SX BLUE GPS iSXblue II+ GNSSTM, User Manual

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SXblue Series User Manual 50
Caution – When the map has been downloaded, you may observe a position
jump due to the potential difference between the GPS ionospheric model and
the ionospheric SBAS map. To minimize the impact of this issue on your
use of the SXblue receiver, you may wish to wait up to five minutes before
using the receiver.
To improve upon the ionospheric map provided by SBAS, the receiver extrapolates
information from the broadcast ionospheric coverage map, extending its effective
coverage. This allows the receiver to be used successfully in regions that
competitive products may not. Please note that the process of estimating
ionospheric corrections beyond the WAAS broadcast map would not be as good
as having an extended SBAS map in the first place. This difference may lead to
minor accuracy degradation.
Figure 2-1 shows sample grids for WAAS, EGNOS, GAGAN and MSAS systems.
The inner areas are actual broadcast grids by the satellites and the outer areas
are the extrapolation the SXblue receiver achieves. Note that the SBAS grid maps
shown are typical as their extents constantly undergo slight changes due to
ionospheric activities and time of the day. But overall, the coverage map fairly
consistent from one day to another.
Figure 2-1 Sample Extrapolated Ionospheric Grids
2.3 DGPS RadioBeacon (for SXblue II-B)
Many marine authorities, such as Coast Guards, have installed networks of radio
beacons that broadcast DGPS corrections to users of this system. With the
increasing utility of these networks for terrestrial applications, there is an increasing
trend towards densification of these networks inland.