Research project SSRoverDAB+ successfully finished: Project team
demonstrates use of PPP RTK transmission over DAB+

Over a period of 14 months, four partners from industry and science developed and tested software and system solutions for the transmission of precise GNSS correction data via digital broadcasting DAB+. On 29 June 2023, the project consortium consisting of Alberding GmbH (consortium leader), Geo++ GmbH, inPosition gmbh and the Fraunhofer Institute for Integrated Circuits IIS presented the project results in a video conference. More than 60 interested parties followed the online presentation and the subsequent interactive Q&A session.

Current market situation

Modern digitisation and automation applications in agriculture and other fields require a precise spatial reference in real time. Satellite-based positioning (GNSS) can meet these requirements with the help of GNSS real-time correction data for the majority of the outdoor area. Precise correction data is provided, among others, by the satellite positioning service SAPOS® of the state surveying authorities as an open data service via mobile internet. The bidirectional VRS1 method and the RTCM2- data format used by SAPOS® are supported by the mobile GNSS receivers available on the market.

Due to poor mobile phone coverage in rural areas, many customers cannot use the SAPOS®service provided by the administration and have to rely on commercial services from globally operating companies. An additional transmission of GNSS correction data via terrestrial data channels, such as digital broadcasting DAB+, could fill these coverage gaps. In contrast to the bidirectional VRS procedure used so far via mobile radio, DAB+ broadcasting requires the transition to a broadcast able correction data format.

The new PPP-RTK method, which is based on the SSR3 approach, is broadcast able without loss of accuracy and allows a bandwidth reduction for efficient transmission of the correction data via DAB+. The lack of standardisation of SSR correction data at the highest accuracy level is a disadvantage for the market introduction of an open-data PPP-RTK service. The GNSS sensors currently available on the market have so far exclusively used proprietary data formats.

Project results

The ESA NAVISP-EL2 project “SSRoverDAB+” developed software and system solutions for the transmission and use of correction data with GNSS receiver systems available on the market in order to evaluate and practically test the possibilities and performance of PPP RTK correction data transmission via DAB+. The correction data was provided to the project by the associated project partner, the Working Committee of the State Surveying Authorities of the Federal Republic of Germany (AdV), represented by the Bavarian Agency for Digitisation, High-Speed Internet and Surveying (LDBV), in the open data format SSRZ of the company Geo++ GmbH.

In principle, the “SSRoverDAB+” project was divided into three different thematic blocks: the transmission of correction data via DAB+, the use of SSRZ correction data with GNSS receivers available on the market and the development of test systems with practical tests. The DAB+ correction data transmission consisted of the optimising of the server-side provision and transmission of SSRZ correction data and developing of a mobile DAB+ correction data receiver with data decoding. The DAB+ data channel was provided to the project by the associated project partner Federal Agency for Cartography and Geodesy (BKG).

For the correction data transmission, the focus was on optimising the distribution of slowly and rapidly changing SSR parameters (low-rate, high-rate messages) over the transmission bandwidth. For the DAB+ transmission itself, the efficient division of the channel between data bits for the correction data and the error correction of the transmission was investigated. On the mobile side, a prototype was developed for receiving, decoding and forwarding the SSR correction data to the GNSS rover system.

Due to the lack of standardisation, the development of software for the use of the SSRZ correction data was a focal point in the project. As the project partner Geo++ GmbH is familiar with its own data format, the conversion tool SSR2OBS was used to convert the SSRZ corrections into the RTCM 3.2 MSM data format. Geo++ added a feedback channel to this existing software tool in the project. The raw data from the mobile GNSS receiver is used to improve the correction data. In order to use the SSRZ correction data with their own processing solutions, inPosition gmbh and Fraunhofer IIS have developed software for reading and using the SSRZ correction data. Compared to Fraunhofer IIS’s evaluation of Galileo E5 AltBOC signals via a code-based approach for robust vehicle positioning in the 0.5 m accuracy range, inPosition required the full correction data set to compute an RTK solution in the centimetre range.

The Alberding A10-RTK sensor was used as a test and experimental system for the developments in the project. The A10-RTK is a scalable telemetry and positioning system that combines, among other things, a precise GNSS module, a 4G mobile modem and a processor in a single housing. Special features of the A10-RTK are the flexible selection of different GNSS boards and the optional equipment with an integrated embedded PC. The software developments in the project were implemented and tested on the embedded computer with LINUX operating system of the A10 sensor.

For the overall system test and the practical tests in the field, it was necessary to extend the housing to an A10 DAB+ prototype sensor, as the DAB+ receiver module and the INS sensor could not be integrated into the existing A10 housing due to their dimensions. The fully functional prototypes were successfully tested in the field on agricultural machinery belonging to the associated project partner BayWa AG. The tractor’s steering system used the SSR correction data transmitted via DAB+ for automated driving. The feasibility of sending precise correction data via DAB+ was successfully demonstrated.

“The next step is to transfer the results into practice. In order to reach market maturity, future efforts must be directed towards the development of a combined sensor solution with DAB+ modules that can be produced in smaller quantities and at a lower price,” says Jürgen Alberding, project manager of “SSRoverDAB+” and managing director of Alberding GmbH.

Further project information

“SSRoverDAB+” was funded under the 2nd element of the European Space Agency’s “Navigation Innovation and Support Programme”(ESA NAVISP Element 2). The programme aims to develop innovative competitive products in satellite navigation and other areas of positioning, navigation and timing. Detailed information on “SSRoverDAB+” can be found on the project website at www.ssroverdab.eu.

For further information contact

Jürgen Alberding (Project manager)
Alberding GmbH | Ludwig-Witthöft-Straße 14 | D-15745 Wildau | Germany
Tel.: +49 3375 25198-00 | Email: ja@alberding.eu | Web: www.alberding.eu

PRESS RELEASE

Wildau, 9 May 2022

Precise GNSS correction data via digital broadcasting – SSRoverDAB+ project launched

Modern digitisation and automation applications in agriculture and the automotive industry require continuous, high-accuracy GNSS position data in real time. GNSS correction data required for this is often not available to users over a wide area due to mobile internet dead spots. The parallel provision of GNSS correction data via mobile internet and digital radio DAB+ should remedy the situation.

In the ESA project “SSRoverDAB+”, four partners from industry and science will develop and test software and system solutions for the transmission of precise GNSS correction data via DAB+ over the next twelve months. The project is led by Alberding GmbH from Wildau. Project partners are the companies Geo++ GmbH (Garbsen) and inPosition GmbH (Switzerland) and the Fraunhofer Institute for Integrated Circuits IIS (Nuremberg base).

Associated project partners are the Bavarian Agency for Digitisation, High-Speed Internet and Surveying (LDBV) as the operator of the GNSS reference station network, the Federal Agency for Cartography and Geodesy (BKG) as the operator of a nationwide DAB+ data channel and BayWa AG Munich as a partner for practical testing in the field of agriculture. Interested users are welcome as test partners in the further course of the project. 

The project goals are the generation of a broadcast-capable PPP-RTK correction data stream with optimised bandwidth, the coding and decoding of the DAB+ data transmission as well as the development and adaptation of algorithms for precise real-time positioning. For mobile tests, the software modules will be implemented on the embedded computer of the Alberding A10-RTK sensor and evaluated in field tests.

“SSRoverDAB+” is funded under the 2nd element of the “Navigation Innovation and Support Programme” of the European Space Agency ESA (ESA NAVISP Element 2). The programme aims to develop innovative competitive products in satellite navigation and other areas of positioning, navigation and timing. Further information on ESA NAVISP can be found here: https://navisp.esa.int/

For further information contact:

Jürgen Alberding (project coordinator)

Alberding GmbH                                             

Ludwig-Witthöft-Straße 14, D-15745 Wildau

Tel.: +49 3375 25198-00

E-Mail: ja@alberding.eu

The current Galileo constellation consists of 23 healthy satellites available for navigation.

Status Summary

Status: May 05, 2022 NAGU 2022016

The launches of two more Galileo satellties planned for begin of April 2022 has been delayed.

The current Galileo constellation consists of 22 healthy satellites available for navigation.

Status Summary

Status: End of March, 2022, April 03, 2022 see for details (nextspaceflight)

Launches of two more Galileo satellties are planned for April 6 2022 0:31:51 GMT.

The current Galileo constellation consists of 22 healthy satellites available for navigation.

Status Summary

Status: 2022 01 25, 2022 01 29 (update for launch date and time)

On December 05, 2021 00:19 (GMT), 01:19 (CET) respectively December 04, 2021 21:19 (Kourou time), two more satellites launched to join the Galileo constellation.

The current Galileo constellation consists of 22 healthy satellites available for navigation.

Status Summary

Status: 2021 12 18

Source: https://www.gsc-europa.eu/notice-advisory-to-galileo-users-nagu-2021024

On December 05, 2021 00:19 (GMT), 01:19 (CET) respectively December 04, 2021 21:19 (Kourou time), two more satellites launched to join the Galileo constellation.

The current Galileo constellation consists of 22 healthy satellites available for navigation.

Status Summary

Status: 2021 12 05

Source: https://www.euspa.europa.eu/newsroom/news/euspa-ready-leop-ahead-galileo-launch-11
and https://www.arianespace.com/mission/soyuz-flight-vs26/

On December 03, 2021 00:27 (GMT), 01:27 (CET) respectively December 02, 2021 21:27 (Kourou time), two more satellites are planned for launch to join the Galileo constellation.

The current Galileo constellation consists of 22 satellites available for navigation.

Status Summary

Status: 2021 11 22, updated 2021 11 27 (launch time) , updated 2021 12 01 (launch time)

Source: https://www.euspa.europa.eu/newsroom/news/euspa-ready-leop-ahead-galileo-launch-11

Status Summary

Image ©ESA-P. Carril

Under the management of the European GNSS Agency (GSA), a collision avoidance manoeuvre for satellite GSAT0219 was performed over the past weekend. This manoeuvre was conducted following a collision risk alert received from EU Space Surveillance and Tracking (EUSST).

On 25 February, the Galileo Service Operator (GSOp) received from the EUSST a collision risk alert between GSAT0219 and an inert Ariane 4 upper stage launched in 1989. Following this warning, GSOp started to closely monitor the risk, in close cooperation with EUSST that was refining its predictions. 

In line with operational procedures, GSOp informed the GSA of the situation. In a joint effort with the European Commission, the GSA managed the follow-up activities. The effective cooperation between EUSST and the GSA/GSOp was instrumental to the success of the mission and bears testimony to the need for efficient cooperation between different organisations in the space sector.

Manoeuvre authorised

Following refinement of the Ariane 4 orbit, the risk of collision was still unacceptably high, so, after assessment of different strategies and associated risks on the service provision, the GSA authorised the execution of an avoidance manoeuvre. The satellite was taken out of service on 5 March, and users were informed via NAGU #2021009. The collision avoidance manoeuvre was performed shortly thereafter, by temporarily relocating the satellite away from its nominal position. Satellite GSAT0219 was expected to be reintroduced into service in Calendar Week 11 (15.03 – 21.03) after the completion of two station keeping manoeuvres to reposition it into its nominal operational orbit. Users were kept informed via NAGUs.

This is the first time a collision avoidance manoeuvre has been performed for a satellite in the Galileo constellation.

Source: GSA Press release accessed on March 25, 2021

In contrast to other GNSS Galileo has an additional feature called Open Service Navigation Message Authentication (OSNMA). OSNMA allows the authentication and validity of information broadcasted by Galileo satellites.

All GNSS are vulnerable for manipulation of their signals and the information transmitted with those signals. In recent years more cases of intentional malicious manipulation of signals have been reported especially in critical areas such as disputed international borders and military / economic conflict zones. Results are often completely wrong position information delivered by navigation equipment. The reported cases include travel path’ of ships on land and strange travel patterns such as circles for all vessels in the area. While those detections have been obvious other cases might cause serious disasters when not detected during maneuvers.

The Galileo navigation satellite system has the authentication feature in its design for along time. Within recent years the feature has been pushed forward and an in-orbit test has been conducted. While hardware encryption would require changes to satellites and user equipment the authorities are opting for a pure digital solution which would allow rollouts through software updates.

The major obstacle for authentication of broadcasted information is the constraint digital transmission possibilities within the satellite signals. Basically the satellite is transmitting a delayed authentication tag within 30 seconds which allows the receiving position device to validate the origin of the information. The testing was performed at ESA’s Navigation Laboratory using a two-hour window with eight visible Galileo satellites on November 18, 2020.

(Source: GPSworld accessed Mar 17, 2021)

The quality of GNSS positioning depends on direct view to GNSS satellites. In urban canyons are reflected by large structures and the direct line of sight to satellites is often obstructed. In combination with its 3D feature of Google maps these obstructions may be detected and the excessive travel path for signals is calculable.

Google has already a first version available. The main application is for locating pedestrians in urban canyons. The target is to reduce the placement of pedestrain position on the wrong side of streets. There are claims that the positioning with the first version is already 50% correct. With a roll-out of an updated second version the street side is detected correctly at a 75% rate.

Currently the feature is for pedestrians only, but future version may also allow improved positioning for other urban GNSS applications.

(Source: https://www.xda-developers.com/google-gps-tracking-improved-accuracy/ )

With the Chinese GNSS Beidou a fourth GNSS became available for worldwide positioning purposes. In July 2020 Beidou has officially completed its constellation. This sparks patriotism especially in China and apparently quite a number of users download applications onto their smartphones for using Beidou in navigation (abacus 2020).

The hurdles are the same for all and especially those being patriotic by using “their” GNSS. First of all, a constellation requires enough satellites in a favorable constellation. The same as with GPS only in “ancient” times when GPS started out with initial set of satellites.

At next the observations have to have a good quality. Beidou and also Galileo have the advantage of having the better start since the science moved on from early start of GPS. However, phones must be able to support also signals from those newer systems. Recent phone chipsets like the Snapdragon 855 do so, but even then, the chipsets provide the best estimate based on all signals.

Depending on the actual phone manufacturer the raw observation set is provided through the Android API. The delivery of raw observations allows the separation of observations by GNSS and allow a parallel computation of navigation positions in different combinations.

The next possible difference is the supported signals per GNSS. Most advanced phone chips allow dual-frequency GPS and Galileo observations, but only single-frequency observations for GLONASS and Beidou.

The example given here is showing the different positioning results using all four GNSS independently and at the bottom the combined solution of all GNSS in one solution.

abacus 2020, August 6 https://www.scmp.com/abacus/tech/article/3096168/apps-claiming-use-chinese-satellite-navigation-system-beidou-see-surge

The Galileo incident created a number of questions which are partly answered by the presentation shown in the video prepred by the FinnRef.

(Link: https://youtu.be/CLsofmws_n4 )

The mystery about the complete failure of the Galileo constellation has been clarified. While the timing facility in Italy failed, the German backup part was not able to take over because of an software security update.

Obviously the overall update procedure will be a major part of the lessons learned discussion following the complete outage of the constellation.

(Source: https://www.politico.eu/article/galileo-blackout-followed-effort-to-guard-against-cyber-threats/ )

[2019 07 18 16:00 UT]
Galileo satellites have resumed transmitting signals. According to NAGU 2019027 the system is back online since 2019-07-17 20:52 UTC. All satellites have been declared as usable again. The current service is relying basically on the same satellites as prior to the system outtage. The NAGU subject claims “SERVICE RESTORED (POTENTIAL INSTABILITY)”.

As described in the post before, user devices may exclude Galileo satellites from tracking for a while. This is typically dependent completely on the logic of the receiver device. GNSS receivers decide on the content of the so-called almanac. As with GPS and other GNSS the almanac collection requires tracking one satellite of the system and some time until an older almanac has been replaced. Eventually a restart of the device may help to speed up this replaement process.

(Source: https://www.gsa.europa.eu/newsroom/news/galileo-initial-service-recovery-actions-underway?fbclid=IwAR2_9xI9p_I3He9wIrKx9cMhvL33n_diBfz4yirXFzxyh1VsiHM0fThLsPA and https://www.gsc-europa.eu/notice-advisory-to-galileo-users-nagu-2019027 )

[July 17, 2019 8:00 UT] After the complete system outtage over the weekend Galileo is recovering. Several receivers of the MGEX project are tracking Galileo satellite again. Collected Galileo broadcast orbits are available from several stations through a couple of Ntrip mount points of https://mgex.igs-ip.net/
The quality of observations and the derived orbits are probably to be considered with care. The Galileo recovery actions are still underway as indicated by the GSA webpage.

The MGEX project is using professional GNSS receiver equipment. These receivers allow typically reception also of specially marked satellite signals for scientific purposes. Consumer equipment such as smartphones are typically waiting until satellites marked as usable until the signals are tracked and used for positioning.

(Source: https://www.gsa.europa.eu/newsroom/news/galileo-initial-service-recovery-actions-underway )

Currently the European Galileo satellite system is down since July 11 or 12, 2019. Apparently the satellites are transmiting no valid broadcast orbit information. The constellation service webpage indicates “Service Outage”. No sound information on the actual reasoning is given.

[Update 2019 07 15 15:00 UT]

The reasons for the current unavailability is clearer according to GSA webpage and also an Inside GNSS article. The issue is not with the space segment but the ground facilities. Apparently the Precise Timing Facility (PTF) in Italy is not working as expected. Without precise timing the calculation of broadcast orbits is in jeopardy and there is nothing to be supplied to the satellites.

However, this information opens a bunch of more questions such as why did the backup PTF in Germany not take over? Also the Galileo satellites have as satellite other GNSS (GPS, GLONASS and Beidou) a stack of precomputed broadcast orbits available. Therefore why is the Galileo system not operating on those precomputed broadcast orbits?
The accuracy of the brodcast orbits may deteriorate over time, but at least the system should be operational for a couple of days or a week. If the precomputed stack of orbits is already used up, there would be then the question of why there was no advance notice?

(Source: https://www.gsa.europa.eu/newsroom/news/update-availability-some-galileo-initial-services and https://insidegnss.com/update-galileo-service-degraded-on-all-satellites-precise-timing-facility-problems-cited/ )

On February 11, 2019 four more satellites joined the Galileo constellation.

The current Galileo constellation consists of 22 satellites available for navigation.

Status Summary

Status: 2019 02 11

(Source: Galileo Constellation Information)

On October 12, 2018 the last satellite of the previous launch in December joint the usable constellation.

The current Galileo constellation consists of 18 satellites available for navigation.

Status Summary

Status: 2018 10 12

(Source: Galileo Constellation Information)

On August 2, 2018 three satellites of the previous launch in December joint the usable constellation.

The current Galileo constellation consists of 17 satellites available for navigation.

Status Summary

Status: 2018 08 06

(Source: Galileo Constellation Information)

The successful launch of 4 Galileo satellites on July 25, 2018 at 11:24 GMT has added  scheduled .

Eight Galileo satellites (GSAT0215 to GSAT0222, four from December 2017 launch and four from recent July launch) are under commssioning.

The current Galileo constellation consists of 14 satellites available for navigation.

Status Summary

Status: 2018 07 27

(Source: NAGU201817, SpaceFlightNow)

Galileo satellite GSAT0215, GSAT0216, GSAT0217, and GSAT0218 are still under commssioning.

Another launch of 4 Galileo satellites has been scheduled for July 25, 2018 at 11:24:48 GMT.

The current Galileo constellation consists of 14 satellites available for navigation.

Status Summary

Status: 2018 06 17

(Source: Space Flight Now)

Galileo satellite GSAT0215, GSAT0216, GSAT0217, and GSAT0218 are still under commssioning.

Another launch of 4 Galileo satellites has been scheduled for July 25, 2018.

The current Galileo constellation consists of 14 satellites available for navigation.

Status Summary

Status: 2018 04 22

Near a 100 million chips supporting Galileo signals are in the market. Certainly more are to come in the future with new devices supporting GNSS through consumer chips.

Currently a better coverage with more Galileo satellites is required. The full constellation is still being build up to completeness. Currently stand-alone Galileo navigation would have too many drop-outs when a sufficient number of four satellites is missing. The constellation consists momentarily 14 satellites in full service, while two satellites are out of service. Therefore the community is waiting for the commissioning of the satellites launched on December 12. After completion of commissioning the number of satellites in service may be between 18 and 20.

(Source: CNES)

Galileo satellite GSAT0215, GSAT0216, GSAT0217, and GSAT0218 were successfully launched and entered their designated orbits. In the mean time they are under commssioning.

The current Galileo constellation consists of 14 satellites available for navigation.

Status Summary

Status: 2017 12 15

According to GPSworld launch overview of August 28, 2017 is the next Galileo satellite launch scheduled for December 12, 2017 around 18:30 UTC.

The current Galileo constellation consists of 15 satellites available for navigation.

Status Summary

Status: 2017 08 29

On August 9, 2017 at 18:58 UTC the remaining Galileo satellite from last year’s launch joined the Galileo constellation.

The current Galileo constellation consists of 15 satellites available for navigation.

Status Summary

Status: 2017 08 10

On August 1, 2017 at 16:03 UTC another Galileo satellite joined the Galileo constellation leaving until next launch in December one remaining satellite in commissioning phase.

The current Galileo constellation consists of 14 satellites available for navigation.

Status Summary

Status: 2017 08 05

Due to the issues with Galileo satellite clocks the next launch of four Galileo satellites has been postponed until December 2017.

The current constellation consists of 13 satellites available for navigation.

Status Summary

Status: 2017 07 05

(Source: ESA launch schedule 2017)