The NavData card contains over 100 map datums for you to use when navigating.
By default, your unit calculates positions using the WGS 84 map datum. If you are
using charts based on another datum, you must set the GNC 250XL to use the same
datum. Using a map datum that does not match the charts you are using can result in
significant differences in position information. If you are using maps for reference
only, the GNC 250XL will provide correct navigation guidance to the waypoints
contained in the database, regardless of the datum selected.
To change the map datum to one listed in Appendix F:
1. Press and hold
M
, and use
O
to highlight the map datum page.
2. Press
C
twice.
3. Use
O
to highlight the current map datum.
4. Use
K
to change the datum.
5. Press
C
to complete.
To create a user datum:
1. Press and hold
M
, and use
O
to highlight the map datum page.
2. Press
C
twice.
3. Use
O
to highlight ‘Define user datum?’. Press
E
.
4. Enter the five parameters of the map datum using
K
and
O
. Press
E
to accept a
field. The signs of each value (+/-) should follow the convention: WGS84-local geodetic
system.
5. Use
O
to highlight ‘ok?’, and press
E
.
6. To activate the user datum, select ‘USER’ on the map datum page as described above.
85
User datum page. To use this function you must
enter the parameters as differences from the WGS
84 default.
Map datum page showing the default WGS 84
datum. This setting should be used unless your
paper chart specifies a different datum.
SECTION
6
UNIT SETTINGS
Map Datums
250xl manual 2 7/17/98 1:33 PM Page 85
