The SBAS augmentation system operates differently from LBAS. This system has a modular architecture similar to that of a GNSS constellation, which includes 3 components:
- terrestrial (reference stations)
- space (geostationary satellites),
- user.
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- LBAS and SBAS precision augmentation systems
- LBAS and SBAS precision augmentation systems
- LBAS and SBAS precision augmentation systems
- LBAS and SBAS precision augmentation systems
- LBAS and SBAS precision augmentation systems
- LBAS and SBAS precision augmentation systems
- LBAS and SBAS precision augmentation systems
- LBAS and SBAS precision augmentation systems
- LBAS and SBAS precision augmentation systems
- LBAS and SBAS precision augmentation systems
LBAS and SBAS precision augmentation systems
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LBAS & SBAS precision enhancement systems
LBAS and SBAS are two distinct systems for optimising the accuracy of geolocation using GNSS satellites…
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The LBAS system (Local Based Augmentation System) transmits corrections directly to the receiver via communications media such as the cellular network, radio, internet, etc.)
The SBAS (Satellite Based Augmentation System) allows corrections to be broadcast via geostationary satellites.
The local augmentation system: LBAS
The LBAS correction system is based on an observation differentiation process that removes sources of GNSS positioning error and improves its integrity.
The principle consists of evaluating the difference between the coordinates derived from the GNSS determination and the actual coordinates of a known point. The result is a set of corrections that can be transposed to nearby geographical areas.
These corrections are then applied to the mobile receiver in real time or in post-processing software.
This is known as differential GNSS or DGPS.
There are several types of local differential correction:
LBAS System
- DGPS differential correction:
This is the historical method for correcting GNSS errors in real time. It is based on communication between the reference station receiver and the mobile receiver. This method uses measurements of the L1/E1 carrier code. Communication equipment transmits the corrections in real time to the mobile, enabling it to be positioned sub-metrically. - RTK :
RTK uses the same differential correction principle as DGPS. The advantage of RTK is that it uses the phase of the carrier wave. This phase enables sub-centimetre measurements of “pseudo-distances” and therefore RTK positioning of a mobile with centimetre accuracy. - Post-processing:
It is also possible to record the data from the base station receiver as well as the data from the mobile. This enables the vectors to be post-processed using post-processing software. The accuracy achieved in this way is equivalent to real-time, or even better in the case of so-called static measurements. This means recording data continuously at the same point over a long period.
The space augmentation system: SBAS
SBAS System
The principle: geostationary satellites will deliver real-time corrections to increase accuracy. They will also transmit information to guarantee the integrity of these corrections. It is the network of ground stations that will enable errors to be observed.
Example: EGNOS (European Geostationary Navigation Overlay Service) is the SBAS service covering Europe. It currently has 2 reference stations in mainland France.
This system takes into account the satellites of the GPS constellations and soon GALILEO. Three geostationary satellites transmit positioning corrections to Europe. By activating this optimisation system on the receiver, an accuracy of between 1 and 3 metres can be achieved in 3D.
Several geographical areas around the world have their own service, as can be seen on the map below.
Like EGNOS, which is available in Europe, other services implement SBAS technology across the globe. These include WAAS, MSAS, GAGAN, etc.
SBAS – Accuracy 1m-3m, open area
LBAS – Centimetre accuracy, urban area
Agriculture Standard
Precision Agriculture
Aviation
Land transport
Public Works
Topography
The SBAS system was first developed for applications where telephone coverage is either restricted or completely absent and where the need for precision is not the priority.
This is the case in civil aviation, where only satellite transmission is possible at flight altitude. Today, this technology has been extended to the agricultural sector, where high precision is not always required. However, for agricultural self-guidance applications (see article), centimeter precision is essential. The LBAS solution is the favored choice for this application. It offers greater flexibility in terms of precision.
The exception of TERIA solutions
TERIA solutions combine the advantages of these two technologies. The TERIA network (NRTK) can provide LBAS-type corrections and TERIAsat works like an SBAS system, while providing centimetric positioning in real time. TERIA solutions can therefore systematically provide centimetric accuracy in real time, combining SBAS and LBAS technologies.
This is due to the quality of the TERIA network and, above all, the density of the reference station mesh.
In fact, if we take the case of mainland France, there are almost 200 stations throughout the country. This density is equivalent to having a station every 50km.
