Ljubljana, Slovenia
Ljubljana, Slovenia

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Cekada M.T.,Geodetski Institute Slovenije
Geografski Obzornik | Year: 2015

200 years from Tambora eruption - the last advance of Little Ice Age: Consequences testified in Slovenian oral tradition from Solĉava Glaciers advanced during the Little Ice Age until the year 1850. Last decade of this quite long period of cold weather, very favourable for the growth of glaciers, can be attributed to two volcanic eruptions in 1809 and 1815. The last eruption of the volcano Tambora, has caused "year without a summer" in 1816 and further two more years of distinctly bad weather, which caused widespread famine in the world. This famine also affected the population of Slovenia, as it is documented in the records of Joža Vršnik from the Solĉava Region. In 1810 the famine around Solĉava was supposedly so severe that people were dying from it.

Berk S.,Geodetski Institute Slovenije | Komadina Z.,Geodetska uprava Republike | Triglav J.,Geodetska uprava Republike Slovenije
Geodetski Vestnik | Year: 2011

A consistency analysis of D48/GK and D96/TM coordinates of more than 62,000 cadastral boundary (CB) points in the Mura region, which were determined after 1st January 2008, i.e. according to the new Real Estate Recording Act, is presented. Such an analysis can be realized without any additional measurements being taken, but only by using a high quality transformation model. The country-wide triangle-based transformation, Version 3.0, was used as a reference model. The reasons for the inconsistency between D48/GK and D96/TM coordinates of CB points according to the reference transformation model are low accuracy or gross errors in D96/ TM coordinates (GNSS measurements) and D48/ GK coordinates (classical measurements). Rather than in direct measurement, D48/GK coordinates are obtained indirectly by using transformation. In that case, the inconsistency is caused by poor quality transformation parameters. In addition to possible low quality tie points, there may be an insufficient number of tie points used, or their inadequate spacing. The inconsistency between the coordinates of CB points could also be caused by some problems in the control network and low accuracy of the reference transformation model. The aims of the consistency analysis are quality control of surveys of CB points and quality control of the triangle-based transformation model. To achieve these aims, independent surveys were carried out at the selected locations within the testing area.

Mongus D.,University of Maribor | Triglav Cekada M.,Geodetski Institute Slovenije | Zalik B.,University of Maribor
Geodetski Vestnik | Year: 2013

This paper reviews two methods for digital terrain model generation from LiDAR data in test cases in Slovenia; both methods are based on concepts of mathematical morphology. A general overview of methods is given in the introduction, one of which is presented in more detail. The results show that both methods are able to correctly extract terrain points in more than 90% of the cases and are, therefore, suitable for usage even for such geographically diverse regions as Slovenia. Although the accuracy of both methods is comparable in cases of flat areas, the described method performs significantly better in problematic cases, such as hilly areas with relatively steep variable slopes, and terrains containing terraces. Even in these cases, the average absolute height error is not higher than 15 cm.

Aerial laser scanning (LIDAR) enables quick acquisition of terrain data and it can be used for the study of terrain under the vegetation. Therefore LIDAR is very appropriate for different geomorphologic studies. In this paper different characteristics of LIDAR are described, especially those which are important for decision, if LIDAR data are appropriate for the possible needs. The most important factors are the number of points per area unit (points/m 2) and the positional accuracy of the LIDAR data. On the example of landslides, rockfalls and different karst features the most suitable LIDAR data sets are defined. Based on the dimension of different geomorphologic features the number of LIDAR points per square meter will be defined. The largest landslides and different karst features can be studied with LIDAR data of 5 to 12 points/m 2. For medium extent landslides and smaller rockfalls the usage of more than 12 points/m 2 is recommended. For monitoring of more dynamic geomorphologic features, such as landslides, very accurate LIDAR data is needed. For static features, such as different karst features, only average LIDAR accuracy is needed.

Radovan D.,Geodetski Institute Slovenije
Geodetski Vestnik | Year: 2011

The geodetic profession provides geodetic data obtained in the fields of fundamental geodetic system, real estate and topography. Users integrate this data with other spatial data. The quality of such applications depends on the data quality; however, the providers and the users are not sufficiently aware of the cascading transfer of errors from the primary data layers to the secondary, derived data. Geodesy has traditionally considered errors mainly as positional errors, according to the law of the transfer of errors. Since the era of widespread digitizing of geodetic data began in the 1990s, data quality in the realm of geographic information systems has been expressed with the standardized parameters of data quality, and with metadata, of which positional accuracy is just one type. Unfortunately, in this way, the knowledge about which data is a reference can be obscured. To many users, it is not clear what is the specified quality referred to. This article describes, and intentionally uses, the term 'cascading', since for the rise of data quality one needs to upgrade data level by data level, starting first with the reference data and the semantic definitions of object types, and continuing by updating and harmonizing the secondary data, which were developed from the primary level. The reasons for the change of paradigm regarding the treatment of quality are considered. As the cascading poor quality of geodetic data can become a serious threat for the reputation of the profession of geodesy, several contemporary applications and projects are described in which this has already happened. In the conclusion, proposals are given for improving the situationion.

Cekada M.T.,Geodetski Institute Slovenije | Zorn M.,Geografski Institute Antona Melika | Kaufmann V.,University of Graz | Lieb G.K.,University of Graz
Geodetski Vestnik | Year: 2012

In the last century and a half, average summer temperatures have slowly been rising worldwide. The most observable consequence of this is the change in glacier sizes. For monitoring glacier area and volume, various measuring techniques exist-from measurements with a measuring tape and geodetic measurements to remote sensing and photogrammetry. A comparison of different measuring techniques on two Slovenian glaciers (the Triglav and Skuta glaciers) and two Austrian glaciers (the Gössnitzkees and Hornkees glaciers) is made. A long-term glacial retreat trend is presented for the Gössnitzkees, Hornkees, and Triglav glaciers because these glaciers can be monitored throughout the entire twentieth century by means of archival data. Despite their different sizes, the annual trend of glacial retreat was approximately the same in the period between 1929 and 2006.

A procedure of robust determination of the approximate coordinates of points in a horizontal geodetic network is presented. The primary aim is not accuracy but the reliability of the obtained coordinates. The motivation is to enable further processing according to the Gauss-Markov model. It is a linear mathematical model, thus the approximate values of unknowns are necessary input data. Disposable methods of determining coordinates of points and combinatorics of over-determined solutions dependent upon redundant observations are discussed. A geometrical approach is used, based on the fact that every point is an intersection of a pair of curves. The geometrical quality of each individual solution is evaluated from the intersection angle of both curves. A weight assigned to each solution is a function of that angle. Calculating coordinates is a successive procedure; each step assures the determination of one network point. The algorithm comprises searching for a typical solution among all solutions for an individual point. In order to avoid eventual gross errors, the procedure is based on robust statistics. The efficiency of three basic measures of location is tested on a practical example. The point is a generalization of mean, median, and mode i.e. the centre of mass, spatial median, and spatial mode. Gross errors are introduced into the network by using a Monte Carlo simulation.

Lenarcic A.S.,Center odlicnosti Vesolje | Mesner N.,Geodetski Institute Slovenije | Ostir K.,Institute za antropoloske in prostorske studije
Geodetski Vestnik | Year: 2015

Sentinel satellites and the European Copernicus programme have begun to provide huge amounts of high spatial and temporal resolution images, which need to be processed quickly and preferably automatically. Object based classification is the most commonly used method for the interpretation of high spatial resolution optical images. It is a challenging process of object borders recognition (segmentation) and classification of segments in the user-defined classes (classification). The quality of the segmentation is crucial because it has a direct impact on the quality of final classification results. Several algorithms have been developed for optical remote sensing imagery segmentation with varying (depending on the purpose of the analysis) accuracy. Knowledge of algorithms and adequacy of application are crucial for high quality segmentation results. In this paper, we give an overview of optical remote sensing imagery segmentation algorithms and the possibility of their application. Besides, an overview of object based classification software, with a focus on segmentation process, is given. The intent of this paper is not to provide a recipe for the best algorithm and software selection, but to support users with knowledge they might need to be able to obtain the best possible segmentation results of an analysis in given circumstances. © 2015 Zvava Geodetov Slovenije. All rights reserved.

A set of cyclical aerial photogrammetric measurements of Slovenia (CAS) taken over the course of many years is available. Among other things, their use in geography has been connected with exploring changes in land use, studying environmental degradation, and determining specific physical geographical changes in the landscape, such as changes in glaciers and river beds. This article presents the usefulness of CAS for monitoring the intensity of slope processes. CAS stereoimages were used to measure the size of two rock-falls: one at Čedca Falls in the Kamnik-Savinja Alps and one on the slopes of Mt. Glava below Mt. Triglav. Also studied were terrain changes on the Birški plaz talus below Mt. Veliki Vrh on the Košuta Ridge in the Karavanks, and in the torrent valley of Suhelj Creek in the Upper Sava Valley. © 2014 Zveza geografov Slovenije. All Rights reserved.

Bric V.,Geodetski Institute Slovenije | Berk S.,Geodetski Institute Slovenije | Triglav Cekada M.,Geodetski Institute Slovenije
Geodetski Vestnik | Year: 2013

This paper deals with the problems of quality assurance for airborne laser-scanning data. Partial results of the project entitled 'Laser Scanning and Aerial Photographing of Slovenia 2011' are presented, and the quality control procedure is described. The focus is on the quality assurance of the geo-referencing used for water resource management. Important issues with an impact on the quality of data are addressed and evaluated. The quality of direct geo-referencing was investigated, and some experiences gained in the quality control of the project results are presented. The quality of the transformation of data into the national horizontal and height reference systems is also discussed. Some recommendations for the quality improvement of airborne laser-scanning data are given. This will be possible with the realisation of the new national height reference system and with the creation of the new geoid model.

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