built-model scale) with a standard deviation of 38.0 m (5.4 cm). The results are represented by a picture of absolute distances. We also produced a smaller 3D print of the Triglav model and the actual shape of the mountain.

In coordinate calculation from terrestrial measurements, the reduction due to the Earth's gravity field should be one of the main topics of consideration. The problem is of extreme importance especially in steep areas, where geoid surface is not parallel to the rotational ellipsoid. In this, the knowledge of the deflection of the vertical is significant. There are two ways for its acquisition: from the comparison of astronomic versus geodetic coordinates, or from the indirect way of calculation by using global, regional, or local geoid models. This paper reviews the deflection of the vertical and its use at the steep area under Krvavec. The computation followed from three models, EGM2008 and two Slovene models: the current SLOAGM2000 and the test model SLOAGM2010. In addition, the local geoid model was established from the ellipsoidal and the normal-orthometric heights. Significant differences in vertical deflection components originated from the EGM2008. We can confirm the expectation that in steep areas it is necessary to consider the geoid inclination. The best way to do this is the local geoid surface determination from the ellipsoidal in physical heights. In other cases, local geoid models are still appropriate. Contrary, we should avoid using global models because of their lower resolution.

Tide gauges are used to assess sea level changes. Usually, they are placed on the coast (piers), which can be unstable. Consequently, the vertical movement of the tide gauge should be included in the series of observations. The paper deals with the stability of the tide gauge Station Koper (MP Koper), the stability of which was determined relatively on the basis of the levelling network, which was stabilised nearby. The stability of the individual benchmarks was analysed and the velocity vector of vertical displacement of each benchmark was determined with respect to the benchmark 9000 tide gauge. The stability of the tide gauge was also determined in a global reference system by using the series of GNSS observations of the KOPE continuously operating reference GNSS station. The KOPE station is stabilised at the MP Koper and is included in the Slovenian GNSS network of the SIGNAL continuously operating reference network of permanent stations. The vertical velocity vector of the point KOPE was compared with the vertical velocity vectors at other tide gauges, which are located along the Croatian coast, and the tide gauges in Trieste.

The RANSAC (RANdom SAmple Consensus) is often used to identify points belonging to the objects whose shape can be modeled with geometric primitives. These points, called inliers, are of great interest in some applications but often the goal is also to estimate the parameters of geometric shape and their accuracies. The quality of RANSAC results is rarely analysed. The accuracies of estimated parameters are usually calculated based only on the residuals of inliers, selected by RANSAC, from a mathematical model. However, the analysis does not indicate if the right points were selected. The result of RANSAC depends on the random selection of the minimum number of points that uniquely describe a mathematical model; in the case of multiple repetitions of the method, the results are not necessarily the same. This paper presents an analysis of RANSAC reliability based on repeating the selection of points from the point cloud by RANSAC one hundred times. A standard deviation of one hundred parameter values is used to estimate the parameters’ accuracies. An analysis is made for three different examples of geometric objects: a sphere, a cone, and a plane. Finally, we suggest repeating the algorithm several times and checking the consistency of the results to obtain a more reliable estimation of parameters and their accuracies.

A prototype of a low-cost GNSS (Global Navigation Satellite System) monitoring system was installed on a deep-seated landslide in north-western Slovenia to test its performance under field conditions. The system consists of newly developed GNSS stations based on low-cost, dual-frequency receivers and open-source GNSS processing software. It automatically receives GNSS data and transmits them over the Internet. The system processes the data server-side and makes them available to the end user via a web portal. The detected surface displacements were evaluated through a comparison with the network of classic geodetic measurements. The results of a nine-month monitoring period using seven GNSS stations provided a detailed insight into the spatial and temporal pattern of deep-seated landslide surface movements. The displacement data were correlated with precipitation measurements at the site to reveal how different parts of the landslide react to rainfall. These data form the basis for the further development of an early-warning system which will help to manage the risk the landslide poses to the local population and infrastructure.

Ski jumping hills should be prepared for competitions in accordance with project documentation in order to ensure safe and fair conditions for competitors. Geodesy/surveying is essential for guiding preparations and controlling the actual shape of the hill. In this article, we present a methodology for the control measurements and preparation of an inrun for a ski-flying hill in Planica. On each side of the track, there is metal tube that guides the trolley, which mills tracks into the ice. A special platform containing three measuring prisms was designed to control the position of the tubes. The proposed method was thoroughly analyzed in terms of its measurement quality and compared to previously used methodologies. The empirical results suggest that our proposed platform provides inrun geometry with a higher quality than previously used methods.

Technologies of massive spatial data acquisition from air, compared to a classical terrain measurement, enables an acquisition of large amounts of data in shorter time and with comparable quality. Unmanned aerial vehicle (UAV) photogrammetry is increasingly used in the area of the earthwork volumes determination of landfill or excavation of the building material. Dense multi-image matching obtains high-density point cloud. The input data for the earthwork volumes calculations is a filtered point cloud. The earthwork volume calculations are calculated with the method of surface comparisons of two term measurements, created by a triangulated irregular network (TIN) or grid network. The impacts of different methods for surface interpolation and grid cell size on the earthwork volume calculation are analysed. Reference quantity is the volume, calculated from TIN surfaces. Good interpolation methods and appropriate grid cell sizes are determined with the comparison of volumes from grid and TIN surfaces. The difference between volumes should not exceed 5%.

A point cloud is the result of laser scanning; in the case of terrestrial laser scanning, the point cloud is composed of points scanned from one or more positions. To register these points into one point cloud, so-called tie points are needed; these may be object points (natural targets) or selected stabilized targets (artificial targets). Spherical targets are often used as artificial targets; these must have their centre coordinates and radius determined. The centre coordinates of a sphere are calculated on the basis of scanned points on the spheres’ surface. This paper presents two procedures for determining the best reflection region on the sphere to determine its parameters, and the procedure for determining the optimal distance between the scanner and sphere.The best reflection area on the sphere is determined in two ways. The first is based on minimizing the difference between sphere radii when, in the adjustment process, the radius of the sphere is treated as a known and unknown quantity. The second is based on the standard deviation of the sphere’s centre coordinates at the independent determinations of sphere parameters from randomly chosen scanned points on the sphere surface. For each of the spheres, the best ratio between the laser beam footprint area and the target surface area is calculated for the optimal combination of scanning distance and region. For the best combination of scanning distance and region, we chose the one with the smallest standard deviation of the sphere centre coordinates.

The main goal of our research was to design and implement an innovative target that would be suitable for accurately registering point clouds produced from unmanned aerial vehicle (UAV) images and terrestrial laser scans. Our new target is composed of three perpendicular planes that combine the properties of plane and volume targets. The new target enables the precise determination of reference target points in aerial and terrestrial point clouds. Different types of commonly used plane and volume targets as well as the new target were placed in an established test area in order to evaluate their performance. The targets were scanned from multiple scanner stations and surveyed with an unmanned aerial vehicle DJI Phantom 4 PRO at three different altitudes (20, 40, and 75 m). The reference data were measured with a Leica Nova MS50 MultiStation. Several registrations were performed, each time with a different target. The quality of these registrations was assessed on the check points. The results showed that the new target yielded the best results in all cases, which confirmed our initial expectations. The proposed new target is innovative and not difficult to create and use.

Po poplavah, ki so prizadele Slovenijo v septembru 2010, je Inštitut za vode Republike Slovenije z GNSSvišinomerstvom določil višino geodetskih točk, ki so bile uporabljene za določitev višine poplavne vode na Ljubljanskem barju in v Ljubljani. Višine točk, določene z GNSS-višinomerstvom, smo kontrolirali s trigonometričnim višinomerstvom, z navezavo na reperje mestne nivelmanske mreže Ljubljana. Analizirana je natančnost določitve višin točk in določena razlika med višinami točk, ki so bile določene z GNSS- oziroma trigonometričnim višinomerstvom ; After the floods that hit Slovenia in September 2010, the Institute for Water of the Republic of Slovenia measured the heights of geodetic points (with the GNSS levelling method) used to determine the height of flood water on the Ljubljana moor and Ljubljana. The heights of these points were controlled by trigonometric levelling with connections to the benchmarks of the city levelling network of Ljubljana. An analysis of the accuracy of determining the heights of the points and the differences between the heights of the points, which were determined by GNSS and trigonometric levelling, are presented.

V prispevku je predstavljen predlog za novo oštevilčevanje nivelmanskih poligonov in reperjev. Obravnavana je tudi analiza natančnosti izmerjenih višinskih razlik, opravljena na podlagi odstopanj obojestransko merjenih višinskih razlik in odstopanj pri zapiranju nivelmanskih zank. Na podlagi izravnave nivelmanske mreže in nivelmanskih poligonov je analizirana tudi natančnost na podlagi popravkov merjenih višinskih razlik in izvedena ocena natančnosti določitve nadmorske višine reperjev ; This paper presents a proposal for a new numbering of levelling polygons and benchmarks. Furthermore, an accuracy analysis is done with regard to: measured height differences, residuals calculated from differences of the forward and backward runs, residuals from loop closures, and results from network adjustments.

Topografski podatki, kot pomemben del Nacionalne prostorske podatkovne infrastrukture, so bili v letih po osamosvojitvi Slovenije deležni velike pozornosti, postali so splošno dostopni, bili so dopolnjeni in medsebojno usklajeni. V zadnjem desetletju pa se je vlaganje v topografske podatke v Sloveniji zelo omejilo, zato danes nikakor več ne moremo biti zadovoljni z njihovim stanjem. V prispevku pregledno predstavljamo stanje topografskih podatkov v Sloveniji, analiziramo njihovo kakovost in ustreznost za potencialne in dejanske uporabnike. Posvetimo se izvornim posnetkom stanja, kot je sistemsko ciklično aerosnemanje (CAS), in iz njega izvedenemu proizvodu, ortofotu. Kakovost ortofota je precej odvisna od kakovosti modela reliefa. Topografski podatki so vodeni posamično v sklopu posameznih vsebinskih baz (REZI, ZK GJI, grafični del katastra stavb) ter združeno v topografskih bazah in kartah različnih ravni podrobnosti (DTK 5, DTK 25, DTK 50, sistem DPK). Analizirano stanje primerjamo s stanjem v nekaterih sosednjih ali primerljivih državah ; Topographic data, an important part of the National Spatial Data Infrastructure, have been given serious attention since Slovenia’s independence. It has become publicly available, updated and harmonised. Financing of topographic data in Slovenia has significantly decreased over the previous decade. As a result, the present status is far from acceptable or expected. The current status of the topographic data, as well as its quality and usability for potential users is discussed in this article. The overview starts with basic source data, aerial surveys, photographs and orthophotos. The quality of orthophotos largely depends on the DTM quality. Topographic data is nowadays organised in thematic datasets (geographical names, building cadastre, etc.) or joined in datasets of different levels of accuracy and details. The status in Slovenia is compared to those in some neighbouring and other comparable countries.