u-blox 6

Supported SBAS messages
Message Type Message Content Used from GEO
0(0/2) Test Mode All
1 PRN Mask Assignment Primary
2, 3, 4, 5 Fast Corrections Primary
6 Integrity Primary
7 Fast Correction Degradation Primary
9 GEO Navigation (Ephemeris) All
10 Degradation Primary
12 Time Offset Primary
17 GEO Almanacs All
18 Ionosphere Grid Point Assignment Primary
24 Mixed Fast / Long term Corrections Primary
25 Long term Corrections Primary
26 Ionosphere Delays Primary
As each GEO services a specific region, the correction signal is only useful within that region. Therefore, mission
planning is crucial to determine the best possible configuration. The different stages (Testmode vs. Operational)
of the various SBAS systems further complicate this task. The following examples show possible scenarios:
Example 1: SBAS Receiver in North America
At the time of writing, the WAAS system is in operational stage, whereas the EGNOS system is still in test
mode. Therefore, and especially in the eastern parts of the US, care must be taken in order not to have EGNOS
satellites taking preference over WAAS satellites. This can be achieved by disallowing Test Mode use (this
inhibits EGNOS satellites from being used as a correction data source), but keeping the PRN Mask to have all
SBAS GEOs enabled (which allows EGNOS GEOs to be used for navigation).
Example 2: SBAS Receiver in Europe
At the time of writing, the EGNOS system is still in test mode. To try out EGNOS operation, Testmode usage
must be enabled. Since some WAAS satellites can be received in the western parts of Europe but don't carry
correction data for the European continent, the GEOs from all but the EGNOS system should be disallowed,
using the PRN Mask. It is important to understand that while EGNOS is in test mode, anything can happen to
the EGNOS signals, such as sudden interruption of service or broadcast of invalid or inconsistent data.
Although u-blox GPS receivers try to select the best available SBAS correction data, it is
recommended to disallow the usage of unwanted SBAS satellites by configuration.
3.3 SBAS Configuration
To configure the SBAS functionalities use the UBX proprietary message UBX–CFG–SBAS (SBAS
Configuration).
SBAS Configuration parameters
Parameter
Description
Mode - SBAS Subsystem
Enables or disables the SBAS subsystem
Mode - Allow test mode usage Allow / Disallow SBAS usage from satellites in Test Mode (Message 0)
Services/Usage - Ranging
Use the SBAS satellites for navigation
Services/Usage - Apply SBAS
correction data
Services/Usage - Apply integrity
information
Combined enable/disable switch for Fast-, Long-Term and Ionosphere
Corrections
Use integrity data
GPS.G6-SW-10018-A Public Release Page 6 of 201