3

Augmentation systems

3.1

Satellite-based augmentation system

The Teseo-LIV3FL supports SBAS. SBAS is a wide area differential GPS (WADGPS). It is a system, which

provides differential GPS corrections data. SBAS includes the WAAS within the United States, the EGNOS within

Europe, the multifunctional transport satellite (MTSAT)–based MSAS within Japan and southeast Asia, and the

GPS and GEO augmented navigation (GAGAN) system in India.

SBAS data correction is used in the GNSS algorithm to provide a better position estimation. The overall SBAS

differential correction mechanism can be conceived as built in two phases:

•

The “Acquire and Tracking” phase

•

The “Decoding” phase

The “Acquire and Track” phase concerns the ability of the acquisition engine to reliably track the SBAS satellite

path. During the decoding phase, the SBAS message can be decoded to fetch the differential corrections.

The current longitude limits for each service are:

•

WAAS-180 to-25 degrees

•

EGNOS-25 degrees to +50 degrees

•

GAGAN +50 degrees to +100 degrees

•

MSAS +100 degrees to +180 degrees

The Teseo-LIV3FL software with SBAS capability implements a command interface at the NMEA level to allow

interaction with the SBAS library. It supports commands to enable/disable the SBAS functionality.

3.2

QZSS

The quasi-zenith satellite system (QZSS) is a Japanese regional communication service and positioning

information for the mobile environment in the GPS L1C/A band. QZSS with GPS signals provides the GNSS

augmentation service for the Pacific region covering Japan and Australia. QZSS satellites are placed in a periodic

highly elliptical orbit (HEO). These orbits allow the satellites to “dwell” for more than 12 hours a day at an

elevation above 70° (it means that they appear almost overhead most of the time).

3.3

Differential GPS

Teseo-LIV3FL supports differential-GPS data according to RTCM (radio technical commission for maritime

services) 2.3.

Differential-GPS data improves position accuracy. The Teseo-LIV3FL supports the following RTCM message.

Table 3. Supported RTCM message on Teseo-LIV3FL

Message type

Description

1

Differential GPS corrections

9

GPS partial correction set

31

Differential GLONASS corrections

34

GLONASS partial correction set

Teseo-LIV3FL

Augmentation systems

DS13881 - Rev 4

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