Ag Leader EZ-Guide 250 Getting Started Guide - Manual (Page 60)

Advanced Mode GPS Corrections
Configuring the GPS Corrections
The term GPS corrections refers to the type of GPS signal that you receive.
ITEM DESCRIPTION
WAAS (Wide Area
Augmentation
System)
WAAS corrections are an overlay to the normal GPS signal to improve accuracy.
WAAS is available only in the United States of America, southern Canada, and the
northern parts of Mexico. It is free to use.
When using WAAS corrections, the EZ−Guide 250 system downloads the WAAS
ionosphere model within the first 10 minutes of operation, which improves accuracy
significantly. If you turn off the lightbar for less than 20 minutes and restart it, the
position drift is limited. If you turn of the lightbar for more than 20 minutes and then
restart it, the WAAS ionosphere model needs to be downloaded again. This can result
in absolute position errors of up to 3 m (10 ft) within the first 10 minutes.
EGNOS (European
Geostationary
Navigation Overlay
Service)
EGNOS corrections are an overlay for normal GPS signals. They are available only in
Europe and can be used free.
Note: At mid latitudes, the GPS cross−track errors that occur when you drive East−West are typically double the
cross−track errors that occur when you drive North−South. This is a characteristic of all GPS receivers and
guidance systems, and occurs because the GPS satellite orbits do not go over the poles. For GPS system status
details, go to http://www.navcen.uscg.gov/ado/GpsActiveNanu.asp.
The lightbar is initially configured to use the internal GPS receiver with WAAS/EGNOS. It will automatically
detect the appropriate satellites.
To change the GPS corrections:
Select Configuration / System / GPS / GPS Setup / GPS Correction Source and then press . The GPS
Correction Source screen appears:
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