Garmin GPS Kit Owner's Manual page 48

Appendices
Appendix G
Grid Formats (con't):
FAQ's
Swiss Grid
Taiwan Grid
User Defined Grid
UTM/UPS (Universal Transfer Mercator/Universal Polar Stereographic)
W Malaysian R
Can I turn off the Track Log?
No. You can clear the track log, but it is always activated.
Why is the elevation on my GPS incorrect by several
hundred feet?
GARMIN GPS units have a potential position accuracy of 15 meters.
This is the same accuracy available in all commercially available GPS
receivers. The accuracy of the GPS units is not only dependent upon the
GPS receiver design, but also the U.S. DoD Selective Availability
program (SA). Selective Availability, also known as SA, is a program
that allows the U.S. DoD to degrade the accuracy of non-military GPS
system by as much as +/- 100 meters. At the present time, the accuracy
of all commercial GPS receivers can vary Between 15 to 100 meters
depending on the level of degradation being imposed by the U.S. DoD.
Another factor that will effect the accuracy of the GPS receiver is the
geometry of the satellites in view of the GPS receiver. A poor geometry
situation can provide less accurate position readings, and this
especially applies to GPS altitude measurements. The altitude reading
on the GPS unit can vary by +/- 450 ft. depending on the level of
degradation being imposed under SA. It is not uncommon to see the
altitude continuously drift up and down when SA is being imposed.
What does the message "NO DGPS POSITION" mean?
eTrex had a differential fix and lost it.
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