NAVIGATION SYSTEM
25
DESCRIPTION AND OPERATION
Map
When the map guidance screen is selected a
background map is shown. The map is stored on the
CD-ROM. The map scale cannot be changed as it is
fixed by the map image stored on the CD-ROM. The
following information is displayed on the map:
•
Map scale
•
The current vehicle position (icon as road
navigation)
•
Guidance start position
•
Route waypoints
•
Lines joining route waypoints and start position
•
Terrain information
•
Points of interest.
If a route is not being followed, the lines that join the
waypoints, the current position, the guidance start
position and the destination position, are double pixel
in width with black for the completed part of the
guidance and red for the not achieved part of the
guidance.
Map Display Layering
The information that constitutes the map display has
the displayed information layered as specified below,
starting at the bottom layer and working its way to the
top layer:
Vector map (if available)
Lines joining waypoints and current car position icon
Waypoint icons
Current car position icon
Cursor (cross Hairs)
Scale indicator
Heading Up
The heading up icon remains at the top (0 degrees)
position of the guidance icon. The guidance arrow
indicates the the destination bearing and the compass
arrow indicates the position of North. The heading up
icon indicates to the user the direction the destination
arrow should point to achieve the minimum distance
from the current vehicle position to the destination
(waypoint).
Timing Algorithm
Timing calculation is carried out when the ignition is
on. The ’distance covered’ is that given by the vehicle
speed signal only. The ’time to’ shown on the timing
screen is updated every 30 seconds +/- 5 seconds.
Timing calculations, for both waypoint and route,
commences as soon as the ’distance covered’ is
greater than 100 metres. All times used in the
calculations are to the nearest second and all
distances covered are to the nearest 10 metres.
The ’time to’ for the next waypoint in the route shown
on the timing screen is recalculated as the current
waypoint is achieved. For timing calculations the
’average speed’ remains valid from the current
waypoint to the next waypoint in the route and the
’distance to waypoint’ is reset to that distance to the
next waypoint in the route.
If the average speed is below 1 metre per second,
then the time to the waypoint and time to complete
route is not calculated and the previous data remains
displayed on the timing screen. If the average speed
is below 1 metre per second for more than 2 minutes,
then the average speed calculations are reset but the
previous data remains displayed on the timing screen.
Therefore when the vehicle’s speed is again above 1
metre per second the average speed calculations
begin again as if guidance had just been selected.
When the timing calculations are reset all existing
data is lost and calculations begin again as if
guidance had just been selected.