Raymarine GPS navigation - Manual (Page 65)

3.10.4.3 Averaging for Loran
the
LORAN AVERAGING
menu we can select
AVERAGING
averaging periods for the Loran L/L readouts and
POSITION.
one for the Speed readouts. Averaging periods of
SHORT , MEDIUM , LONG , canbeselected.
SPEED
Press the POSITION repeatedly to
scroll the selections for the position readout. Press
repeatedly to scroll the selections for the Speed readout.
Shortest averaging, quickest response, slightly erratic readings.
“MEDIUM”-Gives smooth readings with more response.
“LONG’‘-Longest averaging period. Gives smoothest readings.
Generally for Loran , For L/L Short or Medium averaging is recommended.
For Speed, Medium or Long is recommended.
When correct, return to the Main Menu Directory.
3.10.5 NAV Setups GPS
This section covers the NAV SETUP menus that are particular to GPS
operation. The menu of the
NAV SETUPS
menu happens
to have the same operations for both Loran and GPS. The operations for
selecting magnetic bearings were covered in section 3.10.4.1. However, for
GPS operations, the
POSITION CORR
. and
AVER
A
GI
N
G
menus are unique to
GPS and are discussed in the following paragraphs.
3.10.5.1 Position Corrections GPS
In the NAV 398 there are actually three forms of correction available in the
GPS mode. They are:
l
Geodetic datum
l
Manual L/L correction
l
Manual TD correction
When the GPS sensor converts the ranging measurements from the satellites
into coordinates it uses a mathematical formula (or datum) to arrive
at the L/L solution. In preparing charts or maps, cartographers also rely on a
particular mathematical formula or geodetic datum (scaling system)on which
to calibrate the Latitude/Longitude coordinate structure of the charts. The
type of datumused to make the chart is normally listed on the chart in the
table area.
OPERATION 3-52