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Notice the information on the map display is slowly moving? That’s how it would
look in actual use as well. The background map information and nearby waypoints
will move across the screen, while your current position remains fixed in the center.
The other primary navigation screens are the Compass and Highway pages, with
the Compass Page appearing first in the sequence of main pages.
To view the Compass Page, press PAGE.
The GPS III’s Compass Page provides graphic steering guidance to a destination
waypoint. The middle of the page features a rotating ‘compass ring’ that shows your
course over ground (track) while you’re moving, and a bearing pointer that indicates
the direction of the destination (bearing) relative to the course over ground. The com-
pass ring and pointer arrow work independently to show—at a glance—the direction
of your movement and the direction to your destination. If the arrow points up, you
are going directly to the waypoint. If the arrow points any direction other than up, turn
toward the arrow until it points up—then continue in that direction. The distance to
the next waypoint, time to the next waypoint and current speed are displayed to the
right of the graphic compass display. To see how all this works on our simulated trip,
let’s head off course and watch the displays change.
To move off course / on course in simulator mode, use the LEFT/RIGHT
keys on the rocker keypad.
The background map moves
while keeping your current
position at the center of the
The Compass Page will also
guide you to your destination.
The rotating ‘compass ring’
shows the direction of travel
(track) and the arrow points
to your destination (bearing).
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To view the Highway Page, press PAGE.
The Highway Page provides a graphic highway display that shows your move-
ment relative to the desired course. The line down the middle of the highway repre-
sents your desired course. As you navigate toward your destination, the highway will
actually move, indicating the direction you’re off course. To stay on course, simply
steer toward the center of the highway. As you approach the waypoint, the highway
will end at the final destination. When the waypoint marker is at the bottom center
of the highway display, you’ve arrived at your destination. A track compass also
shows your current track directly above the highway display, making it easy to see at
a glance which way you’re headed.
The pointer arrow at the bottom of the page indicates the direction to the
destination waypoint (bearing) relative to the direction you are moving (track). If the
pointer points straight ahead, you’re heading directly to the waypoint. If not, turn in
the direction of the pointer and the pointer will swing around, pointing straight
ahead as you begin moving toward the destination waypoint. Try moving on course/
off course again using the rocker keypad and watch as the highway display and bear-
ing pointer change.
That’s it! You’ve covered the basics and you’re ready to venture off on your own.
Operating the GPS III is just as simple as you’ve seen here in the Simulator Tour, but
in real applications you won’t need to change speed and track with the rocker key-
pad. That’s all done automatically utilizing information from the GPS satellites as you
Before ending the tour, try a few experiments of your own, such as going back
to the ‘HOME’ waypoint, retracing your steps utilizing the TracBack feature, or cre-
ating a few more waypoints. Use the Reference section of this manual for more ideas.
To end the Simulator Tour, turn the GPS III off with the red power key.
Use the LEFT/RIGHT keys on
the rocker keypad to move off
course / on course. To return
to your course, steer toward
the highway centerline.
When you reach your destina-
tion, the highway will end at
the waypoint marker. Also
note the ‘distance to next’
waypoint readout. If you pass
the waypoint the pointer will
swing around, pointing down.
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The GPS III’s Satellite Status Page provides a visual reference of various receiver
functions, including current satellite coverage, receiver operating mode, battery level
and position accuracy. As the receiver locks onto satellites, a signal strength bar will
appear for each satellite in view, with the appropriate satellite number (01-32) under-
neath each bar. The progress of satellite acquisition is shown in three stages:
• No signal strength bars— the receiver is looking for the satellites indicated.
• Hollow signal strength bars— the receiver has found the satellite(s) and is
• Solid signal strength bars— the receiver has collected the necessary data and
the satellite(s) is ready for use.
Each satellite has a 30-second data transmission that must be collected (hollow bar
status) before that satellite may be used for navigation (solid bar status). Once a fix has
been calculated, the GPS III will then update your position, track, and speed by select-
ing and using the best satellites in view. You can also access the GPS III’s contrast fea-
ture from this page.
To adjust the screen contrast:
1. Press LEFT or RIGHT on the rocker keypad to adjust the level of contrast, and press
ENTER to save the new contrast setting.
Sky View and Signal Strength Bars
The sky view and signal strength bars give you an indication of what satellites are
visible to the receiver, whether or not they are being used to calculate a position fix,
and the signal quality. The satellite sky view shows a bird’s-eye view of the position of
each available satellite relative to the unit’s last known position. The outer circle rep-
resents the horizon (north up); the inner circle 45º above the horizon; and the center
point directly overhead.
The Satellite Status Page
shows where the satellites are
and how strong the signal is
from each one. A solid signal
bar means the satellite is
ready to use.
Use the LEFT/RIGHT keys on
the rocker keypad to adjust
the screen contrast. Press
ENTER to save the setting.
Satellite Status Page
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You can use the sky view to help determine if any satellites are being blocked,
and whether you have a current position fix (indicated by a ‘2D Navigation’ or ‘3D
Navigation’ in the status field). You can also set the sky view to a ‘Track Up’ config-
uration, causing the top of the sky view to align along your current track heading.
When the receiver is looking for a particular satellite, the corresponding signal
strength bar will be blank and the sky view indicator will not be highlighted. Once
the receiver has found the satellite, a hollow signal strength bar will appear, indicat-
ing that the satellite has been found and the receiver is collecting data from it. The
satellite number in the sky view will appear highlighted. As soon as the GPS III has
collected the necessary data to calculate a fix, the status field will indicate a 2D or 3D
status. (For ‘2D’, you may need to enter your altitude. See page 30.)
Receiver status is indicated at the top left of the page. The status will be shown
as one of the following conditions:
Searching— the GPS III is looking for any available satellites in view.
AutoLocate— the GPS III is initializing and collecting new almanac data. This
process can take up to 5 minutes, depending on the satellites currently in view.
Acquiring— the receiver is collecting data from available satellites, but has not
collected enough data to calculate a position fix.
2D Navigation— at least three satellites with good geometry have been locked
onto and a 2-dimensional position fix (latitude and longitude) is being calculat-
ed. ‘2D Diff ’ will appear when you are receiving DGPS corrections in 2D mode.
3D Navigation— at least four satellites with good geometry have been locked
onto, and your position is now being calculated in latitude, longitude and alti-
tude. ‘3D Diff ’ will appear when you are receiving DGPS corrections in 3D mode.
‘2D Navigation’ means the
GPS III has determined a hor-
izontal position (latitude/
longitude), but is unable to
determine altitude. Additional
satellites may be needed.
‘3D Navigation’ means the
GPS III has determined a hor-
izontal and vertical position
(latitude, longitude and alti-
tude). The receiver is ready
Satellite Status Page
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Poor GPS Coverage— the receiver isn’t tracking enough satellites for a 2D or 3D
fix due to bad satellite geometry.
Not Usable— the receiver is unusable, possibly due to incorrect initialization or
abnormal satellite conditions. Turn the unit off and back on to reset, and reinitial-
ize the receiver if necessary.
Simulating Nav— the receiver is in simulator mode.
‘Need to Select Initialization’ Prompt
If no satellites are received for several minutes (or an insufficient number of satel-
lites are received to determine a position fix) a message will appear, prompting you to
initialize the receiver (see page 5). This allows you to specify a starting location from
which to search for satellites, or to enable the AutoLocate feature, and is useful if you
have traveled over 500 miles with the receiver off. (This message will automatically
appear when you first use your GPS III. The prompt may also appear during normal
use if the antenna is shaded or the unit is used indoors.)
Battery Level Indicator
The Satellite Status Page also features a battery level indicator, located to the left of
the sky view, which displays the strength of the unit’s batteries. The battery indicator
will not appear if the receiver is operating on external power.
NOTE: The battery level indicator is calibrated for alkaline batteries. NiCad and
lithium batteries will display the battery level differently due to voltage differences. To
display battery level accurately select the appropriate type, as described on page 69.
The GPS III features an internal 10-year lithium battery that will maintain the unit’s
memory when the receiver is not running off batteries or external power.
‘Poor GPS Coverage’ means
the receiver isn’t tracking
enough satellites for a position
fix. Check for obstructions,
such as trees, buildings, etc.
This message appears if a
position fix cannot be deter-
mined after several minutes.
After acknowledging the mes-
sage, select ‘Use Map’ or
‘AutoLocate’ from the
Satellite Status Page
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