British, Irish, And Ups Grids - Magellan GPS PROMARK X User Manual

ProMARK X
Appendix 5
The British, Irish, and UPS grids differ from geodetic and UTM coordinates
in that they apply only to a specific part of the world and to a specific map
datum. This has a small effect on how the ProMARK V operates.
When the British, Irish, or UPS grid system is selected in SETUP, the unit
automatically uses the applicable map datum. If the British grid is selected,
the unit uses the OSGB datum; if the Irish grid is selected, the unit uses the
Eire datum; if UPS is selected the unit uses the WGS84 datum.
The unit displays the required
datum when British, Irish, or UPS
grid is displayed with SETUP 7.
The required datum is automati-
cally selected when any of these
grids is selected.
When Map Datums (SETUP 8) is
accessed after selecting any of
these grids, the unit automati-
cally displays the selected da-
tum. A different datum cannot
be accessed until another coor-
dinate system is selected.
The unit stores the positions it calculates (and the waypoints you enter) in the
WGS84 datum and as height above ellipsoid (HAE). A position is converted
from WGS84 and HAE to the systems you have selected when it is displayed.
Since Lat/Lon and UTM are global systems, they can be used to describe
locations anywhere on earth. A position in the area described by British grid
can therefore be described in Lat/Lon, UTM, or British grid. It cannot be
described in UPS or Irish grid.
At the same time, a position that was originally described in Lat/Lon or UTM
may not be convertable to any special grid. In order to be described by
a special grid (British grid, Irish grid, UPS, or any user-entered grid),
the position must lie in the area that is described by that special grid.
Since the special grids describe small portions of the earth, any position that

BRITISH, IRISH, AND UPS GRIDS

COORDINATES
BRITISH GRID
OSGB datum only
MAP DATUM
OSGB
Appendix
~!
~
A-21