Magellan GPS PROMARK X, User Manual

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SETUP
ProMARK X
3-11
Key in the grid’s latitude of origin (refer to Table 4-1 for origin guidelines),
using the
RIGHT ARROW to select N or S. Press ENTER .
NOTE
The unit will not accept an entry that is inappropriate for the
entries already made. An attempt to enter an inappropriate
option or origin will cause the unit to display “INVALID INPUT.”
Key in the grid’s longitude of origin using the RIGHT ARROW to select
E or W. Press ENTER .
Key in a scale factor. The scale factor is normally a number that is close
to 1. Press
ENTER , then key in a units-to-meters conversion factor for all
subsequent displays in this coordinate system. Press ENTER .
Key in a false easting, followed by ENTER , then a false northing followed
by ENTER . (These entries are required to avoid displaying negative
coordinates.)
To save the grid just entered, press any function key. To reset the grid
parameters, press
CLEAR . To select a different coordinate system and
return the parameters to default, press the RIGHT ARROW .
NOTE
You must exit SETUP to save the user-entered grid.
SETUP 9 — Selecting a Map Datum The ProMARK X provides 66 geodetic
map datums for use with charts and maps worldwide. (These datums are
identifed in
Appendix 4 .) The unit also allows you to key in or upload up to
five map datums that are not currently in the unit’s memory.
The Map Datum feature allows you to operate the ProMARK X on a datum
that corresponds to the maps you are using. Which horizontal datum your
map uses can usually be found in the legend.
A datum refers to a mathematical model of the earth. The coordinates of a
position differs from one model (datum) to another. It is therefore important
to know which horizontal map datum you will be using if you want to relate
your positioning information to a map, since using a different datum may
result in positioning errors of more than 300 meters when the unit’s position
is compared with the map.