5
Turning Power On
To turn the unit on, simply press the PWR key. A GPS
logo screen appears, then the screen similar to the one
at right appears. Read the message on the screen,
then press the EXIT key to erase it or wait a few sec-
onds and it automatically clears. The screen shown
below appears next.
Satellite Status Screen
This screen appears each time you turn the unit on. It shows a graphical
view of the satellites that are in view. Each satellite is shown on the circu-
lar chart relative to your position. The point in the center of the chart is
directly overhead. The small inner ring represents 45° above the horizon
and the large ring represents the horizon. North is at the top of the screen.
You can use this to see which satellites are obstructed
by obstacles in your immediate area if you hold the
unit facing north.
The GPS receiver is tracking satellites that are sur-
rounded by a black box. If the satellite number is not
surrounded by a box, then the receiver hasn’t locked
onto that satellite and it isn’t being used to solve the
position.
Beneath the circular graph are the bar graphs, one for
each satellite in view. Although the unit has twelve channels, it dedicates
one channel per visible satellite. Therefore, if only six satellites are visible,
only six bar charts show at the bottom of the screen. The higher the bar
on the graph, the better the unit is receiving the signals from the satellite.
The number in the upper left corner is the “expected horizontal position
error” or expected error from a benchmark location. In other words, if the
expected error shows 50 feet, then the position shown by the unit is esti-
mated to be within 50 feet of the actual location. However, this number is
only valid if you’re using DGPS or if S/A is turned off. Due to S/A, the
accuracy can only be less than 100 meters, 95% of the time, per U.S.
government specifications. Although the expected error is not accurate
unless you have a DGPS receiver, it does give you an indicator of the fix
quality the unit currently has. The smaller the expected error number, the
better (and more accurate) the fix is.
If the expected error is flashing, then the unit has not locked onto the
satellites, and the number shown is not valid.
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