Raymarine GPS navigation User Manual download pdf (Page 63)

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

correction

-0.2 S2 correction

KJSrnON

CORFI.

LORAN

ASF

COlUlECTiON

~MANU

OFF

o.ous

N 00.00’

14L

w 00.00’

PREssaEARToExtT

AVERAGING LORAN

After subtraction, the values

1.2~s

for

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

highlight MANU and press

thel[key.

TD will be highlighted to

indicate numeric values should now be entered.

OPERATION 3-50

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Raymarine GPS navigation User Manual Page 63

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