Garmin aera 500 - Manual (Page 185)

Garmin aera 500 Series Pilot’s Guide 190-01117-02 Rev. A
appendix i
173
Overview
GPS Navigation
Flight Planning
Hazar
d
Avoidance
Additional F
eatur
es
Appendices
Index
aPPeNdix i: MaP datuM aNd lOcatiON
FOrMatS
MaP datuMS
A datum is a mathematical model of the Earth that approximates the shape of the
Earth and enables calculations to be carried out in a consistent and accurate manner.
The datum is physically represented by a framework of ground monuments (such as
trig. stations) whose locations have been accurately measured and calculated on this
reference surface. Lines of latitude and longitude on a chart are referenced to a specific
map datum. Every chart has a map datum reference and the aera can be set to match
most of those commonly used.
lOcatiON FOrMatS
Your current location can be viewed on the GPS in the form of coordinates. Since
different charts use different location formats, Garmin GPS units allow you to choose
the correct coordinate system for the type of chart you are using. The most common
format is latitude and longitude, which is used by all Garmin units. You can change the
location format to use with other coordinate systems. Several other grids, including a
user-definable grid (for the advanced user), are available.