The implementation of the precise satellite positioning system ASG-EUPOS

Artur Oruba, Marcin Ryczywolski, Szymon Wajda, Jarosław Bosy, Wiesław Graszka, Marcin Leończyk, Jarosław Somla

Head Office of Geodesy and Cartography

BIOGRAPHY The authors are representatives of the ASG-EUPOS project conducted by the Head Office of Geodesy and Cartography – the Polish authority for geodesy and cartography. INTRODUCTION In the last few years the evolution of telecommunication, electronics, IT, geodesy and many other scientific fields have led GNSS to develop in the direction of ground-based reference station systems. They enable real-time positioning with high availability and precision that are constantly improving. The region-wide EUPOS (European Position Determination System) initiative is one of the biggest projects introducing GNSS reference systems in Central and Eastern Europe. The project was started in 2003 based on the success of the German SAPOS system and unites 16 European countries into one GNSS reference system. All member countries build up their individual systems, but cross-border real-time data exchange enables the separate systems to work as one region-wide system. The EUPOS initiative created standards for establishment of national systems, services compatibility and data exchange with foreign countries. The most important features, that every EUPOS-based system has to fulfil are:

- existing EPN and IGS reference stations have to be included in the EUPOS systems,

- reference stations coordinates are to be determined in ETRS’89 (European Terrestrial Reference System) and national coordinate systems of member countries,

- receivers used for reference stations are to be compliant with Galileo system (and GPS/GLONASS before Galileo operational phase),

- only precise dual-frequency receivers are to be used for reference stations,

- reference stations’ position has to be constantly monitored.

Those standards created the basis for establishing the multifunctional precise satellite positioning system ASG-EUPOS (Active Geodetic Network EUPOS) in Poland. ASG-PL and Malopolska Precise Positioning Sytem were the testing field for implementing a nation-wide

reference system in Poland. The first polish project, called ASG-PL, was carried out by the Head Office of Geodesy and Cartography and the Silesian Voivodship in 2004. It enabled free access to observational data from 6 reference stations (later some additional stations were added) and an automated postprocessing mode. In 2006 Malopolska Precise Positioning Sytem was founded and instantly joined the ASG-PL reference stations. It used a module for real-time corrections, which helped to turn the network into a regional system (Małopolskie and Silesian Voivodships) for economic purposes. Simultaneously the concept of a nationwide reference system that could be a part of the EUPOS was born. THE PROJECT REALISATION On 2 January 2007 the contract between the Head Office of Geodesy and Cartography and the consortium: WASKO S. A., Geotronics Polska Sp. z o. o., Trimble Europe BV., for building the ASG-EUPOS system was signed. This was the beginning of the project realisation. In order to support the project, the General Surveyor of Poland established the Project Steering Committee and two counselling bodies: the Programme Council of the Project and the Team of Experts. The agreement encompasses the ASG-EUPOS system establishment along with the delivery of 75 mobile RTK equipment sets for field GNSS measurements. The realisation has been divided into two parts, and those into stages shown below: Part 1

Stage 1 – the delivery of 30 dual-frequency GPS receivers with the equipment and software of the reference stations, the delivery of servers, computer and telecommunication equipment, system and application software,

Stage 2 – the delivery of 40 dual-frequency GPS receivers and 8 dual-frequency GPS/GLONASS receivers with the equipment and software for the reference station, mounting of reference stations in 75 locations, delivery and installation of supplementary equipment, installation of servers, IT equipment, system and application software in Management Centres, connecting all the system elements and training of the personnel operating the stations and positioning services,

Stage 3 – consisting of: launching of real-time and postprocessing precise positioning services, preparing the documentation for services, preparing the reference station installation documentation, and also training of the staff,

Stage 4 – consisting of: plugging the border stations in and connecting the National Management Centre with National Management Centres in neighbouring countries, testing and authorisation of the precise positioning system in Poland,

Stage 5 – administration of the system by the contactor, Stage 6 – technical support for the system by the

contractor, Part 2

Stage 1 – the delivery of 15 dual-frequency GPS receivers with equipment and software for RTK/DGPS field measurements,

Stage 2 – the delivery of 50 dual-frequency GPS receivers will also be provided, with equipment and software for RTK/DGPS field measurements and training of operating personnel will be con-ducted.

Currently the project is being finished which means that stages 1-3 of part 1 and the whole part 2 has been completed. The system full operability is planned for the end of May 2008. ASG-EUPOS STRUCTURE AND FEATURES The ASG-EUPOS system structure is divided into four basic segments (fig. 1): satellite, reference, management and user segment. Those segments working together provide the system for precise positioning in real-time and postprocessing applications.

The satellite segment is basically the composition of GPS and GLONASS satellite systems. When Galileo becomes fully functional and operable, it is planned to either add its functionalities to the ASG-EUPOS system or replace GPS and GLONASS with Galileo. The reference segment (ground control) consists of a network of GNSS reference stations that have been built according to the EUPOS standards. This means that mean distance between neighbouring reference stations is around 70 km and the stations are regularly distributed, creating a uniform network that covers whole Polish territory. The stations are located mainly on roofs of public institutions’ buildings. Antenna locations were chosen in a way to ensure the best possible observation conditions along with the possibility to locate a 19-inch rack with GNSS receiver and a communication module in short proximity to the antenna (generally not exceeding 30 m of antenna cable). Two sets of GNSS reference stations have been established during the project. 68 GPS stations (an example of LOMZ station’s mounting and equipment is shown on fig. 2) consist of: - Trimble Zephyr Geodetic I antenna (TRM41249.00

TZGD), - Trimble NetRS receiver, - UPS system PowerWare 9125 2000i, - communication module: Juniper Networks NetScreen-

5GT ADSL, D-Link DES-1016D switch, RS-232/TCP-IP Moxa NPort 5110 converter.

Another 8 GPS/GLONASS reference stations (an example of BPDL station’s mounting and equipment

Fig. 1. ASG-EUPOS system structure and relations between specific segments

Fig. 2. LOMZ GPS reference station mounting and equipment is shown on fig. 3) consist of: - Trimble Zephyr Geodetic II antenna (TRM55971.00

TZGD), - Trimble NetR5 receiver, - managing module: HP ML350R05 server with

GPSBase software, - UPS system PowerWare 9125 3000i, - communication module: Juniper Networks NetScreen-

Fig. 3. BPDL GPS/GLONASS reference station mounting and equipment

5GT ADSL, D-Link DES-1016D switch, RS-232/TCP-IP Moxa NPort 5110 converter.

Additionally 22 (6 of them are GPS/GLONASS stations) existing public GNSS reference stations (including EPN and IGS stations) were included in the ASG-EUPOS network. This sums up to 98 national reference stations.

Fig. 4. ASG-EUPOS national and foreign reference stations

All new reference stations have been connected to Management Centers using highly efficient and reliable ATM links creating a private Intranet network (fig. 5). Seven new GPS/GLONASS reference stations have been proposed as part of EPN and currently their status can be observed via EPN website. Following EUPOS standards, agreements with neigbour countries taking part in the initiative are being signed to enable cross-border data exchange. Technical details are being discussed in order to connect additional reference stations’ real-time data streams from Czech Republic (CZEPOS), Germany (SAPOS), Lithuania (LITPOS), Russian Federation, Slovakia (SKPOS) and Ukraine. All reference stations of the ASG-EUPOS system are shown on fig. 4. The management segment of the ASG-EUPOS system consists of two Management Centers: in Katowice and Warsaw. The purpose of running simultaneously two Management Centers is to ensure full redundancy of services that leads to higher availability and reliability of the whole system. In case of disabling one of the centers the services are switched to the remaining one. The reference network is being managed by Trimble Infrastructure Software™ installed in both MC’s. The software constantly monitors the network (antenna stability, communication delays, network integrity), collects observational data from reference stations, calculates real-time RTN and DGNSS corrections and provides services for the users. In order to independently analyse the network stability a script based on Bernese GPS Software 5.0 and EPN standards was created. As it was mentioned earlier, a dedicated communication network based on VPN was created to ensure efficient and secure communication between all segments of the ASG-EUPOS system. More than a half of the links to reference stations utilizes previusly existing connections of another Head Office of Geodesy and Cartography project – GEOPORTAL.GOV.PL. All the existing reference stations were connected to the system via Internet connection, outside of the VPN network.

Fig. 5. ASG-EUPOS communication network scheme Currently the whole infrastructure of the systems is being tested. Field measurements with ASG-EUPOS services are being conducted to verify their availability and declared precision. Additionally a calibration campaign is planned in order to connect the ASG-EUPOS with existing Polish ground control – EUREF-POL, POLREF and EUVN networks – and calculate the coordinates in one uniform reference frame (one of ETRS’89 realisations). USER SEGMENT AND SERVICES The ASG-EUPOS system provides numerous services all to the users. Basically they can be divided into two groups: real-time and postprocessing. Table 1 presents the services provided by the system. One of the most important features of ASG-EUPOS is that it can provide various network solutions for real-time applications. In example, the most precise real-time service NAWGEO enables a large variability of corrections:

Tab. 1. ASG-EUPOS services and their description

- RTCM SC 104 v. 2.3 and 3.1 VRS, - RTCM SC 104 v. 2.3 FKP, - RTCM SC 104 v. 3.1 Net (MAC/MAX), - RTCM SC 104 v. 2.3 and 3.1 RTK (single station). Currently no services are provided via FM or GSM transmission but in case of future needs the distribution of all corrections using GSM communication lines is being planned. Also FM transmission of DGNSS services is possible. For this moment all services are provided via Internet. Multifunctionality of the ASG-EUPOS system is shown in its open structure and ability to be adjusted to users’ needs. Diversity of services and their precision meets the demands of various user groups. The most possible applications of differential positioning provided by ASG-EUPOS can be found in:

- navigation, - geodesy and geodynamics, - hydrography, - GIS, - civil engineering, - transportation, - energetics, - telecommunication, - urban infrastructure management, - public safety, - threat management, - health service, - environmental protection, - agriculture and forestry, - sport and tourism.

ACKNOWLEDGEMENTS The ASG-EUPOS multifunctional precise satellite positioning system project is realised utilising the resources of the European Regional Development Fund within the Sectoral Operational Programme „Improvement of the Competitiveness of Enterprises”. The contract for project subsidising was signed on the 2nd of August 2005. The Ministry of Regional Development is the Managing Authority, while Department of European Funds acting within the Ministry of Science and Higher Education is the Implementing Authority and the General Surveyor of Poland is the Final Beneficiary. Additional information about the ASG-EUPOS system and latest news on project realisation can be found on http://www.asgeupos.pl/. REFERENCES ASG-EUPOS (2008), Information about the ASG-

EUPOS system, April 2008, http://www.asgeupos.pl/

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EUPOS (2007), EUPOS – General Information, January 2007, http://www.eupos.org/

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Somla J., Wajda S., Oruba A., Ryczywolski M., Leończyk M., Bosy J. (2008) ASG-EUPOS w fazie testów (ASG-EUPOS testing in progress), Geodeta, Geoinformational Magazine, vol. 2. (153), Feb. 2008, pp. 4-8 (NAWI)

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