Waypoint Entry Of Present Position (Evt Key In Wpt Mode) - Furuno LC-90 Owner's Manual

You will note that these umbrella-shaped lines are symmetrical about the
baseline between the master and slave transmitting station. You might
think of the baseline as a mirror, where a TD line of position on one side
has a mirror-image on the other side of the line.
While it is true that for a particular Latitude/Longitude position there is at
least one set of two TD's that cross at that point, it is also true that for
any one set of two TD numbers there are two Latitude/Longitude positions.
You'11 probably have to think about that one for a while and look closely at
the drawing.
Another iinportant point: if the automatic ASF compensation function is
activated (as reeominended for most operations), and if you wish to make a
conversion from TD's to L/L, you should manually compensate your TD's to
reflect local ASF values before making the conversion to L/L. See the
section "USING ASF WHEN ENTERING TD'S FOR WAYPOINTS" under
Advanced Level Operations for details.
Alternatively, you might disable the ASF function when using a waypoint
converted from raw TD's to L/L in order to obtain accurate Range/Bearing
readings, especially when you get near the desired waypoint, You can
disable the automatic ASF compensation function using Function #4.
The sequence of operations is:
1. Call up Function #4 and disable the ASF Auto function, if it is on. The
. keystroke sequence is as follows:
B E fflffllciLR] [+Z3 HH
Fig. 19 Function #4 Screen
What it all boils down to is that in order to convert a set of two TD's to a
set of Latitude/Longitude coordinates, you have got to be on the correct
side of the baseline (and its associated "baseline extension," where the
baseline between the master and slave station is extended on through past
the slave.) Without all the jargon, the TD's for the position you want to
put into a waypoint must be within about one hundred miles or so of your
present position in order to use the TD to L/L conversion, and they
shouldn't be on the opposite side of a baseline extension from your present
position. It is a good idea to plot the resulting L/L reading that the LC-90
comes up with in making the conversion between TD's and L/L on a chart
to see if the calculated position makes sense to you.
Let us use the following numbers as an example. The GRI in use is 9940,
and the Slave stations in use are the "11" and the "27" lines. We assume
here that LC-90 has already locked onto the signals, and that the desired
TD's are relatively close by — for example, they may have been sent to
you over the VHF radio by a fishing buddy. The TD's to be converted
are: 12885.0 and 27932.4 microseconds. The approximate Latitude/
Longitude at these TD's is 44 degrees, 30 minutes North Latitude, and 124
degrees, zero minutes West Longitude.
(Note that the slave stations that the LC-90 is presently tracking should be
the same as the TD's you want to use to make the conversion between
TD's and Latitude and Longitude, and it is necessary for the GRI in actual
use to be the same as the one that was originally used for generating the
TD's you want to enter.)
2. Call up the WPT Function by moving the left or right arrow key until
the Mode indicator arrow is lined up directly over the "WPT" label on
the panel under the display. Specify the waypoint nuinber into which
you wish to store the TD information (we'll use waypoint zero eight
here), and then enter the desired information. The following touchpad
sequence would be used:
fcLRirol
GO IentI rfp^-L/Liril m
DO do E
no Ibnti
rcLRim
0 GD 0 E GO (MB
3. Now switch back to the L/L display to see the resulting L/L. You must
wait for the L/L display to settie down with all numbers and indications
stable before proceeding on to any other Mode or Function.
Waypoint Entry of Present Position ( |EVT~1 key in WPT Mode:):
There are times when you will want to store your present location into a
waypoint. For example, you might have coine across a particularly good
fishing spot, and want to record it as a waypoint so that you may return
to this location at a later date. The procedure is simple: first, make sure
that you are in the L/L format, and then get into the WPT Mode. Then
specify < the waypoint number into which you want to store the present
location.
Now, hit the IÉVtI key.
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