S3 User Guide 66 PN 875-0196-000 Rev C1
Appendix B: Frequently Asked Questions
About GPS Guidance
Q: What is GPS?
A: Global Positioning System (GPS) is a satellite-based signal operated by the U.S.
Department of Defense and is available to anyone to provide position information to
receivers on the ground. Several satellites are used by the receiver to pinpoint the
exact position.
Q: What is DGPS?
A: DGPS stands for differential GPS (or differential correction GPS). It means that a
second signal is used to correct inherent errors in the GPS signal making it even more
precise. S3 can utilize SBAS, e-Dif, or RTK corrections.
Q: What is WAAS?
A: Wide Area Augmentation System (WAAS) is a satellite-based correction signal
operated by the U.S. Federal Aviation Administration that is free to those who use it.
WAAS provides relatively uniform accuracy and coverage from the Arctic Ocean to
Hawaii to the mid-Caribbean to the mid-Atlantic and the shores of Greenland. Other
SBAS systems, such as EGNOS (Europe) and MSAS (Japan), offer corrections in other
areas of the world. For more information about WAAS go to
http://gps.faa.gov/.
Q: What is LOCRTK?
A: LOCRTK is a proprietary localized differential correction signal generated by a
BaseLineX system consisting of a stationary base station receiver that broadcasts the
LOCRTK corrections over a radio link to a moving rover receiver.
Q: What is e-Dif?
A: Hemisphere GPS’ patented e-Dif technology is capable of achieving GPS accuracies
of a few feet without the need for a differential signal broadcast. e-Dif generates
internal differential corrections based on the starting location—these corrections are
modeled over time and applied to the GPS data to maintain a very consistent relative
position. You can use e-Dif over long time periods with minimal accuracy drift or
return to the starting location at any time to update the differential corrections.
Q: How accurate is S3
DGPS?
A: Using SBAS corrections and operating under normal conditions (where each
subsequent pass is being made within minutes of the last), swath to swath accuracy is
just a few inches. The more time elapsed from one pass to the next may reduce
accuracy.
Q: What about foam markers and disk markers?
A: The answer is … use them if they help. The best guidance is what works for you.
The more visual indicators to guide from the better; however, GPS guidance will be
the primary guidance means and everything else will be secondary.
Q: Can I plant using GPS guidance?
A: GPS guidance is a great planting aid, especially for making the straightest rows
possible. Outback Guidance recommends differential GPS (like RTK) to provide you
with every possible advantage.
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