RayTech Navigator User’s Guide
Figure 5-9. Radar Target Symbol Key
Target Vector and History
The MARPA targets can be displayed with a vector line showing where they will be at a certain time in the future, (assuming present course and speed). You can select a relative or true vector and the vector length.
You can also select to view the targets history, this appears as a series of dots that are dropped by the target as it makes way. The interval between them is selectable.
A relative vector indicates the targets motion related to your own ships motion. The targets relative course and speed are calculated to produce a vector that is displayed on the target only. This mode is used for collision avoidance and threat assessment.
A true vector indicates the targets motion over ground. In this mode true vectors for the target and your own ship are displayed. MARPA measures the direction in which the target and own ship are actually moving over the ground. The result is the vessels true course, the rate of motion is the vessels true speed. Consider this motion as if you were in a helicopter looking down watching the targets move across the water. This mode can aid navigation.
Radar Range Scales
MARPA target acquisition is only available at radar range scales of up to 12nm, although tracking continues at all ranges. If you change to a lower range scale, targets may be beyond the range of the scanner and will be lost.
