Tech Chat | What is SBAS?

2022-10-04

SBAS (Satellite-Based Augmentation System) consists of the space constellations, ground control stations, operation and maintenance stations and the users. Space part is mainly composed of geostationary orbit satellite constellation part, constellations realize enhancement signal effect by sending signals that is similar GNSS navigation information, these signals accepted by SBAS ground control station and decoding process, eliminate part of the navigation error, generate navigation enhance information and sent it the user, the user receives GNSS and SBAS signals at the same time, The error of regional navigation is eliminated by correction, obtaining the navigation and positioning service with higher accuracy.

First of all, a large number of widespread correction stations (known position) to monitor navigation satellites, to obtain the raw location data (pseudorange and carrier phase observation value, etc.) and sent it to the central treatment facilities (main station), the latter obtains the satellite positioning correct information by computing, and sent it to GEO satellites through uplink injection station. Finally, spread correction data to users, to achieve the purpose of improving the positioning accuracy.

Characteristics of SBAS:

1. Release information including GPS satellite ephemeris error correction, satellite clock error correction and ionospheric correction through geostationary satellite (GEO);

2. Broadcast GPS and GEO satellite complete data through GEO satellite;

3. The navigation payload of GEO satellite transmits GPS L1 ranging signal.

Because SABA has the advantages of high accuracy, high efficiency, low cost, and wide area coverage, all countries in the world are developing satellite-based augmentation systems to enhance their regional navigation on GNSS systems.

At present, the SBAS systems with service status in the world include WAAS (USA), EGNOS(Europe), MSAS(Japan), GAGAN(India) and SDCM(Russia). China's BDSBAS (also known as SNAS), South Korea's KASS, and Nigeria's NSAS are among the space-based augmentation systems under construction and testing, as well as others that are undergoing research and deployment.

WAAS

WAAS consists of several reference stations (known position), central stations, geostationary satellites and user receivers with differential processing function. The WAAS system consists of 3 master stations (also as reference stations), 38 reference stations, 1 uplink injection station, and 3 geostationary satellites, covering North America and surrounding Mexico. WAAS is single-frequency pseudoran difference, and uses GEO satellites to broadcast and correction data. The downlink signal adopts L frequency band, which is convenient for user terminals to receive and use, and the positioning accuracy is about 1-2 meters. In addition, WAAS is preparing to transmit differential correction and integrity information on L5 band signals to support dual-band receiver users.

EGNOS

Space part, ground part, user part and support system constitute a complete EGNOS system. The space part consists of 3 geostationary satellites, which are responsible for transmitting correction and integrity information in the L1 frequency band. Generally, at least two GEO satellites transmit operation signals at the same time.

The ground part includes: main control center (MCC, 4), ranging and integrity monitoring station (RIMS, 41), navigation ground station (NLES, 7) and EGNOS wide area network (EWAN); the ground section is mainly responsible for transmitting the wide area differential correction data and integrity information of the GPS and GLONASS system to users in and around Europe. For the user part, in addition to GPS signals, the receiver can receive GLONASS and EGNOS signals.

EGNOS provides three types of enhanced services: ranging capabilities, Wide Area differential (WAD) correction, and GPS integrity channels. These three kinds of information are transmitted to users through GEO satellite, so that navigation accuracy, integrity, continuity and usability can be improved for users.

MSAS

Japan's MSAS, based on MTSAT (Multi-Functional Satellite Augmentation System), is one of the satellite-based Augmentation systems in compliance with ICAO standards and recommended practices. Running with 2 GEO satellites, MTSAT-1R and MTSAT-2, MSAS provides navigation services that cover all aircraft in the entire Japanese airspace. The MSAS system includes 2 main control stations (MCS), 4 ground reference stations (GMS), 2 GEO satellites and 2 ranging monitoring stations (MRS). Most of the Asia-Pacific region can be covered by MSAS signals, making air travel in this region seamless and safer and more reliable.

GAGAN

India has developed a GPS-assisted augmentation navigation system to Geostationary orbit, the GAGAN System. GAGAN is a system dedicated to providing seamless navigation in the Indian region, interoperable with other satellite-based augmentation systems. Although the main purpose of GAGAN is civil aviation, it will also bring benefits to other users.

SDCM

Russia has built its own satellite-based augmentation system, SDCM, for the Glonass. SDCM provides performance enhancements for GLONASS and GPS satellite navigation systems to meet the high accuracy and reliability required. The SDCM consists of 24 monitoring stations, one central processing station and three geostationary satellites. Due to the special nature of the Glonass system, the SDCM system also provides enhanced services for both the Glonass system and the GPS system.

Finally, how to enable SABS with Y1 or SV100?

After connecting, there will be a debug button, click and enter commands debug interface.

Then enter commands as blew one by one:

Commands:

set pvtobsmode sbas //turn on SBAS mode
set sbassys gagan //set SBAS mode, GAGAN as an example,WAAS(America), SDCM(Russia), EGNOS(Europe), MSAS(Japan) and GAGAN(India)
Saveconfig //save configuration

After the command is successfully sent, it will return OK. When you finish, the status will turn to DGNSS, which means you set SBAS mode successfully.