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2. Press
T
to access the variation field, and use the
R
keypad to
enter the desired variation. Press
T
to confirm.
• CDI Scale provides a list of six CDI scale settings for the map page CDI: +/-0.10,
0.50, 1.0 (default). 5.0, 10.0 and 25.0 miles or kilometers. The scale represents the
distance from the center of the scale to either end of the scale.
• CDI Steer To allows you select a steer-to-center or steer-to-D-Bar orientation for
graphic steering guidance. The steer-to-center selection displays your position as
the vertical line on the scale, and your desired track as the center of the scale. The
steer to D-Bar option displays your position as the center of the scale, with the
desired track as the vertical line. The default setting is steer to center.
• Map Datum provides a list of the available map datums for use with the GPSMAP
135 Sounder system. For a list of the available map datums, see Appendix D. The
default setting is WGS 84.
• Velocity Filter allows you to select the GPSMAP 135 Sounder’s response time to
changes in track or ground speed. Three settings are available: automatic, on, or
off. The ‘auto’ (default) setting will monitor the changes in your current track and
speed and adjust the receiver’s response time automatically. The ‘on’ setting allows
you to manually enter a response time up to 240 seconds. Selecting a higher setting
may be desirable in slow-speed applications with frequent changes in track.
To enter a user defined velocity filter value:
1. Highlight the ‘Velocity’ field and press
T
. Select the ‘On’ option and
press
T
.
2. Highlight the time value field.
3. Press
T
.
4. Enter a value in seconds (up to 240) and press
T
to confirm.
76
SECTION
10
SETUP MENUS
Navigation Setup
A
B
A. CAUTION! Using the incorrect map datum can
seriously effect the accuracy of your GPS receiver.
The GPS datum should always match the datum of
the local chart you are using. If no datum informa-
tion is indicated on the charts you are using, contact
the chart manufacturer.
B. Keeping the velocity filter on the ‘Auto’ setting will
allow the GPSMAP 135 Sounder to automatically
monitor and adjust the response time for track and
speed calculations.
GPS 135 Rev C 8/4/98 4:19 PM Page 76