iSXblue/SXBlue II GNSS Series Technical Reference Manual
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Figure C-2 EGNOS Ground Segment (2010)
Provided that a GPS satellite is available to the SBAS reference station network for tracking purposes,
orbit and timing error corrections will be available for that satellite. Ionospheric corrections for that
satellite are only available if the signal passes through the ionospheric map provided by SBAS (ex. the
WAAS ionospheric map covers the entire Central and North American region). As an example, if a
satellite is South of your current location at a low elevation angle, the pierce point of the ionosphere will
be considerably South of your location since the ionosphere is at an altitude of approximately 60 km.
There must be sufficient ionospheric map coverage beyond your location in order to have ionospheric
correctors for all satellites.
To enhance the information provided by SBAS, the iSXBlue/SXBlue II GNSS has a unique ability to
extrapolate the ionospheric information beyond the broadcast information. This feature increases the
usable geographic coverage area of a SBAS system.
Signal Information
A SBAS transmits correction data on the same frequency as GPS from a geostationary satellite (the space
segment), allowing the use of the same receiver equipment used for GPS. Another advantage of having
SBAS transmit on the same frequency is that only one antenna is required.
