iSXblue/SXBlue II GNSS Series Technical Reference Manual
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SBAS or other code-phase differential correction services for up to about 40 minutes, depending on the
amount of tolerable performance drift. Section 2.5 provides with a description of the Coast technology.
The estimated positioning precision is accessible through the use of NMEA 0183 command responses as
described in Chapter 4 (The GST NMEA data message). As the receiver is not able to determine
accuracy with respect to a known location in real time (this is traditionally performed in post-mission
analysis), the precision numbers are relative in nature and are approximates.
2.1.3
Update Rates
By default, the iSXBlue/SXBlue II GNSS is supplied with a 1Hz update rate. A higher
10Hz or
20Hz
update rate option can be purchased via your dealer and a code will be used to unlock the feature. Carrier
phase output is standard on all models of the iSXBlue/SXBlue II Series.
The update rate of each NMEA and binary message of the iSXBlue/SXBlue II GNSS can be set
independently with a maximum that is dependent upon the message type. Some messages have a 1 Hz
maximum, for example, while others are up to 20 Hz.
Higher update rates are valuable for applications where higher speeds are present (such as aviation, UAVs
or racing cars) or more frequent updates are required for manual navigational tasks, such as Agricultural
Guidance.
2.2
SBAS
The following sections describe the general operation and performance monitoring of the SBAS
demodulator within the iSXBlue/SXBlue II GNSS receiver. See Appendix C for more information on
SBAS currently available in the world (at time of print).
2.2.1
Automatic Tracking and Ranging
The SBAS demodulator featured within the iSXBlue/SXBlue II GNSS will automatically scan and track
the SBAS satellite signals. At time of print, SBAS signals available are WAAS (USA and covering
Central and North America), EGNOS (Europe), MSAS (Japan) and GAGAN (India). This automatic
tracking allows the user to focus on other aspects of their application rather than ensuring the receiver is
tracking SBAS correctly.
The SBAS demodulator features three-channel tracking that provides an enhanced ability to maintain
acquisition on a SBAS satellite in regions where more than one satellite is in view. This redundant
tracking approach will result in more consistent acquisition of a signal when in an area where signal
blockage of either satellite is possible.
Furthermore, the iSXBlue/SXBlue II GNSS is set by default with the SBAS ranging feature activated.
This feature uses the SBAS satellites in the position computation. In other words, the geosynchronous
SBAS satellites, besides providing with the differential correction and when broadcasting ranging
information, are also used as “extra” GPS satellites. As an example, WAAS satellites provide with
ranging information whereas EGNOS’ do not.
2.2.2
SBAS Performance
The performance of the SBAS receiver is described in terms of a differential LED. SBAS requires a line
of sight to the SBAS satellites in order to acquire the signal.