SXBlue GPS Reference Manual
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6. Frequently Asked Questions
6.1 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 both WAAS and EGNOS are in test mode currently, they are not to
be used as a sole means of navigation. Additionally, as they are under test, there may
be 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
regarding the broadcast schedule of WAAS and EGNOS.
Q – Can the COAST technology work with corrections from an external source?
A – Yes, the SXBlue GPS 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 separate error components, allowing the SXBlue GPS 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 e-Dif the solution for my positioning needs?
A – It is difficult to say without knowing more about your application. e-Dif is not a
different solution / replacement for everyone’s application. Certain applications lend
themselves to successful e-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, e-Dif can be successfully used in geographic regions
where the only differential services available are subscription-based. E-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 SXBlue GPS compare to competitor’s products?
A – The SXBlue GPS 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
Agricultural Guidance or GIS & Mapping due to their positioning performance and their
update rates. The SXBlue GPS is up for this task and meets the needs for these
applications. The SXBlue GPS also offers the facility of outputting raw measurement
data for post-processing in the office.
