Search

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.

High sensitivity GPS receivers represent an attempt at seamless navigation in conditions that are not favourable for satellite reception. Reception of very weak signals is enabled through the special structure of these receivers and special signal processing techniques. Observation error sources, especially multipath, can cause large errors in position. The concept of high sensitivity GPS receivers operation is presented. The potential of signal processing using robust statistic methods and Doppler observables is discussed. The multipath error can be estimated using Doppler observables.

Unmanned aerial vehicle (UAV) photogrammetry is one of the most effective methods for capturing a terrain in smaller areas. Capturing a steep terrain is more complex than capturing a flat terrain. To fly a mission in steep rugged terrain, a ground control station with a terrain following mode is required, and a quality digital elevation model (DEM) of the terrain is needed. The methods and results of capturing such terrain were analyzed as part of the Belca rockfall surveys. In addition to the national digital terrain model (NDTM), two customized DEMs were developed to optimize the photogrammetric survey of the steep terrain with oblique images. Flight heights and slant distances between camera projection centers and terrain are analyzed in the article. Some issues were identified and discussed, namely the vertical images in steep slopes and the steady decrease of UAV heights above ground level (AGL) with the increase of height above take-off (ATO) at 6%-8% rate. To compensate for the latter issue, the custom DEMs and NDTM were tilted. Based on our experience, the proposed optimal method for capturing the steep terrain is a combination of vertical and oblique UAV images.

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.

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.

SI: Navigacijski sistemi običajno temeljijo na sprejemnikih GNSS. Članek predstavlja trenutno stanje sistemov GNSS, navigacijo s tehnologijami GNSS in opisuje GPS-navigacijske instrumente. Nekatere naloge zahtevajo neprekinjeno navigacijo, česar ne moremo zagotoviti samo z uporabo GNSS-navigacije. Sistem za neprekinjeno navigacijo dopolnjujejo inercialni navigacijski sistemi. Predstavljene so osnove inercialne navigacije, opisane so inercialne merilne enote,navedeni tipi IMU in tipični pogreški inercialnih senzorjev. Predstavljeni sta dve metodi obdelave podatkov združenih sistemov GNSS/INS, tradicionalni Kalmanov filter in umetne nevronske mreže, ki po nekaterih raziskavah dosegajo boljše rezultate kot Kalmanov filter. Omenjeni sta še dve dodatni možnosti za izboljšanje ali celo zagotovitev neprekinjene navigacije, psevdoliti in širokopasovni radijski valovi. EN: Navigation systems are commonly based on GNSS receivers. The article presents the current status of GNSS, discusses GNSS navigation and describes GPS navigation instruments. Some applications require seamless navigation which cannot be provided byGNSS itself. The system for uninterrupted navigation uses Inertial Navigation System besides GNSS. The bases of inertial navigation, Inertial Measurement Units, types of IMU and typical inertial sensorerrors are presented. The processing of data from an integrated GNSS/INS is usually performed either by a traditional Kalman Filter or an artificial neural network. According to some of the research, the latter performs better than the conventional Kalman Filter.Seamless navigation can be improved or even made possible by the use of pseudolites or Ultra-wide Band.