You
may find these answers to many of the frequently asked questions about
GPS technology and Magellan® GPS products helpful in resolving
your issues.
Q:
My GPS receiver will not accept Latitude Longitude coordinates.
A: Change the coordinate system from Deg/Min/Sec
to Deg/Min/MM.
Q: My GPS
receiver does not acquire satellites.
A: Check the initial position, time and date displayed in the GPS to be sure
they are correct. Initialization can take up to 10 minutes with a clear view
of the sky.
Q: My GPS
receiver will not communicate with my computer.
A: Make sure the GPS Baud rate is set to 4800
Set GPS NMEA to 0183B or 2.1 GSA
Set COM port to 4800 baud, 8 bits per second, no parity, one stop bit and set
flow control to hardware.
Disable or remove any conflicting software from the COM port, such as answering
machines, fax software, personal organizers, etc.
Q: Why does
my GPS receiver show I'm moving when I'm standing still?
A: The GPS satellites may on rare occasion broadcast a signal error (Selective
Availability) that can account for up to 2.5 mph of movement.
Q: What
is Selective Availability (SA)?
A: SA is an intentionally introduced degradation in the accuracy of civilian
GPS by the United States Department of Defense. SA errors can degrade the GPS
accuracy up to 100 meters. However, this error is adjustable and random. Typically,
errors of 30 meters or more are not unusual. Now that SA has been removed,
typical GPS position accuracy is approximately 15 meters (50 feet).
Q: What
is differential GPS (DGPS)?
A: Differential GPS allows the user to overcome the effect of SA interference,
correct for other GPS errors and increase the overall accuracy of the GPS receiver.
With DGPS, one GPS receiver is placed at a known location and the position
information from that receiver is used to calculate corrections in the position
data transmitted by the satellites. This corrected information is then transmitted
to other GPS receivers in the area. The resulting real-time accuracy is in
the 10-meter range. Sub-meter accuracy can be obtained by using DGPS and post-processing
calculations in static positioning. A separate DGPS receiver is required.
Q: Why does
the elevation fluctuate on my GPS receiver?
A: GPS elevation will vary up to 150 meters due to Selective Availability.
Now that SA has been turned off, the accuracy of GPS elevation may vary +/-
15-20 meters (50-65 feet) due to random errors caused by atmospheric delay,
incorrect satellite positioning or poor geometry in the satellite constellation.
Q: Do I
have to leave my GPS receiver on to track my position?
A: If you want a record of the track history, leave your GPS turned on. Otherwise,
it is not necessary.
Q: Can I
interface my GPS receiver with a Macintosh?
A: At this time, Magellan products do not support Apple or Macintosh. It may
be possible to connect your GPS to a Macintosh computer by searching Apple.com
for connectivity plugins under COM ports or serial ports.
Q: Now that
Selective Availability (SA) has been turned off, do I need to update
my unit?
A: No, your unit does not require an update to receive the GPS signals.
Q: What
is the accuracy of my unit with SA turned off?
A: The relative accuracy of GPS without SA is 49 feet (15 meters). However,
there are others factors that may affect the accuracy of GPS.
Q: What
other factors affect the accuracy of my unit?
A: Other factors limiting the accuracy of GPS include but are not limited to
atmospheric distortion and multi-path. Increased atmospheric distortion can
be caused by periods of high solar flux/activity. Multi-path is the reception
of two signals from the same satellite, one being the true signal and the other
being the reflected signal from a building or a cliff.
Q: What is the difference between degrees/minutes/seconds (DEG/MIN/SEC)
and degrees/minutes/minutes (DEG/MIN/MMM or DEG/MIN/MM)?
A: There are
different ways in expressing the coordinates computed using Lat/Lon coordinate
system. With DEG/MIN/SEC the final set of numbers (SEC) is expressed
as 0-59 while DEG/ MIN/MM expresses the same value as 0-99 and DEG/MIN/MMM
is from 0-999. It would be the same as if you had one clock that expressed
time as hour/minutes/seconds and another clock that expressed the same
time as hours/minutes/decimals. The accuracy for any of the three is
the same. Which you choose is dependent upon your preference or any chart
you are using in conjunction. You should always make sure that your SporTrak
is setup to be the same as any map or chart you may be using.
Q: What is 2D vs. 3D?
A: The difference is primarily how many satellites
are used to compute the position fix and how elevation is computed. In
2D (two-dimensional) only three satellites are needed for a position
fix and elevation is not computed. Any elevation displayed by the Meridian
during 2D operation is the elevation you entered. In 3D (three-dimensional),
a minimum of four satellites are needed to compute the position and elevation
simultaneously.
Q: When the time changes for daylight savings time will the time, in
the Meridian change automatically?
A: No. The time transmitted by the
satellite atomic clock are UTC (Universal Time Coordinated) and provides
no correction for daylight savings. When daylight savings time changes
(or when you move to a new time zone), you need to go into Setup - Time
Format and re-select the time format you are using unless you are using
UTC. After selecting the format, you will be given the opportunity to
change the time.
Q: When the time changes for daylight savings time will the time, in
the SporTrak change automatically?
A: Yes. It is automatically selected when the receiver is used for the
first time or all of the memory has been cleared. If you need to change
the settings for daylight savings, you can use the Setup menu item and
access Daylight savings. There you can select United States, European
Union or you can use the customize option to set the rules for daylight
savings in your area.
Q:
How often do I need to initialize the Meridian/SporTrak?
A: Initializing the
Meridian/SporTrak decreases the time it takes to get a position fix during
cold start. What is meant by a cold start is that the Meridian/SporTrak
has no reference
to use as a guide to tell it what satellites should be overhead. Without
a reference to start with, the Meridian/SporTrak will have to search
the sky to find the satellites in view. This may take up to 10 minutes
in
severe
conditions.
Q: So where does this initial reference come from?
A: Under normal operating
conditions, the last position fix computed before the receiver was turned
off is stored in memory and will be used as the reference the next time
the receiver is turned on. If you cleared the memory, this stored reference
point is removed and you will want to initialize the receiver. If you
travel more than 500 miles with your receiver turned off, the reference
point may be too inaccurate to be useful and you may want to initialize
your receiver.
Q:
Why does my Meridian compass not point in the right direction?
A: The Meridian
computes direction by comparing your present position to the last position
taken, it requires that you be moving to compute your compass heading.
To eliminate error, you must be moving at a minimum of 2.0 mph. The exception
is the Meridian Platinum, which has an electronic compass that will compute
the compass heading below 2.0 mph. This includes computing your compass
heading while you are standing still.
Q: Why does my SporTrak compass
not point in the right direction?
A: The SporTrak computes direction by comparing your present position
to the last position taken, it requires that you be moving to compute
your compass heading. To eliminate error, you must be moving at a minimum
of 0.5 mph.
Q: What is a backtrack route?
A: A backtrack route allows you to retrace
your steps. As you are moving, the Meridian/SporTrak automatically creates
and stores hidden waypoints in memory. These waypoints are the ones that
the Meridian will use to retrace your steps. When you create a backtrack
route, the Meridian converts these hidden waypoints into User Waypoints.
Q: How do I know which route is active?
A: Access the route menu by
pressing the MENU button and select the option Routes. The route menu
lists all of the routes in memory with the active route displayed in
bold characters.
Q:
Why doesn't my Meridian/SporTrak make an audible beep when I have an
alarm active?
A: Check your setup settings for the Beeper. If the selection
is Off or Keys Only, the beeper will not sound for alarms.
Q: What is NMEA?
A: NMEA (National Marine Electronics Association) is
the standard used for interfacing marine electronic devices. This standard
has also been adapted for use in a variety of third-party mapping software
programs.
Q: What are the NMEA message strings?
A: The Meridian supports version
1.5 and 2.1 of the NMEA 0183 standard.
Additional information on NMEA can be found at: www.nmea.org, where
you can purchase the NMEA Interface Standards.
Q: My receiver is not communicating with my computer. What can I do?
A: Check your baud rate and check the baud rate that
your software is using. If they don't match, change either the software
or the Meridian/SporTrak
baud rate.
Q:
Can I interface my Meridian/SporTrak with a Macintosh computer?
A: Magellan® does
not supply cabling or software for the Macintosh line of computers.
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