Raymarine GPS navigation - Manual (Page 66)

Geodetic Datums
Mariners may find considerable errors (up to 200 meters) in plotting own
ship’s position if their charts were created using one type of geodetic data
system while the GPS calculates positions using another data system.
398 can program the 108 to provide position calculations
utilizing several geodetic data systems. For maximum plotting accuracy, you
should set the GPS to match the datum used for your marine chart. The
datums available in the 108 are listed below and in Table A on the
following page:
1. WGS-84
2. WGS-72
3. BESSEL (JAPAN)
4. NAD-27 (USA)
5 NAD-27 (CANADA)
6. EURO-50 (Europe)
7. AUST-66 (Australia)
9. NAD-83
10. Other datums (see table)
When the
POSITION
menu is dis-
played the screen displays the current Geodetic
datumused by the GPS sensor. To move through
the datum list and select a different datum, press
down
to scroll the datum list.
POSITION
GEODETIC SYSTEM
N 00.00’
w 00.00’
N M
,
3.1
DGPS BEACON SELECT
Datums named on the list above will appear first in the sequence. When the
two digit numbers appear, continue holding the key until the desired number
is displayed. The numbers correspond to the datums listed on Table A. When
the datum or datum number you desire is displayed, it will become the datum
used for L/L calculations.
If you are finished with this menu, press to return to the
MAIN MENU
Directory. more time to get back to the normal
navigating screens.