iSXblue/SXBlue II GNSS Series Technical Reference Manual
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7.
Frequently Asked Questions
7.1
General
Q – Are the SBAS services reliable for differential operation?
A – Yes, these services have proven themselves for some time now and have shown excellent results. As
WAAS (North and Central America), EGNOS (Europe) and MSAS (Japan) are operational, they can be
used as sole means of navigation. GAGAN is currently in test mode and might experience some periods
of outage or times when the signal should not be used. We recommend that you refer to Appendix D -
Resources of this manual for Web sites that provide details on the status of WAAS, EGNOS, MSAS and
GAGAN.
Q – Can the COAST technology work with corrections from an external source?
A – Yes, the iSXBlue/SXBlue II GNSS will operate in a similar fashion with the COAST technology as
when using SBAS. However, SBAS corrections have the advantage that they are separated into distinct
error components, allowing the iSXBlue/SXBlue II GNSS to anticipate how errors will change over the
coasting period with more consistent accuracy and for a longer period than regular RTCM range
corrections.
Q – Is Auto-Dif the solution for my positioning needs?
A – It is difficult to say without knowing more about your application. Auto-Dif is not a different
solution / replacement for everyone’s application. Certain applications lend themselves to successful
Auto-Dif operation, such as crop dusting. In this application, the aircraft must refuel and be filled with
chemicals quite frequently, perhaps every 20 minutes. This allows for a new initialization when the
aircraft lands. Provided that the user feels that it’s efficient to do so, Auto-Dif can be successfully used in
geographic regions where the only differential services available are subscription-based. Auto-Dif, in this
application, would require an initialization as frequently as the user feels is necessary to maintain a level
of performance that they’re comfortable with. This may mean an initialization every 30 minutes or so.
Also, if absolute positioning accuracy is needed as opposed to relative positioning, a point of known
coordinates should be used for initializing the system. Of course, more points in the area of the system
use could be used, provided that their coordinates are correctly entered into the system. This can be easily
implemented through development of a custom software application running on a PDA product.
Q – How does the iSXBlue/SXBlue II GNSS compare to competitor’s products?
A – The iSXBlue/SXBlue II GNSS is a unique solution in that it is very compact, yet offers a high degree
of performance. There are a number of DGPS products on the marketplace, however, very few of these
are suitable for commercial use in applications such as GIS & Mapping due to their positioning
performance and their update rates. The iSXBlue/SXBlue II GNSS is up for this task and meets the needs
for these applications. The iSXBlue/SXBlue II GNSS also offers the facility of outputting raw
measurement data for post-processing in the office.
Q – What should I do if I want to evaluate Auto-Dif?
A – We suggest that you contact your dealer to see if they have a unit available with Auto-Dif activated
for your testing.