SXBlue II GPS 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 SXBlue II GPS 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.
