Streaming GNSS data via internet using Ntrip protocol

The article presents a means of GNSS data transfer\ud via internet by using the Ntrip protocol. Ntrip is used\ud for streaming data in the standard RTCM form, but it\ud also supports any other data form. The basic elements\ud and the basis of Ntrip operation are presented. Use of\ud Ntrip is related to mobile internet, especially to packet\ud data transfer GPRS. The article discusses the use of\ud Ntrip and GPRS data transfer from user’s perspective\ud in the Slovenian GNSS network SIGNAL

Development of GNSS data processing procedures for pedestrian navigation in challenging environments

High sensitivity GPS receivers have expanded the use of the GNSS to areas with difficult reception of the signals from the satellites. Difficult conditions indicate attenuation and reflection of the signals. Receivers achieve higher sensitivity of signal reception by larger number of correlators and longer integration time. The present doctoral dissertation deals with classical methods of observation processing in normal conditions used for observation processing in challenging environments. Some of the methods are more effective in difficult conditions than others. Processing of observation data in dynamic and quick changing conditions requires careful and consistent treatment. Otherwise a gross error in position determination can occur. Multipath has the biggest influence on final results and has a special effect on code observations. Therefore, Doppler observations are also included in the position determination. The custom developed procedure of positioning in challenging environments beside well known and established methods includes additional methods which assure higher accuracy and reliability of the determined position. Processing procedures have been tested in different conditions in static and kinematic cases. The acquired results have been compared to those processed inside the receiver. A so-called conditional DGPS has been developed, which determines the position differentially by using only data from strong signals.

What about topography? Status and quality of topographic data in Slovenia

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

Sturdy Positioning with High Sensitivity GPS Sensors Under Adverse Conditions

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

Optimization of UAV flight missions in steep terrain

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

Geodetic methods for documenting and modelling cultural heritage objects

Creating digital models of important cultural heritage objects for documentation or reconstruction purposes is usually challenging: the object can be a complex building, may be placed on remote areas, entirely or partly difficult to access, survey has to be done in different conditions, etc.however, final resulting models should provide adequate geometrical accuracy and completeness. Using a combination of different technologies and methods, where accuracy estimation of each methodology and often also an establishment of basic geodetic network are fundamental for ensuring the geometrically accurate final product (model), we can create three-dimensional (3D) models for documentation, inspection, maintenance and restoration purposes. Attractive 3D augmented reality (AR) and other presentations can be created, too. These outputs can be used by authorities, maintainers, conservators, investors and also public communities. Procedures and results are presented in selected cultural heritage objects in Slovenia: Chapel on Krvavec, Smlednik castle, Brestanica castle and Ljubljana castle

Iz znanosti in stroke kaj pa topografija? Stanje in kakovost topografskih podatkov v Sloveniji : What about topography? Status and quality of topographic data in Slovenia

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