Alpha-nav AN5700NV Manuel d'utilisateur télécharger pdf (Page 85)

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, reach your destination or you quit ALPHA-NAV navigation. See also:

Route.

City Center

The city/town center is not the geometric centre of the city/town but an arbitrary point

the map creators have chosen. In towns and cities, it is usually the most important

intersection; in larger cities, it is one of the important intersections.

Color theme

ALPHA-NAV navigation comes with different color themes for daytime or night use of

the map and menu screens. Themes are custom graphic settings and they can have

different colors for streets, blocks or surface waters in 2D and 3D modes, and they

display shades or shadows in different ways in 3D mode.

One daytime scheme and one night scheme is always selected for the map and for

the menus. ALPHA-NAV navigation uses them when it switches from day to night and

back.

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

ALPHA-NAV navigation 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 colors.

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.

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Alpha-nav AN5700NV Manuel d'utilisateur Page 85