Glossary - Alpine X009-FD2 Quick Reference Manual

6 Glossary

2D/3D GPS reception
The GPS receiver uses satellite signals to calculate its (your) position and needs at least four
signals to give a three-dimensional position, including elevation. Because the satellites are
moving and because objects can block the signals, your GPS device might not receive four
signals. If three satellites are available, the receiver can calculate the horizontal GPS position
but the accuracy is lower and the GPS device does not give you elevation data: only 2D
reception is possible.
Active route
The currently navigated route. Whenever the destination is set, the route is active until you
delete it or you reach your destination. See also: Route.
City Centre
The city/town centre is not the geometric centre of the city/town but an arbitrary point the map
creators have chosen. In towns and villages, it is usually the most important intersection; in
larger cities, it is one of the important intersections.
GPS accuracy
Several factors have impact on the deviation between your real position and the one given by
the GPS device. For example, signal delay in the ionosphere or reflecting objects near the
GPS device have a different and varying impact on how accurately the GPS device can
calculate your position.
Map
The software works with digital maps which are not simply the computerised versions of
traditional paper maps. Similarly to the paper road maps, the 2D mode of digital maps show
you streets, roads, and elevation is also shown by colours.
In 3D mode, you can see the altitude differences, for example valleys and mountains,
elevated roads, and in selected cities 3D landmarks and 3D buildings are also displayed.
You can use digital maps interactively: you can zoom in and out (increase or decrease the
scale), you can tilt them up and down, and rotate them left and right. In GPS-supported
navigation, digital maps facilitate route planning.
North-up map orientation
In North-up mode the map is rotated so its top always faces North. This is the orientation for
example in Find on Map.
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