Projects / Programmes
The increase of reliability of public GNSS network SIGNAL and combined zero order geodetic network
| Code |
Science |
Field |
Subfield |
| 2.17.00 |
Engineering sciences and technologies |
Geodesy |
|
| Code |
Science |
Field |
| P515 |
Natural sciences and mathematics |
Geodesy |
| Code |
Science |
Field |
| 2.07 |
Engineering and Technology |
Environmental engineering
|
GNSS, SIGNAL network, zero order combined geodetic network, reliability
Researchers (12)
Organisations (2)
Abstract
Quality spatial data registries are an important part of every national spatial data infrastructure. The most important part of the national spatial data infrastructure is national geodetic reference system since all national spatial data registries must be referenced to it. Furthermore, it is also used for majority of surveying and other geodetic tasks. Slovenian national geodetic reference system consists of separate horizontal and vertical component.
Horizontal component of Slovenian national coordinate system is realised by sixteen permanent GNSS (Global Navigation Satellite System) stations of Slovenian national GNSS permanent network named SIGNAL (Slovenia-Geodesy-NAvigation-Location). Furthermore, the SIGNAL network is also a public network. It provides access to the national horizontal coordinate system to different public users, which use it for obtaining accurate positions of objects and phenomena on the Earth's surface. The SIGNAL network has been operating since 2000. SIGNAL's data are used by users for RTK (Real-Time Kinematic) positioning as well as for post-processing positioning. RTK positioning can be done as Single Base RTK (user receives data from only one permanent station) or as network RTK (user receives one of the supported network product). The SIGNAL network supports two network products – VRS (Virtual Reference Station) and MAC (Master-Auxiliary Concept). For the purpose of post-processing users can order RINEX files, which are stored in RINEX archive. Post-processing positioning has higher accuracy compared to RTK and makes possible to obtain accurate coordinate even in case when SIGNAL's real-time products are not accessible due to some failure.
Recently, the modernisation of Slovenian national spatial data infrastructure has been carried out. One of the most important things that has been done within this project is establishment of the zero order CGN (Combined Geodetic Network). The main goal of the zero order CGN is realisation of Slovenian national horizontal and vertical coordinate system. A part of it is also GNSS permanent network that consists of six permanent GNSS stations and is used for continuous monitoring of possible deformation of the national coordinate system. The SIGNAL network remains a public network while the zero order CGN is not meant to be a public network. The zero order CGN is also used as a part of SIGNAL's quality control.
Given the importance of both networks (the SIGNAL network and the zero order CGN) it is necessary that they operate continuously without major interruptions and provide GNSS observations, products and services of the highest quality. In reality, both networks are sometimes facing several different problems, which are causing interruptions of their operation and affecting the quality of their products and services.
Reasons for interruptions in operation of considered networks are different, some are predictable (hardware/software upgrades), others are not (hardware/software failures and other problems). In addition to mentioned problems the SIGNAL network is faced also with problems of individual users and (user) problems that are not directly related to the SIGNAL network but still affect the quality of acquired position.
The starting point of the project are the following problems of the SIGNAL network and the zero order CGN:
problems that are causing interruptions in operation of the SIGNAL network and/or affecting the quality of its products and services (e.g. hardware/software problems),
problems of the individual users of the SIGNAL network (e.g. network connection problems, lost passwords, wrong rover settings),
problems that are not directly related to the SIGNAL network (e.g. incorrect execution of RTK/post-processing positioning, faulty GNSS instrument) but users usually first consider that they have problems with the SIGNAL network and therefore unnecessarily contact the technical support,
problems that are causing interruptions in ope
Significance for science
Two basic parts of Slovenian geoinformation infrastructure are GNSS network SIGNAL and new combined geodetic network (CGN) of the zero order. Using data those two networks provide, users are able to measure coordinates in Slovenian national horizontal coordinate system and also to obtain high quality coordinates in global reference systems (ITRS, ETRS, WGS 84). The new zero order CGN was built in accordance with the latest international guidelines. The main purpose of CGN is to connect geometric height system obtained via GNSS positioning with gravity-referenced heights. That means both components (horizontal and vertical) of national, regional or global reference system are combined in a modern CGN and so it allows to do all types of geodetic measurements. Slovenia is currently in a process of developing of a new realization of a national vertical datum (for land and sea areas) and the zero order CGS represents important connection between reference surface (quasi-geoid) and new national vertical coordinate system. Thus, it is essential that the zero order CGN operates flawlessly.
Since both networks (SINGNAL and the zero order CGN) represents the realization of Slovenian national horizontal coordinate system, they can also be used for long-term monitoring of geodynamics of Slovenian territory. This insight can give us important guidelines for feature development of our national reference system, especially about implementing a time-dependant coordinate system.
With fast technological development more and more numerous sensors, used for positioning are publicly available. Being able to connect different sensors in a way that we preserve advantages of an individual sensor but at the same time remove or reduce their deficiencies is today a major research and technological challenge in the field of geodesy. Improved operational reliability and quality control of SIGNAL network and zero order CGN will increase chances of including those two networks into larger regional or global networks, used for studying and monitoring the Earth, its surface and interior structure, its hydrosphere and atmosphere, and its dynamic processes through its physical and chemical properties. Such studies are becoming increasingly important in natural disasters and human-caused pollution risk management projects.
Relative GNSS positioning using SIGNAL network can also be used to obtain gravity-referenced heights with high accuracy if appropriate data are available. This method is called GNSS levelling. Ellipsoidal heights (h) obtained via GNSS positioning are in geometric height system. Reference surface is defined as an ellipsoid, and has no connection with Earth's gravity field. Therefore, those heights cannot be directly used for geodetic or everyday purpose. The link between geometric (ellipsoidal) heights (h) and gravity-referenced heights (H) is a reference surface called geoid (or quasi-geoid): h = H + N, where N is undulation of the geoid. So, if an undulation of the geoid is known (usually via interpolation on a geoid model grid) for a location where only GNSS measurements are available, we can calculate gravity-referenced height using upper equation. Of course, this method is effective only when accuracy of a geoid model is (at least) comparable to the accuracy of ellipsoidal heights acquired via GNSS positioning. With the upcoming implementation of the newly defined vertical component of Slovenian national reference frame, a new geoid model, from which it will be possible to interpolate undulation of the geoid with centimetre-level accuracy. Hence the quality of gravity-referenced heights determined with GNSS levelling will mostly depend only on quality of ellipsoidal heights obtained via GNSS positioning.
Data from the SIGNAL network are important source for many studies not only in the field of geodesy but also in many other fields. In geodesy the main purpose of GNSS observations is to determine object's position in a global refer
Significance for the country
The SIGNAL network and the zero order CGN are public networks. They are the foundation of the Slovenian national geoinformation infrastructure and the data are publicly available but not for free. The Surveying and Mapping Authority of the Republic of Slovenia provides paid access to the SIGNAL network data needed for real-time and also post-processing positioning. Collected funds are spent for regular maintenance of the network along with upgrades and development of the network itself and services it provides. The SIGNAL network has nearly 300 commercial users, mainly from geodetic and utility companies. The network is used by different commercial users for several hours on daily basis. They perform surveying services for customers who can be natural or legal person. For natural persons a cadastral survey is usually carried out while different surveying services related to real estate recording and taxation, different engineering projects and investments in real estate and public infrastructure are performed for legal persons.
The SIGNAL network must operate autonomously 24/7/365 without interruptions. In the event of an error, quality control procedures have to detect the error as soon as possible and alarm system administrators of the GNSS Service Centre so they can identify and fix the problem. The main goal of this project is to enhance network's operational reliability as well as reliability of the network quality control. Enhanced operational reliability would mean less unpredicted downtime of the whole network or individual permanent GNSS station and consequently less unforeseen expenses on users' side indirectly caused by network unavailability.
The SIGNAL network is used also by users from other professional fields than geodesy, such as spatial planning, hydrology, marine hydrography, civil and construction engineering, cultural heritage, aviation, maritime, road and rail transport, military and others. The network is also used in many location-based services. In agriculture the GNSS measurements can be utilized for optimization of navigation of the agricultural vehicles.
In public administration the network is used by different ministries and agencies, especially by The Surveying and Mapping Authority of the Republic of Slovenia for the purposes of maintaining data about national geodetic reference system, real estate, topography and public infrastructure.
Accurate and precise GNSS positioning has also great future potential in fields of IoT (Internet od Things), smart homes, smart buildings and smart cities, circular economy, energetics, mobility, transport and logistics, etc. In automotive industry implementation of real-time positioning techniques with centimetre-level accuracy is one of the essential parts in development and production of autonomous vehicles. All new technologies, including GNSS positioning are also important for startup IT companies. The global trend has already moved from 100 meters and 10 meters accuracy level to accuracy level of 1 meter. With further development real-time positioning with centimetre-level accuracy will soon be reality.
Important aspect in the use of the SIGNAL network is also international data exchange. The SIGNAL network also includes permanent GNSS stations from Austria, Croatia and Hungary that are close to the border. The SIGNAL's permanent GNSS stations close to the border are reciprocally included in national GNSS networks of those three countries (APOS, CROPOS and GNSSnet.hu). Thus, quality GNSS positioning is also possible at border areas. Connection of SIGNAL and cross-border permanent stations extends the SIGNAL network on cross-border areas. For example if one Slovenian permanent station near the border is temporary unavailable due to some failure, it is replaced with adjacent cross-border permanent station.
The SIGNAL network was implemented as a new real-time positioning technology and it has revolutionised the surveying profession greatly. Survey
Most important scientific results
Annual report
2018,
final report
Most important socioeconomically and culturally relevant results
Annual report
2018,
final report
