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arrival at the waypoint, the ships’ L/L must match WPT L/L. If the ship’s
displayed L/L is ASF corrected, the waypoint memory must have corrected
L/L coordinates if you are to arrive at the same location again. The NAV 398
takes care of this automatically for you.
If you see some difference between the waypoint’s L/L in memory and the
ship’s position at the waypoint location, we suggest that you save the
waypoint
as an Event, while sitting next to the mark. This will put a corrected
position into the waypoint memory and will permit the repeatable accuracy
of loran (+/- 50 feet) to guide you to the same location the very next time.
Auto ASF
Normally the ASF program is set to Automatic when the 508/A sensor
leaves the factory. However you should check the POSITION CORR. menu
and verify that the program is ON at the first opportunity. On the Main Menu
Directory, press
thelPOSITION
CORR]
softkey.
On the menu verify that the
ASF correction is highlighted at AUTO. Pressing the
softkey
steps the
selections from AUTO to MANUal to OFF, etc.
Manual TD Corrections
Although adding TD correction values to correct
your
Lat/Lon
position is not a common practice,
there are times when
TDs
of a fixed landmark are
available. It is fairly easy to correct your
Lat/Lon
reading using TD difference values. The procedure
for making manual TD corrections appear in the
following example:
Example:
The actual TD readings given on a chart
for a sea buoy are
13900.7~s
and
25590.0~s.
The
loran display reads 13899.5~s for S 1 and 25590.2~s
for S2 while sitting next to the buoy.
13900.7 Chart
25590.0
Chart
-13899.5 TD readout
25590.2 TD readout
1.2
Sl
correction
-0.2 S2 correction
1
KJSrnON
CORFI.
LORAN
1
ASF
COlUlECTiON
#
~MANU
OFF
o.ous
rm
*
o.ous
N 00.00’
14L
*
w 00.00’
PREssaEARToExtT
1
AVERAGING LORAN
1
After subtraction, the values
1.2~s
for
Sl
and
-0.2~~
for S2 were obtained
and can now be entered manually for the ASF values. To enter these values,
select the POSITION CORR. menu . Press the ASFCORRECTION
softkey
to
highlight MANU and press
thel[key.
A
TD will be highlighted to
indicate numeric values should now be entered.
OPERATION 3-50