Lowrance 100 Installation And Operation Instructions Manual page 13

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 chan-
nels, it dedicates one channel per visible satellite. There-
fore, 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 re-
ceiving 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.
The fix indicator on the left center shows either 2D or 3D. A 2D fix means
the unit has locked onto three satellites and has calculated its position. A
3D fix means the unit has locked onto at least four satellites and has
calculated both the position and altitude. (Remember, it takes three satel-
lites to determine the position - four to determine position and altitude.) If
neither 2D nor 3D are showing, then the unit doesn't have the position or
altitude.
A battery level indicator on the lower right side of the screen shows the
approximately how much life is in the batteries. This runs from "F" (fully
charged) to "E" (expired).
A light bulb indicator at the top right corner of the screen appears when
the backlights are on.
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